Revista Brasileira De Herbicidas 2016; 15(2): 165-174
Physiological changes in pequi (Caryocar brasiliense) leaves caused by glyphosate application
The use of herbicides is essential for the control of weeds and increase crop productivity, but these products can affect the physiology and growth of non-target organisms, including native plants. The objective of this research was to evaluate in the heated greenhouse the gas exchange, fluorescence of chlorophyll a and chloroplastid pigment content of pequi plants (Caryocar brasiliense) submitted to simulated drift of glyphosate. The treatments were arranged in a randomized block. Seven doses of glyphosate were tested: 0 (control), 50, 100, 250, 500, 1,000 and 1,500 g ha-1 of the acid equivalent. The herbicide was applied at 120 days after transplanting the seedlings. Evaluations of gas exchange and chlorophyll fluorescence were taken 24, 48 and 240 hours after application (HAA) of the herbicide. The chloroplastid pigments was evaluated the 240 HAA. There were reductions in photosynthetic and transpiration rates, stomatal conductance, the effective quantum yield of photosystem II, in the potential quantum yield of photosystem II and apparent electron transport rate, except for the relationship between internal and external CO2 concentration and extinction coefficient photochemistry not that there was an increase, due to the increase of the glyphosate doses. Similarly, the 240 HAA were observed reductions linear in the values of the variables chlorophyll a, b, carotenoids and relation chlorophyll a/b. Glyphosate causes changes in photosynthetic variables with reductions in the characteristics of gas exchange, photochemical efficiency and chloroplastid pigment content, especially as exposed to higher doses of the herbicide.
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