Regulation of photosynthetic function in maize plants under spatially heterogeneous light environment at reproductive stage

Background: To copy with spatially heterogeneous light environment, photosynthesis of plants can be regulated systemically. Till present, most of these studies were carried out with various plants in the vegetative growth period. Yet the regulation of photosynthesis at reproductive stage has remained elusive under spatially heterogeneous light environment in the field. Methods: Therefore, the changes of light intensity within canopy, chlorophyll content, gas exchange and chlorophyll a fluorescence transient were carefully investigated at heading and grain-filling stages of maize under various planting densities. Results: In this study, high planting density of maize induced significantly spatial heterogeneity of light environment within canopy. Chlorophyll content, photosynthetic capacity and photosystem II performance in the ear leaf and the fourth leaf below the ear were reduced apparently with the increase of plant density. Moreover, these differences between the both leaves were enlarged with increasing plant density. After the tassel and top leaves of the maize plants were removed (RTL), the spatial heterogeneity of the light environment decreased. The photosynthetic capacity and photosystem II performance in the ear leaf decreased slightly after RTL, while these parameters in the fourth leaf below the ear were improved considerably. Obviously, the removal of the tassel and top leaves reduced the spatial heterogeneity of photosynthetic function of maize plants. Conclusions: Taken together, these results demonstrate that maize plants could enhance the spatial heterogeneity of their photosynthetic function to adapt heterogeneous light environment at the reproductive stage; the systemic regulation of photosynthesis under spatially heterogeneous light environment could be weakened by reproductive growth.