Gas exchange and chlorophyll synthesis of maize cultivars are enhanced by exogenously-applied glycinebetaine under drought conditions

Abstract

Glycinebetaine acts as an osmoprotectant and is closely related with drought resistance. In the present study, glycinebetaine (GB) was exogenously-applied to two contrasting maize cultivars, Dongdan-60 and ND-95, to see whether GB improves drought resistance. Maize cultivars were grown with normal water supply till the heading stage and then exposed to two levels of soil moisture, well-watered control and drought-stressed, and then GB solution of 100 mmol was foliar applied five days after moisture treatments were imposed. The gas exchange and chlorophyll concentration were substantially declined in both maize cultivars under water stressed conditions. However, this reduction was less in Dongdan-60 than ND-95. Nonetheless, GB-treated plants considerably maintained higher gas exchange rate and chlorophyll concentration during drought stress than non-GB treated plants. The GB-induced improvement in gas exchange and chlorophyll synthesis under water stress ultimately resulted in improved growth and yield in both maize cultivars. Furthermore, the positive responses to exogenous GB application were more pronounced in Dongdan-60 as compared to ND-95 in all traits examined under water-deficit conditions. In conclusion, exogenously applied GB to maize crops could improve gas exchange, chlorophyll synthesis, growth and yield of maize.