Ecologia Mediterranea
Ecologia Mediterranea
Ecologia Mediterranea
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placed in 10 cm diameter plastic dishes. The<br />
filter papers were moistened daily with the<br />
five different concentrations of the extracts<br />
used. Control experiments whose filter papers<br />
were moistened with distilled water were set<br />
(30 seeds each). Each experiment was replicated<br />
four times. All Petri dishes were kept in<br />
dark incubators maintained at room temperature<br />
at 15/25 o C. Germination was monitored<br />
daily. The germinated seeds were recorded<br />
every day for a period of 14 days after sowing.<br />
Seeds were considered germinated when<br />
the radical had protruded 2 mm through the<br />
seed coat. After 14 days of incubation, germination<br />
was expressed as the Final Percentage<br />
of Germination (FG%) and Rate of Germination<br />
(germination time) (GR) was<br />
calculated by seeds day.<br />
Statistical analysis<br />
Averages of the main effects and their interactions<br />
were compared using the revised<br />
Least Significant Difference test (LSD) at<br />
0.05 level of probability (Tukey test).<br />
Results<br />
Germination rate: the percentage of germination<br />
was the lowest at 10 o C (25%). It reached<br />
its maximum at 25 o C (80%) (Fig. 1A). Germination<br />
in the control started on day 10<br />
under 25 o C (Fig. 1B).<br />
The percentage of germination decreased with<br />
the increase of the osmotic potential especially<br />
at –7 bar (Fig. 2). It reached its maximum<br />
at 0 and at –1bar, 100-98% respectively<br />
(Fig. 2A). The delay before germination<br />
severely increased at –7 bar (Fig. 2B). The<br />
germination was influenced by the soil depth<br />
(Fig. 3). Although the lowest depth (1-2cm)<br />
tested was suboptimal (100% of germination<br />
Fig. 3A). In contrast, highest soil depth (5cm),<br />
caused germination inhibition and seeds<br />
buried at 6cm showed no emergence (Fig.<br />
3B).<br />
The highest germination rate (98%) was<br />
observed at 0.0g/l NaCl. The lowest germination<br />
rate (22%) occurred under 15g/l (Fig.<br />
4A). Germination treatment under NaCl 0.0-<br />
3.0 g/l started on day 1 (Fig. 4B).<br />
The Rate of Germination (RG) of P. dichotomum<br />
under 12g/l NaCl was 42% at day -8,<br />
then no radical and no hypocotyl length can<br />
ecologia mediterranea – Vol. 38 (2) – 2012<br />
percentage of germination (%)<br />
germination time (day)<br />
Effects of abiotic stress on the germination of Pennisetum dichotomum<br />
120<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
16<br />
14<br />
12<br />
10<br />
8<br />
6<br />
4<br />
2<br />
0<br />
B<br />
A<br />
10 25 35<br />
10 25 35<br />
temperature (°C)<br />
Figure 1 – Percentage of seed germination<br />
of Pennisetum dichotomum (A)<br />
and germination time (B)<br />
in response to three temperature values.<br />
germination (%)<br />
time of germination (day)<br />
120<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
10<br />
9<br />
8<br />
7<br />
6<br />
5<br />
4<br />
3<br />
2<br />
1<br />
0<br />
B<br />
0 -1 -3 -7 -10 -16<br />
0 -1 -3 -7 -10 -16<br />
hydric potential (bar)<br />
Figure 2 – Percentage of seed germination<br />
of Pennisetum dichotomum (A)<br />
and germination time (B)<br />
in response to hydric potential values.<br />
A<br />
19