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The illustration on the cover is of Lotus glaber Mill. has again been graciously provided by Ana Arambarri (Argentina) . The Lotus illustration is the 5th in a series of illustrations that started with Volume 23. Many scientists are familiar with the name of this species to be Lotus tenuis Waldst. et Kit. Note that according to the International Code of Botanical Nomenclature the correct nomenclature is Lotus glaber Mill.
Introduction
In a plant breeding material of Lotus glaber it was observed,
in two successive generations, the presence of a lower frequency
of individuals that were differentiated with regard to the typical
phenotype by numerous characteristics. Among these are underlined
waved branches and larger leaflets. Individuals of both phenotypes
were cloned and it has been begun a comparative study of characters
with possible agronomic importance.
According to Tichá (1985), the stomatal density and size
are important anatomical parameters that contribute to the leaf
resistance (conductance) to CO2 and water vapour transport, determining
the efficiency in the use of water. The ratio of stomata density
in the adaxial/abaxial leaf surfaces also has been registered
in various species. This information has been used by Willmer
(1985) and Lüttge et al. (1993) for to classify the leaves
of the plants as: amphistomatic (present their stomata in both
surfaces, but generally they are more numerous in the abaxial
surface; as in the majority of herbaceous plants ); hypostomatic
(stomata are only on the abaxial leaf surface of arboreal species;
epistomatic (stomata are only on the adaxial surface; it is presented
by aquatic plants with floating leaves). In typical plants of
L. glaber has been determined that the stomata are predominantly
on the adaxial surface (Arambarri and Colares, 1993).The objective
of this experience was to analyze comparatively the density, dimensions
and the distribution adaxial/abaxial of the stomata of two contrasting
phenotypes highly differentiated in a L. glaber population.
Materials and methods
It was analyzed a typic phenotype (TP) and a phenotype highly
differentiated (DP), found in two successive generations of a
population in process of selection. Plants of both types were
cloned by stem cutting and were cultivated in pots with homogeneous
ground, in natural conditions. A plant of each type was used for
this study.
The leaves were obtained of the middle sector of branches of each
plant. The epidermis was removed from the third middle of the
central leaflet of fresh leaves by the peeling technique. The
adaxial or upper epidermis (UE) and abaxial or lower epidermis
(LE) were extracted from the same sector but of different leaves.
The epidermal samples were mounted in 90% glycerine. The observations
of both epidermic samples were fulfilled with a Leitz microscope
equipped with a lucid camera. Stomata number was register in 50
samples of each epidermis of different leaves. Stomata width and
length were measured in 10 stomata from each sample.
The evaluated stomata characters on both epidermis were: density
(number . cm-2), width and length (µm), the ratio length
/ width and the density ratio UE /LE. Due to the fact that UE
and LE not belonged to the same leaf, the analysis of the density
ratio UE /LE was on four whole pairs at random combined of the
n=50 stomata density data determined on UE and LE.
Data of each character were analyzed statistically and it was
applied the "t" test to validate the null hypothesis
(H0): DP is not different of TP. Besides were determined
the coefficients of single correlation among the characters.
Results and discussion
Table 1 indicates that were found significant differences (t test,
P < 0,01) among DP and TP for the characters: stomata density
on UE and LE, length of the stomata in UE and the ratio width
/length of the stomata in UE.
The stomata density and the stomata size found in both epidermal
surfaces of TP was very approaching to those that had been communicated
by Arambarri and Colares (1993). The DP showed lower stomata density
on both epidermis and stomata on UE longer than the TP plant.
This "dilution" of stomata density of DP has been apparently
balanced by the increasing size, in length of individual stomata,
but it was only on the upper epidermis. In addition to this, similar
changes in stomata characters has been associated with a increase
in the ploidy level (Willmer, 1983).
The variation coefficient indicated that was a wide variation
among the analyzed samples for the stomata density on UE and LE
surfaces, especially in the case of DP. By the contrary, the coefficient
of variation was low for the width and length of the stomata,
especially in the case of DP. These results point out that the
stomata size was more constant character than stomata density
and that this pattern to become more accentuated in DP than TP.
On the other hand, the stomata density ratio UE /LE, the Table
2 shows that the analysis based on random combinations UE-LE density
data denote significant differences among DP and TP (test of "t",
P < 0,01). In L. glaber has been determined that the
leaves present greater stomatal number in the upper epidermis
(Arambarri and Colares, 1993). This sort of distribution adaxial/abaxial
of stomata was confirmed in this experience and more over it was
found that in the "new" (DP) phenotype was significantly
more remarkable (Table 2). Stomata distribution on adaxial/abaxial
epidermis was related with the loss of water from leaves that
is greater from the stomata of adaxial surface (Robins et al ,
1965). According this interpretation the DP plants presents a
ratio that would be favorable to a greater loss of water than
TP plants.
It was determined by the analysis of single correlation that in
TP the analyzed characters varied in independent form (P >
0,05), while in DP only was significant the correlation width
vs. length of the LE stomata, (r=0,48, P=0,0003).
Results indicate that the phenotype "new" (DP) present
differences from the normal (TP) in the stomata density, stomata
length on the UE and density ratio UE /LE. The precedents on the
origin of the evaluated materials and the uniformity of the environment
conditions during their development permit to suppose that the
registered differences could be genetics. This will be studied
in future experiences.
Acknowledgments
The authors wish to express their appreciation to Prof. Ana María
Arambarri, Area de Botánica, for her assistance.
References
Arambarri AM and M Colares, 1993 L. corniculatus L. and L. tenuis Waldst. et Kit (Leguminosae) anatomy of the leaf. Lotus Newsletter, 24: 38-39.
Tichá I, 1985 Ontogeny of leaf morphology and anatomy. In: Photosynthesis during leaf development, De. Zdenek Sestak. 16-50.
Lüttge U., M. Kluge and G. Bauer, 1993. Botánica. McGraw Hill/Interamericana de España, Madrid. 573 pp.
Willmer C M, 1983. Stamata. Longman Group Limited. London. 192 pp.
Robbins WW, TE Weier and CR Stocking, 1965. Transpiration, conduction
and absortion. In: Botany. An introduction to plant science. John
Wiley & Sons, Inc., third edition. 167-181.
| Table 1. Means and variation parameters of the foliar stomata characters in two contrastant phenotypes of Lotus glaber (TP= typical phenotype and DP= differentiated phenotype). The characters were determined on upper epidermis (UE) and on lower epidermis (LE). n=50 | ||||
| Stomata density on UE (no. cm-2) | TP: 20,720.1**
DP: 16,845.1 | 5,073.97 | 5,284-28,861 | 30.12 |
| Stomata density on LE (no. cm-2) | TP: 15,698,8** DP: 8,072.74 | 3,996.36 | 2,845-19,105 | 40.83 |
| Stomata length on UE (µm) | TP: 22.6** DP: 25.72 | 1.49 | 20.5-29 | 5.78 |
| Stomata width on UE (µm) | TP: 20.01 n.s. DP: 20.05 | 0,31 | 19.5-21 | 1.53 |
| Width/length ratio on UE | TP: 0.89** DP: 0.77 | 0.04 | 0.69-0.91 | 4.94 |
| Stomata length on LE | TP: 23.9 n.s. DP: 24.02 | 1.38 | 21.5-28.5 | 5.76 |
| Stomata width on LE | TP: 20.3 n.s. DP: 19.7 | 0.61 | 17-20.5 | 3.07 |
| Width/length ratio on LE | TP: 0.86 n.s DP: 0.82 | 0.04 | 0.7-0.93 | 4.49 |
(**): indicated significant differences (t test, P < 0,01),
between the means of TP and DP for each character.
(n.s.): differences are not significant.
| Table 2. Distribution adaxial/abaxial of stomata determined by density ratio (stomata density on upper epidermis/stomata density on lower epidermis). (A), (B), (C) and (D) are whole of random combinations (n=50) of stomata density on upper epidermis and lower epidermis, obtained of different leaflets. TP and DP are typical and differentiated phenotypes of L. glaber, respectively. | ||||
(X) | coefficient | |||
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(**): difference between XTP and XDP is
significant (t test, P<0.01)
Lotus glaber Mill. (syn. L. tenuis Waldst. et Kit ex Willd). is the only important pasture legume for the Flooding Pampa (Depresión del Río Salado), the most extensive region for calf production in Argentina (7.5 million hect.). The species has perfectly adapted to the unfavorable environmental conditions of this area, to such an extent that during spring and summer it is a dominant species in the natural grasslands that cover the region (Collantes et al. 1988).
Our previous studies in birdsfoot trefoil have demonstrated the dependence of flavonoid composition on developmental stage (Strittmatter et al. 1992, 1994; Wagner et al. 1996). Kaempferol and its glycosides were identified during the whole life cycle of the plant in different organs, whereas free quercetin (Q) and its two glycosides could only be detected in the seeds of L. glaber (Strittmatter et al. 1994; Wagner et al. 1996).
In the present study, the identification of seed flavonoid was
completed including the isoflavones. Their distribution was examined
during germination, as well as in exudates from seeds, in order
to evaluate the role of these flavonoids in response to soil bacteria.
Experimental procedures
Lotus glaber cv. Tresur Chajá, the only registered cultivar in Argentina, was used. Five grams of authentic seeds were extracted with boiling water during 30 min. The aqueous solution was subjected to reduced pressure and the residue redissolved in methanol.
Other 5 g from the same seed lot were washed with a mixture of hydrogen peroxide 100 vol. and methanol 1:1 for 7 min. After rinsing in sterile water, seeds were transferred to a refrigerator (4C) in 50 ml of sterile water during 72 h. This water was evaporated and the residue redissolved in methanol.
The imbibed seeds were then transferred onto pre-wetted filter paper in sterile Petri dishes. Seeds were then germinated at 25C under fluorescent light with a 16 h photoperiod during 4 days. The exudates from germinated seeds were collected by extracting the filter papers with 50 ml of distilled water. This aqueous solution was evaporated under reduced pressure and the residue redissolved in methanol. The germinated seeds were submitted to the same extraction procedure as described previously for dry seeds.
