Influence of High Temperature on Seed Yield of Popular Tamil Nadu Rice Cultivars

Abstract

Rice cultivation will be subjected to much warmer environments in near future. In the present study four popular rice cultivars (ADT 46, CO (R) 50, CORH 4 and TKM 9) of Tamil Nadu were exposed to elevated temperature i.e., ambient + 5°C in a Climate Control Chamber from transplanting to harvesting, to quantify its effect on pollen dispersal, viability, pollen tube growth, seed set and seed yield. Exposure of plants to high temperature resulted in early flowering in all the cultivars which were tested. Microscopic analysis revealed that all the pollen related parameters like pollen viability, pollen germination and also pollen tube growth were adversely affected to an extent of 22-47%, 4-13% and 4-12% respectively by the heat stress. Scanning Electron Microscopic analysis revealed the shrivelling of pollen grains under heat stress. In addition to viability, tube growth was also very much affected, as a result the tube could not able to reach the egg cell to fertilize it, causing spikelet sterility (24-72 %). Total number of spikelets per panicle (9- 17%) and number of filled seed per panicle (21-68%) were reduced under high temperature conditions which resulted in reduced seed yield/plant (29-63%) and also harvest index (13-33%). High temperature negatively influenced root and shoot lengths. Among the four cultivars TKM 9 was found to be more tolerant to heat stress compared to other three cultivars.