Estudo ecofisiológico e bioquímico de progênies de cupuaçuzeiro Theobroma grandiflorum submetidas à deficiência hídrica.

Abstract

In the Amazon rainfall distribution is irregular, being common to the occurrence of well defined dry periods with low rainfall index. This region is considered the main producer of cupuaçuzeiro and knowing that long periods of drought cause a decrease in the agricultural production, the objective of this work was to select preliminarily, progenies of cupuaçuzeiro with indicative of tolerance to water deficit as a function of the ecophysiological and biochemical behavior. The progenies were obtained from the Genetic Improvement Program of Embrapa Amazônia Oriental, being evaluated the experiment carried out in the greenhouse of the same Institution, and the biochemical analyzes done at the Laboratory of Biodiversity in Upper Plants (EBPS) of the Federal Rural University of Amazonia . The seedlings selected from seeds from the parental clones of the BRS Carimbó cultivar were grown in 20 x 45cm plastic bags, filled with 8 kg of substrate, and the water supplement was regularly maintained until the beginning of the evaluations. The experimental design was completely randomized in a 2x7 factorial scheme, totaling 14 treatments with 5 replicates each, in which the two water regimes (with water deficiency and no water deficiency) were analyzed as factor A and as a B factor seven progenies totaling 70 experimental units each Which consists of a plant / bag. The analysis of variance was applied in the results and when significant difference occurred, the means were compared by the Scott-Knott test adopting the level of 5% of probability. The analyzed variables were gas exchanges and variables related to carbon and nitrogen metabolism. The ecophysiological variables were negatively affected by water deficiency, in which progeny 1074 presented greater sensitivity to water restriction with a significant reduction of 2,438%, 642%, 84.9%, 100%, 100%, 84.3% and 92%, respectively. As for Ψam, Ψx, A, gs, E, EIC and EIUA, respectively. However, the progenies submitted to water deficiency promoted the increase in EIUA, with the exception of progeny 1074 that showed a significant reduction in instantaneous water use. It was also possible to identify the decrease of nitrate, starch and glutamine synthetase activity in foliar and root tissues for all progenies. Water deficiency promoted an increase in ammonium concentrations, total soluble amino acids, total soluble proteins, proline, glycine betaine, total soluble carbohydrates, sucrose and reducing and non-reducing sugars for all progenies. Progenies 32, 42, 46, 47, 57 and 215 showed lower sensitivity to water deficit, suggesting a certain tolerance to this type of stress, considering the 16 day period of water deficiency.