Night temperature effects on transpiration response to atmospheric drought and leaf area in wheat

Increasing evidence indicates that limited transpiration rate (TR) response to high (>3 kPa) vapour pressure deficit (VPD) is a valuable trait in identifying water-saving, drought-tolerant genotypes. However, the relevance of this trait under a warming climate is much less investigated. In particular, the effect of different night temperature (NT) regimes on wheat TR sensitivity to increasing VPD and whole-plant evaporative area remains unknown. A controlled-environment study was undertaken on 11 diverse bread and durum wheat lines in order to identify the extent of variability in terms of (i) sensitivity of TR response to increasing VPD in the 0.8 to 4.3kPa range (SlopeTRvsVPD) and (ii) leaf area (LA) following 22d-long exposures to 2 NT warming scenarios (20 and 30C). The effect of these two NT conditions was investigated in combination with 3 different daytime (temperature and VPD) warming regimes (25C & 2kPa, 30C & 2.7kPa and 36C & 4kPa)