Increased contribution of wheat nocturnal transpiration to daily water use under drought

Abstract

Increasing evidence suggests that in crops, nocturnal water use could represent 30% of daytime water consumption, particularly in semi-arid and arid areas. This raises the questions of whether nocturnal transpiration rates (TR ) are (1) less influenced by drought than daytime TR (TR ), (2) increased by higher nocturnal vapor pressure deficit (VPD ), which prevails in such environments and (3) involved in crop drought tolerance. In this investigation, we addressed those questions by subjecting two wheat genotypes differing in drought tolerance to progressive soil drying under two long-term VPD regimes imposed under naturally fluctuating conditions. A first goal was to characterize the response curves of whole-plant TR and TR /TR ratios to progressive soil drying. A second goal was to examine the effect of VPD increase on TR response to soil drying and on 13 other developmental traits. The study revealed that under drought, TR was not responsive to progressive soil drying and - intriguingly - that TR seemingly increased with drought under high VPD consistently for the drought-sensitive genotype. Because TR was concomitantly decreasing with progressive drought, this resulted in TR representing up to 70% of TR at the end of the drydown. In addition, under drought, VPD increase was found not to influence traits such as leaf area or stomata density. Overall, those findings indicate that TR contribution to daily water use under drought might be much higher than previously thought, that it is controlled by specific mechanisms and that decreasing TR under drought might be a valuable trait for improving drought tolerance.

Quantification and Prediction of Nighttime Evapotranspiration for Two Distinct Grassland Ecosystems

“…Therefore, our data could not confirm the effect of plant physiological changes due to higher temperatures on transpiration during night that were reported in other studies such as increased cuticular transpiration and incomplete stomatal closure (e.g. Claverie et al, 2017). ET N rates during dusk, nocturnal, and dawn also differed between hot and normal days, but no consistent change in the dynamics of the nighttime ET that could be linked to plant physiological reactions was observed.…”

Root water uptake under heterogeneous soil moisture conditions: an experimental study for unraveling compensatory root water uptake and hydraulic redistribution

“…Various studies have shown that night-time transpiration can be significant (e.g., Caird et al, 2007b;Gleason et al 2017;Claverie et al 2018). In agreement with this, it was observed that night-time transpiration accounted for 8-12% of total daily transpiration under optimal soil water supply.…”

Dynamic leaf energy balance: deriving stomatal conductance from thermal imaging in a dynamic environment

“…Nocturnal stomatal conductance (observed after dark acclimation) was significantly different between individuals, suggesting differences in the regulation of water loss during the night period. Nocturnal transpiration is involved in essential physiological processes such as nutrient transport (Zeppel et al , 2014) and could represent 30% of daytime water consumption in crops (Claverie et al , 2018). The initial g sw values observed here under dark conditions represented up to ~10% of the value reached under the light period, confirming its importance for the regulation of plant water budget.…”