Amounts of winter or summer rain triggering germination and 'the point of no return' of seedling desiccation tolerance, of some Hordeum spontaneum local ecotypes in Israel

摘要

Three generations of ecotypes of Hordeum spontaneum (the wild progenitor of cultivated barley) originating from different locations in Israel were grown under the same environmental conditions at Sede Boker. The amount of rain or irrigation requiredfor seed germination in the field in winter and summer, and the desiccation tolerance of seedlings of different ecotypes at various developmental stages and drought periods, were investigated. There was a relationship between the ability for germinationand seedling emergence after small amounts of rain in winter (10-15 mm), and the desiccation tolerance of seedlings for 1-3 weeks. As rain is low and unpredictable at this time, it is an advantage for seedlings to be able to survive dry conditions and still have the ability to develop adventitious roots and renew coleoptile growth after desiccation. Under summer conditions, seeds require much more water to trigger germination than in winter, and soil water content needs to be higher. It is suggested that in H. spontaneum ecotypes, survival mechanisms have evolved which regulate the proper time of germination, and give the seedlings an ability to overcome a period of drought.