Effects of shade and drought stress on soybean hormones and yield of main-stem and branch
Multiple frequently interactive stress factors naturally influence plant due to global change. The leaf’s hormone concentrations, main-stem and branch yield response to the combination of shade and drought were studied in a greenhouse experiment during 2009 and 2010 seasons. Pot experiments were conducted under shade of maize (LI) and normal irradiance (HI). Shade stress was removed once maize was harvested. Manipulative progressive soil drying period at branching stages under good soil conditions (HW) and water stress treatment (LW) were applied in 2010, while well-watered (WW) and moderate drought (MD) were applied in 2009. Under shade stress, seedling height and first internode length increased, stem diameter decreased, abscisic acid (ABA) and zeatin (ZT) concentration decreased, while indole acetic acid (IAA) and gibberellins 3 (GA3) concentration increased. More also, branch numbers, pod number of branches and seed number of branches increased. Branch yield did not reduce significantly under shade stress, which was related to the decrease of ABA and IAA. Based on the results, soybean yield decreased under shade and drought stresses was mainly due to the yield reduction of the main-stem.
Key words: Abscisic acid, indole acetic acid, relay strip intercropping system, soybean, zeatin.