Abstract:
In natural and field environments, different parts of the plant are exposed to different light conditions, i.e. heterogeneous light. Leaves exposed to more favorable light conditions often improve the efficiency of plant light energy use by enhancing photosynthesis under heterogeneous light environments, a phenomenon known as the photosynthetic compensation response. The photosynthetic compensation of some plants is obviously limited, but the biological characteristics and mechanisms involved are not clear. In this study, maize plants with limited photosynthetic compensation were used as materials, and a pot experiment was conducted. The 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 the leaf thickness, relative mesophyll cell area (
SMC), relative bundle sheath cell area (
SBSC), relative bundle area (
SVB) and bundle sheath and bundle contact area (IL
BSC-VB) of leaves under HL treatment were smaller than those under FL treatment. Meanwhile, the net photosynthetic rate (
Pn) and stomatal conductance (
Gs) of leaves under HL treatment were lower. In addition, the starch content of the leaves under HL treatment was lower, the sucrose content was little changed, and the sucrose phosphate synthetase (SPS) content was higher. Therefore, the restriction of photosynthetic compensation under HL treatment is related to the restriction of leaf morphological and anatomical structure and stomatal behavior. When the photosynthetic compensation was limited, the synthesis of photosynthetic products in the unshaded leaves decreased, but more photosynthate was allocated to sucrose synthesis. However, due to morphological and anatomical limitations, the output capacity of leaf sucrose was weak. These results provided a basis for further analysis of the characteristics and mechanisms of plant adaptation to heterogeneous light environment, and for breeding varieties suitable for intercropping.