Post-x-irradiation effects on petunia pollen germinating in vitro and in vivo

Abstract

The germination of Petunia hybrida L. pollen grains in germination medium, containing 10% sucrose and 0.01% H 3BO 3, was linearly related to relative humidity (RH): being minimal at 0% RH and maximal at 100% RH. The low germination at 0% RH was completely restored after transfer to 100% RH. Germination in medium decreased with increasing X-ray exposures between 0 and 400 kR. This decrease was caused by pollen rupture. No in vitro germination occurred at exposures of 400 kR and more. The radiosensitivity of pollen in vitro was minimal at 80% RH. Transfer of pollen to the stigma post-X-irradiation resulted in resistance to much higher exposures of irradiation (750 kR). The differences in radiosensitivity of the pollen germinated in vitro and in vivo are due possibly to the differences in composition of the germination medium and the stigmatic exudate. Pollen tube growth of irradiated pollen after compatible or incompatible pollination at first showed retarded then normal tube growth. A conclusion is that X-irradiation of pollen cannot influence the characteristics of pollen tube growth after compatible or incompatible pollination.