Effect of a new antitranspirant on the physiology and water use efficiency of soybean under different irrigation rates in an arid region

Antitranspirants are exogenous substances applied to leaves to reduce luxury transpiration by regulating stomatal conductance to increase water use efficiency (WUE). A cheap and environmentally-friendly antitranspirant, FZ, was newly developed, extracted mainly from Alhagi sparsifolia. Its effects on soybean water use were investigated in a field experiment using the locally-used irrigation rate and a low irrigation rate (The lower and upper limit of irrigation is 40%–70% of field capacity). Foliar application of FZ and measurement of leaf physiological characteristics, final biomass, seed yield and water use efficiency were carried out during the pod bearing and pod filling stages of drip-irrigated soybean with film-mulching. Under the low irrigation rate, leaf stomatal conductance (gs) and transpiration rate (Tr) decreased significantly by 7 d after spraying, but photosynthesis (Pn) and instantaneous water use efficiency (WUEin) were not significantly affec ted. The stomatal frequency, stomatal aperture, gs, Tr and Pn decreased by 1 d after spraying, without significantly increasing WUEin. However, applying FZ during the pod bearing and pod filling stages did not significantly affect the final biomass, water consumption, seed yield and WUE of soybean. Under the locally-used irrigation rate, applying FZ increased the activities of superoxide dismutase and peroxidase in the leaves by 38% and 33%, respectively, but did not significantly affect gs, Tr, Pn, stomatal aperture and stomatal frequency. Applying FZ three times during pod bearing and pod filling stages enhanced seed yield and WUE by 24% and 21%, respectively, but did not significantly affect the final biomass and water consumption. Therefore, seed yield and WUE of soybean were significantly increased by foliar application of FZ during the pod bearing and pod filling stages under the locally-used irrigation rate in arid region, but applying FZ did not have a positive effect on water use efficiency of soybean under a low irrigation rate