The ecological and functional correlates of nocturnal transpiration

Abstract

Contrary to the conventional theory of optimal stomatal control, there is substantial transpiration at night in many tree species, but the functional significance of this phenomenon remains uncertain. To investigate the possible roles of nocturnal transpiration, we compared and contrasted the correlations of both nocturnal and diurnal sap flow with a range of traits in 21 temperate deciduous tree species. These traits included soil water affinity, shade tolerance, cold hardiness, nitrogen concentration of tissues, minimum transpiration rate of excised leaves, growth rate, photosynthetic capacity, stomatal length and density, and the water potential and relative water content of leaves at the wilting point. Nocturnal sap flow was higher in species with higher leaf nitrogen concentrations, higher rates of extension growth and lower shade tolerances. Diurnal sap flow was higher in species with higher leaf nitrogen concentrations and photosynthetic capacities on a leaf area basis. Because leaf metabolism and dark respiration, in particular, are strongly related to leaf nitrogen concentration, our findings suggest that nocturnal transpiration functions to sustain carbohydrate export and other processes driven by dark respiration, and that this function is most important in fast- growing shade-intolerant tree species.

Disturbances in European beech water relation during an extreme drought

“…Such phenomenon can be explained by night transpiration, especially in the upper part of the crowns, since the stomata are partly open under non-saturated air conditions. This phenomenon has been reported in several studies (Dawson et al 2007), including on 3-year-old Fagus grandifolia (Marks and Lechowicz 2007) and on adult F. sylvatica (Seibt et al 2007;Samson et al 2003). During the period of strongest water stress (DOYs 200 to 235), when predawn water potential measurements were performed, the air was not saturated and air vapour pressure deficit was 5.6 hPa on average above the canopy.…”

Environmental stress and genetics influence night-time leaf conductance in the C4 grass Distichlis spicata

“…Marks and Lechowicz (2007) correlated higher sap flow with higher leaf nitrogen and dark respiration across 21 temperate tree species, suggesting that g night may have a role in dark respiration. However, in this study we found a negative relationship between g night and A in the 7 and 600 mM treatments (Fig.…”

“…However, several benefits for night-time water loss have been proposed, including enhanced nutrient supply (Snyder et al 2008), prevention of excess cell turgor , and enhanced early morning carbon gain . Although any proposed benefits have yet to be quantified directly, several studies have used natural variation in g night both among and within species to develop adaptive hypotheses explaining the occurrence of high g night (Marks and Lechowicz 2007;Christman et al 2008).…”

Reduced nighttime transpiration is a relevant breeding target for high water-use efficiency in grapevine

“…Although plants actively close their stomata in the dark, stomatal closure is largely incomplete and nighttime transpiration can be substantial, accounting for up to 30% of the plant's daytime water loss (15). Furthermore, variation in E n has been identified across (15)(16)(17) and within (15,(18)(19)(20) plant species, but little is known about the underlying genetic determinisms. In the model plant Arabidopsis thaliana, natural variation in nighttime transpiration was detected (21,22) and found to contribute significantly to total transpiration (23).…”

“…First, night transpiration may lower leaf temperature by evaporative cooling, thereby decreasing carbon losses through dark respiration (42). Night water fluxes may otherwise have beneficial roles in nutrient transport (43) and O 2 supply to the xylem parenchyma (16,44). Incomplete stomatal closure at night may also accelerate photosynthesis resumption at sunrise (45), but this has not always been observed (46).…”