Influence of water regime and photoperiod treatments on resource allocation and reproductive successes of two annuals occurring in the Negev Desert of Israel

Two annuals from the Negev Desert, Plantago coronopus and Anastatica hierochuntica, were grown outdoors under two irrigation regimes and photoperiod treatments of 16, 12 and 8 h, and natural daylength. Measurements included whole plant mass, resource allocation, fitness payoff, maternal effects of daylength and water regimes on seed germination. In both species seed germination percentages were affected by maternal and environmental factors. P. coronopus showed higher plasticity according to the daylength; plants under long days were larger and produced more seeds that germinated to higher percentages. The plasticity shown in A. hierochuntica correlated mainly to water regime and less to daylength. Both species are common in the arid environment, but P. coronopus, which has a stronger response to daylength, is more widely distributed.