The isolation and purification of flavonoids was achieved by descending chromatography using HOAc 15% on 3 MM Whatman paper. Each band was eluted with methanol and chromatographied again in BAW (n butanol-HOAc-H2O, 4:1:5, upper phase). The obtained compounds were eluted in methanol and analysed using standard procedures (Mabry, Markham and Thomas, 1970; Markham, 1982 and Waterman and Mole, 1994).
The experiments were performed twice with similar results.
Results
When dry seeds of L. glaber were tested for their flavonoid
composition, not only kaempferol (K), quercetin (Q), quercetin-3-O-galactoside
(QGa) and quercetin-3-O-glucoside (QGl) were identified (Wagner
et al. 1996); a kaempferol-3-O-triglucosyl-7-O-rhamnoside (KSR)
and a possibly polysubstituted isoflavone (I) were also detected.
The structure of this isoflavone will be confirmed with MS techniques.
These latter metabolites (KSR and I) are extremely soluble in
water as shown by their high Rf values (0.77 and 0.95, respectively)
(Table 1).
| Table 1: Rf values of the different compounds | |
| quercetin-3-O-glucoside (QGl) | |
| quercetin-3-O-galactoside (QGa) | |
| kaempferol-3-O-sophoroside-7-O-rhamnoside (KSR) | |
| isoflavone (I) | |
The results indicate that when relative concentrations of each flavonoid were compared (Table 2), dry seeds (control) and the filter papers showed the highest concentration of all compounds analysed. Aglycones were released during germination, wheras it was possible to detect KSR and I in the water used for the imbibition of the seeds, because of their high solubility.
After a period of 4 days all flavonoids remained in the germinated
seeds in their lowest relative concentration (Table 2).
| Table 2: Relative concentrations of flavonoids in Lotus glaber seeds during the first stages of germination | ||||
| (+ ) traces; + presence; ++ abundance; +++ high abundance | ||||
Discussion
Analysis of the flavonoids released during imbibition and germination of L. glaber seeds confirmed our previous results (Wagner et al. 1996) that Q and its glycosides are the dominant flavonoids in the seeds.
These results agree with Hartwig et al. (1991) and Tsai and Phillips (1991), who detected that nearly half (46%) of the flavonoids fraction released from intact alfalfa seeds consisted of Q or its derivatives.
The presence of an isoflavone in dry seeds of L. glaber is also noteworthy. Bonde et al. (1973) and Ingham (1977) reported the isolation of the two isoflavans sativan and vestitol in leaves of L. corniculatus, a closely related species to L. glaber, but in response to inoculations with fungi. Flavonols and isoflavones released from L. glaber seeds were also identified in dry seeds, and thus, they would not function as phytoalexins; they must have been synthesized previously.
It remains to be determined which seed tissue is the source of the mentioned flavonoids; alfalfa seeds most apparently store the flavonoids in the seed coat (Hartwig and Phillips, 1991), whereas in soybean the amounts of isoflavones were much larger in the cotyledons than in the roots or hypocotyls (Suganuma and Takaki, 1992).
Data from this study suggest the following preliminary model of how flavonoids diffuse from seeds during the initial stages of germination. Seeds release the isoflavone and KSR during imbibition into aqueous solution as well as Q glycosides. The aglycones, which are less soluble in water than glycosides, diffuse away from the already germinating seed as revealed the filter paper (Table 2).
Although it could be questionable to extrapolate directly the
results from this experiment to the soil environment, the mentioned
flavonoids should certainly affect soil microorganisms.
References
Bonde, M.R.; Millar, R.L. and Inham, J.L. 1973. Phytochemistry
12: 2957-2959.
Collantes, M.B.; Kade, M.; Miaczynski, C. and Santanatoglia, O. 1988. Studia Oecologica V: 77-93.
Hartwig, V.A.; Joseph, C.M. and Phillips, D.A. 1991. Plant Physiol. 95: 797-803.
Ingham, J.L. 1977. Phytochemistry 16: 1279-1282.
Mabry, T.J., K.R. Markham and M.B. Thomas. 1970.The Systematic Identification of the Flavonoids, Springer-Verlag, Berlin, New York. pp. 1-175.
Markham, K.R. 1982."Techniques of Flavonoid Identification, Academic Press ed. pp. 1-113.
Strittmatter C.D., Wagner M.L., Kade M. and Gurni A.A. 1992. Bioch. Syst. and Ecol. 20 (7): 685-687.
Strittmatter C.D., Wagner M.L., Kade M., Rivero M., Ricco R.A. and Gurni A.A .1994. Proceedings of The First International Lotus Symposium pp. 199-202.
Suganuma, N. and Takaki,M. 1993. Soil Sci. Plant Nutr. 39 (4): 661-667.
Tsai, S.M. and Phillips, D.A. 1991. Appl. Environ. Microbiol. 57 (5): 1485-1488.
Wagner M.L., Strittmatter C.D., Kade M., Rivero M., Ricco R.A. and Gurni A.A. 1996. YTON 58(1/2): 141-146.
Waterman, P.G. and S. Mole. 1994. Analysis of Phenolic Plant Metabolites,
Blackwell Scientific Publications pp. 1-238.
Flooding effects on the reproduction of Lotus glaber Mill.
and Lotus corniculatus L. were studied under experimental
conditions. The hypothesis that, the effects of flooding on the
reproduction differ with species and plant age, was tested.
Flooding were carried out in winter (42 days flooding), spring
(49 days) and summer (17 days),in pots under field conditions.
Spring flooding was applied to young (133 days) and old (208 days)
plants. Winter flooding did not affect weight and number of fruits
and seeds per plant. Reproductive characteristics in plants of
different age and treatment of the same species were not affected
by spring flooding. Lotus glaber produced more fruits and
seeds than Lotus corniculatus in the spring flooding.
Indeterminate reproduction and higher reproductive effort of young
plants, determined that reproductive traits for each species had
no significant differences between treatments and plant age. Summer
flooding (17 days) promoted both flower and fruit abortion and
a plant mortality of 100 % in L. corniculatus and 50 %
in L. glaber.
Lotus glaber (L.g.) and Lotus corniculatus (L.c.)
were introduced as forage plants in the Flooding Pampa around
50 years ago. While L.g. has naturally colonized the frequently
flooded habitats. L.c. has not shown the same expansion.
In this paper we studied the tolerance to flooding of seeds of
both species. The seeds were flooded during 7 weeks, in controlled
conditions of temperature and light, and samples were taken at
increasing time intervals. Germination percentage (G.P.) of the
seeds was taken as a measure of tolerance to flooding and it was
found that although G.P. decreased with flooding time in both
species, the soft seeds of L.c. lost viability earlier
than those of L.g. With 49 days of flooding, hard seeds
were the only ones that maintained the G.P. and were more frequent
in L.g. (approximately 50 % in L.g. and 6 % in L.c.,
in 5 months old seed). These characteristics probably play an
important role in the capacity of L.g. of colonizing habitats
that are periodically flooded.
Ecología Austral Vol.5, No 2: 157-163, 1995.
INTRODUCTION
The Salado River Basin is an extense area in Buenos Aires province (Argentina) dedicated to beef and dairy cattle production, which is mainly sustained on a grazing system based on native grasslands with a minor portion of cultivated pastures. Therefore, proven the extensive conditions of cattle production in the area, nitrogen contents of the forage biomass is a critical point determining yield for the process. Any future intensification in animal production within a pasture based system will demand an increase in the amount and the quality of forage supply. In this way, great amounts of nitrogen should be incorporated to the plant-soil system (Simpson and Stobbs, 1981). Basically, this can be achieved by periodical applications of nitrogen-containing fertilizers or, alternatively, through the symbiotic fixation of atmospheric nitrogen.
Legumes associate in a symbiotic way with bacteria belonging to the genus Rhizobium, thus producing root nodules where the nitrogen fixation process occurs. Recent agronomic studies about Lotus species cultivated in the introduction garden of the Instituto Tecnológico de Chascomús (INTECH), project L. pedunculatus and L. corniculatus var. hirsutus by their good adaptability to local conditions (Remis et al, 1996). The former is a commercial forage and the latter is a non commercial botanical variety. Both of them have still not been tested nor cultivated in the region. Nutritional evaluations done by our group (Locatelli et al., this issue) suggest that this two species might substantially improve the quality of pastures present in the zone by increasing their protein content.
Condensed tannins are known to be present in Lotus species and their compositions usually differ between them (Pankhurst and Jones, 1979; Pankhurst et al., 1987). These compounds could affect nodulation of such legumes and indirectly diminish plant persistence and quality, particularly in low fertile and poorly drained soils. Pankhurst and Jones (1979) found that delphinidin rich tannins accumulated in roots and ineffective nodules of L. pedunculatus. They suggested that such ineffectiveness could be due to the sensitivity of Rhizobium strains located in the nodules to those compounds. L. corniculatus var. hirsutus roots also contain a high level of delphinidin rich tannins, but lower than roots of L. pedunculatus plants. On the contrary, condensed tannins present in L. glaber do not contain delphinidin in their structure (Pankhurst and Jones, 1979; Pankhurst et al., 1987).
R. loti strains commonly found in soils of the Salado River
Basin are able to form nodules in L. glaber roots. However,
no data concerning the capacity of these strains to nodulate other
Lotus species are currently available. The aim of the present
work was to determine the ability of an indigenous strain of R.
loti isolated from L. glaber to form effective nodules
in other Lotus species. Data are compared with two additional
strains of R. loti: one of them (NZP 2037) is known to
form effective nodules in roots of both Lotus species used
in this study, while the other (NZP 2213) forms ineffective nodules
on some species which contain delphinidin rich tannins in their
roots (e.g. L. pedunculatus) (Pankhurst et al., 1987).
