Aerial seed bank and dispersal traits in Anthemis chrysantha (Asteraceae), a critically endangered species

Mature plant density and fruit production were monitored in the main population of four successive cohorts of the endangered winter annual Anthemis chrysantha (Asteraceae) in southeastern Spain. Experiments were conducted with artificial rainfall and a wind tunnel to determine the temporal and spatial dispersal pattern of the species and the relationship with rain and wind.     

Ombrohydrochory: Rain-operated seed dispersal in plants – With special regard to jet-action dispersal in Aizoaceae

The present review describes the ombrohydrochoric dispersal syndrome in plants, i.e. seed expulsion by raindrops. There are two different ombrohydrochoric dispersal modes – dispersal by rain wash and by ballistic forces. Both have been reported from the understory of tropical and temperate forests, from wetlands and from deserts, and from numerous families and genera. A special form of ombrohydrochoric dispersal is the jet-action rain-operated seed dispersal mechanism which is restricted to the semi-desert ice plants, Aizoaceae, one of the major families of the angiosperms. Within this family, 98% of the species possess hygrochastic capsules with an ombrohydrochoric seed dispersal mechanism which in part are also responsible for the remarkable speciation burst and radiation. The highly complex capsules open when wet, and the seeds are expelled by a ‘jet action’ with the kinetic energy of raindrops. The halves of the covering membranes of a locule form a nozzle near the centre of the capsule which serves as a jet. Drops of water falling on the distal opening (after the locule has been filled with water) result in an explosive expulsion of water droplets and seeds through that jet. More seeds are dispersed further away from the capsule than in those capsule types without such a jet mechanism.