ArticlePDF Available

Environmentally induced variation in germination percentage and energy of naked caryopses of Loxodera ledermannii (Pilger) W.D. Clayton ex Launert in subhumid Benin (West Africa) 1

Authors:

Abstract and Figures

Environmentally induced variation in germination percentage and energy of naked caryopses of Loxodera ledermannii (Pilger) W.D. Clayton ex Launert in subhumid Benin (West Africa) ABSTRACT This study investigated the conditions for maximizing germination of Loxodera ledermannii, an earlier and nutritional tropical fodder grass species. We examined the correlation of percentage germination with seed container, substrate, sowing depth, methods and date of sowing. Naked caryopses of L. ledermannii were subjected to various growth conditions. Results showed that percentage germination depended on growth conditions (P = 0.001) and energy of germination (P = 0.0001). Effects of the seed container, substrate, sowing depth, methods and sowing period were significant (P < 0.05). Refining of the substrate improved the percentage germination. Seed container coverage and sowing depth substrates increased the energy of germination (P = 0.000); their magnitudes were dependent on substrate types, being average for sterilized soil (56%) and higher with blotting paper (84.9%) and refined soil (121%). Highest germination energy was recorded for covered and deeper seed containers (< 5 days). Tamping increases notably the caryopses germination and the plant density through the growth period. Further studies are needed to well characterize constitutive variation of these traits.
Content may be subject to copyright.
320
Advances in Environmental Biology, 7(2): 320-329, 2013
ISSN 1995-0756
This is a refereed journal and all articles are professionally screened and reviewed ORIGINAL ARTICLE
Corresponding Author
Kindomihou Missiako Valentin, Department of Animal Production, Laboratory of Applied Ecology
(LEA), Faculty of Agronomic Sciences (FSA), University of Abomey Calavi (UAC)
BP 348, Fidjrosse-Cotonou, Benin Republic.
Tel.: 00-22-995-023-058, E-mail: valentin.kindomihou@fsa.uac.bj or kindomihou@gmail.com
Environmentally induced variation in germination percentage and energy of naked
caryopses of Loxodera ledermannii (Pilger) W.D. Clayton ex Launert in subhumid Benin
(West Africa)
1Kindomihou Missiako Valentin, 2Romain Lucas Glele Kakai, 3Achille Ephrem Assogbadjo,
4Roland Ahouelete Yaovi Holou, 5Brice Augustin Sinsin
1Department of Animal Production, Laboratory of Applied Ecology (LEA), Faculty of Agronomic Sciences
(FSA), University of Abomey Calavi (UAC) BP 348, Fidjrosse-Cotonou, Benin Republic.
2Department of Natural Resources Management, LEA, FSA, UAC 01 BP 526 Cotonou, Benin Republic
3Department of Natural Resources Management, LEA, FSA, UAC 05 BP 1752, Cotonou, Benin Republic
4Monsanto Company, 800 N. Lindbergh Blvd., Mail Zone Q4B/Q420E-A, St. Louis, MO 63167, USA
5Department of Natural Resources Management, Head of the LEA, FSA, UAC 01 BP 526 Cotonou, Benin
Republic
Kindomihou Missiako Valentin, Romain Lucas Glele Kakai, Achille Ephrem Assogbadjo, Roland
Ahouelete Yaovi Holou, Brice Augustin Sinsin: Environmentally induced variation in germination
percentage and energy of naked caryopses of Loxodera ledermannii (Pilger) W.D. Clayton ex Launert
in subhumid Benin (West Africa)
ABSTRACT
This study investigated the conditions for maximizing germination of Loxodera ledermannii, an earlier and
nutritional tropical fodder grass species. We examined the correlation of percentage germination with seed
container, substrate, sowing depth, methods and date of sowing. Naked caryopses of L. ledermannii were
subjected to various growth conditions. Results showed that percentage germination depended on growth
conditions (P = 0.001) and energy of germination (P = 0.0001). Effects of the seed container, substrate, sowing
depth, methods and sowing period were significant (P < 0.05). Refining of the substrate improved the
percentage germination. Seed container coverage and sowing depth substrates increased the energy of
germination (P = 0.000); their magnitudes were dependent on substrate types, being average for sterilized soil
(56%) and higher with blotting paper (84.9%) and refined soil (121%). Highest germination energy was
recorded for covered and deeper seed containers (< 5 days). Tamping increases notably the caryopses
germination and the plant density through the growth period. Further studies are needed to well characterize
constitutive variation of these traits.
Key words: Germination percentage, energy, caryopses, Loxodera ledermannii, growth conditions.
Introduction
Perennial pasture species are essential for the
long-term economic and environmental sustainability
of Sudanian farming systems in Benin. Because their
roots are deeper than those of most annual plant
species, their water uptake and use throughout the
year is improved [8]. Therefore, such species can
provide critical ground cover, reducing erosion while
providing high-quality livestock feed. They can also
assist in the management of dryland salinity and soil
acidity [30].
About 70 native pastures have been identified
and described in Benin [19,22,34,32,17,31,14]. Most
of the northern pastures are dominated by Loxodera
ledermannii, Andropogon and Brachiaria species
[33]. These perennial pasture species are widely used
by livestock and mixed farmers to provide high-
quality feed on a year-round basis [22]. As the
natural availability of forage has become a major
constraint to ruminant production [28,6], L.
ledermannii might offer a useful fodder option, as it
grows well in the dry seasons, flowers early and
produces good-quality fodder [34,35].
Because this species is strongly grazed by
ruminants, it is also favoured by stockbreeders and
pastors [34-35]. L. ledermannii has spread naturally
on the Sudanian and Sudano–Sahelian savanna in the
following countries: Nigeria, Uganda, Cameroon,
Benin and Niger [15,37,34]. It has also recently been
321
Adv. Environ. Biol., 7(2): 320-329, 2013
identified in the Guinea–Sudanian and Sudano–
Guinean zones. The species has been threatened by
desertification, overgrazing and climate change [31].
Apart from studies of its spread area, caryopses and
morphological characteristics [18], no published
information exists on the establishment of the
species.
The domestication of this species will certainly
be important in order to save a potentially important
fodder crop and to increase its availability. To be able
to propagate the species through domestication, a
better understanding is needed of the optimum
conditions for its germination. Previously, suitable
temperature and light environments, water inhibition
and a cold pre-treatment were cited as species-
specific prerequisites to ensure the germination of
grasses during reclamation work [3].
Imbibed water quantity, stratification, light and
harvest time have also been found to affect seed
germination in the dune-building grass Leymus
arenarius (L) Hocht [13] and Echinochloa crus-galli
(L) [P.Beauv.] [20]. Appropriate experimental
conditions for germination clearly should reflect the
environmental conditions of the microhabitat in the
field and may act as phenological signals for
germination.
Parihar and Pathak’s [26] study of the flowering
phenology and seed biology of selected tropical
perennial grasses revealed that seed germination was
very low (depending on percentage seed set),
whereas germination in caryopses was much higher
(up to 92%).
As constitutive and ecological adaptation of
caryopses has been proven with a few temperate
grass species such as Chenopodium spp. and Rumex
sp. [27], we hypothesized that this may also be true
with L. ledermannii. To this end, we investigated the
effects of environmental factors on the germination
rate and energy of the caryopses of L. ledermannii,
sward establishment. Our main objectives were: (i) to
determine the germination abilities of naked
caryopses of L. ledermannii and (ii) to determine the
optimal sowing depth.
