Evaluation of the concentration-response relationship between film antitranspirant and yield of rapeseed (Brassica napus L.) under drought

Drought can cause large yield losses of rapeseed (Brassica napus L.), particularly during the flowering stage. Effective methods of crop management are required to improve the resistance to drought. Film antitranspirants (AT), as an effective method of crop management, can reduce water loss by forming a waterproof layer to block stomata mechanically. In our study, three pot experiments were conducted in the glasshouse at Harper Adams University in 2019-2020 to investigate the effect of two levels of irrigation - well-watered (WW) and water-stressed (WS); and AT at five concentrations - 0 (water), 0.25%, 0.5%, 0.75% and 1% at flowering stage on spring rapeseed. Results showed that water stress during the flowering stage depressed gas exchange significantly. Seed dry weight per plant reduced by an average of 70%, compared to WW control. Following AT application, stomatal conductance and photosynthesis rate were linearly associated with the concentration of AT for WW and WS plants in two of three experiments. With increasing AT concentrations, stomatal conductance was predicted to decrease similar to 1.4fold faster than photosynthesis rate. Some yield components showed an increase by AT application, however, the compensatory trade-off between pod number and seed number per pod accounted for the lack of a significant improvement in seed yield from AT-treated plants. Our results indicate that application of AT at flowering stage may be a potential method of mitigating the drought damage to rapeseed by blocking stomata, thereby sustaining seed yield. As AT-induced restrictions on leaf gas exchange are related to the concentrations, higher concentrations of film AT than those tested may be needed in future studies.

Automated summary

The study investigated the effect of film antitranspirants (AT) on drought damage in spring rapeseed during the flowering stage. Results showed that water stress significantly affected gas exchange and yield components. Application of AT improved water use efficiency but did not significantly impact seed yield. The study suggests that AT application has the potential to mitigate drought damage in rapeseed, and higher concentrations of AT may need to be studied in the future.