Explosive Anther Dehiscence in Ricinus communis L. Involves Cell Wall Modifications and Relative Humidity

Explosive anther dehiscence in Ricinus communis L. (castor bean) was analyzed with regard to changes in anther wall cell structure and to shifts in relative humidity. The single cell layer of the anther was made up of four cell types based on shape and wall thickening. The major type present, except at the site of the stomium and connective tissue, was isodiametric cells with lignified inner tangential and lateral walls. Another type situated near the stomium had five to 10 rings of lignin. Cells at the stomium and connective tissue, the third and fourth types, had no lignin and were covered with a thicker exterior cuticle than other sites. Explosive dehiscence may be triggered by a rapid dehydration of thin cuticle cells, which generates structural changes in these cells, forcing separation of the anther at the stomium. Pressure released by the stomium opening causes the anther walls nearest the filament to snap together, forcing pollen to be launched. Relative humidity inhibited anther opening and decreased the distance pollen was launched. Thus, patterns of cell differentiation in the single-layered anther wall of R. communis L. appear to be responsible for explosive pollen release. Both anther opening and distance pollen is launched are influenced by relative humidity.