MATERIALS AND METHODS
Plant material and culture: Legumes used in this study were L. corniculatus var. hirsutus and L. pedunculatus. Seeds obtained from the introduction garden were surface disinfected with concentrated sulfuric acid for 15 min, thoroughly rinsed with sterile distilled water and then kept in water for 24h. After that, they were placed in culture tubes containing 20 ml of solid Jensen medium (Vincent, 1970) and incubated in a climatized room at 25°C with a photoperiod of 16 h.
Rhizobium loti strains: Strain 1-INTECh was originally isolated from nodules of L. glaber plants naturally growing in the outskirts of the INTECH. Strains NZP 2037 and NZP 2213 from Beltsville Rhizobium Culture Collection were kindly gifted by Dr. Paul Beuselinck, USDA-ARS, University of Missouri, Columbia, MO, USA. Bacteria were cultured in AMA medium (Vincent, 1970), at 28°C with rotatory shaking.
Nodulation assay: Three days after transfer to culture tubes, seedlings were inoculated with 0.1 ml of bacterial culture and incubated in the above stated conditions for a 6 week period. Combinations of each Lotus species and bacterial strain were done, each one consisting of 24 plants. Control plants were inoculated with the same volume of AMA medium.
Nitrogenase activity determination: Nitrogenase activity
of nodules was measured by using the acetylene reduction technique
(Hardy et al., 1968) on the same plants used for the nodulation
assay. Six weeks old plants were placed in 50 ml culture tubes
(8 plants each) and hermetically closed with rubber caps. Each
treatment included three replicate tubes. Air (5 ml) was withdrawn
and replaced by an equivalent volume of acetylene. Tubes were
incubated at 25°C during 2 h, and then 0.5 ml gas samples
were removed and analysed for acetylene and ethylene content using
a Hewlett-Packard 5890-A gas chromatograph fitted with a flame
ionization detector and "Poropak N" in a 1.5 mm x 1.32
m column.
RESULTS
Figure 1 shows whole plants of L. pedunculatus (Fig. 1A)
and L. corniculatus var. hirsutus (Fig. 1B) inoculated
with three different strains of R. loti: the two collection
strains NZP 2213 and NZP 2037, and the indigenous strain 1-INTECh.
L. pedunculatus plants inoculated with strains NZP 2213 and 1-INTECh
had a morphological aspect similar to that of non-inoculated plants
(Fig. 1A). Their aerial parts were scarcely developed and exhibited
chlorotic leaves. On the contrary, L. pedunculatus plants
inoculated with strain NZP 2037 showed a normal development of
aerial parts and no symptoms of chlorosis were detected on leaves.
On the other hand, L. corniculatus var. hirsutus
plants inoculated with all three strains grew more vigorously
than controls (Fig. 1B), although some chlorosis was observed
in leaves of plants inoculated with strain 1-INTECh. Nodules formed
by strain NZP 2037 in both Lotus species looked similar
. They were spherical and pink coloured. Strains NZP 2213 and
1-INTECh also formed this type of nodules in L. corniculatus
var hirsutus plants but in L. pedunculatus
plants they formed pseudonodules.
Figure 1: Nodulation of plantlets of L. pedunculatus (A)
and L. corniculatus var hirsutus (B) by Rhizobium
strains (from left to right : control, 1-INTECh, NZP 2213 and
NZP 2037).
Table 1 shows results obtained when nitrogenase activity was measured in nodules of Lotus plants inoculated with the three different R. loti strains. As shown, strain NZP 2037 was capable of forming effective, nitrogen-fixing (Nod+ fix+) nodules with the two species of Lotus. Strain NZP 2213 formed (Nod+ Fix+) nodules in L. corniculatus var. hirsutus and ineffective (Nod+ Fix-) nodules in L. pedunculatus. Indigenous strain 1-INTECh formed (Nod+ Fix-) nodules in both species, even when the morphology of those formed in L. corniculatus var. hirsutus was very similar to that of effective ones.
| Table 1. Atmospheric nitrogen fixing ability of root nodules of Lotus species inoculated with three different R. loti strains. | ||
| Rhizobium strain | ||
| None | ||
| NZP 2037 | ||
| NZP 2213 | ||
| 1-INTECh | ||
DISCUSSION
The observed ability of the R. loti collection strains NZP 2213 and NZP 2037 to nodulate L. pedunculatus and L. corniculatus var. hirsutus, as well as efectiveness of such nodules is in agreement with results reported by Pankhurst et al. (1987), except for the interaction between NZP 2213 and L. corniculatus var. hirsutus. In our hands, the latter symbiosis association rendered effective nodules (Nod+ fix+), which is in contrast with previous results reported by Pankhurst el al. (1987) showing the formation of ineffective nodules. A possible explanation for this discrepancy could be attributed to physiological changes in L. corniculatus var. hirsutus performed after adaption to soils of our region.
Concerning the inability of the indigenous R. loti strain
1-INTECh to form effective nodules in roots of both Lotus
species studied, it is concluded that Rhizobium strains
capable of forming effective nodules and succesfully compete with
native strains should be obtained to introduce these plant species.
Thus, if future attempts to cultivate L. pedunculatus or
L. corniculatus var. hirsutus are made in the region,
the use of such adequate bacterial strains could greatly contribute
to the improvement of legume forage productivity and quality.
However, it is necessary to point out that these experiments should
be checked by using a greater number of indigenous isolates, to
confirm that the behavior of strain 1-INTECh is representative
of the local R. loti population.
ACKNOWLEDGMENTS
The authors wish to thank M.L. Locatelli for helpful discussion. MJE is a Fellow from Comisión de Investigaciones Científicas (CIC, Bs. As.). RAU and AAI are Members of the Investigator Career from Consejo Nacional de Investigaciones Científicas (CONICET).
REFERENCES.
Hardy, R.W.F.; R.D. Holsten; E.K. Jackson and R.C. Burns (1988) Plant Physiol. 43: 1185-1207.
Pankhurst, C.E. and W.T. Jones (1979) J. Exp. Bot. 30: 1109-1118.
Pankhurst, C.E.; D.H. Hopcroft and W.T. Jones (1987) Can. J. Bot. 65: 2676-2685
Remis, J.L.; O.A.Ruiz; R.A.Ugalde and A.A.Iglesias (1995) Lotus Newsletter 26:17-20
Simpson, J.R. and T.H. Stobbs (1981) In: Grazing Animals (Morley, F.W., ed.). pp. 261-287. Elsevier Scientific Publishing Company, Melbourne.
Vincent, J.M. (1970) A Manual for the Practical Study of Root Nodule Bacteria. Blackwell Scientific Publications, Oxford.
INTRODUCTION
Beef and dairy cattle production in the Salado River Basin is essentially a grazing system mainly based on natural grasslands, with a minor portion of cultivated pastures. Edaphic characteristics: limed and poorly drained soils with severe phosphorus deficiency, medium organic matter levels, high alkalinity and salinity; together with periodic exposition of soils to waterlogged conditions, significantly decrease persistence and yield of common legume species (red clover, alfalfa, white clover) in this region (Mazzanti et al., 1986). A strategy to be developed to solve these problems is the introduction of foreign legume species. In this way, Lotus spp. is an important alternative, after their growing conditions and significant nutritional value. Currently, the genus Lotus has been introduced in the Salado River Basin which counts with L. corniculatus and L. glaber (already naturalized) species. However, at the present time, information about nutritional quality (and its variability throughout the year) of commercial species in the area is scarce, and an exhaustive analysis on the productive performance of Lotus in the region is far from complete.
In grazing systems (preferentially extensive) animal production will be highly influenced by nutritional variability of forage offer along the year. Therefore, it is relevant to know (besides biomass production) the nutritional attributes (protein, energy, etc.) and the efficiency by which ruminants profit different legume forage species. After this information, it is possible to design different utilization and agronomic management strategies to obtain a maximum yield from a specific forage material. It has been reported (McGraw et al., 1989) the relevance of an early evaluation of quality parameters in introduction trials of unknown species, in order to identify desirable or undesirable characteristics and thus to postulate rationale strategies for the improvement of forage quality.
Last year, we reported studies carried out at Instituto Tecnológico
de Chascomús (INTECH) concerning green and dry matter production
for different Lotus spp. growing at an introduction garden
located in the Salado River Basin region (Remis et al., 1995).
The present study completes that previous evaluation by analysis
of chemical and biological parameters determining the quality
of the different plant species.
MATERIALS AND METHODS
Aerial biomass (whole plant) of the different Lotus entries (perennial species) was sampled from small plots of the introduction garden during years 1994 and 1995. According to seasonal periods and plant species, these samples included leaves, stems, flowers and/or fruits. Distribution in the different seasonal periods was made by considering the time of sample collection as follows: i) Fall-winter: from late March to early August, ii) Spring: from mid October to mid November, and iii) Summer: from late December to mid February. Samples were oven-dried at 60°C until constant weight to determinate dry matter (DM) content (data expressed as % of the aerial biomass), and then milled to 1 mm by using a Wiley-type mill.
Crude protein (CP) was estimated in the samples by total nitrogen
determination after sulfuric acid digestion, distillation and
titration by the Kjeldahl method (N x 6.25). Neutral detergent
fiber (NDF) was determined according to Goering and Van Soest
(1970). The enzymatic pepsin-cellulase method (Donofer et al.,
1963) was use to measure DM in vitro digestibility (DMIVD) of
the samples. CP, NDF and DMIVD are expressed as % of the DM.
RESULTS AND DISCUSSION
Table 1 shows quality parameters determined for periods of spring and summer in different Lotus spp. grown at the introduction garden in INTECH. Data corresponding to Medicago sativa and Trifolium pratense are included to establish a comparison with two commonly used forage species. As shown (Table 1) besides L. glaber and L. corniculatus (the two commercial species already used in the region) other forage materials exhibited relatively low NDF levels, as well as CP and DMIVD values higher than the mean found for the different Lotus spp. analyzed. In this way, L. corniculatus var. hirsutus showed a good pattern of quality parameters, thus reinforcing the promising data previously obtained with this species (Remis et al., 1995). Table 1 also shows that the hybrid L. corniculatus x L. pedunculatus exhibited high values of CP and DMIVD during the spring, whereas similar results are observed for L. parviflorus during the summer peirod. Concerning L. rectus, Table 1 shows that this species exhibited low parameter values estimating quality. However, it needs to be considered that L. rectus was the only arbustive species in the introduction garden, and that the data could be masked by a significant proportion of lignified stems in the samples. Periodic defoliations of aerial biomass could reverse the low leaf to stem ratio found in our samples and renders a more actual picture of the nutritive value of L. rectus when utilized by ruminants.
