干旱区生态环境知识资源中心

Genotypic and phenotypic influences were found in local ecotypes of Hordeum spontaneum (wild barley) occurring in the Negev and other parts of Israel. These have varied responses to: (i) post-maturation temperatures and duration to allow afterripening; (ii) amounts of irrigation for germination in winter or summer conditions; and (iii) differences in seedling 'point of no return' and duration of drought tolerance according to ecotype and root length when dehydrated, as in some other annual plant species of the Negev Desert. Seed germination of Plantago coronopus of the Negev was regulated by local desert soils collected, from ten natural locations along the annual average rainfall gradient, from 50 to 325 mm, which affects soil carbon and crust flora and thickness. The afterripening and optimal temperatures for P. coronopus seed germination are affected by post-maturation temperatures, duration, as well. as temperatures and hours of light during wetting. Annual plants in the Negev were found to have different sets of survival strategies of seed dispersal and germination. The genotypic differences and phenotypic plasticity, affected by environmental factors during seed maturation include seed dispersal 'escape' or 'protection' strategies, preventing massive seed collection by seed eaters. The 'opportunistic' or 'cautious' germination strategies reduce the risk to species survival, as only a small part of the large seed bank is 'ready to germinate' after a rain event. The delayed point of no return and seedling drought tolerance may also increase species survival under unpredictable distribution of rain.