Tolerance of eucalyptus genotypes to glyphosate / Tolerância de genótipos de eucalipto ao glyphosate

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Glyphosate is the most widely used herbicide in weed management in the eucalyptus culture. Since it is a non- selective herbicide, many are the problems, when contact occurs, either by drift or incorrect application of this product with eucalyptus plants. In literature, there are few studies performed to elucidate the differential tolerance of eucalyptus genotypes to this herbicide. With that in mind, this study aimed to evaluate the tolerance of eucalyptus clones to glyphosate as well as absorption, translocation and root exudation and physiological changes in eucalyptus plants subjected to contact with glyphosate. Three experiments were conducted in a greenhouse. The effect of glyphosate on growth and development of eucalyptus genotypes was evaluated in standardized transplanted seedlings of 15 eucalyptus clones, in a randomized block design with four replications. At 30 days after transplanting (DAT) it was made the application of glyphosate at a dose of 172.8 g ha-1 in half the number of plants of each clone and the other half received no herbicide, being considered as the control. Visual evaluations of intoxication were made and, 45 days after application (DAA), the determination of plant height and shoot dry mass. The absorption, translocation and root exudation of glyphosate were evaluated in two clones using 14C-glyphosate, observing the radioactivity of 14C in different plant tissues, as well as leaves rinse water and nutrient solution, at intervals of 0, 2, 8, 32 and 72 h after herbicide application. The characteristics associated with the photosynthetic efficiency and water use by plants subjected to glyphosate were evaluated in an experiment conducted in a 4 x 5 factorial, with four eucalyptus clones and five doses of glyphosate and a control without herbicide, considered zero dose, with four replications. At 7 and 21 DAA, using an infrared gas analyzer (IRGA), model LCA 4 (Analytical Development. Co. Ltd, Hoddesdon, UK), the stomatal gas flow rate (U), photosynthetic rate (A), stomatal conductance rate (gs), transpiration rate (E), being calculated the water use efficiency (WUE). At 50 DAA, there was difference in the tolerance to glyphosate between the Eucalyptus grandis clones and the hybrids from the crossing between Eucalyptus urophylla x Eucalyptus grandis, being the clones C3733, C3748, C3837 and C4143 least tolerant, while clones 57, 1213 and C3635 were more tolerant to the herbicide. The clone 531 showed a lower absorption of the herbicide when compared to the clone 2277 and there was no difference between the clones on root exudation and translocation of the herbicide by the plant. There was no difference between clones on photosynthetic intensity, stomatal conductance, transpiration and water use efficiency, when subjected to contact with glyphosate. With increasing dose of the herbicide there was higher reduction in stomatal conductance, stomatal gas flow rate, photosynthetic rate and water use efficiency for clones 57, 386, 1203 and 1213. It was concluded that eucalyptus genotypes have differential tolerance to glyphosate and, in case of incorrect application or occurrence of product drift, plant death may occur, decreasing plant stand. Therefore, this product must be used with care in order to reduce possible damage, mainly due to failures in application.

ASSUNTO(S)

eucaliptus spp photosynthesis fitotecnia eucalyptus spp eficiência no uso da água tolerance fotossíntese water use efficiency tolerância deriva drift

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