Results obtained with L. corniculatus and L. pedunculatus are in agreement with those reported by Carámbula et al. (1994) for acid, poorly drained, and phosphorus depleted soils in the East of Uruguay. Concerning the latter species, Table 1 shows relatively high levels of CP content but low DMIVD values. It is necessary to point out that the methodology we applied in this study determines only ruminal digestibility. Since L. pedunculatus species possesses high condensed tannin levels (5-10% of the DM) (Lowther et al., 1987; Roberts and Beuselinck, 1992), it is feasible that these compounds decrease DM digestibility at rumen (Chiquette et al., 1989; Waghorn et al., 1994), although DM digestion of this species at hind gut could equilibrate the global process (Barry et al., 1986).
As shown in Figure 1, quality parameters for L. corniculatus
var. hirsutus are maintained relatively high along
the year, being the variations comparable with those observed
in L. corniculatus and L. glaber. It has been reported
(Forde and de Lautour, 1978; Kelman and Tanner, 1990) that L.
corniculatus var. hirsutus contents higher amounts
of condensed tannins (3.5-7% of the DM) than L. corniculatus
and L. glaber, which determines a nutritional advantage
for the former species. Taking into account these results, and
considering the reseed capacity and high yields of DM found for
L. corniculatus var. hirsutus at the introduction
garden (Remis et al., 1995), together with the high quality nutritional
characteristics reported herein; it is concluded that this species
is potentially important for the region. Future incorporation
of L. corniculatus var hirsutus into forage mixed
pastures or through interseed on natural grasslands, as well as
its use to obtain hybrid species possessing higher productivity
and quality are important alternatives to be developed for the
improvement of pastures in the region. Works in our Institute
are on the way, looking for technological tools to reach an increase
of productivity in the Salado River Basin.
ACKNOWLEDGMENTS
The authors are greatly indebted to D.F. Gómez Casati and
G.A. Polenta for helpful suggestions on the experimental procedures.
AAI is a Member of the Investigator Career from CONICET.
REFERENCES
Barry, T.N., Manley, T.R. and Duncan, S.J. 1986. The role of condensed tannins in the nutritional value of Lotus pedunculatus for sheep. 4. Sites of carbohydrates and protein digestion as influenced by dietary reactive tannin concentration. British J. Nutr. 55:123-137.
Carámbula, M., Ayala, W. and Carriquiry, E. 1994. Lotus pedunculatus. Adelantos sobre una forrajera que promete. Serie Técnica Nº 45. INIA, Uruguay.
Chiquette, J., Cheng, K.J., Rode, L.M. and Milligan, L.P. 1989. Effect of tannin content in the two isosynthetic strains of birdsfoot trefoil (Lotus corniculatus L.) on feed, digestibility and rumen fluid composition in sheep. Can. J. Anim. Sci. 69:1031-1039.
Donefer, E. Niemann, P.J., Crampton, E.W. and Lloyd, L.E. 1963. Dry matter disappearance by enzyme and aqueous solutions to predict the nutritive value of forages. J. Dairy Sci. 46:965-970.
Forde, M.B. and de Latour, G. 1978. Plant introduction trials. Classification of Lotus introductions. N.Z. J. Exptl. Agr. 6:293-7.
Goering, H.K. and Van Soest, P.J. 1970. Forage fiber analysis (apparatus, reagents, procedures and some applications). Agric. Handbook 379. USDA.
Kelman, W.M. and Tanner, G.J. 1990. Foliar condensed tannin levels in Lotus species growing on limed and unlimed soils in South-Eastern Australia. Proc. N.Z. Grassl. Assoc. 52:51-54.
Lowther, W.L., Manley, T.R. and Barry, T.N. 1987. Condensed tannin concentrations in Lotus pedunculatus cultivars grown under low soil fertility conditions. N.Z. J. Agric. Res. 30:23-25.
Mazzanti, A., Darwich, N.A., Cheppi, C. and Sarlangue, H. 1986. Persistencia de pasturas cultivadas en zonas ganaderas de la Pcia. de Buenos Aires. Rev. Arg. Prod. Anim. 6 (Sup. 1):65.
McGraw, R.L., Beuselinck, P.R. and Marten, G.C. 1989. Agronomic and forage quality attributes of diverse entries of birdsfoot trefoil. Crop Sci. 29:1160-1164.
Remis, J.L., Ruíz, O.A., Ugalde, R.A. and Iglesias, A.A. 1995. Evaluation of Lotus spp. growth in the Salado River Basin. Lotus Newslett. 26:17-20.
Roberts, C.A. and Beuselinck, P.R. 1992. Condensed tannins in Lotus species. Lotus Newslett. 23:41.
Waghorn, G.C., Shelton, I.D. and McNabb, W.C. 1994. Effects of condensed tannins in Lotus pedunculatus on its nutritive value for sheep. 1. Non-nitrogenous aspects. J. Agric. Sci. 123:99-107.
| Table 1: Nutritive parameters (%) in whole plants of Lotus spp. during spring-summer periods. | ||||||||
| Species | ||||||||
| M. sativa1 | ||||||||
| T. pratense1 | ||||||||
| L. glaber | ||||||||
| L. corniculatus | ||||||||
| L. corniculatus var. hirsutus | ||||||||
| L. corniculatus var. alpinus | ||||||||
| L. corniculatus x pedunculatus | ||||||||
| L. filicaulis | ||||||||
| L. parviflorus | ||||||||
| L. pedunculatus | ||||||||
| L. rectus | ||||||||
| MEAN | ||||||||
| DEVIATION | ||||||||
1 Data from Fernández and Galli. 1993 (INTA Rafaela, Argentina) corresponding to studies carried out in the humid pampa region (Argentina).
Figure 1: Seasonal variation for quality parameters obtained from whole plants of L. glaber (continuous lines), L. corniculatus (big dashes) and L. corniculatus var. hirsutus (small dashes). Spg = spring; Sum = summer; and F/W = fall/winter.
Ethephon (2-chloroalkylphosphonic acid) is regarded as "liquid"
ethylene and is probably widely used as plant growth regulator
in agriculture. Ethephon is an ethylene generator. Their breakdown
occurs primarily on the leaf surface and in the aqueous plants
fluids (Abeles et al. 1992). The ethylene acting as a natural
volatile hormone and have an effect on many physiological process.
The objective of this communication was to inform about some abnormalities
registered by the seedlings growth of Lotus glaber, presumably
due to an accidental exposition to exogenous ethephon.
L. glaber seeds were sown in vermiculite contained in a
tray. They were cultivated in a greenhouse with a supply of nitrofoska
2 (BASF) 3gr/l. The substrate was maintained at the water saturation
point. From their sowing this tray remained accidentally exposed
to an ethephon sprinkled (10-4 a 10-5 M)
applied on another trial.
After the seedling emergence it was observed a notorius alteration
in the uniformity size of the seedlings aerial part. Among the
fourth and fifth weeks the seedlings were removed from the tray
and it were evaluated the roots and the aerial components.
The seedling abnormalities observed were: The roots of the most
seedlings showed some alterations in their morphology and size,
inhibition of roots elongation coupled with lateral swelling ,
hypertrophyes, be bent into curls and a negative gravitropism
in lateral roots. The more important seedling abnormalities are
shown in the figure 1 (a). Seedlings with their roots affected
and also normal seedlings were registered, (n=114). The frequency
of seedlings affected and unaffected was 73.68% and 26.32%, respectively.
Figure 1. (a) Seedling abnormalities: small size of aerial part,
hypertrophyes and curls in the root system. (b) Recovery of the
abnormal seedlings after fourth weeks cultivated at the open air.
The abnormal plants were cultivated during fourth weeks at the
open air in pots with agricultural ground to evaluate their following
behavior. During the fourth weeks that the plants were cultivated
in the open air it was register that the affected plants were
recovering gradually their normal growth. Immediately to the end
of this period was observed that, from the affected roots had
been originated roots with normal morphology (figure 1 ( b)).
REFERENCES
Abeles FB, PW Morgan and ME Saltveit Jr (1992) Ethylene plant
biology. Academic Press Inc.. New York. 414 pp.
Abstract. The Lotus strigosus var. tomentellus
complex from Lower California and Sonora, Mexico in which "phases"
to denote aberrant forms or intermediates within a species have
been found was studied morphologically. Until present the phases
1 and 2 are knowledge for L. strigosus var. tomentellus
Isely. The specimens of herbarium (MEXU) were examined with a
stereoscopic microscope and the topographic features of the testa
were analyzed by SEM. According to morphological characteristics
found the specimens studied were separated in three groups. The
group 1 correspond to L. strigosus var. tomentellus
"phase 1" Isely. It is characterized by the presence
of peduncled inflorescence with flowers more than 7 mm length,
and the bract 1-2 (-3) leaflets. The groups 2 and 3 agree with
L. strigosus var. tomentellus Isely by the presence
of flowers no more than 6 mm length, subsessiles or shortly peduncled
and bract absent. However, fruit and seed characteristics delimit
two new morphological phases to L. strigosus var. tomentellus
from Lower California and Sonora, Mexico. They are "phase
3" to group 2 with fruit incurved, falcate, and seed with
the hilum superficial, and "phase 4" to group 3 with
fruit distally incurved and seed with the hilum sunken in a lateral
notch.
Key words: Fabaceae; Loteae; Lotus; Lower California;
Mexico; morphology; phases; Sonora.
