Variations in photosynthetic parameters and leaf water potential in oil palm grown under two different moisture regimes

Irrigation is considered as one of the most critical inputs for realizing higher yields of oil palm, as water deficits not only leads to reduced growth but also affects yields. As oil palm is grown in India under irrigated conditions, accurate irrigation scheduling based on physiological indicators is very much essential for improving water use efficiency. Field grown mature Oil Palm Dura (Elaeis guineensis Jacq.) was subjected to two jet irrigation treatments namely control (irrigated to 100% of seasonal crop evapotranspiration) and a continuous water deficit (irrigated to 50% of the control throughout the year). Photosynthetic rate (P_N), stomatal conductance (g_s) and leaf water potential (ψ_w) were studied at three different times during the season and results revealed a diurnal and seasonal pattern in response to water deficits and evaporative demand of the atmosphere. The seasonal variation in environmental conditions along with soil water availability did not alter the diurnal pattern of gas exchange parameters in oil palm. Palms grown under water deficit conditions showed a pronounced decrease in ψ_w and g_s. The photosynthesis in oil palm is strongly controlled by stomata, which is sensitive to environmental conditions. Stomatal conductance and leaf water potential can be considered good indicators of leaf water status in mature oil palm plantations and can therefore be used for irrigation scheduling.