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Removal of lemma improved germination at
low water potentials, and this beneficial effect
of lemma removal remained after dry storage
(Table 5, to be compared with Figure 5).
Discussion and Conclusions
Mature dispersal units of the two cytotypes of
Lygeum spartum (polyploid one with 2n = 40
and diploid one with 2n = 16), collected in
Algeria in June were considered as dormant
(Figures 1 and 2). They germinated poorly in
darkness (Figure 1), and their germination
was very slow (Table 2). The thermal optimum
for germination (20-25 o C) was similar
to that found for numerous species from hot
semideserts and deserts (Baskin & Baskin
1998), such as Stipa sp. (Lodge & Whalley
1981; Fulbright et al. 1983; White & Van
Auken 1996) and Aristida sp. (Mott 1974).
Continuous white light inhibited germination
of freshly harvested L. spartum dispersal units
(Figure 4), suggesting that germination in nat-
ecologia mediterranea – Vol. 36 (1) – 2010
Environmental control of germination and dormancy of seeds of two cytotypes of Lygeum spartum L.,
a perennial grass of semi-arid and arid areas in Algeria
Table 4 – Germination percentages obtained after 14 days at 25 o C,
in darkness and in continuous white light, with freshly harvested
and after-ripened isolated caryopses collected in arid highlands
and semi-arid littoral coast. Means of the results obtained
in 2 replicates of 25 seeds ± arithmetical spread.
ural conditions is considerably restricted
when seeds are exposed to direct sunlight.
Such a negative photoblasty has been reported
for numerous xeric grasses such as Bromus
rubens, B. scoparius and B. rigidus (Corbineau
et al. 1992; Kigel 1995), Hordeum
spontaneum (Gutterman et al. 1996), Panicum
turgidum (Koller and Roth 1963), Stipa bromoides,
S. lagascae, Aristida caerulescens
and Aegilops longissima (Kigel 1995), and in
other species including Schismus arabicus
Germination (%) obtained in
Cytotype (Origin) Caryopses darkness light
Diploid freshly harvested 90 ± 6 68 ± 8
(Arid highlands) after-ripened 90 ± 4 92 ± 2
Polyploid freshly harvested 80 ± 4 52 ± 4
(Semi-arid littoral coast) after-ripened 92 ± 2 72 ± 4
Table 5 – Germination percentages obtained after 14 days at 25 o C, in darkness, in water (0 MPa) and in PEG solutions at –0.2, –0.5,
1.0 and –1.5 MPa with freshly harvested and after-ripened isolated caryopses collected in arid highlands and semi-arid
littoral coast. Means of the germination percentages obtained in 2 replicates of 25 seeds ± arithmetical spread.
Germination (%) after 14 days in
water PEG solutions at (MPa)
Cytotype (Origin) Caryopses (0 MPa) – 0.2 – 0.5 – 1.0 – 1.5
Diploid freshly harvested 90 ± 6 82 ± 6 66 ± 4 32 ± 6 6 ± 2
(Arid highlands) after-ripened 90 ± 9 96 ± 2 88 ± 6 76 ± 6 6 ± 2
Polyploid freshly harvested 92 ± 2 66 ± 4 42 ± 6 18 ± 4 0
(Semi-arid littoral coast) after-ripened 80 ± 4 90 ± 6 70 ± 6 30 ± 6 0
Figure 5 – Effects of
water potential of
the medium on the
germination
percentages
obtained after
14 days in darkness
with freshly
harvested () and
after-ripened ()
dispersal units of
the diploid cytotype
collected in arid
highlands (A) and of
the polyploid
cytotype collected in
semi-arid littoral
coast (B). Means of
the results obtained
in 2 replicates of 25
seeds ± arithmetical
spread.
95