Nighttime transpiration represents a negligible part of water loss and does not increase the risk of water stress in grapevine

Dayer, Silvina; Herrera, José Carlos; Dai, Zhanwu; Burlett, Régis; Lamarque, Laurent J.; Delzon, Sylvain; Bortolami, Giovanni; Cochard, Hervé; Gambetta, Gregory A.

Nighttime transpiration represents a negligible part of water loss and does not increase the risk of water stress in grapevine

2021

Nighttime transpiration has been previously reported as a significant source of water loss in many species; however, there is a need to determine if this trait plays a key role in the response to drought. This study aimed to determine the magnitude, regulation and relative contribution to whole plant water‐use, of nighttime stomatal conductance (gₙᵢgₕₜ) and transpiration (Eₙᵢgₕₜ) in grapevine (Vitis vinifera L.). Our results showed that nighttime water loss was relatively low compared to daytime transpiration, and that decreases in soil and plant water potentials were mainly explained by daytime stomatal conductance (gdₐy) and transpiration (Edₐy). Contrary to Edₐy, Eₙᵢgₕₜ did not respond to VPD and possible effects of an innate circadian regulation were observed. Plants with higher gₙᵢgₕₜ also exhibited higher daytime transpiration and carbon assimilation at midday, and total leaf area, suggesting that increased gₙᵢgₕₜ may be linked with daytime behaviors that promote productivity. Modeling simulations indicated that gₙᵢgₕₜ was not a significant factor in reaching critical hydraulic thresholds under scenarios of either extreme drought, or time to 20% of soil relative water content. Overall, this study suggests that gₙᵢgₕₜ is not significant in exacerbating the risk of water stress and hydraulic failure in grapevine.

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