Magnitude of nighttime transpiration does not affect plant growth or nutrition in well-watered Arabidopsis

Significant water loss occurs throughout the night via partially open stomata in many C-3 and C-4 plant species. Although apparently wasteful in terms of water use, nighttime transpiration (E-night) is hypothesized to benefit plants by enhancing nutrient supply. We tested the hypothesis that plants with greater E-night would have improved plant nutrient status and greater fitness, estimated as pre-bolting biomass, for Arabidopsis thaliana. Two very different levels of E-night were generated in plants by exposing them to high vs low nighttime leaf-to-air vapor pressure deficits (VPDleaf) in controlled environment chambers. An assessment of responses of nighttime leaf conductance (g(night)) to VPDleaf indicated that E-night differed by at least 80% between the treatments. This large difference in E-night, imposed over the entire vegetative growth phase of Arabidopsis, had no effect on leaf nutrient content (N, Ca, K) or pre-bolting rosette biomass. The lack of response to differences in E-night held true for both a high and a low nitrogen (N) treatment, even though the low N treatment decreased leaf N and biomass by 40-60%. The N treatment had no effect on g(night). Thus, higher E-night did not provide a nutrient or growth benefit to Arabidopsis, even when the plants were N-limited.