Fluxo de seiva e área foliar da atemóia no Submédio São Francisco

Abstract

Atemoya is a plant that adapts well to tropical and subtropical conditions. However, like all fruit trees, it requires adequate irrigation to exploit its full productive potential, especially in regions with scarcity and irregular rainfall, as is the case in the Northeast of Brazil. Irrigation management acts, therefore, as a primordial tool, however, due to the differentiated management of the crop, with the occurrence of drastic pruning for production, the use of conventional methods to determine the blade to be applied presents limitations. The aim of this work was to quantify the water consumption of two atemoya cultivars, in irrigated orchards, by the thermal dissipation probe method, and to relate the transpiration with the leaf area and the atmosfhere evaporative demand. The first stage of the study aimed at calibrating the thermal dissipation probe to estimate the sap flow of the crop; and the second was to estimate the sap flow of two atemóia cultivars, in two orchards of different ages, relating it to the leaf area and the evaporative demand of the atmosphere in the region of Submedio São Francisco. The experiments were performed in the experimental field of the Universidade do Estado da Bahia, in the city of Juazeiro-BA. The first study was conducted with early developmental atemoya plants transplanted into 21.5 liter pots. The pots were arranged on weighing platforms that functioned as lysimeters. The sap flow was determined by the thermal dissipation probe method using 1 cm long probes and considering the effective section area of the xylem that conducts the raw sap. The angular coefficient of the Granier equation was adjusted by minimizing the absolute deviations between the accumulated sap flow of the day and the daily sweating measured by the lysimeter. According to the results, it is necessary to adjust the angular coefficient of the general Granier equation. The absolute mean error between FS and TR was 3.1%. The second experiment was installed in atemoya orchards (young and adult), with cultivars Gefner and African Pride. Plant transpiration was determined through thermal dissipation probes, plant vegetative growth (leaf area and stem diameter) and meteorological variables obtained from a meteorological station located near the experimental area. The data obtained were related through regressions, seeking to establish the existing relationships between the study factors. In response, the relationship between sap flow and leaf area showed linearity only for a given leaf area range in both cultivars and orchards. The estimation of sap flow from the plant leaf area product and reference evapotranspiration can be used in the planning of atemoya irrigation provided that the leaf area limits in which this relationship occurs in each variety under study are considered.