Effects of Epibrassinolide and Abscisic Acid on Sorghum Plants Growing under Soil Water Deficit : II. Physiological basis for drought resistance induced by exogenous epibrassinolide and abscisic acid

[摘要] It was reported that pretreatment with abscisic acid (ABA) increased the drought resistance of sorghum plants and that 22R, 23R epibrassinolide (EBR) enhanced the effects of ABA. To explore the mechanistic basis for drought resistance induced by ABA and/or EBR, the effects of the treatments on water retention were examined using the transpiration decline curve of excised leaves. The results are summarized as follows. Spray treatment with ABA or EBR increased in situ relative water content (RWCi.s). RWCi.s in ABA+EBR-treated plants was larger than in plants treated with ABA or EBR alone. This suggested that EBR enhanced the effect of ABA. Using the transpiration decline curve, we found that both ABA and EBR diminished the stomatal transpiration rate, but continued it at a lower RWC for a longer time. This effect of ABA + EBR was also larger than that of ABA or EBR alone. ABA treatment significantly decreased the cuticular transpiration rate. EBR did not show this effect by itself, but enhanced the effect of ABA. The effects of these treatments on glaucousness of the leaf surface coincided well with those on cuticular transpiration. This suggests that ABA promoted wax deposition on the leaf surface. Relative water content when stomata closed was in the order of Control > EBR > ABA > EBR + ABA. This suggests that treatment with EBR, ABA and their combination not only increased water retention but also enhanced physiological tolerance to low water status. Synergistic interaction between ABA and EBR was observed in all the instances examined. The increase in water maintaining capacity and enhanced tolerance accounted for the drought resistance reported in the previous paper.

[学科分类] 农业科学（综合）

[关键词] Abscisic acid;アブシジン酸;Brassinolide;気孔蒸散;Cuticular transpiration;クチクラ;Drought resistance;ソルガム;Sorghum;耐乾燥性;Stomatal transpiration;ブラシノライド;Water stress;水ストレス