Ecologia Mediterranea

placed in 10 cm diameter plastic dishes. The
filter papers were moistened daily with the
five different concentrations of the extracts
used. Control experiments whose filter papers
were moistened with distilled water were set
(30 seeds each). Each experiment was replicated
four times. All Petri dishes were kept in
dark incubators maintained at room temperature
at 15/25 o C. Germination was monitored
daily. The germinated seeds were recorded
every day for a period of 14 days after sowing.
Seeds were considered germinated when
the radical had protruded 2 mm through the
seed coat. After 14 days of incubation, germination
was expressed as the Final Percentage
of Germination (FG%) and Rate of Germination
(germination time) (GR) was
calculated by seeds day.
Statistical analysis
Averages of the main effects and their interactions
were compared using the revised
Least Significant Difference test (LSD) at
0.05 level of probability (Tukey test).
Results
Germination rate: the percentage of germination
was the lowest at 10 o C (25%). It reached
its maximum at 25 o C (80%) (Fig. 1A). Germination
in the control started on day 10
under 25 o C (Fig. 1B).
The percentage of germination decreased with
the increase of the osmotic potential especially
at –7 bar (Fig. 2). It reached its maximum
at 0 and at –1bar, 100-98% respectively
(Fig. 2A). The delay before germination
severely increased at –7 bar (Fig. 2B). The
germination was influenced by the soil depth
(Fig. 3). Although the lowest depth (1-2cm)
tested was suboptimal (100% of germination
Fig. 3A). In contrast, highest soil depth (5cm),
caused germination inhibition and seeds
buried at 6cm showed no emergence (Fig.
3B).
The highest germination rate (98%) was
observed at 0.0g/l NaCl. The lowest germination
rate (22%) occurred under 15g/l (Fig.
4A). Germination treatment under NaCl 0.0-
3.0 g/l started on day 1 (Fig. 4B).
The Rate of Germination (RG) of P. dichotomum
under 12g/l NaCl was 42% at day -8,
then no radical and no hypocotyl length can
ecologia mediterranea – Vol. 38 (2) – 2012
percentage of germination (%)
germination time (day)
Effects of abiotic stress on the germination of Pennisetum dichotomum
120
100
80
60
40
20
0
16
14
12
10
8
6
4
2
0
B
A
10 25 35
10 25 35
temperature (°C)
Figure 1 – Percentage of seed germination
of Pennisetum dichotomum (A)
and germination time (B)
in response to three temperature values.
germination (%)
time of germination (day)
120
100
80
60
40
20
0
10
9
8
7
6
5
4
3
2
1
0
B
0 -1 -3 -7 -10 -16
0 -1 -3 -7 -10 -16
hydric potential (bar)
Figure 2 – Percentage of seed germination
of Pennisetum dichotomum (A)
and germination time (B)
in response to hydric potential values.
A
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