Patterns of night-time water use are interrelated with leaf nitrogen concentration in shoots of 16 deciduous woody species

Although the impact of nitrogen availability on the night-time water relations of plants has received a lot of attention during the last decade, knowledge of how these two traits are interrelated is contradictory and still limited. The aim of the current study was to investigate the impact of leaf nitrogen concentration on night-time (Enap) and daytime (Ed) transpiration rate, nightly water-use percentage of daytime water use (NWU), and increase in night-time transpiration rate (INT) in artificial predawn hours in the cut shoots of 16 woody species measured in the controlled conditions of a growth chamber. Two distinct patterns of night-time water use associated with leaf nitrogen concentration ([N]) were observed: shoots with high NWU were characterised by significantly (P < 0.05) lower [N], whereas shoots with highest INT had greater [N]. The forward stepwise regression analysis revealed that variability in Ed, NWU and INT depended on [N], whereas the impact of other predictor variables (leaf phosphorus concentration, habitat soil water content and light availability) was insignificant (P > 0.05). Our results suggest that high NWU could potentially compensate limited nitrogen uptake in species able to grow in nutrient-poor habitats. Furthermore, night-time stomatal regulation mechanisms may differ between species according to their [N] and this may explain the contradictory results between previous studies.