B. Mandak et P. Pysek, The effects of light quality, nitrate concentration and presence of bracteoles on germination of different fruit types in the heterocarpous Atriplex sagittata, J ECOLOGY, 89(2), 2001, pp. 149-158
1 We investigated the effect of light quality, nitrogen supply, fruit size
and age on germination of the three types of fruit produced by Atriplex sag
2 Regardless of fruit type, seed germination was significantly reduced in t
he dark. Light quality had no significant effect on germination of seeds fr
om fruit types A and B, both of which are dormant, but seeds from fruit typ
e C, which are non-dormant, germinated better in green light (low photon fl
ux and red : far-red ratio, simulating conditions in the canopy) than in wh
3 Optimum nitrate concentration differed between seed types but, for all, g
ermination was reduced at the highest concentration used.
4 The effects of cold stratification and its interaction with light and nit
rogen effects were also studied. Strong interactions between stratification
and light were found in all seed types but other interactions were less fr
5 Three size classes of type C fruit showed similar final germination perce
ntages but large seeds germinated more slowly.
6 The effect of seed age was highly significant: over a 3 year period, the
germinability of dormant seeds (types A + B) increased while that of non-do
rmant seeds (type C) fell.
7 The salt concentration in bracteoles of freshly ripened fruits was too lo
w to mediate an inhibitory effect on germination. Moreover, the first autum
n rain would be sufficient to remove all the salt from bracteoles.
8 Differences between fruit types in depth of dormancy, and in response to
the quality of light and to nitrate concentration in the soil, allows A. sa
gittata to respond to the spatial and temporal variation in environmental c
onditions encountered by this annual of disturbed habitats.