Effects of low temperature on pepper pollen morphology and fertility: Evidence of cold induced exine alterations

The effects of low night temperatures on pollen viability and pollen grain morphology were investigated in bell pepper (Capsicum annuum, L.) commercial hybrids 'Latino' and 'Novi'. Night temperatures of 10 and 15 degrees C decreased pollen viability, estimated by an in vitro assay and acetocarmine staining, and by decreased seed number per fruit. At anthesis, in a separate experiment, pollen grains that developed at low temperature (25/14 degrees C, day/night) were smaller and appeared aggregated and shrunken with a differently sculptured exine which was thinner than the pollen exine developed at the 30/20 degrees C temperature regime. The results obtained when a 10 degrees C night-temperature treatment was applied to plants grown at 30/20 degrees C with flower buds of different diameters, indicated that meiosis and the young microspore stage were affected. However, the later phases of microspore development and pollen maturation were not affected by the same temperature treatments.