ECOLOGICAL SIGNIFICANCE OF THE AERIAL SEED POOL OF A DESERT LIGNIFIEDANNUAL, BLEPHARIS-SINDICA (ACANTHACEAE)

Reproductive traits of a lignified annual plant, Blepharis sindica wer e studied in relation to the formation of an 'aerial seed pool' on dea d plants in an arid grassland in the Thar Desert of northwestern India . The dead plants remained standing on the soil surface and retained f ruits for more than one year. Aerial seed pools developed about 6 cm a bove the ground. There were no seed pools on or below the ground surfa ce. Only 5.7% of seeds died on dead plants because of insect predation or fungi infection during one year. Seed release was cued by rainfall , and a fraction of seeds on the aerial seed pools was released in eac h rainfall event. After 13 rainfall events during the monsoon season, 25% of seeds was still retained on the plants. Seed predation on the g round surface was intensive; all cones placed on the soil surface were removed within four days, and 97% of fruits were removed within 10 da ys. Fifty percent of seeds germinated within 3.5 h, and there were no differences in viability and time required for germination between fir st year seeds and older seeds. The results indicate that the aerial se ed-holding on dead plants is an available way to avoid seed predation in harsh desert environments where seed predation is intense and favor able periods for growth are temporally limited and unpredictable.