Long-term protected ‘seed bank’ in dry inflorescences of Asteriscus pygmaeus; Achene dispersal mechanism and germination

The desert annual plant Asteriscus pygmaeus germinates during winter and dries up at the beginning of summer. Its woody stems terminate in inflorescences. The achenes which remain enclosed by the woody bracts are protected against granivors and serve as a ‘seed bank’. Swelling of the cohesion tissue in the receptacle when wet opens the inflorescence and the shrinking of the tissue when dry closes it. This action causes some achenes of the peripheral whorl to become disconnected and later dispersed by the rain and wind. Each season a few achenes are dispersed. Disconnected peripheral achenes were found to germinate to a higher level in comparison with achenes from the peripheral and sub-peripheral whorls which were disconnected shortly before the start of the germination experiments. The ecological importance of these unique dispersal and germination mechanisms is discussed.