水分胁迫下的大豆叶取向

LEAFLET ORIENTATION IN WATER-STRESSED SOYBEANS

通过大田及盆栽实验,初步探讨了植株水分状况对大豆叶取向运动的影响。大豆末端小叶在木质部水势约为-9.1×10~5Pa时,开始呈直立状态,且大水势下降到-14.4×10~5Pa时开始发生倒位现象。随着水分胁迫加剧(超过两个临界值),大比例的末端小叶发生上述两种现象。中午木质部水势与叶片角有显著相关性。实质上,水分胁迫有诱导并加剧避日性叶取向的作用。干旱植株在复水后不到2个小时,其叶取向便可逆转。大豆叶片避日性取向通过降低接收辐射可防止叶温升高和木质部水势的下降.高度避日态并不影响叶片净光合率。

Field and pot experiments were carried out on soybean (Glycine max L. )to study the influence of wafer stress on leaflet orientation. Terminal leaflets were observed to become erect when xylem water potential was approximately -9.1×10~5Pa and then to invert at xylem water potential of about -14.4×10~5 Pa. With more severe water stress a greater proportion of terminal leaflets was affected. Blade angle is strikingly correlated to xylem water potential at midday. Paraheliotropism was substantially induced and became more obvious with the development of water stress. Responses of leaflet orientation are reve sible within 2hs after irrigating droughted plants. The paraheliotropic movement substantially reduced leaflet temperatures and water loss by reducing radiation interception. Advanced sun-avoiding leaflet position didn't affect leaflet net photosynthetic rate.