Acúmulo e remobilização de compostos nitrogenados e sistema de defesa antioxidante na aclimatação de palma de óleo a repetidos eventos de déficit hídrico.

Abstract

The objective of this study was to evaluate the accumulation and remobilization of nitrogenous compounds in two oil palm hybrids subjected to repeated water deficits, and to determine whether this process supports the antioxidant defense system in mitigating cellular damage. For this purpose, nine-month-old oil palm seedlings (Elaeis guineensis Jacq.) of two hybrids (Deli x Ghana and Deli x Nigeria) were subjected to three water regimes: irrigated plants (Control) and one and three water deficit events (1WD and 3WD). Physiological assessments and biochemical sampling were performed when reductions in photosynthetic rate (A) in stressed plants corresponded to approximately 50% compared to control plants. In the Ghana hybrid, 1WD plants showed reductions in A by 27%, in Vcmax by 36%, in Cc by 31%, and an increase in NPQ by 96%. 3WD plants exhibited reductions in A by 16%, in qP by 9%, in Vcmax by 20%, in Cc by 19%, and an increase in NPQ by 20% compared to control plants. In 1WD Ghana hybrid plants, mature leaves showed higher concentrations of carotenoids, and in 3WD plants, mature leaves had higher concentrations of carotenoids and nitrogen and lower concentrations of amino acids compared to control plants. In the young leaves of 3WD plants of the same hybrid, lower nitrogen concentrations and higher activities of SOD and APX were observed compared to control plants. In the Nigeria hybrid, 1WD and 3WD plants were similar in reductions of A and ETR by 22% and 9%, and in the increase of PR by 48%, compared to control plants. Additionally, 1WD plants showed reductions in Fv’Fm’ by 13%, in Vcmax by 37%, in gm by 18%, in Cc by 27%, and an increase in NPQ by 83% compared to control. Meanwhile, 3WD plants showed reductions in Vcmax by 19% compared to control plants. In 1WD Nigeria hybrid plants, young leaves had higher protein concentrations and lower carotenoid concentrations. In 3WD plants of the same hybrid, young leaves had higher amino acid concentrations and lower carotenoid concentrations compared to control plants. It has been deduced that in the Ghana hybrid, there was a remobilization of nitrogenous compounds from mature leaves to young leaves, which is associated with the antioxidant system, resulting in a reduction of cellular damage. In the Nigeria hybrid, it is concluded that it is less sensitive to water deficits, although it shows damage to the photosynthetic apparatus. These adjustments are therefore not conserved between the two hybrids.