Materials and Methods
Study area:
The experiments were carried out from March to
June 2003 at the Laboratory of Applied Ecology and
from May to October 2004 at the experimental
station of the Faculty of Agronomic Sciences of
Abomey Calavi University (Benin Republic). The
perimeter is located in the subequatorial zone
(latitude 6–7° N, and longitude 2–3o E). The region
experiences a climate with a bimodal rainfall. There
are two dry seasons – mid-July to mid-September,
and mid-November to mid-March. In 2003, the
annual rainfall averaged 1300 mm, including 915.8
mm for the long rainy season. Annual temperatures
ranged from 25.9°C to 29.1°C. There were 2300
hours of annual sunshine and relative humidity
ranged from 30 to 90%; the potential
evapotranspiration (ETP) of Penman rate in the
period was 1650 mm [1]. The variations in climatic
parameters from March to October during the years
1975 to 2004 are presented in Table 1. The soil in the
garden of FSA/UAC is ferralitic, relatively acid, with
a fragile structure, poor in exchangeable bases,
nitrogen and phosphorus, but with appreciable
sodium concentration; C/N mass ratio is 10.6. The
vegetation of the experimental site environment is
the prairie type of Panicum maximum C1, and soil
ranges from alluvial to sandy of the littoral Table 2,
[18].
Plant materials and experimental design:
A collection of caryopses of L. ledermannii
(Pilger) W.D. Clayton ex Launert, collected from a
full Sudanian field of northern Benin (Tanguieta-
Natitingou: 10–12°N, 0.16–2°E; Nikki-Kalale: 9.5–
10°N, 3–3.58°E), was thrashed in a mortar and
pestle, and a dissection kit. These naked caryopses
were conserved at 15–25°C and 40–90% relative
humidity. The naked caryopses were used at a rate of
30 caryopses per seedling. Temperature in the
Laboratory ranged from 9 to 13°C.
Laboratory trials: To study the effects of the seed
container on percentage germination, three types of
substrate were compared – blotting paper (BP –
Weifa Co., Ltd.), fine soil (FS) from Fairfield,
Cotonou, and sterilized soil (SS). (The soil was
sterilized by heating at 65°C for 30 minutes). The BP
substrate was placed in molded containers (V = 3695
cm3; length = 36.5 cm; width = 22.5 cm; depth = 4.5
cm); the FS was placed in tubular vats (V = 2669
cm3: diameter = 20 cm; height = 8.5 cm); and the SS
was placed in conical pots (V = 175 cm3: height =
6.3 cm; lower diameter = 5 cm; upper diameter = 6.8
cm). Both uncovered and seed containers covered
with glass plates were prepared. All the seed
containers were watered (30 ml in the molded
containers, 20 ml in the tubular vats and 15 ml in the
conical pots) before being planted with 30 naked
caryopses of L. ledermannii. About 10 ml of water
was provided every 3 days until day 45. The whole
design was replicated three times and the resulting
combinations of three substrates and three types of
seed container were arranged in complete
randomized blocks in the laboratory. Two sowing
depths were tested – at 1 cm and 3 cm; the growing
period effect was also observed on days 15 and 30 of
the month.
Field trials: In the field, 100 m2 was divided into
subplots sized 15 m2 (5 m × 3 m) to test the effects of
the planting depth and method on percentage
germination. The sowing in broadcast was compared
to that in-line. In-line sowings were undertaken in
furrows opened at the depths of 1 cm, 3 cm and 5
322
Adv. Environ. Biol., 7(2): 320-329, 2013
cm; a slight soil tamping was applied and the seeds
were spaced out at 50 cm × 30 cm. Controls and
treatments were compared. Among the three in-line
depths, only 3 cm-depth was considered in the test of
seedling planting method and growth period on
germination rate.
Parameters measured:
The time (days’ number) between the sowing
and the appearance of the first shoots, the number of
days between sowing and the maximum germination,
and the number of caryopses that germinated were
recorded. The number of days between sowing and
the appearance of the first shoots was used as a proxy
for the germination energy of the caryopses.
Percentage germination (GR) was calculated as
follows:
GR=NFC/USQ × 100%; with NFC = number of
fertile caryopses; USQ = number of plants produced
per total caryopses used. As used here, the
germination energy is the time (number of days) at
which 50 percent of the total germination has been
attained.
Statistical analysis:
Statistical analyses were performed using SAS
(SAS, Institute Inc., Cary, NC, 27513-2414 USA).
The effects of the substrates, sowing depths in
covered and non-covered treatments, growth periods
and sowing methods on the germination energy, the
germination rate, were compared in a 3-way analysis
of variance (ANOVA) using the general linear mixed
models procedure (Proc GLM). Factors were the
types of seed containers, substrates and replicates,
seed container and sowing depth, sowing depth and
growth period, and sowing method and growth
period. A one-way ANOVA was used to compare the
percentage of germination of the naked caryopses of
L. ledermannii with the different groups of factors
and treatments. Significant differences were
identified using Student Newman–Keuls tests as
post-hoc procedures (at α = 0.05).
Results:
Effects of seed container and substrate type on the
germination rate:
The germination rate of naked caryopses of L.
ledermannii ranged from 21.7% to 93.3%, depending
on the type of seed container and whether the seeds
were covered or uncovered (Figure 1). These
caryopses showed highly significant differences for
percentage germination (Table 3). The covered seed
containers had much higher values (> 41.6%),
whereas the non-covered generally had lower values
(< 60%).
Apart from the seed container effect, the effect
of the substrate was also significant (Table 3). The
germination rate of the caryopses generally increased
significantly in response to the substrate refinement
(P < 0.0001). The germination rate increased
significantly with the depth of substrate coverage in
all cases (Figure 1). The magnitude ranged from
58.2% to 93.3%. The caryopses planted on the
blotting paper substrate had much lower germination
rates (<41.7%) than those with other substrates. The
germination rate for caryopses planted in the
sterilized soil was generally higher ( 59%) and
ranked first in all treatments. In addition, the time for
the first appearance of shoots and for achieving
maximum germination varied significantly from a
substrate to another (Table 4). Generally, the first
appearance of shoots after sowing did not exceed 7
days (Tables 3 & 4). The time taken to germinate was
significant in respect to the substrate type (P <
0.001). Fine sand had the lowest value ( 4 days) and
the blotting paper had the highest ( 6 days).
Effect of seed container and substrate type on the
energy of germination:
The germination energy of the caryopses ranged
from 5 to 10 days, depending on the seed container
and substrate types. There was a significant
difference between the germination energies of the
caryopses in the different seed containers (Table 3).
The uncovered seed containers had much lower
values for germination energies (5 days for 59% of
the caryopses), whereas the covered seed containers
generally had higher values (8 days for 93% of the
caryopses). The sterilized soil generally had the best
germination energy, ranging from 5 to 8 days (Table
3). Pair-wise, the treatments showed a significant
increase in germination energy in only two out of six
cases. The increases were 52% and 56% according to
the seed container and substrate type, respectively.
There was a highly significant seed container
substrate interaction (P = 0.002), indicating that
germination energy generally increased in response
to covering the substrates. This change was
significant in all cases. The effect varied strongly
depending on substrate type, being average for
sterilized soil (56%) and largest for fine sand and
blotting paper (121% and 84.9%, respectively).