Introduction
Isely (1981) uses the word "phases" to denote aberrant forms or intermediates within a species. Such "phases" have been found in this study in the L. strigosus var. tomentellus complex from Lower California and Sonora, Mexico.
Lotus strigosus (Nutt.) Greene, L. strigosus var. hirtellus (Greene) Ottley and L. strigosus var. tomentellus (Greene) Isely are distributed in California, Lower California, and Mexico.
The Lotus strigosus group shows a continuous variation in its morphological characteristics. According to Isely (1981), Nuttall's (1838) names Hosackia nudiflora, H. rubella and H. strigosa illustrate local population variance. Greene (1890) examined and subdivided Nuttall's species in the L. strigosus group. He renamed L. tomentellus to one species from Lower California.
Later, Ottley (1923, 1944) distinguished three taxa, namely, L. strigosus, L. strigosus var. hirtellus and L. tomentellus which she based on seed characteristics. She described the seed of L. strigosus, and L. strigosus var. hirtellus as: "cubical, notched at the hilum" and that of L. tomentellus as "globose to oval an occasional one cubical."
Isely (1981) reduced L. tomentellus to a variety of L. strigosus. At the same time he established two phases, both for L. strigosus (phase 1 and 2) and for the var. tomentellus (phase 1 and 2) based on the fact that the phases represent "aberrant forms or intermediates."
This study redefines the characteristics found in specimens of
L. strigosus var. tomentellus from Lower California
and Sonora.
Materials and Methods
The specimens studied were from (MEXU), Herbario Nacional de Mexico,
Instituto de Biologia, Universidad Nacional Autónoma de
Mexico. The acronym for the herbarium is given according to Holmgren
et al. (1990). The morphological characters were examined with
a Wild M 8 stereoscopic microscope equipped with a camera lucid.
The topographic features of the testa were examined from whole
seeds and portions of them by means of a Jeol JSM T100 scanning
electron microscope (SEM). Drawings of the characters were prepared.
Results and Discussion
According to morphological characteristics, the specimens studied have been separated in groups as follows:
Group 1.
LOWER CALIFORNIA. Western base of Cocupah Mts., on shores of Laguna Maguata, C. Epling, M. Darsie, W. M. Stewart and W. M. Robison, s. n. Feb-19-1933 (552731 MEXU).- Loc. Puerto Refugio, Punta Norte de la Isla Angel de la Guarda, Mpio. Ensenada, 029º 33' 00 N lat, 113º 34' 00 W long, Elev. 50 m s. n. m. Pedro Tenorio L. 10849, C. Romero de T., Feb-07-1986. Desierto sarcocaulescente, suelo arenoso-pedregoso (523662 MEXU).
SONORA. Tiburon Island, Ensenada Blanca, vicinity 28º 59'
N lat, 112º 29½' W long, Joe Edmundson; Alexander Russell,
R. S. Felger , R.S.F. 17276, Feb-20-1968. (447029 MEXU).
Group 2.
LOWER CALIFORNIA. Loc. Desierto de Vizcaino, Arroyo San José de Castro, Mpio. Mulejé. Elev. 160 m s. n. m.; Jorge Cancino Hernández 6, Jun-26-1983. Hierba anual de 7 cm . Abundancia regular. Vegetación circundante matorral subinerme, vegetación halófila, en potrero. (354700 MEXU).- Loc. Desierto de Vizcaino, E de Bahía Asunción, Mpio. Mulegé. Jorge Cancino, Carlos Plata, C. 68; Feb-11-1984. Hierba anual escasa, 10 - 15 cm altura. Vegetación primaria de ecotono, duna mat. halófilo; suelo arenoso. (428089 MEXU).- Loc. La Bocana, Mpio. Santa Rosalía, 26º 53' N lat, 113º 44' W long. Elev. 20 m s. n. m. Pedro Tenorio L 12927, C. Romero T. Apr-17-1987. Hierba escasa, flores amarillas. Vegetación de dunas; suelo amarillo arenoso. [(282843 MEXU), both L. strigosus var. tomentellus and L. salsuginosus var. brevivexillus are on the same sheet].
SONORA. Tiburon Island, Ensenada de La Perra; vicinity 28º
47' N lat, 112º 16' long. R. S. Felger, J. Edmundson, N.
Thomas, R. S. F. 17724, Apr-12-1968. (453698 MEXU).
Group 3.
LOWER CALIFORNIA. Loc. San Ignacito, 14 km al SW de Cataviña, por la carr. transpeninsular, Mpio. Ensenada. 29º 47' N lat, 114º 45' W long. Elev. 640 m s. n. m. Pedro Tenorio L. 13110, C. Romero de T. Apr-28-1987. Hierba postrada, abundante, fl. amarilla, fr. inmaduro. Vegetación matorral desértico, primaria; suelo arenoso amarillo. [(155141 MEXU), specimen corresponds to L. strigosus var. tomentellus, the envelope attached contains a mixture of the specimen L. strigosus var. tomentellus with L. salsuginosus var. brevivexillus].
SONORA. On hillsides of volcanic rock 2.5-3 mi N of Sáric,
approx. 31º 07' N lat, 111º 20' W long. Elev. 2900 ft.;
Grady L. Webster 22517, Mar-26-1978. Scrub of mesquite, saguaro,
Cercidium, et al. Postrate, fls. yellow. (305643 MEXU).- Coast
of the Gulf of California near the mouth of the Rio Concepcion,
10.6 mi. NE of El Desemboque on the road toward Caborca. Near
30º 40' N lat, 112º 57' W long. Elev. 100 ft. A. C.
Sanders, M. Dimmitt, G. Montgomery, et al. 3479, Mar-7-1983. Sandy
coastal flats with low dunes; creosote Bush Scrub with Larrea
and Ambrosia dunosa. A fairly common yellow-flowered annual. (358773
MEXU).- Loc. km 71 de la carr. Sonoyta-San Luis Río Colorado.
32º 04' N lat, 113º 34' W long. Alvaro Campos V 4435a,
J. L. Panero, L. I. Cabrera, Feb-28-1992. Hierba 20 cm altura,
fl. blanca, fr. verde, frecuente. Vegetación matorral espinoso
con Opuntia. (578101 MEXU).
Group 2 fruit incurved, falcate and seed with the hilum superficial.
Group 3 fruit distally incurved and seed with the hilum sunken in a lateral notch.
KEY TO "PHASES" OF L. STRIGOSUS VAR. TOMENTELLUS
FROM LOWER CALIFORNIA AND SONORA, MEXICO
Acknowledgments
I express my appreciation to Curators of the Herbario Nacional
de Mexico (MEXU). I also thank Prof. William F. Grant for his
helpful comments on the manuscript, and Rafael Urrejola for technical
assistance using SEM.
References
Greene, E. L. 1890. Enumeration of the North American Loti. Pittonia 2: 133-150.
Holmgren, P. K. , N. H. Holmgren and L. C. Barnett. 1990. Index Herbariorum. P. 1. The Herbaria of the World. [Regnum Veg. 120]. NY Bot. Gard., Bronx.
Isely , D. 1981. Leguminosae of the United States. III. Subfamily Papilionoideae: tribes Sophoreae, Podalyrieae, Loteae. Mem. NY Bot. Gard. 29(3): 124-264.
Nuttall, T., Torrey, J. and A. Gray. 1838. Leguminosae. In: Flora of North America 1: 326. NY.
Ottley, A. M. 1923. A revision of the Californian species of Lotus. Univ. Calif. Publ. Bot. 10: 189-305.
Ottley, A. M. 1944. The American Loti with special consideration
of a proposed new section, Simpeteria. Brittonia 5(2): 81-123.
Crownvetch (Coronilla varia L.) and birdsfoot trefoil (Lotus corniculatus L.) can be used as perennial living mulches in the production of corn (Zea mays L.), soybeans (Glycine max L.) small grains and forages. The primary benefit is the almost total reduction in soil erosion. Other benefits are enhanced productivity through soil conservation, increased soil organic matter and organic nitrogen, improved soil tilth, better footing during spring planting and fall harvesting seasons when it might otherwise be too wet to get into the field. Positive side effects include a reduction in environmental pollution from soil, nutrient and pesticide runoff, recycling of nutrients from deeper in the soil profile and more flexibility in meeting soil erosion criteria, including increasing the amount of corn and soybeans that can be grown on sloping cropland than otherwise would be allowed.
With the recent introduction of imidazolinone resistant (IR) corn and a weed control program based on imazethapyr, it is now possible to establish these legumes in corn without injuring the corn or the legume ground cover. Crownvetch is very slow to establish but when once established it will persist forever with the right management. Birdsfoot trefoil provides quick cover but gradually thins out over a period of years as a result of crownvetch competition and chemical suppression, leaving a predominately crownvetch cover. Corn of any kind can be planted into a one year old stand of birdsfoot trefoil and crownvetch using a recommended rate of rimsulfuron + thifensulfuron (Basis) for weed control with little or no injury to the cover crop or corn. Atrazine at a rate of 0.5 to 0.75 lb/A needs to be tank mixed with Basis to suppress the birdsfoot trefoil so it won't compete with the corn. Generally corn yields have not been suppressed when cover crop suppression is 95 to 98% for the first six weeks after planting. Fortunately crownvetch and to some extent birdsfoot trefoil will recover and provide up to 80% ground cover by fall even after suppression of this magnitude early in the summer.
Birdsfoot trefoil that is one year old and crownvetch that is two or more years old will tolerate 0.5 lb/A of glyphosate applied at about the time dandelion (Taraxacum officinale Weber in Wiggers) is in bloom. This makes it possible to plant Roundup Ready¨ soybeans and use low rates of glyphosate for weed control and crownvetch or birdsfoot trefoil suppression. Roundup Ready¨ soybean yields up to 60 bu/A were obtained when planted into crownvetch in 1996 but yields up to 75 bu/A were obtained where there was no cover crop. It would appear that some refinement of this system may be necessary to prevent soybean yield suppression when planting into a crownvetch or birdsfoot trefoil living mulch.
