LAUSR

Abstract Climate change raises significant challenges for oil palm performance, as its physiology can be differentially affected by water deficit depending on genotype. Therefore, the aim of the present study was to assess the leaf gas exchange and photochemical activity in oil palm seedlings of two genotypes of Elaeis guineensis (G) and four interspecific hybrids of E. oleifera × E. guineensis (OG) and evaluate the effect of water deficit for 15 days on water status and photosynthetic traits in a subset of two OG genotypes. Significant differences in gas exchange and photochemical activity variables occurred among well watered seedlings of G and OG genotypes, showing a wide range of variation in photosynthetic rate, stomatal conductance, water use efficiency and electron transport rate. In the two selected OG genotypes, water deficit caused a reduction in leaf relative water content, photosynthetic rate, stomatal conductance, transpiration rate and water use efficiency of 20, 99, 60, 52 and 98 %, respectively; maximum rate of RuBisCO carboxylation, maximum electron transport rate, and triose phosphate utilization rate were markedly reduced (70 – 80 %) by water deficit. The response of gas exchange and biochemical related variables to water deficit seemed to be bimodal, with stomatal closure being the first response and reduction of biochemical photosynthetic capacity the second one. There were differences in physiological performance among genotypes in well watered plants, and both OG genotypes were sensitive to WD but showed different responses, suggesting possible genotypic differences in tolerance.