Efeitos diretos e indiretos do glyphosate em eucalipto

• Autor(a) principal: Santos, Leonardo David Tuffi
• Data de Publicação: 2006
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1251
• topic: Eucalyptus spp; Puccinia psidii; Anatomia vegetal; Fitotoxidez; Herbicidas; Toxicologia; Ervas daninhas; Glifosato; Eucalyptus spp; Puccinia psidii; Plant anatomy; Phytotoxicity; Herbicides; Toxicology; Weeds; Glyphosate; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PASTAGEM E FORRAGICULTURA::TOXICOLOGIA E PLANTAS TOXICAS

Glyphosate is the most utilized herbicide to weeding control in commercial eucalypt plantations. In these areas, the undesirable contact, through drift, causes a frequent intoxication on eucalypt plants even where high-technology application methods have been adopted. Once glyphosate is of utmost importance in eucalypt culture and also the need to get to know the actual effects of this herbicide on the plant itself and its agrosystem, five experiments have been carried out to evaluate the growth and the leaf micromorphology of eucalypt clones submitted to glyphosate drift, simulated by means of the following subdoses (0; 43,2; 86,4; 172,8 and 345,6 g ha-1 of glyphosate); the epidermic characteristics of five eucalypt species and its relationship with the differential tolerance to glyphosate; to accompany the growth and the production of wood during its cycle at different levels of intoxication by glyphosate and its effects on the severity of rust (Puccinia psidii) on clones of eucalypt with different levels of resistance. The intoxication grades are based on the visual percentage of leaf area of plants with symptoms of intoxication in relation to the control, ranging from 0 to 100% of intoxication, with 0 being absence of symptoms whereas 100% death. Injuries due to glyphosate have been proportional to the increment of subdoses, being represented by leaf wilt, chlorosis towards necrosis, leaf curling and death of apex. Micromorphological damages have been found on tissues apparently healthy at naked eye, being represented by erosion of ceras epicuticulares, cellular hyperplasia and necrosis followed by fungi colonization. There has been a difference between clones and inter-species as to glyfosate tolerance, via drift, highlighting Eucalyptus resinifera which has been the most tolerant when compared to E. saligna, E. grandis, E. pellita and E. urophylla. On the anatomical study of leaf epidermis of the five species has been encountered a high positive correlation (0,94**) between plant intoxication and the number of epidermic cells of the adaxial face; it has not been observed for stomata index, stomata density and cavity density, indicating a possible involvement of the number of cells of adaxial face of epidermis with the differential tolerance to glyphosate. At field conditions, the drift has influenced the growth and wood production. Plants with initial intoxication above 21% presented lesser growth when evaluated 360 days after application (DAA), lesser height and diameter when compared to the control. The drift damage affected the volumetric growth verified at 360 DAA, being the plants with 21 - 30, 31 - 40 and 41 - 50% intoxication rates the ones which presented reduction in wood volume of 17, 26 e 48%, respectively, in relation to the control. On the other hand, under controlled conditions, glyphosate has not reduced the level of resistance to eucalypt rust (P. psidii) on resistant clones, there has been a reduction in numbers of urediniospores per pustules, urediniospores per area and in the area affected by rust on clones non-resistant to the patogen. The results confirm the negative effects of glyphosate drift in eucalypt growth, highlighting the differential tolerance to the herbicide among different genotypes and the absence of connection between glyphosate drift and the increment of severity of rust caused by P. psidii. The effects of glyphosate drift on growth and wood production will be evaluated during the cycle of the culture and the effects of the herbicide on P. psidii should be evaluated in vitro so as to understand better the relationship between patogen x glyphosate x hust.