Reflexos da adubação potássica e do níveis de água em aspectos fisiológicos e bioquímicos de mudas de espécies arbóreas da caatinga.

Abstract

In order to minimize the effects of water deficiency on plants, mainly due to the current global scenario, it is necessary that strategies be adopted to increase the tolerance of plants to this adverse condition. However, researches aiming at mitigating the effects of water deficit in caatinga species are scarce. So, this study aimed to evaluate the effects of water availability on physiological and biochemical aspects of young plants of Myracrodruon urundeuva Fr. Allem, Libidibia ferrea Mart. Ex Tul and Mimosa tenuiflora (Willd) Poiret, as well as to analyze the role of K in mitigating these effects. The experiment was conducted in a completely randomized design (DIC), factorial scheme 3x3, corresponding to three potassium doses [0, 97.5 and 195 mg dm-3 K] and three water levels [100%cv (control), 50%cv (moderate deficit) and 25%cv (severe deficit)], with potassium chloride (KCl) as the nutrient source. Plants were kept in plastic bags (28cm x 15cm) containing 5kg of substrate, relative water content (RWC), transpiration rate (E), stomatal conductance (gs), photosynthetic rate (A), water use efficiency intrinsic (WUEi) and leaf concentrations of total sugars, total soluble amino acids and proteins. The water deficit promoted a progressive reduction in the rate of transpiration, stomatal conductance, photosynthetic rate and in the instant efficiency in the use of water in the three species studied, with the magnitude of the responses varying with the species and the time of evaluation. The supply of 195 mg/dm3 of K positively influenced the gas exchange of the studied species when water availability reduced. There was an accumulation of osmotically active solutes (amino acids and soluble sugars) in the aroeira and jucá species as the water deficit increased.