Effects of Vapour Pressure Deficit on Gas Exchange of Coconut Palm Tree Grown under Irrigation

Little is known about the effect of vapour pressure deficit (VPD) on the gas exchanges of coconut palm tree. The present work evaluated the influence of VDP on the diurnal courses of gas exchanges and leaf water potential of green dwarf coconut palm (Cocos nucifera L.) measured in irrigated plantations in the wet and dry seasons, on the coastal plateau in Neopolis municipality in Sergipe state, northeastern Brazil. The measures of gas exchange were performed in adult dwarf coconut palms (cultivar 'Jiqui Green Dwarf') distributed in an equilateral triangular space (7.5 m) on irrigated commercial plantation with three treatments: T1 = 150 L per plant day(-1), T2 = 100 L per plant day(-1) and T3 = 50 L per plant day(-1). The irrigation water was delivered during the day by two sprinklers placed at 0.8 m from the coconut palm stem. In the dry seasons, the average value of stomatal conductance, leaf transpiration, net photosynthesis and leaf water potential had significant decrease for all treatments with increasing VPD. Based on the results presented in this work, the high sensitivity of gas exchange and leaf water potential to increasing VPD, may suggest that coconut plantations would not be appropriate to areas with high VPD.