Film antitranspirants increase yield in drought stressed wheat plants by maintaining high grain number

We investigated the use of film-forming antitranspirants (AT) to reduce transpiration and alleviate the adverse effects of late-season drought on wheat (Triticum aestivum L.) growth and yield. Two experiments were conducted in a controlled-temperature glasshouse from April to November 2014, to compare two watering regimes (well watered and water deficit) and three AT treatments (unsprayed control, sprayed before boot swollen and sprayed before anthesis complete). We measured plant water use, transpiration rate, stomatal conductance and photosynthesis. Relative leaf turgor was measured in real time using a non-destructive method of leaf patch clamp pressure. Drought stress reduced daily water use, transpiration rate, stomatal conductance and leaf turgor in wheat plants after about four days. In contrast, these measurements rapidly declined soon after AT application in both well-watered and water-deficit plants. Nevertheless, once soil moisture deficit increased markedly, AT-treated water-deficit plants maintained significantly higher levels of photosynthesis than untreated plants. Drought stress reduced grain yield in unsprayed control plants by more than 40%, compared to well-watered control plants, mainly due to fewer grains per spike. In contrast, drought stress with AT application prior to the most drought-sensitive boot stage reduced yield by only 14%. These results suggest that AT has the potential to improve wheat yields with late-season drought, as is common in semiarid regions; although, more research is required to test the wider applicability of these results in field conditions.