Potencial osmótico, solutos orgânicos e comportamento hídrico do feijão vigna cultivado em solos salinizados.

Abstract

Salinization of soils is one of the abiotic stresses which most limits the growth and crop productivity. To withstand salt stress, plants have developed complex mechanisms which contribute to the adaptation to osmotic and ionic stresses. The cowpea, as a species adapted to semiarid conditions, can develop in saline environments without great loss. The quantification of the permanent wilting point constitutes an important information for water management in irrigated soils. Some researchers report that the soil permanent wilting point soil varies not only with soil texture, but also with the cultivated plant species. Two experiments carried out in a greenhouse at UFRPE, in Recife (Brazil), aiming to evaluate the effect of salt stress on plant growth, accumulation of organic solutes, water use and leaf osmotic potential, and determine the physiological wilting point of cowpea. The statistical design was completely randomized with a factorial 2 x 4, composed of two soil textures and four levels of soil electrical conductivity (4, 8 and 12 dS m-1 at 25°C, and the control without addition of salt, with five replications, totalizing 40 plots per experiment. Cowpea [Vigna unguiculata L. (Walp.)], cultivar pele de moça, was used as test crop. The results were subjected to analysis of variance and regression, using the statistical program SAEG. It was concluded that the permanent wilting point of cowpea was lower by the physiological method than as determined by Richards chamber; the osmotic potential of cowpea leaves decreases with increasing of soil salinity; soil salinity caused a reduction of plant height, leaf number and shoot dry biomass of cowpea and, the increase on soil salinity resulted in higher levels of proline and total soluble carbohydrates of cowpea.