Effects of seed container and sowing depth on the
germination rate:
The germination rate of the naked caryopses
ranged from 41.2% to 56.7%, depending on the seed
container and the depth of planting. Naked caryopses
of L. ledermannii showed highly significant
differences for their rate of germination (Table 4).
The deeper seedlings ( 3 cm) had much higher
values (> 56.5%), whereas the less deeply planted
seedlings ( 1 cm) generally had lower values (<
41.5%) (Table 4). In addition, the sowing depth
323
Adv. Environ. Biol., 7(2): 320-329, 2013
covered seed container interaction is highly
significant for the germination rate of naked
caryopses (P < 0.0001). This result indicated that the
germination rate generally depended on the sowing
depth. For the covered containers, there appeared to
be a limit to the sowing depth after which the seeds
would no longer germinate. In the uncovered
containers, this was not the case. The 37% increase
in the germination percentage for seeds in covered
containers was significant. There was a 10% decrease
in the germination rate for seeds in uncovered
containers. Otherwise, the germination energy was
the best (< 5 days) for the containers with the more
deeply covered seeds (Table 4). The last new shoots
of caryopses planted at a shallow depth in covered
containers appeared about 4 days before those
planted more deeply, indicating that the ability to
germinate and the energy of naked caryopses
generally decreased with increased sowing depth.
However, this finding was not true with the
uncovered seed containers.
Effect of sowing methods and period on the
germination rates:
The sowing methods had a significant effect on
the germination rates of naked caryopses in the field
experiments. The density of the plants ranged from 9
to 28 per m2 (Table 5a and table 5b). Differences
were highly significant. Seeds that had been
broadcast showed a much lower plant density (< 10
plants/m2) compared to the other methods of sowing.
The in-line sowing at a depth of 3 cm (with a
backfilling and tamping of the soil) generally had
higher values (> 28 plants/m2). Apart from the
sowing methods, the period in which these methods
were used significantly affected the density of the
plants. First, the comparison of treatment periods (15
days, 30 days) (Table 5a and table 5b) showed a
significant increase in the plants density in all cases –
an increase of 31–50%.
Second, the intra-specific comparison of
methods of sowing (broadcasting + tamping and in-
line sowing at 3 cm + tamping) with their controls
(broadcastings and in-line sowing at 3 cm-depth)
(Table 5b) showed a significant increase in the plants
density – between 44% and 85%. And, finally, the
comparison among treatments also showed a
significant increase in plant density between
broadcasting and in-line sowing at a depth of 3 cm-
depth; the increase being in the range 18–44%.
Discussion:
Naked caryopses of L. ledermannii were
subjected to different growth conditions and the
percentage germination and energy of germination
were analyzed. In general, growth conditions
significantly affected the percentage germination and
the energy of germination. Our results showed the
influence of seed container type, substrate, sowing
depth and method, and sowing period on the
germination rate of the naked caryopses. Moreover,
the energy of germination was similarly affected by
those variables. These results suggest that the
germination processes of naked caryopses of L.
ledermannii significantly depend on growth
conditions. The hypothesis that the percentage
germination and energy of germination of caryopses
are the result of caryopses’ adaptation to ecological
conditions has rarely been tested. In contrast, El
Hassani [11] found that, for most cultivated and
invasive species, which spread by means of seeds 7–
30 days after germination, the embryos and plants
depend completely, except for water, on the nutrient
reserves stocked in the endosperm. Moreover, the
difference in germination abilities may be related to
differences in the energy of germination,
physiological maturity, and seed harvest and
conservation conditions.
Effect of environmental factors:
The hypothesis that seed germination is
environmentally inducible is not well documented in
tropical grass species. Our results showed that the
germination rate of caryopses strictly varies across
environmental factors. Water, temperature and
irradiance are known to be crucial factors that affect
seed germination. The data we report are noteworthy.
In general, the environmental factors that we tested
(i.e. recovery rate, humidity, seedling depth, sowing
method, growth period) for their effect on percentage
germination and the germination energy were
significant (Tables 3, 4). The factors that did not have
a significant effect on percentage germination and
the germination energy were seed container type and
the amount of shade (i.e. whether the containers were
covered or not). The caryopses responded in similar
ways to substrate, degree of shading, growth period,
depth and methods of sowing.
Relationship between soil conditions and caryopses’
germination rates:
Covering to a depth of 3 cm resulted in the
highest percentage germination and the best energy
of germination, whereas covering to a depth of 1 cm
produced the lowest percentage germination and the
longest period for the first shoots to appear. This
provides evidence that germination of caryopses of
L. ledermannii depend on temperature and soil
moisture. In addition, those caryopses planted 3 cm
deep showed the lowest number of days to the last
germination, whereas those planted 1 cm deep
showed the highest. These results suggest that seeds
that are not superficially sown germinate easily due
to the temperature and humidity and also the required
distance that they need to cross before emerging from
the soil. L. ledermannii might join such perennial
324
Adv. Environ. Biol., 7(2): 320-329, 2013
grass species as Stipa tenacissima L. and Lygeum
spartum L., which grow in arid conditions. Like
Ammophila arenaria caryopses grown in the
laboratory [2], the caryopses of these species have an
optimal germination in the temperature range 15–
25°C. It is known that seeds dried with less than 15%
humidity [23,36] and grass seeds thrive by being
sown at the start of the rainy seasons [5]. Planting at
a depth of 1 cm may prove fatal. It is, therefore,
essential that the caryopses are placed on top of
freshly prepared and rolled soil so that the seed
settles into the soil in close contact with the soil
particle following some rain [4]. Our results showed
that the long time taken for the caryopses to
germinate might be related to the intrinsic
performance of the seeds. Generally, with grass seed
embryos, the coleoptiles shrivel up in the ground
when the seeds are sown deeply and the plant dies
because the organ lacks firmness [12] Conversely, we
found a higher percentage of germination in response
to deeper sowing. Previously, Manske [24] had found
that the seed reproductive phase, which is triggered
primarily by photoperiod, can also be slightly
modified by temperature and rain.
The naked caryopses may show a lower
germination rate in particular conditions. Because the
caryopses are generally resistant, it may be possible
that the embryo of L. ledermannii was destroyed, as
is the case with Phleum pratense L., a well-known
temperate grass species [12]. Apart from
morphological parameters, which have been
previously elucidated [18], no data exist for the
parasitism and purity of L. ledermannii seeds. These
seeds might be immature or harvested very early, or
badly conserved or dormant, which can affect about
0–70% of grains [12]. Part of the variability in
germination rate might be related to an extra
environmental investment. The much higher
germination rate in sterilized soils suggests that
microbial activity affects the germination of
caryopses. Microorganism contamination might
either occur in soils that were not sterilized or
microorganisms might interact with blotting paper.
This is compounded with the effects of aeration –
that is, depth, humidity, temperature, pH and
exchangeable Ca presence. Furthermore, Chiang and
Soudi [9] hypothesised that soil aeration might affect
seed germination, as it ranges from 0.7 to 1 kg per
square meter and from 10 to 15 cm in the superficial
soil layer. However, our experiment was conducted
within depths of 1 cm and 3 cm; in hot weather,
topsoil temperatures rise and seed desiccation may
occur. Changes in shallow soil sowing depths are
related to the higher presence of algae in wetland
soils and horizons and where sunbeams are available
for the oxygen capture of photolithotrophs [9]. In
addition, temperatures drop when it is raining and
seeds consequently get soaked. Parts of the seed
might perish if the conditions are too extreme or
when they change too abruptly.
