异质性光下玉米光合补偿限制与光合同化物的关系

Relationship between photosynthetic compensation limitation and photoassimil-ates of maize under heterogeneous light

在异质性光环境中,植物通常会表现出光合补偿现象以增强对光能的利用。而有些植物的光合补偿会受到明显的限制,但其中所涉及的生物学特征和机制并不清楚。本研究以光合补偿受限的玉米植株为材料,对比分析了异质性光(HL)和同质性光(FL)下未遮光叶片的解剖结构、气体交换特征、光合同化物及关键合成酶含量,探讨光合补偿限制相关的生物学过程及其机制。结果表明:与FL相比,HL处理下叶片的厚度、相对叶肉细胞面积、相对维管束鞘细胞面积、相对维管束面积和维管束鞘与维管束接触长度较小。同时,HL处理下叶片的净光合速率和气孔导度较低。此外,HL处理下叶片的淀粉含量较低,蔗糖含量变化不大,而蔗糖磷酸合成酶含量较高。因此,HL处理下光合补偿受限与叶片解剖结构限制及气孔行为相关。光合补偿受限时,未遮光叶片中光合产物合成减少,但其会更多地向蔗糖合成方向分配。然而,由于叶片解剖结构的限制,叶片蔗糖的输出能力较弱。这些结果为进一步解析植物适应异质性光环境的特征和机制,以及选育适合间套作等栽培模式的品种提供了基础。

In natural and field environments,different parts of plants are exposed to various light conditions,such as heterogeneous light.Leaves exposed to more favorable light conditions typically improve the efficiency of plant light energy use by enhancing photosynthesis in heterogeneous light environments,a phenomenon known as the photosynthetic compensation response.Photosynthetic compensation in some plants is limited;however,the biological characteristics and mechanisms involved are unclear.In this study,maize plants with limited photosynthetic compensation were used in a pot experiment.A nylon mesh with a light transmittance of 25%was used to shade maize plants unilaterally and two treatments of homogeneous light(FL)and heterogeneous light(HL)were set up.We compared the anatomical structure,gas exchange characteristics,photosynthetic assimilates,and key synthase contents of unshaded leaves under HL and FL treatments.The results showed that leaf thickness,relative mesophyll cell area,relative bundle sheath cell area,relative bundle area,and vascular sheath-vascular bundle contact length of leaves under the HL treatment were smaller than those under the FL treatment.Meanwhile,the net photosynthetic rate and stomatal conductance of leaves under the HL treatment were lower.In addition,the starch content of the leaves in the HL treatment was lower,the sucrose content was slightly changed,and the sucrose phosphate synthetase content was higher.Therefore,the restriction of photosynthetic compensation under HL treatment is related to the limitation of leaf anatomical structure and stomatal behavior.When photosynthetic compensation was limited,the synthesis of photosynthetic products in the unshaded leaves decreased;though,more photosynthates were allocated to sucrose synthesis.However,owing to morphological and anatomical limitations,the output capacity of leaf sucrose was weak.These results provide a basis for further analyses of the characteristics and mechanisms of plant adaptation to heterogeneous light environ-ments and for breeding varieties suitable for intercropping.