干旱条件下大豆叶水分状况与渗透调节

WATER RELATIONS AND OSMOTIC ADJUSTMENT IN SOYBEAN PLANTS UNDER DROUGHT STRESS

本试验利用夏大豆品种鲁豆４号和小粒豆１号为材料，研究了叶片水分状况和渗透调节对水分胁迫的响应特性。土壤的缓慢水分胁迫降低了两个大豆叶片的最低水势［ψｗ（ｍｉｎ）］及相对含水量（ＲＷＣ），鲁豆４号降低的程度大于小粒豆１号，说明鲁豆４号的御旱能力不及小粒豆１号。在分枝期和开花期，水分胁迫降低了叶片的饱和渗透势（ψｓ°），叶片仍可维持一定的膨压，说明大豆在此生育期内具有渗透调节能力；结荚期和鼓粒期水分胁迫只使ψｓ°轻微降低，膨压则急剧减小或消失，甚至出现负值，说明此期渗透调节能力很小或完全消失。在快速土壤水分胁迫下，两大豆品种均无渗透调节能力。

Responses of leaf water relations and osmotic adjustment to water stress were studied with two soybean (Glycine max) cultivars- summer soybean Ludou No. 4 and small - grain soybean (SGS) No. 1. Minimum leaf water potential (ψw (min) and relative water content (RWC) of both cultivars were reduced along with gradually developing of soil water stress, yet in Ludou No. 4 (ψw(min) and RWC reduced more quickly than those in SGS No. 1,applying that drought resistance of Ludou No. 4 was less than SGS No. 1. Durins branching and flowerins periods, the saturated osmotic potential (ψs°)of leaves for both cultivars were reduced along with gradually develuped water stress. As a result, the turgor pressure of leaves could be maintain positive, suggesting that osmotic adjustment existed in soybean plants during these periods. During pod - setting and seed - filling periods, however, the ψs° reduced just slightly owing to water stress. as a result, the turgor pressure sharply reduced, disappeared, even turned to negative, suggestins that the osmotic adjustment was rather limited or absent at all during these two periods. As water stress developed very quickly, osmotic adjustment could not be observed in neither of the two cultivars.