Effects of seed containers on caryopses’germination
rates:
Different temperatures and moisture regimes in
different seed beds presumably elicit different
patterns of physiological response from the
developing embryo [10,12,29,7]. In our study, this is
highlighted by the fact that embryos from covered
seed containers grew more rapidly in larger numbers
than embryos from the non-covered seed containers
(table 3). Humidity and temperature reserves were
mobilized in the scuttelum during the germination
process. Consequently, only a small energy reserve
remained for sustainable germination processes. Our
results showed that 50% of L. ledermannii caryopses
germinated between 2 and 3 weeks after sowing. In
addition, many caryopses that took only a few days
for the first appearance of shoots to occur also
showed a low percentage of germination. This is
consistent with the general trend [12]. Moreover, the
extraction of such caryopses by rough manipulation
in a pestle and mortar may affect the percentage of
germination, improving the energy of germination.
On the other hand, differences in germination can be
related to differences in germination energy,
physiological maturity, and crop conditions and seed
conservation. Therefore, lack of seed rising might
result from deteriorated embryos caused by
mechanical thermal shock [11]. For example,
incomplete development of the embryo might relate
to the amount of light received. Therefore,
manipulating temperatures and scarification in order
to remove tegument inhibition could cause caryopses
to rise.
Effect of substrate type on caryopses’ germination
rate:
Temperatures inside a substrate are usually
lower, on average, and less variable near the bottom
than at the top, and water potential typically
increases with depth in the soil [10,6,36]. Our
laboratory experiment results showed a low
percentage of germination of the naked caryopses,
depending on the type of substrate – that is, non-
optimal temperatures, a bad water supply and a
highly compacted soil. Every pot and plot was
consistently watered without compacted soil. The
covered treatments showed a significant difference,
with low percentage germination occurring mainly in
the laboratory. For Boudet [5], the sowing of small
seeds was carried out on a sharply crumbled soil and
tamped to avoid soil erosion. In studies by Boonman
[4], (i) light coastal sands develop high soil
temperatures at the end of the dry season and at the
beginning of the rainy season (direct sunshine and
dry, windy conditions may kill seedlings); (ii) black
clays (e.g. vertisols) shrink, leaving cracks in the
drought-ridden soil – this causes the young roots to
break off and swelling occurs when it starts to rain;
325
Adv. Environ. Biol., 7(2): 320-329, 2013
therefore, pasture establishment is very difficult.
The time taken for growth to occur may also be
attributed to the environmental conditions. We
observed a significant increase in the number of
plants per square meter in seedlings from the 15th to
the 30th day (P < 0.001). These findings suggest that
naked caryopses respond to change in soil
temperature and moisture, and these factors play a
significant part in germination percentage; this has
been corroborated by previous studies. Indeed,
Boonman [4] and Sounon et al. [36] observed that
the rate of germination declined as the rainy season
advanced. At the onset of the rainy season, the soil
was warmer and showed a better structure. Soil
temperatures decline rapidly as the rainy season
proceeds.
Effect of sowing methods on caryopses’germination
rate:
Variations in plant density depend on variation
in germination of naked caryopses in the field which
might result from developmental plasticity. Our
results show that higher plant density occur when
tamping is applied to the soil where seedlings have
been planted, suggesting that tamping creates the
best ambient conditions for caryopses germination.
Consequently, non-tamping caryopses had low plant
density (Table 5b). Additionally, 63% and 71% of the
variations in germination percentage of naked
caryopses were induced by tamping in broadcasting
and in-line sowing at a depth of 3 cm (Table 5b).
This is not the case of temperate caryopses as the
seedling emergence decreased with increasing depth
of sowing. Indeed, Maun and Riach [25] observed
that the highest germination rate of caryopses and the
emergence of seedlings of the temperate grass
Calamovilfa longifolia (Hook) Scribn. occurred from
a depth of 1–2 cm in Canada. They found that the
maximum depth of sand from which a seedling can
emerge is about 8 cm. But, the tropical grass species
have been less documented. Kindomihou et al. [18]
have characterized caryopses of L. ledermannii (i.e.
4.5 mm long and 1.0 mm wide) enclosed in lemma
and palea. In this study, we have tested only three
sowing depths have been tested: (i) sowing at 1 cm-
depth; (ii) sowing at 3 cm-depth and (iii) sowing at 5
cm-depth (data partly treated). More sowing depths
are needed to be tested. Nevertheless, for pasture
purposes, broadcasting is customary, resulted in low
seed rates, because the risk of the seeds scorching in
the soil are small as the tropical grass seeds are very
slight, with 1000-seed (spikelet) weight of usually
less than 500 mg [4]. The most common method of
broadcasting for grass seeds is to bury the seeds
deeply in the furrow, ensuring that sufficient
overlapping occurs. In addition, seeds establish faster
when sown in rows, which enable a more rapid
establishment. Boonman [4] observed good contact
between seeds and the soil when seeds are sown in
freshly drawn furrows.
Specific adaptation:
We observed that caryopses of L. ledermannii
take 8–12 days to germinate depending on the
substrate used (Table 3), and 37–41 days depending
on the sowing depth, with the best value (>37.5)
being achieved in covered, deeply sown seedlings
(Table 4). These results suggest that the
establishment of L. ledermannii pasture depends on
the environment. First, the speed or vigour with
which the caryopses germinate depends on the
species and might be poorly correlated with seed
weight. Indeed, Boonman [4] proved that, under
good conditions, Rhodes grass (Eustachus
paspaloides) seeds usually take 8–10 days to emerge,
and grow rapidly some weeks after. Second,
dormancy is affected by temperature, so that any
method that manipulates temperatures is likely to
produce an effect on dormancy. The naked caryopses
of L. ledermannii have shown different
morphological measurements (length, width,
thickness, weight) [18], that all might affect the
germination process. These results suggest a somatic
polymorphism, i.e the seeds that have been used
belong to a population of different morphology and
behaviour. Similar processes were reported to occur
in other perennial herbaceous species, such as
Chenopodium spp. and Rumex spp., the seeds of
which have different characteristics in dormancy;
these characteristics explain why their seed
populations showed the same germination rate at
different times of the year [27]. Seeds might also
have been produced in unfavourable conditions (i.e.
dryness, extreme temperature), as it has been
reported that many dormant seeds in agricultural
lands provide vapour raised from CO2 and low
temperatures in O2 in soils [27]. Moreover, seedlings
develop favourable moisture and temperature
conditions in reduced competition and when
resources are easily available to the seedlings for
growth [24].
As conclusion, the germination of the caryopses
of L. ledermannii depends on environmental factors.
The percentage and energy of germination might be
phenotypic in response to environmental factors.
Caryopses might be sown 3 cm deeper and may be
subjected to slight tamping. Further studies are
needed to appreciate whether these abilities are also
constitutive of somatic polymorphism. Moreover,
adaptive dormancy and growth speed needed to be
characterized for this earlier forage grass species.
