Diurnal Change in Water Droplets Adhering to Rice Panicles at the Booting Stage

[摘要] Many water droplets adhere to the surface of a rice panicle located inside the protective sheath of flag-leaf at the booting stage. Since the adhering water is formed by the exudation of liquid water from the plant, we can expect that the amount of adhering water varies diurnally with the change of root pressure. To test this hypothesis, we examined the amount of the adhering water and the bleeding sap from the cut surface of the stub for 24 hours. Wetland rice cultivars, Akenohoshi and Ukonnishiki, were grown under submerged and water stressed soil conditions. The amount of adhering water changed diurnally in response to the potential evapotranspiration : the amount increased during the night and decreased during the day. A similar trend was also found in bleeding rate, except under drought conditions where both bleeding and adhering water were negligible. Furthermore, the adhering water increased proportionally with the increase of bleeding sap during the night. Bleeding occurs when root pressure develops. These results suggest that the adhering water is formed through the efflux of water under root pressure during the night, and is lost by transpiration during the day.

[学科分类] 农业科学（综合）

[关键词] Adhering water;イネ;Bleeding;出液;Booting stage;穂ばらみ期;Oryza sativa;水含量;Rice;水ストレス;Water content;幼穂;Water stress;Young panicle