Effect of shade treatments on morphology, photosynthetic and chlorophyll fluorescence characteristics of soybeans (Glycine max L. Merr.)

Abstract

In maize soybean intercropping-system maize plants significantly increase the shade density at soybean canopy, and few people studied the threshold level of shade for sustainable production of soybean in this system. This experiment was started to determine the effect of four different shade treatments T75 (75%); T50 (50%); T25 (25%); T0 (0%, control) on morphology, physiology and yield of soybean plants. Relative to T75, treatments T25 and T0 significantly increased the stem diameter and stem breaking strength while plant height was decreased. The chlorophyll a, chlorophyll b, and chlorophyll a + b, photosynthetic and chlorophyll fluorescence characteristics were improved as shade decreased, and maximum values were observed in T25 and T0. Similarly, enzymatic activity of Rubisco was accelerated from T75 to T0. However, genes related to sucrose synthesis (SS and SPS) were down-regulated by increasing shade (T75). Importantly, non-significant differences were measured for seed-yield between T25 and T0, and the plants of soybean under T25 produced 88% of T0 yield. Overall, these results implied that agronomist should develop an appropriate intercropping planting pattern where the maximum shade density ranges from 20 to 30 % to obtain higher seed yield of soybean crop under intercropping-system.