326
Adv. Environ. Biol., 7(2): 320-329, 2013
Tab le 1: Climatic data for 1975-2004
RHMi
(%)
RHMa (%) RHM
(%)
Tmi
(oC)
Tma
(oC)
TM
(oC)
P
(mm)
IR
(hours)
Months M SD M SD M SD M SD M SD M SD M SD M SD
J 62.2 11.3 93.7 2.4 77.5 6.5 24.1 1.3 32.3 3.6 28.3 2.0 12.7 21.5 209.5 27.9
F 63.7 6.1 91.8 2.1 77.8 3.4 25.6 0.8 32.5 0.8 28.8 0.6 41.5 40.4 208.3 21.5
M 67.5 2.5 90.5 1.9 78.6 1.6 26.2 0.6 32.6 0.6 29.6 0.5 76.8 61.4 219.3 22.0
A 68.8 2.7 90.9 2.1 79.6 1.9 26.4 0.8 31.9 0.6 28.9 0.6 132.7 71.0 219.1 19.3
M 70.5 1.9 93.3 1.7 81.7 1.5 25.5 0.5 31.8 0.6 28.4 0.5 205.5 83.9 210.7 20.2
J 74.7 1.8 94.5 1.4 84.1 1.3 24.7 0.4 29.8 0.5 26.9 0.4 308.9 143.9 152.2 27.3
J 76.9 1.5 92.9 1.7 84.7 1.4 23.8 0.5 28.8 0.7 25.9 0.6 123.5 112.7 147.3 31.5
A 75.8 1.7 93.6 1.6 84.3 1.3 23.6 0.5 27.9 0.5 25.8 0.5 55.4 79.5 148.4 28.3
S 75.2 1.9 93.4 1.4 84.8 1.2 23.9 0.4 28.7 0.5 26.4 0.4 114.2 82.3 161.2 23.5
O 72.7 1.8 93.9 1.7 82.8 1.3 24.5 0.5 29.9 0.6 27.2 0.5 130.7 76.7 209.6 15.3
N 67.9 2.4 93.8 1.9 80.7 2.1 24.6 0.6 32.1 0.6 27.9 0.5 37.5 27.8 244.3 15.4
D 63.4 6.1 94.5 1.9 78.5 3.7 24.3 0.8 31.7 0.7 27.6 0.6 19.7 26.2 219.7 25.1
Note. RHMi: relative humidity minima; RHMa: relative humidity maxima; RHM: mean relative humidity; Tmi:
temperature minima; Tma: temperature maxima; TM: mean temperature; P: Precipitation; IR: Sunny period. M:
mean; SD: standard deviation.
Tab le 2: Characteristics of the soil of experimentation garden of the Faculty of Agronomic Sciences where the field trials were performed.
Granulometry (%)
0 - 2 mm
2 - 20 mm
20 - 50 mm
50 - 200 mm
200 - 2000 mm
10.4
2.7
1.9
19.7
65.2
pH (H2O)
pH (KCl)
Ca++ ech.meq/100g
Mg++ ech.meq/100g
K+ ech.meq/100g
Na+ ech.meq/100g
CEC meq/100g
P2O5 p.p.m
N (%)
Organic matter (%)
C (%)
C/N
6.4
5.4
2.58
1.32
0.47
0.10
6.23
6.89
0.077
1.40
0.81
10.60
Source: Kindomihou et al. (2009)
Tab le 3 : Effect of seed container and substrate type on the germination percentage (GerP) and respectively on the time (number of days) to
the first appearance of shoots (TFAS), the maximum germination (TMAG) or germination energy in the laboratory trials. The
adjusted means of the traits and the results of 3-way ANOVA, mixed model to test these effects are reported.
TFAS (days) TMAG (days) GerP (%)
m SE m SE m SE
Seed container NCC 5.2a 0.2 5.6b 0.2 40.8b 1.1
CC 4.7a 0.2 10.3a 0.2 66.1a 1.1
Substrate
BP 5.8a 0.3 9.5a 0.3 31.7c 1.4
FS 4.3b 0.3 7.5b 0.3 52.5b 1.4
SS 4.7b 0.3 6.8b 0.3 76.2a 1.4
Seed container (SC)
NS *** **
Substrate type (ST) *** *** ***
Replicats (R) NS NS *
SC x R NS NS NS
ST x R NS NS NS
SC x ST NS NS NS
Coefficient of variation 12.61 7.81 6.30
a,b,c are means within a column with different superscripts differ significantly (P < 0.05). m: mean; SE: standard error. *P < 0.05; ** P <
0.01; *** P < 0.001; NS = not significant. For each factor, values with the same letter in the same column are not significantly different.
NCC: non covered containers; CC: covered containers. BP: blotting paper; FS: fine soil; SS: sterilized soil
327
Adv. Environ. Biol., 7(2): 320-329, 2013
Table 4: Effects of the sowing depth and the seed container on the germination percentage (PGer) and the time (i.e. number of days) from
sowing to: (i) the first appearance of shoots (TFAS); (ii) the maximum germination (TMAG); (iii) the latest germination (TLAG)
in the laboratory trials. The adjusted means and the results of 3-way ANOVA, mixed model are reported.
TFAS (days) TMAG (days) TLAG (days) PGer (%)
m SE m SE m SE m SE
Sowing depth S1 5.8a 0.3 17.2a 1.7 45.7a 0.5 44.4b 0.4
S3 5.2a 0.3 12.8a 1.7 43.3a 0.5 49.7a 0.4
Treatments NCC 5.7a 0.3 14.3a 1.7 49.7a 0.5 45.2b 0.4
CC 5.3a 0.3 15.7a 1.7 39.3b 0.5 48.9a 0.4
Sowing depth (SD) NS NS * **
Seed container (SC) NS NS ** *
Replicate (R) NS NS NS NS
SD x R NS NS NS NS
SC x R NS NS NS NS
SD x SC NS NS NS **
CV (%) 13.89 27.15 2.59 1.92
a and b are means within a column with different superscripts differ significantly (P < 0.05). m: mean; SE: standard error. *P < 0.05; ** P <
0.01; NS = not significant. For each factor, values with the same letter in the same column are not significantly different. NCC: non covered
containers; CC: covered containers.
Table 5a: Effects of the sowing method and the period on the plants density (number of plants per m2) in the field trials. The adjusted means
of the plants density and the results of 3-way ANOVA, mixed model to test these effects are reported.
Plants density (Number plants /m2)
m SE
Periods P/1-15 9.7b 0.4
P/1-30 19.5a 0.4
Sowing method
Broadcasting 9.8d 0.5
LiSo1cm 12.8c 0.5
LiSo3cm 15.7b 0.5
LiSo5cm 19.5a 0.5
Sowing method (SM) ****
Period (P) **
Replicate (R) NS
SM x P NS
SM x R NS
P x R NS
R2 0.99
Coefficient of variation 8.35
a, b, c and d are means within a column with different superscripts differ significantly (P < 0.05).
*P < 0.05; ** P < 0.01; *** P < 0.001; NS = not significant. For each factor, values with the same letter in the same column are not
significantly different. m: mean; SE: standard error.
Tab le 5b: Effects of the sowing method and the period on the plants density (number of plants per m2). The adjusted means of the plants
density and the results of 3-way ANOVA, mixed model to test these effects and are reported.
