Increased Ring-Shaped Chalkiness and Turgor Maintenance in Rice Grains Grown Under Typhoon/Foehn-Induced Dry Wind Condition.

In rice (Oryza sativa L.) plants, we found that chalky kernels increase by Typhoon/Foehn-induced dry wind after insufficient light in grain filling.  We subjected rice plants to low light intensities and water deficit in a paddy field where a plastic film-covered greenhouse having an electric fan was constructed over the plants. The fan was used to generate dry high-speed wind.  Additionally, growth chamber experiment was conducted with plants in pots to study the water status under the dry wind condition by combining in situ turgor (P) measurements with a cell pressure probe in developing endosperms with the water potential measurements.  It was confirmed that shade followed by 24 h dry wind treatment produced the largest number of ring-shaped chalky kernels, compared to each treatment of low light intensities or low VPD wind.  Both field and growth chamber experiments indicated that an increase in ring-shaped chalky kernels was accounted for a decrease in perfect kernels through dry wind treatment.  We discovered that the inner endosperm cells, where a high frequency of chalkiness was observed, spatially maintained P prior to the chalky formation at low water potentials by dry wind without any significant decline of grain weight.  Dry wind treatment reduced photosynthesis due to a partial stomatal closure after water deficit developed.  However, these events including the declined plant water status were recovered close to the level of control plants after the dry wind was stopped.  We conclude that P maintenance contributes to grain development at water deficit under Foehn conditions.  Since the number of ring-shaped chalky kernel became larger under dry wind condition after shade, our findings suggest that the regulatory mechanism of endosperm P by osmotic adjustment has a role in temporally altering the metabolisms on starch accumulation in endosperms under Foehn-induced water deficit condition.