Diurnal curves of leaf gas exchange indicate differential drought tolerance in young plants of two palm oil hybrids 

The aim of this study was evaluate the magnitude of the drought effects on leaf water potential and leaf gas exchange in two oil palm hybrids (BRS Manicoré and BRS C 2501) and infer about their inherent ability to tolerate drought. For this, 12-motnh old plants were subjected to full irrigation and (Control) or to complete suppression of irrigation (Water-deficit). Comparisons among hybrids and watering regimes were accessed 21 days after watering regimes differentiation by determining diurnal curves of net CO2 assimilation rate (A), stomatal conductance to water vapor (gs), transpiration (E) and instantaneous water use efficiency (A/E). The effects of drought in diurnal curves of A, gs, E and A/E were more striking in BRS C 2501 than in BRS Manicoré. The integrated A (AInt.) and E (EInt) in watered plants of BRS Manicoré were 46% and 15% higher than in watered plants of BRS C 2501. Relative to watered plants, the drought caused 95%, 85%, 81% and 73% decreases in maximum A, gs, E, and A/E in BRS C 2501; and 90%, 73%, 66% and 70% decreases in maximum A, gs, E, and A/E in BRS Manicoré, respectively. The AInt. and EInt. were 83% and 56% higher in stressed plants of BRS Manicoré than in stressed plants of BRS C 2501 and drought induced 95% and 78% decreases in AInt. and EInt. for BRS Manicoré and 98% and 88% decreases in AInt. and EInt. for BRS C 2501. The presented results permit to infer that BRS Manicoré tolerates drought more satisfactorily than BRS C 2501.