Manipulating Panicle Transpiration Resistance to Increase Rice Spikelet Fertility during Flowering Stage Water Stress1
- D. P. Garrity,
- E. T. Vidal and
- J. C. O'Toole2
Rice (Oryza sativa L.) is much more sensitive than other cereal crops to drought stress during the flowering period. Anthesis is reduced when the panicle water potential decreases, resulting in largescale spikelet sterility. Improvement of the crop's capacity to flower successfully during water stress will require the improvement of mechanisms to exploit stored soil water or conserve water by reducing transpiration losses from the panicle. Rice panicles typically have very low resistance to water loss even under severe desiccation. This study explored the effects of increased resistance to panicle transpiration as a tactic to maintain high spikelet fertility when anthesis occurs during a drought period. Cultivar IR36 was grown in each of two environments in a phytotron: 1) a glasshouse room with 85% relative humidity (RH), 29/21°C day/night temperatures, and natural light conditions; and 2) Koitotron cabinets (Tokyo, Japan) with 50% RH, 29/21°C day/night temperatures, and natural light conditions. Three water stress treatments were imposed at flowering in each environment by irrigating at a fraction of potential evapotranspiration. Four treatments were applied for 6 days to emerging panicles: Glassine caps open at both ends (GO), or closed at both ends (GC), aluminum foil caps closed at both ends (AC), or no treatment (C). The panicle treatments reduced panicle transpiration rates from 18 to 78% compared to the control. Spikelet temperatures were increased by 1.0 to 2.5°C by the panicle treatments. In the absence of water stress, spikelet fertility was the same for the C, GO, and GC treatments. Under moderate and severe stress in the glasshouse, GO had slightly but not significantly higher spikelet fertility than C. In the Koitotron, all panicle treatments had lower fertility than C when the flowering plants were drought stressed. The panicle treatments decreased transpiration and increased panicle resistance over a substantial range but did not enhance spikelet fertility in the drought stressed treatments. The results indicate that an attempt to improve flowering-stage drought resistance by breeding morphological changes that increase panicle resistance may not be fruitful.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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