Effects of High Temperature Stress on Brassica Pollen: Viability, Germination and Ability to Set Fruits and Seeds

Pollen grains of Brassica juncea (L) Czern. were exposed to high temperature (45, 60 and 75°C, for 4–24 h) and their viability [using the fluorochromatic reaction (FCR) test], germination, and ability to set fruits and seeds were investigated. High temperature up to 60°C did not affect pollen viability; these pollen samples germinated on the stigma and produced fruits and seeds. There was no correlation between viability and seed set in pollen samples exposed to 75°C; they showed only about 25% reduction in viability but failed to germinate on the stigma and, consequently, to set seeds. However, these pollen samples induced parthenocarpy. A clear relationship between viability and seed-set was observed when the extent of retention of fluorescence in pollen over a 2-h period was used to assess viability. The fluorescence was retained even after 2 h in pollen samples which induced seed-set, while in those which failed to induce seed-set the fluorescence was lost in about 60 min due to the leakage of fluorescein. Thus, in stressed pollen, the extent of retention of fluorescence may give a better indication of pollen function than initial fluorescence, as is being done routinely in FCR test.