Caracterização fisiológica e bioquímica de variedades de feijão-caupi (Vigna unguiculata (L.) Walp) quando á tolerância ao déficit hídrico

Abstract

Cowpea is a legume of national importance and has great notoriety in the Northeast and North regions serving as a food base because it is rich in proteins, vitamins and minerals; and income generation of small farmers. The water deficit, especially in the critical phases of the crop, is one of the factors that most compromises the high productivity, being in the Northeast one of the most serious problems due to the short rainy season. Plants subjected to drought present a series of changes at the morphological, physiological and biochemical levels. In this context, the characterization of varieties that have mechanisms to mitigate the deleterious effects of drought is important for breeding programs of this crop. Therefore, the present study aimed to evaluate the morphological, physiological and biochemical parameters of the local varieties of cowpea when submitted to different levels of water restriction. The experiment was carried out in a greenhouse in a completely randomized design in the 3 x 3 factorial scheme, in which the first factor was defined as the three genotypes (two local varieties (Sempre-verde and Cabeça-de-gato) and one standard (control, moderate stress and severe stress), and the plants were conducted in pots up to the V4 stage (pre-flowering (plant height, leaf number, leaf area and dry mass), ψw in the morning, gas exchange, chlorophyll a fluorescence, pigment content (chlorophylls and carotenoids), lipid peroxidation , measurement of organic solutes (proline, total carbohydrate, reducing carbohydrate, non-reducing carbohydrate), starch content and activity of catalase enzymes, ascorbate peroxidase, guaiacol peroxidase and desmutase of superoxide. Pingo-of-ouro-1,2 genotype showed tolerance to drought, with better water economy when subjected to severe stress, largest independent net photosynthesis rate of fluid restriction, and high levels of efficiency of use water content and high proline content. The Sempre-verde variety presented some tolerance mechanisms similar to those observed in the tolerant genotype, presenting a lower rate of inhibition of photosynthesis than the Cabeça-de-gato. No changes were observed in the pigments when submitted to different levels of stress, but there were changes in the ETR. In relation to the osmoregulatory solutes, the tolerant genotype presented higher levels of non-reducing carbohydrates and higher levels of proline, followed by Sempre-verde. The genotype Pingo de ouro 1,2 confirmed its tolerance pattern when compared to the tested genotypes, with Cabeça-de-gato presenting some parameters superior to Sempre-verde.