Sazonalidade e condições de estresse sobre o comportamento fisioquímico de espécies lenhosas da caatinga em ambiente natural e controlado

Abstract

The Brazilian semi-arid region is an environment with great climatic variability, especially in relation to long periods of water deficit. The low water availability entails different plant strategies, such as growth restriction, physiological changes, depending on the species affected, phenological status, duration and intensity, affect not only the root system, but also the reduction of leaf area production, acceleration of senescence and leaf abscission, accumulation of solutes such as carbohydrates, amino acids (proline) or soluble proteins, which reduce the osmotic potential of the cell. In addition, reduction in water availability may also lead the plant to oxidative stress, due to the disordered increase in the formation of reactive oxygen species (ROS). Understanding the mechanisms that promote greater stability of species in semi-arid environments such as the Caatinga is fundamental for a sustainable use of natural resources. Therefore, the objective of the research was to evaluate the seasonality of the water deficit in the production of compatible solutes and oxidative enzymes in Caatinga species, in region Sertão do Araripe, Pernambuco. Samples of fresh matter were collected from the aerial part of the species Myracrodruon urundeuva, Spondidas tuberosa, Aspidosperma pyrifolium, Cynophalla flexuosa, Neocalyptrocalyx longifolium, Cnidoscolus bahianus, Anadenanthera colubrina, Poincianella pyramidalis, Senna spectabilis var. excelsa and Zizyphus joazeiro in an area located in the Ouricuri-PE, during the dry and rainy period, during 2016, 2017 and 2018. Measurements of leaf characteristics were carried out by means of estimates of leaf area, specific leaf area, (total soluble amino acids, soluble proteins, total carbohydrates and free proline) and activity of antioxidant enzymes (ascorbate peroxidase, catalase and superoxide desmutase). The data were submitted to analysis of variance and the means were compared by Tukey the 5% level of significance. The leaf area showed great variation among the species during the rainy and dry period. Aroeira, canafístula and favela brava reduced its leaf area in 43%, 22% and 30%, respectively, during the dry period. In the rainy season, the catingueira presented the largest accumulation of carbohydrate, followed by the angico and icó. However, in the dry period, canafístula, catingueira, feijão-bravo, juazeiro and pereiro presented a reduction in the carbohydrate content. A significant reduction in protein content during the dry period is observed in all species, except for the canafístula and icó. There was an increase in amino acid contents during the dry season in all species, except for icó, which did not alter amino acid content. The increase in the activity of the antioxidative enzymes, SOD, CAT and APX, in the favela brava, icó, umbuzeiro, angico, canafístula, catingueira and pereiro, between dry and rainy periods is an efficient antioxidative defense strategy for the elimination of Reactive Species of Oxygen (ROS). The occurrence of variations of foliar characteristics of solutes accumulation and activity of antioxidative enzymes among the species indicate a diversification of strategies in the acquisition of available resources during the period of drought in the semiárido.