Efeito de paclobutrazol em tomate cereja sob salinidade da água de irrigação.

Abstract

Tomatoes are the second most cultivated and consumed vegetable in the world. Production in the Brazilian Northeast is generally low, due to various factors, including low technology and poor quality irrigation water, which highlights the importance of studies aimed at minimizing the deleterious effects of salt stress on its cultivation. In view of the above, the aim was to evaluate the effects of applying paclobutrazol to cherry tomatoes under saline irrigation water. The research was carried out in a protected environment (greenhouse) belonging to the Agricultural Engineering Academic Unit of the Federal University of Campina Grande (UFCG). The experimental design was randomized blocks, in a 3 x 5 factorial scheme with 4 replications. The treatments consisted of three concentrations of Paclobutrazol (0, 1.5, 2.5 ppm), and five levels of electrical conductivity of the irrigation water (0.4; 1.4; 2.4; 3.4 and 4.4 dS m-1), totaling 60 experimental units. The use of paclobutrazol at a concentration of 2.5 ppm improved the tolerance of cherry tomato plants to salinity up to 2.4 dS m-1 in terms of CO2 assimilation rate, internal CO2 concentration, instantaneous carboxylation efficiency, electrolyte leakage and chlorophyll a content, indicating that PBZ does not attenuate salinity above the crop's threshold. On the other hand, plant height was reduced by both concentrations of PBZ at all salinity levels. Paclobutrazol improved initial fluorescence, the Fv/Fm ratio and led to an increase in the number of leaves, the fresh and dry masses of leaves, roots, total fruit production per plant, the number of fruits per bunch and the number of bunches per plant compared to the control. Irrigation water salinity from 0.4 dS m-1 led to reductions in the physiological parameters of gas exchange, chlorophyll fluorescence, photosynthetic pigments, number of leaves, total leaf area, relative water content, fresh and dry mass of leaves, roots, stems, total fruit production per plant, average fruit weight, number of fruits per bunch and number of bunches, longitudinal diameter and transverse diameter of cherry tomato plants.