Number of plants per m2
m SE
Period P/1-15 15.3b 0.3
P/1-30 21.5a 0.3
Sowing method
Broadcasting 11.7d 0.5
Broadcasting + Tamping 20.3b 0.5
LiSo3cm 16.5c 0.5
LiSo3cm+Tamping 25.0a 0.5
Sowing method (SM) ****
Period (P) *
Replicate (R) NS
SM x P NS
SM x R NS
P x R NS
Coefficient of variation (%) 6.32
a, b, c and d are means within a column with different superscripts differ significantly (P < 0.05).
*P < 0.05; ** P < 0.01; *** P < 0.001; NS = not significant. For each factor, values with the same letter in the same column are not
significantly different. m: mean; SE: standard error.
328
Adv. Environ. Biol., C(): CC-CC, 2013
Fig. 1: Change in germination percentage following substrate type and amount of shade.
Acknowledgements
The Laboratory of Applied Ecology of
University of Abomey-Calavi (Benin), CUD & DRI
(Belgium), BecA – ILRI, Scriptoria-UK and Bill &
Mellinda Gate Foundation have funded these
researches.
References
1. ASECNA, 2004. Données climatologiques:
Station d'Agonkanmey. Abomey-Calavi, Bénin.
2. Bendimered, F.Z., Z. Mehdadi and H.
Benhassaini, 2007. Study of germination and
foliar growth of Ammophila arenaria (L.) Link
under Controlling Conditions. Acta Botanica
Gallica, 154: 129-40.
3. Bewley, J.O. and M. Black, 1982. Physiology
and biochemistry of seeds in relation to
germination. Volume 2: Viability, Dormancy
and Environmental Control. Springer Verlag.
New York.
4. Boonman, J.G., 1993. East Africa’s grasses and
fodders: their ecology and husbandry. Kluwer
Academic Publishers. 343 pp.
5. Boudet, G. 1991. Manuel sur les pâturages
tropicaux et les cultures fourragères, IEMVT,
Collection Manuel et Précis d’élevage. Paris,
France. 266 pp.
6. Carr, P.M., W.W. Poland and L.J. Tisor, 2005.
Natural reseeding by forage legumes following
wheat in Western North Dakota. Agronomy
Journal, 97: 1270-1277.
7. Ceri, E.E. and J.R. Etherington, 1990. The effect
of soil water potential on seed germination of
some british plants. New Phytologist, 115: 539-
548.
8. César, J., 1992. La production biologique des
savanes de Cote d’Ivoire et son utilisation par
l’homme. Biomasse, valeur pastorale et
productions fourragères. These de Doctorat,
Univ. Paris VI., France. 671 pp.
9. Chiang, C.N. and B. Soudi, 1994. Biologie du
sol et cycles biogéochimiques. In El Hassani TA
and Persoons E. Bases physiologiques et
agronomiques de la production végétale.
Agronomie moderne. Hatier, AUPELF-UREF.
pp. 85-118.
10. Dasberg, S. and K. Mendel, 1971. The effect of
soil water and aeration on seed germination.
Journal of Experimental Botany, 22: 992-998.
11. El Hassani, T.A., 1994. Croissance et
développement des plantes cultivées. Bases
physiologiques de l’élaboration de rendement.
In: El Hassani TA. and Persoons E. 1994. Bases
physiologiques et agronomiques de la
production végétale. Agronomie moderne.
Hatier, AUPELF.UREF. pp. 119-152.
12. Gillet, M., 1980. Les graminées fourragères.
Description, fonctionnement, applications à la
culture de l’herbe, collection Nature et
agriculture, Paris. France.
13. Greipsson, S. and A. Davy, 1996. Aspects of
seed germination in the dune building grass
Leymus arenarius. Buvisindi Icelandic
Agricultural Sciences, 10 : 209-217.
14. Holou, R.A.Y. and B. Sinsin, 2002.
Embroussaillement des pâturages artificiels et
naturels exploités par les bovins en zone
guinéenne au Bénin. Annales des Sciences
Agronomiques du Bénin, 3 : 40-66.
15. Hutchinson, J.L.D.F.R.S.V.M.L.S and
J.M.D.F.S. Dalziel, 1972. Flora of West Africa.
Vol 3, part 2.
16. Jonathan, S. and G. Struik, 1964. A Possible
Ecological relation between soil disturbance,
light-flash, and seed germination. Ecology, 45 :
884-886.
17. Kindomihou, V., C. Adandedjan and B. Sinsin,
1998. Performances agronomiques et
zootechniques d’associations mixtes fourragères
329
Adv. Environ. Biol., C(): CC-CC, 2013
tropicales In Godet et Grimaud : Actes de
l’Atelier Régional sur les Cultures fourragères et
Développement Durable en zone subhumide,
Korhogo, Cote d’Ivoire-26-29 mai 1997. pp. 85-
90.
18. Kindomihou, V.M., M. Oumorou, G.A. Mensah
and B.A. Sinsin, 2009. Morphological traits and
germination of Loxodera ledermannii (Pilger)
W.D. Clayton ex Launert caryopses in Southern-
Benin. Bulletin de la Recherche Agronomique
du Bénin, 65 : 37- 43.
19. Kreis, M., J. Lejoly and B. Sinsin, 1989. Etude
agrostologique des parcours naturels du sud-
Borgou (Benin). XVIe Congrès des herbages,
Nice, France. pp. 1409-1410.
20. Kucewicz, M., C. Holdynski and E. Gojlo, 2006.
Ecophysiological conditions of germination of
barnyard grass [(Echinochloa orus-galli (L.)
P.Beauv.] D diaspores. Journal of Plant
Protection Research, 46: 73-84.
21. Lambert, J., N. Tremblay and C. Hamel, 1994.
Nutrition minérale des plantes. In El Hassani,
T.A. and E. Persoons. 1994. Bases
physiologiques et agronomiques de la
production végétale. Agronomie moderne.
Hatier-AUPELF-UREF. pp. 269-292.
22. Lejoly, J. and B. Sinsin, 1991. Structure et
valeur pastorale des pâturages soudaniens de
bas-fonds dans le Nord-Bénin. IVème Conférence
Internationale des Terres de Parcours.
Montpellier, France.
23. Lhoste, P., V. Dolle, J. Rousseau and D. Soltner,
1993. Manuel de zootechnie des régions
chaudes : Les systèmes d’élevage. IEMVT.
Paris, France. pp. 243-253.
24. Manske, L.L., 2001. General description of
grasses growth and development and defoliation
resistance mechanism. NDSU Dickinson
Research Center. Dakota, USA.
25. Maun, M.A. and S. Riach, 1981. Morphology of
caryopses, seedlings and seedlings emergence of
the Grass Calmovilfa longifolia from Various
Depths in Sand. Oecologia, 49: 137-142.
26. Parihar, S.S. and P.S. Pathak, 2006. Flowering,
phenology and seed biology of selected tropical
perennial grasses. Tropical Ecology, 47: 81-87.
27. Peeters, A. and J.F. Salembier, 1994. Contrôle
des mauvaises herbes. Centre de recherche
agronomiques de Gembloux. In El Hassani TA.
and Persoons E. 1994. Bases physiologiques et
agronomiques de la production végétale.
Agronomie moderne. Hatier, AUPELF.UREF.
pp. 427-464.
28. Peters, M. and C.E. Lascano, 2003. Forage
technology adoption: Linking on-station
research with participatory methods. Tropical
Grasslands, 197-203.