Small grains and alfalfa have also been planted into crownvetch and grown without a loss in yield and without losing the cover crop. A blanket treatment of glyphosate or paraquat is commonly necessary before planting small grains or alfalfa to suppress the cover crop for the first six weeks of crop growth. Post treatments may be necessary for annual or winter annual weed control. Two herbicides that crownvetch will not tolerate are clopyralid and 2,4-DB but it will tolerate recommended rates of most other small grain or alfalfa herbicides and still be there in sufficient amounts so reseeding is not necessary when rotating back to corn.
The whole program is explained on the web at: Living Mulch
Two species of the genus Lotus are agriculturally important
in Argentina because they are adapted to harsh environmental conditions
marginal for alfalfa production. Lotus corniculatus L.
is the main forage legume in Entre Ríos Province (Vertisol
soils) and L. glaber Mill. has become naturalized along
the Flooding Pampa (Molisols and Alfisols).
In spite of the mentioned characteristics practically no breeding
efforts have been performed on these species in Argentina in order
to increase their productivity and persistence.
The basis of any breeding program is to identify and quantify
the species variability (Brown, 1978). To manage this, one possibility
is to characterize isozyme polymorphisms and their distribution
within and among populations (Tanksley and Orton, 1983; Ibañez
et al., 1993). Indeed, isozyme patterns were used to elucidate
the origin of L. corniculatus (Raelson and Grant, 1988).
It was proposed that L. corniculatus is an allotetraploid
being probably L. glaber and/or L. alpinus the maternal
parents of the original hybrid (Ross and Jones, 1985). To our
knowledge, no such studies have been performed in L. glaber.
In this context, preliminary results of isozyme polymorphisms
were investigated, including other enzyme systems, in order to
assess the extent of isozyme variability among and within the
Argentine cultivars of L. glaber and L. corniculatus.
Experimental procedures
Plant material: Commercial seeds of L. glaber
(2n=2x=12) cv. Tresur Chajá and L. corniculatus
(2n=4x=24) cv. El Boyero INTA were subjected to chromosome number
determination and germinated following ISTA Rules (1985). When
seedlings developed the first leaves, they were transferred to
greenhouse conditions (15-25C) during 60 days.
Isozyme electrophoresis: To obtain crude extracts, leaf material was crushed thoroughly in chilled mortars with cold extraction buffer (1:1,5 w:v). Each sample consisted of young leaflets of at least 5 plants for each species. Experiments were replicated twice with similar results. Extracts were absorbed onto 10 x 5 mm wicks of filter paper (Whatman No. 3) and inmediately inserted into slots performed in the starch gel. Electrophoresis was carried out using 11% starch (Sigma) gels prepared with a tris-citrate pH 7.0 buffer for malate dehydrogenase (MDH), 6-phosphogluconate (6-PG) and aspartate aminotranspherase (AAT), tris-citrate/lithium borate pH 8.3 buffer for esterase (EST) and diaphorase (DIA) and histidine/citric acid pH 5.7 buffer for acid phosphatase (ACP). These methods and staining procedures to resolve isozymes are described elsewhere ( Scandalios and Sorensen, 1977).
Gels were incubated at 37C for one hour, in the dark; then they
were fixed in methanol 50%.
Results
The enzymes characterized displayed different patterns for each
cultivar analyzed, with the exception of AAT and 6-PG.
There was an apparent monomorphism among and within L. glaber
and L. corniculatus cultivars for these isozymes.
MDH produced different electrophoretic patterns for each
species showing the greatest variability inside the cultivars
evaluated. Lotus glaber exhibited three patterns, which
had two or three bands in different possitions. That pattern composed
of two bands was also found in some L. corniculatus individuals.
L. glaber samples consisted of one or three bands resulting
in four different patterns.
EST showed two isozyme patterns in each species: L.
glaber samples produced a third esterase band not found among
L. corniculatus patterns, but both cultivars shared the
pattern composed of two variable bands.
DIA enzymes were only evaluated in L. glaber and
two different electrophoretic patterns were characterized consisting
of two bands each.
Patterns of the ACP system provided the greatest differentiation
between species. The cathodal region of the ACP gels in both species
showed a common band. However, in the anodal region L. glaber
ACP bands were almost always faster than L. corniculatus
bands.
Discussion
Differences in electrophoretic patterns of isozymes for cv. Tresur
Chajá (L. glaber) and cv. El Boyero INTA (L. corniculatus)
were detected between and among cultivars. MDH, EST and ACP systems
showed some same patterns. Such a finding may be related to the
presumed hybrid ancestry of L. corniculatus. Ross and Jones (1985)
suggested that either L. alpinus and/or L. glaber could
be the maternal parent of the original hybrid.
Further studies would confirm if ACP system can be used effectively
to differentiate one cultivar from another. The fast band for
L. glaber pattern showed a higher mobility than the same band
for L. corniculatus. This difference was not observed to
be constant, but it is evident from this survey that its frequency
is high. It is clear that these results need to be confirmed with
a larger set of individuals, and perhaps, with small refinements
of the procedure. Besides, Raelson and Grant (1988) did not examined
ACP system in their review concerning the origin of L. corniculatus.
Electrophoretic analysis, which can be also performed on ungerminated
seeds, would resolve questions of seed identification. L. glaber
and L. corniculatus seeds are very similar, therefore
a relatively rapid and accurate method of discriminartion, as
well as the flavonol analysis based on a chromatographic procedure
(Kade et al., 1997), would facilitate classification of seed samples.
References
Brown, A.H.D. 1978. Theor Appl Genet, 52: 145-157.
Ibañez, M.A., Di Renzo, M.A. and M.M. Proverene.
1993. Scientia Horticulturae 53: 281-288.
International Rules for Seed Testing. Rules 1985. 1985.
Seed Sci. and Technol. 13: 299-355.
Kade, M., Wagner, M.L., Strittmatter, C.D., Ricco, R.A. and
A.A.Gurni. 1997. Seed Sci. and Technol.. (in press).
Raelson, J.V. and W.F. Grant. 1988. Theor Appl Genet
76:267-276.
Ross, M.D. and W.T. Jones. 1985. Theor Appl
Genet 71: 284-285.
Scandalios, J.G. and J.C. Sorensen. 1977. 1. Isozymes
in Plant Tissue Culture. In: Plant Cell, Tissue and Organ Culture.
Chapter VII, pp. 719. Ed. by J. Reinert and P.S. Bajaj. Springer
Verlag.
Tanksley, S.D. and T.J. Orton. 1983. Isozymes in
Plant Genetics and Breeding. Part A, B. Elsevier, Amsterdam.
Test and Trial Phase (1998-1999)
Introduction
Subject to ratification by the XVI International Botanical
Congress (St Louis, 1999) of a rule already included in the International
code of botanical nomenclature (Art. 32.1-2 of the Tokyo
Code), new names of plants and fungi will have to be registered
in order to be validly published after the 1st of January
2000. To demonstrate feasibility of a registration system, the
International Association for Plant Taxonomy (IAPT) undertakes
a trial of registration, on a non-mandatory basis, for a two-years
period starting 1 January 1998. The co-ordinating centre will
be the Secretariat of IAPT, currently at the Botanic Garden and
Botanical Museum Berlin-Dahlem, Germany. Co-ordination with present
indexing centres for major groups of plants is being sought, in
view of their possible active involvement at the implementation
stage. The International Mycological Institute in Egham, U. K.,
has already accepted to act as associate registration centre for
the whole of fungi, including fossil fungi.
Registration procedure
The co-ordinating registration centre (IAPT Secretariat),
and any associated centre operating under its auspices, will register
and make available all names of new taxa, all new combinations
or rank transfers that are brought to their attention in one of
the following ways:
by being published in an accredited journal or serial;
by being submitted for registration (normally by the author or
one of the authors), either directly or through a national registration
office; or
(for the non-mandatory trial phase only) as a result of scanning
of other published information by the registration centres' own
staff.
Registration by way of publication in accredited journals
or serials
For a journal or serial to be accredited, its publishers must
commit themselves, by a signed agreement with the IAPT, to
point out any nomenclatural novelties in each individual issue
of their journal or serial, either by including a separate index
of novelties or in another suitable, previously agreed way;
submit each individual issue, as soon as published and by the
most rapid way, to a pre-defined registration office or centre.
Accredited journals and serials will be entitled, and even encouraged,
to mention that accreditation on their cover, title page or in
their impressum.
A permanently updated list of accredited journals and serials
is being placed on the World Wide Web (http://www.bgbm.fu-berlin.de/iapt/registration/journals.htm).
This list will be published annually in the journal Taxon.
Registration by way of submission to registration offices
Authors of botanical nomenclatural novelties that do not
appear in an accredited journal or serial (but e.g. in a monograph,
pamphlet, or non-accredited periodical publication) are strongly
encouraged to submit their names for registration - and will be
required to do so once registration becomes mandatory - in the
following way:
all names to be registered are to be listed on an appropriate
registration form, using a separate form for each separate publication;
the form (in triplicate) must be submitted together with two copies
of the publication itself, either to a national registration office
(see below) or, optionally, directly to the appropriate registration
centre. Reprints of articles from books or non-accredited periodicals
are acceptable, provided their source is stated accurately and
in full;
one dated copy of each form will be sent back to the submitting
author in acknowledgement of effected registration.
Registration forms can be obtained free of charge (a) by sending
a request to any registration office or centre, by letter, fax
or e-mail, or (b), preferably, by printing and copying the form
as available on the World Wide Web (http://www.bgbm.fu-berlin.de/iapt/registration/regform.htm).
Registration offices are presently being arranged for in as many
different countries as possible. They will serve (a) as mailboxes
and forwarding agencies for registration submissions and (b) as
national repositories for printed matter in which new names published
locally appear.
A permanently updated address list of all functioning national
registration offices is being placed on the World Wide Web (http://www.bgbm.fu-berlin.de/iapt/registration/offices.htm).
