盐胁迫下高粱新生叶片结构和光合特性的系统调控

以C₄作物高粱为材料，研究了盐胁迫下新生叶片结构和光合特性的系统调控。结果表明：(1)盐胁迫导致成熟叶和新生叶水势、光合速率、气孔导度明显下降，光抑制程度略有增强；并且新生叶片上下表面气孔密度均增加。(2)非盐胁迫条件下，成熟叶遮荫对其自身和新生叶水势影响不显著，但两者光合速率、气孔导度和叶片可溶性糖含量降低，对强光敏感性增强；同时，降低成熟叶光强还显著降低新生叶的叶片厚度、气孔密度、维管束鞘细胞表面积；(3)盐胁迫下成熟叶遮荫诱导的新生叶结构和光合功能变化与非盐胁迫条件下趋势相似。双因素方差分析显示，盐胁迫下成熟叶遮荫能明显加剧高粱成熟叶和新生叶两者光合速率和气孔导度的下降并增强对强光的敏感性。因此认为，盐胁迫下高粱新生叶片的结构和光合功能均受到系统信号调控；提高成熟叶所处环境光强有助于改善盐胁迫下新生叶发育和碳同化能力，并一定程度上缓解光抑制。这对理解盐胁迫下高粱抗盐性具有重要意义。

Systemic Regulation of Anatomic Structure and Photosynthetic Characteristics of Developing Leaves in Sorghum Seedlings under Salt Stress

The influences of a systemic signal, from mature leaves, on the photosynthetic characteristics of developing leaves in sorghum seedlings under salt stress were carefully investigated. Salt stress significantly decreased water potential, net photosynthetic rate, stomatal conductance and slightly increased extent of photoinhibition both in mature and newly developed leaves. In newly developed leaves, stomatal density of both adaxial and abaxial surfaces increased. Under non-salt stress condition, water potential both in mature and newly developed leaves was hardly affected when mature leaves exposed to weak light. However, carbon assimilation, stomatal conductance, soluble sugar content decreased markedly and the extent of photoinhibition increased largely in mature leaves and newly developed leaves due to the shading of mature leaves. Meanwhile, stomatal density, mesophyll thickness and surface area of bundle sheath decreased in newly developed leaves when light intensity decreased for mature leaves. In salt-stressed group, changes in photosynthetic structure and function had a similar tendency with that in non-salt stress group, but a further decline in photosynthesis was observed. Two-way ANOVA among these four treatments showed that there was a synergistic effect between salt stress and high irradiance which impaired the photosynthetic ability more heavily and enhanced photoinhibition. Accordingly, we concluded that there is a systemic regulation on the photosynthetic structure and performance of newly developed leaves under salt stress. The enhancement of the light intensity of mature leaves is very important for the improvement of development, carbon assimilation and the alleviation of photoinhibition in newly developed leaves under salt stress.