Spikelet Sterility and Flowering Response of Rice to Water Stress at Anthesis

Water deficits at the anthesis stage of rice (Oryza sativa L.)induce a high percentage of spikelet sterility and reduce grainyield. This study attempted to elucidate the direct effectsof water stress on panicle exsertion, spikelet opening, andspikelet desiccation leading to spikelet sterility. A well-wateredtreatment and two water stress levels were imposed in pot-grownplants of IRAT 13 (upland cultivar) and IR20 (lowland cultivar)at the time of flowering under greenhouse conditions A cultivar difference was observed in the flowering responseto water stress with a high sensitivity in IR20. The time courseof panicle exsertion showed an inhibitory effect due to thelow panicle water status. Low panicle water potentials significantlyreduced the number of opened spikelets. Spikelet opening wascompletely inhibited at panicle water potentials below –1·8MPa and –2·3 MPa in IR20 and IRAT 13, respectively.However, the peak spikelet opening time in a day was not influencedby the stress treatment. Spikelets in stressed panicles wereobserved to remain open for a longer period than in the well-wateredpanicles. The role of turgor in spikelet opening is also discussedin the study. At low panicle water potentials, severe desiccationof spikelets and anthers was noted. The deleterious effectsof water deficits on spikelet opening and spikelet water losscontributed to reduced spikelet fertility Oryza sativa L., rice, spikelet sterility, flowering, water stress, panicle water potentials, turgor potentials, desiccation