Adaptive strategies of plants to drought and high-temperature conditions and their control for plant cultivation in arid area

点击翻译按钮获取中文摘要

To obtain fundamental knowledge on the adaptive strategies of plants and to develop new methods and plants that could be used for plant cultivation in arid area, we studied the mechanisms for deep-sowing tolerance of seedlings, root hydrotropism, and high-temperature-induced male sterility.Wheat seedlings emerge from the soil by elongating their first internodes. A variety of wheat tolerant to deep-sowing conditions was more sensitive to gibberellin (GA); the first internodes treated with GA elongated longer than 40 cm in the dark. Accordingly, the seedlings successfully emerged even from 40-cm depth in the soil. This GA response of the wheat was achieved by accompanying simultaneous uptake of potassium from the culture media for cellular osmoregulaiion and spiral growth for reducing mechanical impedance in the soil.We established an experimental system for the study of hydrotropism in Arabidopsis roots and revealed the involvement of abscisic acid, auxin and waving response with hydrotropism. In addition, we found that moisture gradient or water stress caused immediate degradation of the starch anchors, amyloplasts, in columella cells of Arabidopsis roots, which reduced the responsiveness of roots to gravity and thus allowed them to exhibit hydrotropism without interference by gravitropism. Also, we isolated unique hydrotropic mutants of Arabidopsis, which enabled us to dissect molecular mechanism for hydrotropism in seedling roots.We found that high temperature during floral organogenesis induced male sterility in barley. In relation to the male sterility, high temperature inhibited the expression of histone H3,H4 and glycine-rich RNA binding protein genes whose expressions are dramatically induced just before anther development. Furthermore, it was suggested that the early development and differentiation of barley anthers are hypersensitive to high temperature stress due to the inhibited transcriptions.