This list will also be published annually in the journal Taxon.
Registration date
The date of registration, as here defined, will be the
date of receipt of the registration submission at any national
registration office or appropriate registration centre. For accredited
journals or serials (and, for the duration of the trial phase,
for publications scanned at the registration centres), it will
be the date of receipt of the publication at the location of the
registration centre (or national office, if so agreed).
For the duration of the trial phase, i.e. as long as registration
is non-mandatory, the date of a name will, just as before, be
the date of effective publication of the printed matter in which
it is validated, irrespective of the date of registration. Nevertheless,
the registration date will be recorded, for the following reasons:
to make clear that the name was published on or before that date,
in cases when the date of effective publication is not specified
in the printed matter;
to assess the time difference between the (effective or stated)
date of the printed matter and that of registration, since it
is envisaged that the date of registration be accepted as the
date of names published on or after 1 January 2000.
It is therefore in the interest of every author to submit nomenclatural
novelties for registration without any delay, and by the most
rapid means available.
Access to registration data
Information on registered names will be made publicly available
as soon as feasible, (a) by placing them on the World Wide Web
without delay in a searchable database (http://www.bgbm.fu-berlin.de/iapt/registration/regdata.htm),
(b) by publishing non-cumulative lists biannually, and (c), hopefully,
by issuing cumulative updates on a CD-ROM-type, fully searchable
data medium at similar intervals.
Registration as a positive step
(comments of Karen L. Wilson, Royal Botanic Gardens, Mrs
Macquaries Road, Sydney, N.S.W. 2000, Australia.]
Registration of nomenclatural novelties seems to me a natural
way to go, heading into the 21st Century.
It will enable us to find quickly what new names have been published,
and to be sure that we have not missed any new name hidden in
the paper mountain of botanical literature that comes out each
year around the globe. This is particularly important for one-off
publications (floras, field guides, etc.), which are notorious
for `hiding' new names.
Some people seem to think that registration implies censorship,
but this is wrong. As in the current Index
kewensis all names will be listed, and without comment
as to status, and as soon as received at one of the registration
centres. My only caution to those looking at the mechanisms for
making registration effective is that they should ensure there
is a large network of registration centres or offices spread evenly
around the world. This is necessary to make it easy to submit
novelties for registration, given the apparently worsening state
of mail services in all areas.
The taxonomy of the genus Lotus is rich in complicated
problems. On the one hand, the boundaries of the genus and its
subdivisions are often discussed. On the other hand, the delimitation
of species and ifraspecific taxa is sometimes doubtful, as for
instance in Lotus corniculatus complex, Lotus creticus
complex, Lotus angustissimus complex, and in a group of
perennial species of subgen. Syrmatium.
In a broad sense, the genus Lotus comprises, according
to different views, from 100 species (Polhill, 1981) to 176 species
(Kirkbride,1994) on all continents except the Antarctic. The majority
of species occur in the Mediterranean region, Macronesia, and
in the western part of North America, especially in California.
Several species are cultivated as forage plants.
J.H. Kirkbride (1994) presented the worldwide Checklist of the
species of Lotus s.l.
The aim of the present database is maintaining data on the taxonomy,
morphology and geography of Lotus species. Taxonomic boundaries
of the genus Lotus are accepted according to J.H. Kirkbride (1994),
i.e. the genus is treated in the wide sense.
FLORIN Information System developed by DataX/FLORIN Inc. was chosen
as a basic software for maintaining Lotus database. The
System allows to store in a database large amounts of information,
keep them in a good order, browse data using queries-by-example,
generate configurable reports, labels and digital maps for herbarium
specimens, and includes other useful possibilities.
The database is maintained by a personal FLORIN version for MS-DOS.
It contains various information, such as morphological descriptions,
bibliographic citations, taxonomic notes for taxa of different
ranks, and also data on type material and herbarium specimens.
The taxonomic part of the database is being regularly transferred
to Unix platform, and the current version of it is available in
the Internet (the URL:http://www.florin.ru/florin/db/lotus.htm).
Data on herbarium specimens and maps of distribution areas of
species and ifraspecific taxa exist only in a personal MS-DOS
version of the Database.
On the first step of database compilation nomenclatural data were
included. The latest version of the database (November 1997) contains
all specific names published in the genus Lotus since 1753
(507 names).The first citation of each name is available. 193
species of Lotus are accepted and attached to sections
and subgenera according to our point of view. 34 names are included
in database as incertae sedis. The remaining 286 names
are treated as synonyms.
On the second step we plan to insert in the database the types
of all taxa. At the present time, 158 types of species and ifraspecific
taxa are included. Now the database also contains about 100 morphological
descriptions and 350 citations of herbarium specimens (with geographical
coordinates for the majority of them).
References
Kirkbride, J. H., Jr., 1994. - Taxonomic Circumscription of
the Genus Lotus Linnaeus (Fabaceae, Loteae), Its Tribal
Position, and Its Species, pp. 11-15, in Proc. 1 Intern. Lotus
Symposium. St.Louis.
Polhill, R. M., 1981. - Loteae DC., Coronilleae (Adans.) Boiss.,
pp.371-375, in R. M. Polhill & P. H. Raven (eds.) Proc. Intern.Legume
Conf., Kew, 24-29 July 1978. 2. Advances in Legume Systematics
1. Kew.
Seed pod shattering in the genus Lotus (Fabaceae): a
synthesis of diverse evidence. Grant, W. F. Canadian Journal
of Plant Science 76 (3): p.447-456. 1996.
Birdsfoot trefoil (Lotus corniculatus L.) is a perennial
dehiscent species with an indeterminate growth habit. Pod shattering
(shedding) has been a major problem, seed loss was high due to
continuous flowering and time of pod maturity. The anatomy of
the pod plays a role in pod shattering. A change in the orientation
of pericarp cells, unequal swelling and shrinkage occurs, and
a lower lignification of the mesocarp were considered major causes
of shattering. The relative humidity (RH) at the time of harvest
was also a major factor. The critical RH for dehiscence varied
with genotypes between 35 and 49%. There was no correlation for
pod dehiscence between plants grown to maturity under greenhouse
conditions and the same plants grown in the field. Management
practices (time of harvest, clipping early in the season, misting,
mowing and turning the windrow during drying, and desiccants)
were not successful in controlling pod shattering. Shattering
resistance is highly heritable and is considered to be controlled
by more than one gene in Lotus. Breeding to reduce shattering
through recurrent selection was unsuccessful. Attempts to transfer
the indehiscent seed pod trait from distantly related indehiscent
species via interspecific hybridization, diploid bridge species,
amphidiploidy, and backcrossing to birdsfoot trefoil, or similarly
by interspecific somatic hybridization, have shown promise. The
molecular approach has so far not been attempted but since genetic
transformation can be carried out in Lotus, this avenue should
be investigated.
Heterospecific pollen transfer between sympatric species in
a midsuccessional old-field community. McLernon, S. M.; Murphy,
S. D.; Aarssen, L. W. American Journal of Botany 83 (9): p.1168-1174.
1996.
The cumulative (season-long) incidence of heterospecific pollen
transfer (HPT) was examined using nine sympatric species in a
midsuccessional old field in Bedford Township, Ontario, Canada.
Inflorescences were collected weekly during the flowering season,
and the proportion of foreign pollen/stigma was recorded. Flowering
phenologies of sympatric species and ovule and seed counts of
study species were also recorded. Heterospecific pollen was detected
on some stigmas of each species. Medicago sativa (Fabaceae)
received the most foreign pollen; in some cases, all of the grains
on a stigma were heterospecific. Lotus corniculatus (Fabaceae)
received the least amount of foreign pollen; the incidence of
heterospecific pollen was near zero in most cases. The mean and
range of foreign pollen received varied by as much as an order
of magnitude between species. The six species with zygomorphic
flowers, all Fabaceae, received more heterospecific pollen than
the three species with actinomorphic flowers, Potentilla recta,
P. simplex (Rosaceae) and Ranunculus acris (Ranunculaceae).
This probably reflects a bias because the data were analysed on
a cumulative basis and the Fabaceae had longer flowering phenologies.
HPT was not correlated with the species' relative abundance within
the community. Proportion of foreign pollen received varied temporally
within species, and this variation generally was not related to
phenology of any sympatric taxa or the species' own phenology.
Pollen grain diameter was positively related to levels of foreign
pollen received by species. This might be caused by poor adhesion
of large pollen grains to small stigmatic papillae or if generalist
pollinators carrying large amounts of heterospecific pollen visit
the large-grained species and specialists with little foreign
pollen visit the small-grained species. The large proportions
of heterospecific pollen on stigmas of many species indicate that
HPT occurs frequently in the community studied and the implications
may include reduced seed set because of occlusion by foreign grains.
As yet, however, it is unclear how important a factor HPT is in
mediating pollen limitation of reproductive success.
The origin of the Lotus corniculatus (Fabaceae) complex:
a synthesis of diverse evidence. Grant, W. F.; Small, E. Canadian
Journal of Botany 74 (7): p.975-989. 1996.
Although sometimes defined to have diploid populations, L.
corniculatus essentially appears to be tetraploid. Biochemical
and genetic evidence indicates that it is an allotetraploid. Although
about a dozen diploid species have been proposed as ancestral
to L. corniculatus, the evidence points strongly to four.
L. uliginosus uniquely shares a rhizomatous habit, an acyanogenic
factor, and a tannin characteristic with L. corniculatus,
clearly showing an especially close relationship, and reflecting
the possibility that it is one of two direct parental species.
Principal candidates for the second parent include L. alpinus,
L. japonicus and L. tenuis. The phenetic analysis presented
here accords well with the hypothesis that L. corniculatus
arose as a hybrid of L. tenuis and L. uliginosus.
Cytogenetic evidence indicates that L. japonicus is especially
closely related to L. corniculatus. Flower colour in the
hybrids between L. uliginosus and L. tenuis suggest
maternal inheritance and that L. tenuis could have been
the female parent. An evolutionary sequence is suggested in which
L. uliginosus hybridized with L. tenuis, followed
by introgression from L. alpinus and L. japonicus.
