© Benaki Phytopathological Institute
Euphorbia heterophylla
in Greece
29
with 4 ml of distilled water. Petri dishes were
sealed with Parafilm. Seed germination was
determined in growth chambers under con-
stant temperatures of 10, 15, 20, 25, 30, 35,
and 40
o
C with (95μmol m
-2
s
-1
) or without
light. Germination percentage was recorded
1 week after incubation (visible radicle pro-
trusion 1 week after incubation). Each mean
germination test was replicated four times.
Maximum germination (82 to 90%) oc-
curred at temperatures from 25 to 35
o
C with
a drastic decline (<38%) at 15 and 40
o
C (Fig-
ure 3). These results are in line with previous
studies (Bannon
et al
., 1978). Light had no
significant effect on seed germination in the
whole range of temperatures tested (Figure
3). However, the effect of light on seed ger-
mination of this species has been contra-
dictory, with some reports recording no ef-
fect on seed germination (Brecke, 1995) as
opposed to others showing significant pos-
itive effect (Suda and Giorgini, 2000). Appar-
ently, the growth conditions of the mother
plants and both the time and the conditions
of seed storage prior to germination tests
might explain to some extent such discrep-
ancies. In our study, no light dependence for
germination indicates that seeds could ger-
Figure 2.
Fruit and seeds of
Euphorbia heterophylla
: a. Capsule; b. Seeds; c. Longtudinal section of the seed.
Figure 3.
Effect of constant temperature on germination of
Euphorbia heterophylla
seeds incubated in the dark or under a
12-h photoperiod for 1 week. Error bars represent standard error of the means.
0
20
40
60
80
100
10 15 20 25 30 35 40
Germination (%)
Constant Temperature (°C)
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