Structure and function of the mucilaginous seed coats of Plantago coronopus inhabiting the Negev Desert of Israel

Plantago coronopus var. crassipes is a common annual plant in many areas of the Negev Desert highlands. The dry seed coat cross section and surface structure of P. coronopus seeds before the first wetting were examined by SEM, as were the freeze-dried mucilage and adhesion of the seeds to the soil crust. When wetted, the mucilaginous layer forms, and seeds on the soil surface adhere to the soil crust. Some P. coronopus mucilaginous seeds may be dispersed by rain, even after less then 10 min of wetting. The dry seeds can float on run-on water for 10-44 min and are then dispersed along runnels into depressions, or adhere within a few minutes to the wet soil crust near the dry mother plant. Seeds matured on dry plants in a natural habitat in spring 1995, germinated in December 1995 to 96% after 72 h at 20 degrees C in light, but only to 2% in dark. The importance of mucilaginous seeds for the survival of the plant species under desert conditions is discussed.