Alternatively, a prototype of L. alpinus, L. japonicus and
L. tenuis could have been the female parent of L. corniculatus,
based on evidence from maternal inheritance of flower colour intensity
and interactions of Rhizobium strains.
Some new results on the host range of Macrophomina phaseolina
in Hungary. Kadlicsko, S. Acta Phytopathologica et Entomologica
Hungarica 29 (1-2): p.61-66. 1994.
The importance of M. phaseolina is continually increasing in Hungary.
The host range of the fungus in a small plot inoculation experiment
was studied. The plant species infected by the pathogen were regarded
as susceptible host plants. Among the 37 cultivated plants examined,
28 became diseased. The infected plants included crops sown over
large areas (maize, sunflower, lucerne, sugarbeet and potato)
as well as papilionaceous plants (e.g. lucerne, sainfoin (Onobrychis
viciifolia), red clover (Trifolium pratense) and birdsfoot
trefoil (Lotus corniculatus)). They were highly favourable
for the propagation and survival of the fungus. The proportion
of susceptible weed plants, though somewhat lower (4 out of 10
tested species) is very important because of their wide distribution.
Growth habit of Lotus tenuis shoots and the influence of photosynthetic
photon flux density, sucrose and endogenous levels of gibberellins
A1 and A3. Clua, A.; Bottini, R.; Brocchi, G. N.; Bogino,
J.; Luna, V.; Montaldi, E. R. Physiologia Plantarum 98 (2): p.381-388.
1996. Paper presented at the European Symposium on Photomorphogenesis
in Plants, Sitges, Spain, 9-13 July 1995.
Single-node explants of L. tenuis cv. Tressur-Chaja with
one axillary branch each were incubated in darkness with different
concentrations of sucrose, gibberellin A3 (GA3), B9 (daminozide)
or their combinations, or whole plants were treated with full
sunlight, artificial shade (AS), AS + uniconazole, or AS + cimectacarb
(trinexapac). A high sucrose concentration induced diagravitropic
growth of the axillary branches. GA3 reversed the effect of sucrose,
both in shoot sections and whole plants, inducing orthotropic
growth and diminishing the sucrose levels at the shoot bases.
High irradiance induced a prostrate growth of the shoots. Artificial
shade increased both internode and branch length and induced an
upward curvature of the shoots. This was correlated with a lower
sucrose concentration and increased content of GA1 and GA3. Cimectacarb
and uniconazole reversed the AS effects, although the sucrose
content in the shoots remained low. These results suggest that
gravitropism of L. tenuis shoots under different light
intensities, but similar light quality, is controlled by the levels
of GA1 and GA3 and sucrose.
Legume seeding trials in a forested area of north-central Washington.
Java, B.; Everett, R.; O'Dell, T.; Lambert, S. Tree Planters'
Notes 46 (1): p.19-27. 1995.
Sowing nitrogen-fixing species is a proven silvicultural practice
to increase site nutrient capital, but species' responses are
site specific. Alsike clover (Trifolium hybridum), white
clover (T. repens), black medic (Medicago lupulina),
cicer milkvetch (Astragalus cicer), two varieties of birdsfoot
trefoil (Lotus corniculatus), and Hederma pine lupine (Lupinus
albicaulis), all commercially grown species, were planted
at several altitudes on the Wenatchee National Forest in Washington
state on recently burned disturbed forest sites. After 2 yr, alsike
clover and Hederma pine lupine were the most successful species
on high altitude sites (>1219 m), and black medic and Hederma
pine lupine were the best performers on low altitude sites. Average
total nitrogen inputs from top growth of planted species during
the 1991 growing season were 20 -115 kg/ha. Nitrogen delivered
by atmospheric fixation was 6-40 kg/ha. It is concluded that legumes
can successfully establish in eastern Washington, ameliorating
losses in nutrients after logging and residue treatment. Legumes
increased total nitrogen on these sites and enhanced nutrient
cycling in planted areas.
Cytology of 2N pollen formation and pollen morphology in diploid
Lotus tenuis (Fabaceae). Rim, Y.W., and Beuselinck,
P.R. American Journal of Botany. 83:1057-1062. 1996.
Two genotypes of Lotus tenuis Waldst & Kit. ex Willd.
PI 204882, a diploid (2n = 2x = 12), were identified as producing
2n pollen (maximum = 6%). The objectives of this research were:
(1) to determine the mechanism(s) of 2n pollen formation in the
L. tenuis genotypes and (2) to morphologically describe
n and 2n pollen using light and scanning electron microscopy.
Meiotic studies revealed that 2n pollen resulted from bipolar
spindles during anaphase II of microsporogenesis. The 2n pollen
germinated well, although abnormal pollen tubes were observed.
The genetic constitution of 2n pollen resulting from bipolar spindles
is equivalent to first division restitution (FDR) of meiosis.
Fresh and air-dried pollen samples exhibited differences in size
and shape under light and scanning electron microscopy. The size
of diploid (2n) pollen was larger than that of haploid (1n) pollen.
Normal haploid (1n) pollen was globose-prolate in shape, while
diploid (2n) pollen was tetrahedral in shape.
Use of poultry manure and plant cultivation for the reclamation
of burnt soils. Vazquez, F.J.; Petrikova, V.; Villar, M.C.,
and Carballas, T. In: Biology and fertility of soils. 22:265-271.
1996.
Annual (Pisum sativum L. and Vicia sativa L.) and
perennial (Trifolium repens L. and Lotus corniculatus
L.) leguminous species were grown in pots containing samples from
the ash layers of two Cambisols under Pinus sylvestris
L., which has been affected by high-intensity wildfires 3 and
15 days before the sampling. The gramineous Lolium perenne
L. was cultivated as a second plant after Trifolium and
Lotus harvesting. Three treatments were compared: soils
without fertilization and soils fertilized with two doses of poultry
manure (1 and 2 g total N kg-1 dry soil). The aim of the work
was to study the capacity of the ash layer to sustain vegetation
and the influence of plants and organic manure on the recovery
of vegetation cover, ash layer fixation and soil structure formation
to avoid erosion. The ash samples were able to sustain vegetation
without fertilization. The organic manure increased the yields
of all the plants tested, the lower dose being the optimal for
the first crop whereas the higher dose was beneficial for the
second crop. The annual legumes grew very quickly. The mixture
of Trifolium and Lotus seemed very suitable for
reclamation of soil degraded by wildfires because Trifolium
produced more phytomass than Lotus in the first growing
stages whereas the development of Lotus was higher in the
later growing stages. Ash layer conditions did not inhibit nodulation,
which was, however, stimulated by the organic manure, particularly
in the case of Lotus. Lolium after perennial legumes
was the best plant combination because it produced the highest
phytomass, particularly root phytomass, and thus improved vegetation
cover and ash layer fixation. All the plants tested improved the
formation of soil aggregates, particularly the combination of
perennial legumes and Lolium. However, wet aggregate stability
was higher when plants were grown on soils fertilized with poultry
manure than when plants were cropped on unmanured soils, which
points to the favourable influence of the organic manure on soil
aggregation.
Uptakeof phosphorus from different sources by Lotus pedunculatus
and three genotypes of Trifolium repens. 1. Plant yield
and phosphate efficiency. Trolove, S. N.; Hedley, M. J.; Caradus,
J. R.; Mackay, A. D. Australian Journal of Soil Research. 1996.
V 34:1015-1026.
The breeding of phosphate (P) efficient pastoral legumes could
reduce the amount of fertilizer required on pastoral farms. Lotus
pedunculatus (L. uliginosus) and 3 genotypes of white
clover (Trifolium repens) known to differ in their ability
to respond to added P were grown on unfertilized soil and soil
to which either monocalcium phosphate (MCP) or North Carolina
phosphate rock (NCPR) were added. White clover genotype 8D (a
selection line from Crau) had a greater (P<0.05) internal P
efficiency (shoot DM production per unit plant P) than 1A (a selection
line from Gwenda) or lotus on unfertilized soil, whereas on fertilized
soil, lotus had a significantly higher (P<0.05) internal P
efficiency than 2 of the white clover genotypes on MCP-fertilized
soil (P<0.01) and all 3 white clover genotypes on NCPR-fertilized
soil (P<0.01). Lotus also had a higher (P<0.01) external
P efficiency (total P uptake) than all 3 white clover genotypes
on the 2 fertilized treatments. This was due to a greater root
length, not a greater P uptake per unit length.
Uptake of phosphorus from different sources by Lotus pedunculatus
and three genotypes of Trifolium repens. 2. Forms of phosphate
utilised and acidification of the rhizosphere. Trolove, S.
N.; Hedley, M. J.; Caradus, J. R.; Mackay, A. D. Australian Journal
of Soil Research. 1996. V 34:1027-1040.
To investigate differences in the ability of legumes to acidify
their rhizosphere and extract various forms of P, Lotus pedunculatus
(L. uliginosus) and 3 genotypes of white clover (Trifolium
repens) that varied in their ability to respond to added P
were grown in root study containers with either unfertilized soil,
or soil fertilized with either monocalcium phosphate (MCP) or
North Carolina phosphate rock (NCPR). After 6 weeks of plant growth,
the containers were dismantled and 10 thin soil slices were taken
0-8 mm from the rhizoplane. These slices were fractionated for
various P forms and pH was measured. All 4 legumes, especially
lotus, acidified their rhizosphere. This resulted in negligible
depletion of the small, H2SO4-Pi fraction (Pi, inorganic phosphorus)
of unfertilized and MCP-fertilized soil, but caused direct dissolution
of NCPR. The predominant forms of P depleted in the MCP-fertilized
soil were the resin-Pi and NaOH-Pi forms, whereas in the NCPR
treatment the H2SO4-Pi fraction was depleted. No significant depletion
of any P fraction was observed in the unfertilized soils as plants
were very small and P change in the soil slices was below that
which could be measured using the expe