Effects of exogenous L-glutamic acid on dry matter accumulation distribution, grain filling characteristis and quality formation under post-anthesis drought stress in wheat

Objectives Glutamic acid (Glu) is capable of regulating plant growth and improving crop stress resistance. The effects of exogenous L-glutamic acid (L-Glu) on dry matter accumulation, distribution and transport, photosynthetic parameters, grain filling characteristics, agronomic and quality characteristics of wheat under drought stress were studied, it provides a theoretical basis for further study on improving drought tolerance of wheat by glutamic acid.

Methods Winter wheat cultivars Xindong18 (XD18) and Xindong22 (XD22) in Xinjiang were used as the field experimental materials. L-Glu solution in concentration of 0, 2 and 4 mmol/L (denoted as G0, G2, and G4, respectively) was sprayed at heading and flowering stages, respectively. Each treatment plot was divided into two parts after flowering stage, one was not watered enough (DT) and the other was watered with adequate amount (WT). The dry matter accumulation in vinous organs at the initial flowering stage and 10, 20, and 30 days after flowering stage (i.e. at early, middle, and late grain-filling stage), the photosynthetic parameters of flag leaves, grain filling characteristics, yield components and grain quality of wheat were determined.

Result Compared with DT-G0, DT-G2 and DT-G4 significantly increased shoot dry matter accumulation (DMA) and the contribution of post-anthesis DMA to grain, the increment rates in XD18 were 24.65% and 24.28%, and in XD22 were 28.44% and 16.03%, respectively. DT-G2 and DT-G4 treatments increased photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), and mesophyll instantaneous carboxylation efficiency (P_n/C_i), elevated the average grain filling rate by 15.17% and 3.59% in XD18 and by 19.92% and 14.70% in XD22. DT-G2 treatment significantly increased the 1000-grain weight, while DT-G4 treatment significantly decreased the wet gluten content of two wheat varieties.

Conclusions Spraying exogenous L-Glu at heading and flowering stages could significantly increase the total dry matter accumulation and the transfer rate of dry matter from shoots to grains at late grain filling stage, and elevate the photosynthetic and transpiration rate of flag leaves under drought stress after anthesis, which is conducive to the distribution of dry matter in ears and high and prolonged grain filling duration, avoid the grain weight loss under drought stress, and form required grain quality finally.