Objective   Effects of gibberellic acid (GA3) and 2, 4-ebrassinolide (EBR) on grain-filling and yield of Tartary buckwheat were studied.

  Method  Grain-filling and starch synthase activity of dominant and weak Tartary buckwheat grains under 6 treatments of GA3 and/or EBR were compared. Antioxidant enzyme activity and photosynthetic properties of the leaves during grain-filling stage and agronomic traits associated with grain yield of the plants were monitored.

  Result   Compared to control, GA3 alone significantly increased the 100-grain weight and activities of adenosine diphosphate glucose coke phosphorylase and soluble starch synthase in the grains as well as the antioxidant enzyme activities, net photosynthetic rate, stomatal conductance, and transpiration rate in the leaves. It also significantly increased the yield per plant and final grain yield. Increasing EBR application, on the other hand, increased the activities of starch synthase, leaf antioxidant enzymes, leaf photosynthetic characteristics, main stem branch number and diameter, grains per plant, grain weight per plant, and final grain yield initially but declined after reaching a peak. Meanwhile, the number of main stem nodes and plant height rose and the starch synthase activity of the weak grains lowered continuously.

  Conclusion   By combining GA3 at the rate of 80 mg·L⁻¹ and EBR at 0.5 mg·L⁻¹ for treating Tartary buckwheat, the grain-filling of dominant grains was enhanced, the leaf senescence delayed, and the grain weight and final yield increased.