小麦叶片光合作用与其渗透调节能力的关系

在缓慢干旱条件下,小麦叶片渗透调节能力在一定范围内随胁迫程度的加剧而增加,而在快速干旱下,渗透调节能力丧失。小麦叶片通过渗透调节使光合速率和气孔导度对水分胁迫的敏感性降低,叶片维持较高的电子传递能力、RuBP羧化酶活性和叶绿体光合能量转换系统活性,并推迟了小麦叶片光合速率受气孔因素限制向叶肉细胞光合活性限制转变的时间。

Relationship Between Photosynthesis and Osmotic Adjustment of Wheat Leaves

Two cultivars (drought-resistant cultivar Fengkang 13 and drought-sensitive cultivar Zhengyin 1) of wheat in pots were used to study the relationship between photosynthesis and osmotic adjustment.The experimental results indicated that the sensitivity of leaf water potential to slow soil drought was less than that to fast soil drought, and at the same drought speed, the sensitivity of Zhengyin 1 was higher than that of Fengkang 13 (Fig. 1). Under slow drought condition, osmotic adjustment of wheat leaves increased to a certain extent with the decreasing of soil water content, and was absent under fast drought condition (Table 1). By the osmotic adjustment of wheat leaves, the sensitivity of photosynthetic rate and stomatal conductance to water stress decreased, and the time needed for the shift of drought inhibition of photosynthetic rate from stomatal limitation to the photosynthetic action of mesophyll cells was delayed (Fig. 2 and 3). It was shown that wheat leaves under slow drought condition could maintain higher apparent quantum yield (Fig. 5), RuBP carboxylation efficiency (Fig. 6), RuBP regeneration (Fig. 6), electric transport capacity (Table 2)and fluorescence yield (Table 2) than those under fast drought condition. The results indicated tha tthe osmotic adjust ment of wheat leaves under water stress could counteract the adverse effect of drought on stomatal movement and the activities of photosynthetic apparatus, and thus help to maintain the photosynthetic rate at or near the normal level.