Revue internationale d'écologie méditerranéenne International ...

A. DJABEUR, M. KAID-HARCHE, D. CÔME, F. CORBINEAU
Figure 1 – Time
course of
germination in
darkness, at 25 o C,
of freshly harvested
dispersal units ()
and isolated
caryopses () of the
diploid cytotype
collected in arid
highlands (A) and
the polyploid one
collected in semiarid
littoral coast (B).
Means of results
obtained in 2
replicates of 25
dispersal units or
caryopses ±
arithmetical spread.
92
Results
Germination of dispersal units and
isolated caryopses at 25 o C in darkness
Figure 1 shows that freshly harvested dispersal
units and isolated caryopses collected in
arid highlands (Figure 1A) germinated in
higher percentage at 25 oC, in darkness, than
those originated from semi-arid littoral coast
(Figure 1B). Figure 1 also shows that isolated
caryopses from both origins germinated better
than whole dispersal units. The lemma had
then an inhibitory effect on the germination
of dispersal units, and its effect was stronger
in dispersal units originated from semi-arid
littoral coast (polyploid cytotype) than in
those collected in arid highlands (diploid
cytotype).
After dry storage in darkness at ambient conditions
for one year, dispersal units collected
in both areas germinated in higher percentages
at 25 oC than at harvest time, and the
time to reach 50% germination (T50 ) was
GERMINATION (%)
100
75
50
25
0
A
2 4 6 8 10 12 14 16
TIME (DAYS)
markedly shorter for after-ripened organs than
for freshly harvested ones (Table 2). Germination
percentages obtained after 14 days
with isolated caryopses is not improved by
after-ripening in the case of the diploid cytotype
and only enhanced in the case of the
polyploid one. But as for dispersal units, T 50
is strongly reduced in after-ripened organs as
compared with freshly harvested ones
(Table 2).
Effects of temperature in darkness
The thermal optimum for the germination, in
darkness, of freshly harvested dispersal units
of both cytotypes was around 20-25 o C (Figure
2). Germination was strongly slowed
down at 15 o C, and was almost impossible
within 14 days at lower temperatures (5-
10 o C) and at 30 o C. Freshly harvested dispersal
units of the diploid cytotype, collected
in arid highlands (Figure 2A) germinated better,
at the optimal temperatures, than those
from polyploid cytotypes growing in semiarid
littoral coast (Figure 2B).
GERMINATION (%)
100
75
50
25
0
0 2 4 6 8 10 12 14 16
TIME (DAYS)
Table 2 – Germination percentages obtained after 14 days at 25 o C in darkness (means of results obtained
in 2 replicates of 25 organs ± arithmetical spread), and time to reach 50% germination (T 50 )
with freshly harvested and after-ripened dispersal units and caryopses collected in arid highlands
and semi-arid littoral coast.
B
Germination (%) of organs T 50 (days) for organs
freshly after- freshly after-
Cytotype (Origin) Organs harvested ripened harvested ripened
Diploid Dispersal units 70 ± 6 92 ± 2 10.7 4.2
(Arid highlands) Caryopses 90 ± 6 90 ± 4 5.9 4.1
Polyploid Dispersal units 44 ± 4 92 ± 4 10.5 4.5
(Semi-arid littoral coast) Caryopses 80 ± 4 92 ± 2 6.2 3.7
ecologia mediterranea – Vol. 36 (1) – 2010