Genotypic, Phenotypic and Opportunistic Germination Strategies of Some Common Desert Annuals Compared with Plants with Other Seed Dispersal and Germination Strategies

Abstract

In the Negev Desert with unpredictable distribution and low amounts of rain, Spergularia diandra is a common annual. Several factors may regulate its low germinability, such as genotypic and phenotypic factors during seed maturation, including seed position and plant age affecting seed coat colour, day length, temperature, and post maturation conditions. Seed dispersability may be influenced by the diversity of seed coat structure and relative weight within the three genotypes and the three phenotypes. The opportunistic strategy and low germination regulated also by light and temperature, and the quantitative long day response for flowering, allow this species to emerge and survive in very great numbers in large areas. It produces large numbers of tiny seeds which disperse after maturation and 'escape' from massive consumption. In Schismus arbicus, another common plant in the Negev, the maternal and environmental influences during seed maturation, and the escape strategy of seed dispersal combined with an opportunistic strategy for germination and flowering are similar to S. diandra. In contrast are plants that protect their seeds which are dispersed by rain and have a 'cautious' dispersal and germination strategy. An example is the rare Blepharis spp. which produces a few relatively large seeds. Mesembryanthemum nodiflorum is an example of a plant with intermediate strategies of seed dispersal and germination.