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Lotus glaber is a species adapted to tolerate long flooding
conditions such as those of the Salade River Basin, province of
Buenos Aires (Argentine). The tolerance of L. glaber is
higher than that of L. corniculatus (L.) and it has been
associated to a higher hypertrophy of the stems of L. glaber
under such conditions (Mazanti et al., 1988; Vignolio et al.,
1994).. The presence of adventitious roots and higher development
of aerenchyma in the stems of plants of L. glaber, which
grew in conditions of flooding have also been observed (Vignolio
and Fernandez, 1997). Apart from the characteristics of the seeds,
a surviving strategy of genotypes in this conditions could be
related to the capacity to produce adventitious roots.
On the other hand, it has been proved that there is no difficulty
for cloning of L. glaber by rooting of cuttings of the
stem in sand or vermiculite, saturated of moisture (Mujica and
Rumi, 1998). The utilization of leaves for vegetative propagation
could permit to enhance the efficiency of cloning for the replication
of genotypes of interest.
The objective of this trial was: I) to evaluate the potential
of rooting of stem and leaf cuttings of two populations of L.
glaber, one of them natural and the other one improved, in
conditions of simulated flooding. II) confirm the capacity for
leaves' rooting in different water mediums in the species and
evaluated it in two improved populations.
MATERIALS AND METHODS
Experiment 1
The trial was conducted on plastic trays of a volume of 800 cm3.
Soil was put in them conforming and homogeneous surface of 3 cm
of depth. It was flooded with water up to 1.5 cm over soil. Over
this water surface vegetal material was scattered which remained
floating. Stem and foliar parts in trial were: medial cutting
with one bud, distal cutting (distal bud), distal 3-leaflet, central
leaflet and laterals leaflet. The medial cuttings were taken from
the base of medial segment of each donor branches according to
techniques applied by Mujica and Rumi (1998). The terminal bud
was separated from the donor branch, by a cut over the last unfolded
leaf. The leaflets were separated manually from the branches.
Plants in vegetative state were used from a natural population
and from an improved one by a recurrent selection. In both cases
a randomized sample of branches (>30cm) of plants that grew
in the experimental field, in similar conditions was taken. The
experimental unit was a tray containing a sample of n=25. A totally
randomized design with 4 replications was used. The experience
was developed during October in a greenhouse at 30-33 ºC.
The water level of the trays was kept constant. The trial lasted
23 days. At the end the % of rooting was determined.
Experiment 2
A second trial in similar experimental conditions, was conducted.
Two improved populations, cv. Tresur Chajá and synthetic
variety LH1(non registered) were used. In both cases, a randomized
sample of branches (>30 cm) of plants cultivated in the experimental
field under the same conditions, was taken. Treatments consisted
in two mediums of rooting (water with and without soil) and two
leaf components (central leaflet and distal 3-leaflets). The experience
took place during November and with the same methodology applied
in experience (1). The totally randomized experimental design
with 4 replications was used. At the beginning and at the end
of the experience a sample of central leaflets (n=20) was taken
to measure the thickness of the mesophyll. This anatomical measurements
were taken in the zone of the medial third of the central leaflet
using a Nikon light microscope equipped with a micrometer ocular
with a magnification of 10 x. The t test was applied to analyze
differences. The leaf cuttings that rooted which at the end of
the experience showed formation of callus on the base of the leaflets,
were cultivated in vermiculite with a solution of Nitrofoska BASF
(3gr/l).
The analysis of variance of the % of rooting was done in both
experiences and Tukey's test was applied for the analysis of differences
between treatments.
RESULTS
Experiment 1
The aerial parts of both populations which were evaluated, showed
capacity of rooting in the simulated conditions of flooding. The
appearance of the first adventitious roots was registered around
the 7-12 days after the experience had begun. The stem cuttings
obtained from the medial segment of the branches showed lower
% of rooting than leaf cuttings in both populations (P<0.01).
The natural population showed a higher % of rooting from distal
cuttings than the improved population (P<0.01). Leaf components
of both populations showed between 83 and 97 % of rooting without
significant differences between treatments (Fig. 1). Materials
which did not root during the first 12 days showed and increasing
deterioration and it was necessary to remove them before the end
of the experience.
Figure 1. Rooting of different types of cutting
of L. glaber in simulated conditions of flooding.
I) medial cutting of stem with one bud, II) distal cutting of
stem (distal bud), III) cutting of leaf (distal 3-leaflet), IV)
cutting of leaf (central leaflet) and V) cutting of leaf (lateral
leaflets). Means followed by different letters differ (P<0.01).
Experiment 2
A capacity for leaf rooting was observed again in the evaluated
populations. Nevertheless, the % of rooting was less than in experience
(1). The general mean ±S was 45.81±16.66 %. The populations
behavior did not present significant differences in the % of rooting
of the evaluated leaf components. With respect to mediums of rooting
significant differences were found favorable for water without
soil (P<0.01) (Fig. 2).
Figure 2. Rooting of cuttings of leaves from two
cultivar of L. glaber, in floating conditions
on two different water mediums. TRC and TRT: central leaflet and
distal 3-leaflet of cv. Tresur Chajá, respectively; LHC
and LHT: central leaflet and distal 3-leaflet of cv. LH1, respectively.
Means followed by different letters differ (P<0,01).
At the end of the experience the central leaflets as the distal
3-leaflets showed good root development preferably for the water
medium composed with water without soil (Fig. 3).
Figure 3. The photograph shows two distal 3-leaflets
and two central leaflet of L. glaber rooted on
the water surface.
In both populations it was determined that the mesophyll of the
rooted central leaflets showed a significant higher thickness
with respect to the initial state (test de t P<0.01). Cuttings
which did not root during the first 2 weeks, in general, showed
and increasing process of deterioration. For this reason, some
of them were removed before the end of the experience. The smaller
% of rooting observed in experience (2) respect experience (1)
is attributed principally to differences in the phenological state
of the donor plants when the cuttings were obtained. Those used
in experience (2) were nearer at the beginning of flowering. With
respect to the rooted leaf cuttings which showed callus at the
end of the experience and were cultivated in vermiculite, it is
noticed that during the following 15 days no differentiation of
buds was registered.
Acknowledgments
The authors acknowledge Prof. Olga Peluso, CONICET Technician,
for their photography contribution
REFERENCES
Mazzanti, A., L. Montes, D. Miñon, H. Sarlangue y C.
Cheppi. 1988. Utilización de Lotus tenuis en establecimientos
ganaderos de la Pampa Deprimida: Resultados de una encuesta. Rev.
Arg. Prod. Animal 8(4): 301-305.
Mujica, M. M. y C. P. Rumi. 1998. A technique of vegetative propagation
by stem cuttings was fitted to Lotus tenuis. Lotus Newsletter.
U.S.A. (ISSN 0316-0106) (http://www.plantsci.missouri.edu/lnl/), vol
29, (en prensa).
Vignolio, O.R., N.O. Maceira y O.N. Fernandez. 1994. Efectos del
anegamiento en invierno y verano sobre el crecimiento y la supervivencia
de Lotus tenuis y Lotus corniculatus. Ecología
Austral 4: 19-28.
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