Tolerância de mudas de Copernicia prunifera e Copernicia hospita a condições de estresses múltiplos

Abstract

Soils degraded by high concentrations of salts, also referred to as halomorphic soils, represent a problem of great magnitude for agricultural productivity and environmental balance. This scenario may be exacerbated by global climate change, negatively affecting, with increasing frequency, regions with more limited infrastructure. In the Brazilian semi-arid region, the occurrence of salt-affected soils is significant. Further intensifying this issue, saline soils are commonly also associated with regions subject to periodic flooding and droughts. The use of plant species for the revegetation of salt-affected areas stands out as an alternative with important environmental benefits; however, it requires the selection of plants capable of tolerating the abiotic stresses present in such areas. Species naturally found in regions with soil salinization problems, such as carnaúba (Copernicia prunifera) and the exotic species Cuban wax palm (Copernicia hospita), may show good suitability for use in revegetation programs in salt-affected areas. Given this context, the present study aimed to evaluate the tolerance of the species Copernicia prunifera and Copernicia hospita to multiple stresses—water deficit and water excess, in addition to salinity stress—under conditions of salinized soils in the Brazilian semi-arid region, with a view to their use in revegetation programs. The experiment was conducted in a greenhouse located at the Agrometeorological Station of the Federal University of Ceará, using a randomized complete block design with sub-subdivided plots (split–split-plot design). The main plots evaluated two tree species of the genus Copernicia: (i) Copernicia prunifera and (ii) Copernicia hospita. The subplots consisted of the soil salinity factor: (i) saline soil, with an electrical conductivity of the saturation extract (ECe) of 8.0 dS m⁻¹, and (ii) non-saline soil (ECe < 2.0 dS m⁻¹). In the sub-subplots, three water regimes were evaluated: (i) well-watered, (ii) water deficit, and (iii) waterlogged soil. Two periods were analyzed: the first was a stress period, during which the water regime treatments were applied for 21 days, and the second was a recovery period, characterized by the standardization of irrigation and the suspension of stresses for 15 days. For plant evaluation, the following variables were measured: soil moisture, plant height, number of leaves, relative chlorophyll index, net photosynthetic rate, transpiration rate, stomatal conductance, and internal CO₂ concentration. The data, except for soil moisture, were subjected to analysis of variance and Tukey’s test at 5% and 1% levels of statistical significance. Water stresses acting in isolation more severely affected leaf gas exchange and growth variables than soil salinity when present alone. Water excess was more detrimental to plant metabolism than water deficit. C. prunifera showed better recovery compared with C. hospita. Both species demonstrated good adaptive potential.