29. Poysa, V.W., and E. Reinbergs, 1983. The
Response of some facultative triticale to
extended vernalisation. Z. Acker- und
Pflanzenbau, 152: 89-99.
30. Rutherglen Burnett, V.V., 2008. Organic
farming. Perennial pasture establishment; AG
1263. Victorian Department of Primary
Industries. ISSN 1329-8062. 4 p.
31. Sinsin, B., and F. Owolabi, 2002. Monographie
nationale de la biodiversité au Bénin.
32. Sinsin, B., J. Essou, A. Saidou, M. Houinato, V.
Kindomihou, I. Bako, and I. Toko, 1996.
Gestion des pâturages naturels de la ferme
d’élevage de l’Okpara, Bétécoucou, Samiondji
PDPA. 80 p.
33. Sinsin, B., S. Oloulotan and M. Oumorou, 1989.
Les pâturages de saison sèche de la zone
soudanienne du nord-Bénin. Revue d’Élevage et
de Médecine Vétérinaire des Pays tropicaux, 42 :
283-288.
34. Sinsin, B., 1993. Phytosociologie, Ecologie,
Valeur pastorale, Productivité et Capacité de
charge des pâturages naturels du périmètre
Nikki-Kalalé au Nord-Bénin. Thèse Doct. Univ.
Libre. Bruxelles, Belgique.
35. Sinsin, B., 1994. Observations préliminaires sur
cinq espèces de graminées fourragères des
savanes du nord-Bénin. Actes de Séminaire
régional sur les systèmes agraires et agricultures
durable. Résumés. Fondation internationale pour
la Science. Stockholm, Suede. pp. 77-90.
36. Sounon, M., R. Glèlè Kakaï, J. Avakoudjo, A.E.
Assogbadjo and B. Sinsin, 2009. Germination
and growth test of Artemisia annua L. anamed
on different substrate in Benin. International
Journal of Biological and Chemical Sciences,
3(2): 337-346
37. Vanderzon, A.R.M., 1992. Graminées du
Cameroun. Vol1 Phytogéographie et Pâturages.
Wageningen Agricultural University, pp: 92-1.
86.
Article
Full-text available
This study examines biological and agronomic responses of Loxodera ledermannii to the compost application. A complete random block of 3 treatments (0 t/ha, 5 t/ha and 10 t/ha of organic fertilizer in 3 replicates was designed. Each plot (1.5 m x 2 m) is seeded 24 tussocks acclimated in the Botanical Garden of the UAC from 2011 to 2013. Leaf morphometric, ecophysiological and agronomic measurements are subjected to ANOVA with STATISTICA 9.0. Results showed that organic fertilization significantly affects the tillers production, Specific Leaf Area (SLA) and aboveground biomass. SLA are the highest under compost (SLA >208.61±10.81 cm 2 .g-1) and the lowest with the controls (153.33 cm 2 .g-1 ≤ SLA ≤ 169.05 cm 2 .g-1). The leaves of L. ledermannii accumulate naturally more biomass per area unit and have a long lifespan. The compost application increases significantly SLA by 25% (P< 0.01). This increase implies a low accumulation of biomass per area unit, indicating that compost would impoverish the leaves of L. ledermannii in carbon reducing by the way its life expectancy. The controls produced 10.33 t DM.ha-1 , which was 46% other than production under 5 to 10 t per hectare of compost. SLA is positively correlated to the leaf dry matter content (R = 0.88; p< 0.01) and negatively to the leaf water content (R =-0.89; P< 0.01). These results suggest that L. ledermannii is a slow-growing species and the organic fertilization tends to disrupt its development. Its utilization in ecological farming requires knowledge on strategies and functional status of this species. Kindomihou et al. 44 RÉSUMÉ PRODUCTION FOURRAGÈRE BIOLOGIQUE : RÉPONSES DE LOXODERA LEDERMANNII CULTIVÉE SOUS ADJONCTION DU COMPOST EN ZONE SUBÉQUATORIALE DU BÉNIN Cette étude examine les réponses biologiques et agronomiques de Loxodera ledermannii à l'apport du compost. Le dispositif expérimental est un bloc aléatoire complet de trois traitements [0t/ha (témoin), 5t/ha et 10t/ha de compost] en 3 répétitions. Sur chaque placette de 1,5m x 2m ensemencée de 24 souches, sont échantillonnées 5 souches provenant du Parc W et acclimatés au Jardin Botanique de l'UAC de 2011 à 2013. Des mensurations morphométriques, écophysiologiques et agronomiques sont soumises à l'Analyse de Variances sous STATISTICA 9.0. Les résultats montrent que la fertilisation organique affecte significativement la production de talles, la surface foliaire spécifique (SFS) et la biomasse aérienne. Les SFS sont les plus élevées sous traitements (SFS > 208,61±10,81 cm 2 .g-1) et les plus faibles chez les témoins (153,33 cm 2 .g-1 ≤ SFS ≤ 169,05 cm 2 .g-1). Les feuilles accumulent naturellement plus de biomasse par unité de surface et ont une longue durée de vie. L'apport du compost accroit la surface foliaire spécifique de 25 % (P<0,01). Cette augmentation qui implique une faible accumulation de biomasse par unité de surface, indique que le compost appauvrirait les feuilles de L. ledermannii en carbone, diminuant ainsi leur durée de vie. Les plants témoins ont produit 10,33 t de MS.ha-1 , soit 46 % de moins que la production sous 5 à 10 t/ha de compost. La SFS est corrélée positivement à la teneur en matière sèche foliaire (R=0,88 ; p < 0,01) et négativement à la teneur en eau (R =-0,89 ; P < 0,01). Ces résultats suggèrent que L. ledermannii est une espèce à croissance lente et la fertilisation organique tende à perturber son développement. Son utilisation en agriculture écologique nécessite plus de connaissances sur ses stratégies fonctionnelles.
Article
Full-text available
The aim of this work is to determinate the thermal optimum of caryopsis germination of Ammophila arenaria in laboratory and to follow the leaves growth under glass. Caryopsis sprouted after a post-maturation in a wide range of temperatures between 15°C and 30°C, the optimum being between 15°C and 25°C and through this character it comes close to other perennials Poaceae such as Stipa tenacissima L. and Lygeum spartum L. A heat pre-treatment fewly affect the viability of caryopsis. The study of the leaves growth showed that the leaves production is important but there was not any tiller formed. The final length of the leaves increases with their order until the fifth leaf.
Article
Full-text available
Phenological variations, seed yielding components, seed and germination characteristics were investigated in fourteen perennial tropical grasses during monsoon growth (1995 and 1996). Brachiaria brizantha and Panicum antidotale were the earliest flowering grasses with floral initiation during August first week, after about 40-45 days of monsoon initiated growth from June end. Six grasses flowered and produced 'seeds' during September - October, while another six species started inflorescence exsertion during the second half of November under short day response, after > four months vegetative growth. Seeds are florets with two spikelets or a group of spikelet with or without appendages. Caryopses are enclosed in the husk and dispersed intact. Five grasses place a high premium in the enclosure of caryopsis as weight of husk exceeds the weight of caryopsis. Seed setting was poor in exotic species compared to indigenous. Seed set was also poor to nil in grasses flowering during winter under short day conditions. Germination in 'seeds' was low depending upon per cent seed set, while germination in caryopses was much higher up to 92 percent.
