Exogenous application of glycine betaine improved water use efficiency in winter wheat (Triticum aestivum L.) via modulating photosynthetic efficiency and antioxidative capacity under conventional and limited irrigation conditions

Abstract

Improving water use efficiency (WUE) is an important subject in agricultural irrigation for alleviating the scarcity of water resources in semiarid regions of the North China Plain. Moreover, glycine betaine (GB) is one of the most effective compatible solutes synthesized naturally in plants for enhancing stress tolerance under abiotic stress, but little information is available on the involvement of GB in regulating crop WUE under field conditions. This study was conducted to explore the role of exogenously applied GB in improving WUE and plant physiological and biochemical responses in winter wheat subjected to conventional or limited irrigation during the 2015–2016 and 2016–2017 growing seasons. Exogenous application of GB significantly enhanced antioxidant enzyme activities and reduced the accumulation of malondialdehyde and hydrogen peroxide under limited irrigation conditions. Furthermore, GB-treated plants maintained higher leaf relative water content and membrane stability, which led to higher chlorophyll content and gas exchange attributes for better intrinsic and instantaneous water use efficiencies compared to control plants under limited irrigation conditions. GB-treated plants had higher indole-acetic acid and zeatin riboside levels but lower ABA levels compared to control plants under conventional and limited irrigation conditions. Additionally, GB enhanced the grain filling rate and duration, grain number per spike, and final grain weight, which resulted in higher grain yield compared to the control. Interestingly, GB significantly improved the integrative and photosynthetic WUE under conventional and limited irrigation conditions, although GB treatment did not markedly affect total water consumption. These results suggest the involvement of GB in improving WUEs in winter wheat by modulating hormonal balance, membrane stability, photosynthetic performance and antioxidant systems to maintain higher grain yield under conventional and limited irrigation conditions. Keywords: Winter wheat, Glycine betaine, Water use efficiency, Limited irrigation, Photosynthetic performance, Antioxidant systems