High temperature stress effects on pollens of rice (Oryza sativa L.) genotypes

Flowering in rice plants is highly sensitive to temperature changes. High or low temperature can affect fertilization and seed production, and consequently rice yield. Tolerance to high temperature stress can vary among different genotypes. Pollens of two groups of genotypes (Group-I of Ranjit, Pooja, and Swarna and Group-II of Annapurna, Khitish and Satabdi, which are suitable for lowland and upland conditions, respectively) were studied after subjecting the plants to six different day/night temperature regimes (25/15, 30/20, 35/25, 40/30, 45/35 and 50/40 degrees C with a constant diurnal temperature variation of 10 degrees C) for three days during panicle initiation. During anthesis of each genotype, various morphological, physiological and biochemical characteristics of pollens were assessed. High temperatures above 35/25 degrees C adversely affected panicle extrusion, flowering period, and number of anthesing (opened) spikelets; there were significant decreases in viability and tube length of pollens, poor anther dehiscence and reduced number of pollens on stigma. Notably, the adverse effect of high temperature stress was more on the pollens of lowland genotypes (Group I) than on those of upland genotypes (Group II). There were both qualitative and quantitative changes in pollen proteins of these genotypes, which probably led to the differential loss of viability. The loss of pollen viability was highest in Swarna among the genotypes examined. The present study clearly suggests that tolerance to higher temperature stress during the development of reproductive organs varied, with viability of pollens distinctly better in the upland genotypes than the lowland genotypes. (C) 2014 Elsevier B.V. All rights reserved.