Article
L'étude dela dégradation par embroussaillement des pâturages artificiels et naturels en zone guinéenne a été effectuée dans 10 types de pâturages. Il s’agit de 3 pâturages artificiels ensemencés respectivement par Andropogon gayanus, Panicum maximum var. C1 et Panicum maximum; de 4 pâturages artificiels dégradés à Cynodon dactylon, à Cynodon dactylon et Panicum maximum, à Brachiaria ruziziensis, à Brachiaria ruziziensis et Chromolaena odorata; et de 3 pâturages naturels à Paspalum scrobiculatum et Panicum maximum, à Panicummaximum et Chromolaena odorata, à Panicum maximum et Motandra guineensis. Les résultats montrent que les thérophytes constituent le type biologique le plus abondant dans les jeunes pâturages. Dans les pâturages les plus âgés ce sont plutôt les phanérophytes qui sont les plus abondants. La valeur pastorale de ces pâturages varie de 15,6 % à 84,4 % ; les plus fortes valeurs pastorales sont obtenues au sein dupâturage artificiel à Andropogon gayanus et le pâturage artificiel dégradé à Cynodon dactylon. Le taux d’embroussaillement varie de 0,06 à 0,63. Les plus forts taux d'embroussaillement sont notés au sein des pâturages naturels, notamment au sein du pâturage à Panicum maximum et Motandra guineensis qui a aussi la plus faible valeur pastorale. La biomasse végétale consommable est réduite lorsque les refussont dominants. Les contributions pondérales des refus varient de 14,3 % à 68,2 % selon les niveaux de dégradation, les types de pâturage et selon les stations. En général, les contributions pondérales des refus augmentent quand on passe des pâturages artificiels dégradés aux pâturages naturels dégradés. La plus forte contribution pondérale des refus est obtenue dans le pâturage naturel à Paspalumscrobiculatum et Panicum maximum, qui est le plus fréquenté par les animaux. L'action sélective des animaux lors des pâtures favorise la croissance des refus au détriment des espèces fourragères. Parmi les refus, l'espèce la plus fréquemment rencontrée au sein des pâturages dégradés de la zone d'étude est Chromolaena odorata. En somme, l'embroussaillement des pâturages est fonction des caractéristiquesbiologiques et morphologiques de l'espèce dominante, de sa densité, de l'âge, de l'histoire de la formation à travers l'action sélective des animaux le fréquentant et de l'action anthropique. La contribution pondérale des refus et le taux d'embroussaillement sont des paramètres qui permettent de mieux expliquer la dégradation quantitative et qualitative des pâturages. Degradation of artificial and native pastures by bushy weed overrunning was studied in the guinea zone of southern Benin. Three artificial pastures were concerned i.e. : Andropogon gayanus pasture, Panicum maximum var. C1 pasture, and Panicum maximum pasture. Four olderly degraded artificial pastures were concerned i.e. : Cynodon dactylon pasture, Cynodon dactylon and Panicum maximum pasture, Brachiaria ruziziensis pasture, and Brachiaria ruziziensis and Chromolaena odorata pasture. Three native pastures were concerned, i.e. : Paspalum scrobiculatum and Panicum maximum pasture, Panicum maximum and Chromolaena odorata pasture, and Panicum maximum and Motandra guineensis pasture. Therophyte species were the most abundant life forms that occurred in young pastures while phanerophyte species were the most abundant in old pasture.Grazing values varied from 15.6 % (in native pastures) to 84.4 % (in artificial pastures). The rate of Bushy weed overrunning varied from 0.06 to 0.63 ; the highest value of this rate was obtained in the native pasture of Panicum maximum and Motandra guineensis. The percentage weight of non palatable species varied from 14.3 % (in artificial pastures) to 68.2 % (in native pastures). The highest value of non palatable species was obtained in the native pasture of Paspalum scrobiculatum andPanicum maximum which was mostly grazed by cattle herds. Selective plant grazing by herds is at the basis of the occurrence of non palatable plant species in pasture, and Chromolaena odorata was the most expansive non palatable species in degraded pasture. Degradation of pastures by bushy weed overrunning depends on manyfactors such as: the life form and the morphology of the dominant species, its density, the age of the pasture, the influence of human activity and the selective grazing action of herds. The weight of the non palatable plant species, and the rate of bushy weed overrunning are seen as good parameters for better explanation of pasture degradation in terms of its quantitative and qualitative aspects.
Article
The aim of the study was to investigate the effect of some different environmental conditions prevailing during the development and ripening of Echinochloa crus-galli diaspores on their germination. Some seeds were tested in the autumn the same year, whereas others were divided into two groups: dispersed seeds and seeds within the inflorescence. Then the seeds of both groups were buried. After eight-month stratification in the soil, the diaspores were tested under the same conditions as the samples examined in the autumn. The seeds tested in the spring germinated faster than those tested in the autumn. Also the germination capacity of barnyard grass caryopses examined in the summer was almost twofold higher than the germination capacity of those examined in the autumn. Both autumn and spring tests revealed that the harvest time affected germination. The seeds obtained in the second half of August and at the beginning of September (in the middle of the growing season) were characterized by a higher germination capacity than the caryopses collected at the beginning and the end of the reproduction period. The results show that the germination capacity and rate were not influenced by the place of origin, habitat conditions and accompanying plants. It was found in spring tests that germination depended on the kind of dissemination unit stored in the soil. After eight-month soil stratification, dispersed caryopses germinated by approx. 20% better than those stored with a part of the inflorescence.
Article
SUMMARY‘Seeds’ of 15 species collected from a range of habitats contrasting in soil water status were germinated in soils of known matric potentials ranging from near field capacity to the permanent wilting potential (– 0.05, –0.5, –1.0 and –1.5 MPa). Germination was very sensitive to soil water potential and species responded in various ways. Some showed germination responses which correlated with the soil water status of their native habitat: none of the wetland species studied could germinate to any great extent at low soil water potentials; in contrast some species associated with drier habitats achieved high levels of germination in soils as dry as –1.0 MPa (and –1.5 MPa for one ruderal species). However, other species from drier habitats failed to germinate at low soil water potentials, and it is suggested that this may be a mechanism to avoid exposing the seedling to an unfavourable environment.
Article
Improved forages play an important role in sus- taining the livelihoods of small- and medium-scale farmers in the tropics, mainly as a result of their positive effects on livestock production and con- tribution to economic and environmental sustain- ability. However, in many regions of the tropics, the potential of forages for sustainable develop- ment is largely untapped and adoption of forage legumes in particular has so far been limited. In general, compared with forage legumes, grasses are often better known as cultivated species by farmers, are more resilient and have broad environ- mental adaptation. Currently, farmers have limited understanding of the benefits of leguminous spe- cies that can be used on their farms. This paper explores reasons for the lack of wider adoption of improved forages and suggests pathways and strategies to meet the needs of smallholder farmers more effectively. Close link- ages between farmers, researchers and extension workers are essential for both the development and diffusion of improved multipurpose grass and legume species. In this context, the importance of developing functional seed-delivery systems is emphasised. However, continuous development of forage germplasm to respond to existing and evolving constraints and changing demands and opportunities is mandatory to ensure wide adop- tion of improved forages by smallholder farmers.