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Characteristics of eucalypt leaf epidermis and its role in glyphosate tolerance

L.D. Tuffi Santos L. Iarema M. Thadeo F.A. Ferreira R.M.S.A. Meira About the authors

In reforestation areas, glyphosate drift causes injuries in Eucalyptus plants. Preliminary research work and field observations point out a differential tolerance to glyphosate among cultivated genotypes. Within this context, the anatomical structures of leaf epidermis of five species of eucalypt, correlated to glyphosate tolerance under simulated drift were studied. The factorial design was used, with the species (Eucalyptus urophylla, E. grandis, E. pellita, E. resinifera and E. saligna) and 05 subdoses (0, 43.2, 86.4, 172.8 and 345.6 g e.a. ha-1 of glyphosate) simulating a drift. Immediately before herbicide application, totally expanded leaves were collected for anatomical analysis of epidermal surface through dissociation methodology. Among the studied species, E. resinifera was found to be the most tolerant to glyphosate drift, presenting the lowest values for intoxication percentage 45 days post-application, with no difference among the others. The five species present glabrous, amphistomatic leaves with anomocytic type stomata and prominent cuticle. Despite being present on both faces, stomata are rare on the adaxial face, exhibiting low index and stomatic density. The highest values for stomatic index were observed on E. resinifera, while E. saligna presented the highest stomatic density. Subepidermic cavities evidenced on the surface by the overlying cells are present in the five species, with the highest density on E. pellita. A high correlation was found between intoxication percentage and number of epidermic cells on the adaxial surface, indicating the involvement of this characteristic with differential tolerance to the herbicide. Studies on absorption, translocation and metabolism of glyphosate in eucalypt must be undertaken to elucidate the differential behaviour of genotypes concerning glyphosate drift.

Eucalyptus spp.; anatomy; herbicide; simulated drift; phytotoxicity

Sociedade Brasileira da Ciência das Plantas Daninhas Departamento de Fitotecnia - DFT, Universidade Federal de Viçosa - UFV, 36570-000 - Viçosa-MG - Brasil, Tel./Fax::(+55 31) 3899-2611 - Viçosa - MG - Brazil