Gas Exchange of Oil Palm in Relation to Light, Vapour Pressure Deficit, Temperature and Leaf Age

Gas exchange in leaves of oil palm (Elaeis guineensis) was measured in the field over a range of photon fluxes, leaf temperatures and leaf-air vapour pressure differences (VPD). There were no differences in leaflet photosynthesis within one frond, but a reduction depending on frond age. For fronds of the same age, between-tree variation was low. The light saturated rate of net CO 2 assimilation was 20 μmol m −2 s −1 when photosynthetically active radiation (PAR) exceeded 1100 μmol m −2 s −1 . Apparent quantum yield averaged 0.051 mol mol −1 . When leaf temperature increased from 30°C to 38°C, net CO 2 uptake showed no variation as transpiration rate andstomatal conductance increased slightly. A small increase in VPD induced rapid stomatal closure and consequently a reduction in the transpiration rate (...)