Abstract
Background and aims - Seed dimorphism is an adaptive feature to harsh environments such as arid and saline habitats. This is explained as an escape from inadequate conditions. In the current study, we investigated the seed germination of a dimorphic species Atriplex inflata Much. (Chenopodiaceae). A. inflata occurs in saline habitats, namely in arid regions. Its bracteoles enclose a brown or a black fruit. This unit constitutes the diaspore.
Methods - Mature fruits were collected from Kelbia (35 degrees 46'06 '' N 10 degrees 07'34 '' E), located in the centre of Tunisia, with semi-arid climate. The effect of cold stratification, nitrate (KNO(3), 10 mM), light, dry storage (for seven months), chemical scarification and salt pretreatment on germination were determined in order to assess the factors that control germination and dormancy.
Key results - The results show that brown fruits germinated rapidly and the final germination percentage was 98% after twenty days. However, germination of black fruits was slower and reached only 19%. This confirms the fact that the difference in morphology is accompanied by a difference in germination capacity and dormancy in A. inflata. Chemical scarification and dry storage increased germination capacity of black fruits. Thus, the black fruit showed a physical dormancy and a non-deep physiological dormancy.
Conclusion - The production of two types of fruit in A. inflata, one dormant and the other non-dormant, is of high ecological importance for the survival of populations. Actually, this ensures both rapid germination (brown fruits) and a permanent seed bank (black fruits), which permit the persistence of the species and population establishment in disturbed environments.