Variáveis fisiológicas em abacaxizeiros submetidos à aplicação do Diuron

Abstract

Currently the herbicides registered for pineapple culture only deal with the vegetative phase. However, culture has long cycle, requiring the control of weeds throughout it to produce fruits of commercial value. The objective of this study was to evaluate the physiological variables four pineapple cultivars submitted to the application of the herbicide diuron in the reproductive phase (4 days after flower induction). The experiment was conducted with the cultivars of pineapple IAC Fantástico, Vitória, MD2 and Pérola using the active principle diuron at a dose of 7.5 mL L. Measurements of CO2 assimilation rate (A), stomatal conductance (Gs), transpiration (E), vapor pressure deficit (VPD) and efficiency of water use (WUE) were made weekly, every time in two plants by cultivating, in a period of 24 hours to two days before the application of herbicide (1 time), and at 8, 15, 22, 29 and 36 days after application (DAA) of the herbicide. Measurement of photochemical efficiency (Fv/Fm) was performed weekly on the same dates and leaf 'D'. Measurements of gas exchange were made with a gas meter infrared (IRGA) and the chlorophyll fluorescence with a fluorometer. The readings with the SPAD were performed at three different points of the leaf, on the same dates of physiological evaluations. The application of diuron reduced CO2 assimilation in varieties of pineapple IAC Fantástico, Vitória, MD2 and Pérola, the reproductive phase, in all phases of CAM metabolism. For physiological variables stomatal conductance and transpiration promoted transient reduction and transient increase in the efficiency of water use. The photochemical efficiency of most pineapple cultivars was negatively affected by the herbicide diuron. However, the IAC Fantástico restored the initial values of photochemical efficiency at 36 days after application of diuron.