ABSTRACT:The present study aimed to evaluate the effect of different doses of the herbicides picloram, glyphosate, glyphosate + 2.4-D, and 2.4-D on the survival and growth of the tree species Croton floribundus and Heliocarpus americanus and Myrsine coriacea. The experimental design was completely randomized with four replicates. The tree species were sprayed with 0; 2.5; 5; 10; 20; 40; 60; 75; 90 and 100% of the commercial dose of each herbicide. The percentage of phytotoxicity, chlorophyll content, height, stem diameter, leaf area and aerial dry biomass of the species were evaluated. For H. americanus, the herbicides glyphosate, 2.4-D and glyphosate + 2.4-D were phytotoxic. Among the evaluated herbicides, picloram was the most phytotoxic for all species. Glyphosate presented lower phytotoxicity at lower doses for M. coriacea compared with C. floribundus and H. americanus. A negative impact of 2.4-D was verified in all species, even at the lowest doses. The mixture glyphosate + 2.4-D also presented high phytotoxicity, with lower values for the species M. coriacea. The results showed that the application of these herbicides should be directed and protected, and even low dosages have deleterious effects on these species. 0; 2,5; 5; 10; 20; 40; 60; 75; 90 RESUMO: O objetivo deste trabalho foi avaliar o efeito de diferentes doses dos herbicidas picloram, glyphosate, glyphosate + 2,4-D e 2,4-D na sobrevivência e no crescimento das espécies arbóreas Croton floribundus, Heliocarpus americanus e Myrsine coriacea. O delineamento experimental foi inteiramente casualizado, com quatro repetições. As espécies arbóreas foram pulverizadas com
Glyphosate is a nonselective herbicide of systemic action that inhibits the enzyme 5-enolpyruvylshikimate-3-phosphate synthase, thus compromising amino acid production and consequently the growth and development of susceptible plants. The objective of this study was to evaluate the hormetic effect of glyphosate on the morphology, physiology, and biochemistry of coffee plants. Coffee seedlings (Coffea arabica cv Catuaí Vermelho IAC-144) were transplanted into pots filled with a mixture of soil and substrate and subjected to ten doses of glyphosate: 0, 11.25, 22.5, 45, 90, 180, 360, 720, 1440, and 2880 g acid equivalent (ae) ha−1. Evaluations were performed using the morphological, physiological, and biochemical variables. Data analysis for the confirmation of hormesis occurred with the application of mathematical models. The hormetic effect of glyphosate on coffee plant morphology was determined by the variables plant height, number of leaves, leaf area, and leaf, stem, and total dry mass. Doses from 14.5 to 30 g ae ha−1 caused the highest stimulation. In the physiological analyses, the highest stimulation was observed upon CO2 assimilation, transpiration, stomatal conductance, carboxylation efficiency, intrinsic water use efficiency, electron transport rate, and photochemical efficiency of photosystem II at doses ranging from 4.4 to 55 g ae ha−1. The biochemical analyses revealed significant increases in the concentrations of quinic acid, salicylic acid, caffeic acid, and coumaric acid, with maximum stimulation at doses between 3 and 140 g ae ha−1. Thus, the application of low doses of glyphosate has positive effects on the morphology, physiology, and biochemistry of coffee plants.
Small changes in glufosinate, glutamate and ammonia levels were found, in eucalyptus plants. The treated eucalyptus plants had defoliation above 80% and 90% pruning with glufosinate application. Pruning using glufosinate ammonium not reduced growth in eucalyptus plants. Glufosinate can be used for chemical artifi cial pruning of eucalyptus plants since it does not affect their physiology and growth.
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