Effect of atmospheric water vapor on photosynthesis, transpiration and canopy conductance: A case study in corn

Abstract

The effect of atmospheric water vapor (AV) on plants has mostly been neglected in climate impact studies. The objectives of this study were to determine the effect of AV on photosynthesis (P_n), dry matter production (DM), transpiration (T_r), leaf conductance (g_l) and water use efficiency (WUE), in climate controlled chambers. The relative humidity (RH) was held near 30, 60, and 85%. DM and WUE increased with RH. δDM/δRH ~ 0.3 from 30% to 60% and ~2.2 from 60% to 85%, δWUE/δRH ~0.2 for all RH’s. The improved WUE at a rate of 0.2 units for each percent of increased RH resulted from a synergy between larger g_l and lower T_r at high RH. This conclusions carries a bleak message to dry regions.