关键词: 景天酸代谢植物(CAM植物), 光合作用, CO₂浓度, 八宝景天, 糖代谢

Abstract: A field experiment was conducted to compare the effects of planting geometries on the canopy structure, functional properties and yield of the spring maize variety Zhengdan958 planted under high density condition. Four planting geometries were adopted: one plant per clump opposite in adjacent rows (DD), one plant per clump staggered in adjacent rows (DC), two plants per clump opposite in adjacent rows (SD), and two plants per clump staggered in adjacent rows (SC). The results indicated that in the SD and SC treatments, the vertical distribution of canopy exhibited a spindleshaped morphological tendency with an accumulation of the dry matter in stem and leaf in the layer of 0-90 cm (under ear leaf) and 90-180 cm (ear leaf)， the stemleaf angle under the lamina of the ear increased significantly by 2.4°-3.4°. The treatments clumps with two plants (SD and SC) provided more niche space for each plant and enhanced tolerance to highdensity planting. Compared with the conventional DD planting pattern, leaf area index (LAI) and chlorophyll relative content (SPAD) values before the filling stage for clumped and scattered planting geometries were lower, while the opposite phenomenon occurred at the filling stage. Compared to the control, the grain yields in these clumped and scattered planting treatments were increased by 11.2%-12.7% but were not significantly different, largely due to increased lodging resistance and higher ear number and thousandkernel weight. Our results confirmed that the population structure and shoot morphological structure under highdensity condition were effectively regulated by the clumped and scattered planting geometries, which improved photosynthesis capacity of middledown leaves at the filling stage and revealed a great potential of highyielding structure and tolerance to highdensity planting.

Key words: Hylotelephium erythrostictum, carbohydrate metabolites, crassulacean acid metabolism plant (CAM plant), CO₂ concentration, photosynthesis