The effects of glyphosate drift during application are harmful to the eucalypt culture. This work evaluated the effects of simulated glyphosate drift on leaf growth and morphoanatomy of the clone 15-CENIBRA (Eucalyptus urophylla X E. grandis). A randomized block design was used with four replications. Each experimental plot was represented by one plant cultivated in a 10 liter pot with soil. The treatments were 0; 43.2; 86.4; 172.8 and 34.6 g a.e. ha-1 of glyphosate, applied 40 days after seedling planting with a precision sprayer, so that the upper third of the plants was unaffected. The morphological alterations in the plant shoot were described .Intoxication percentage in relation to the control was evaluated 7, 15, and 30 days after application (DAA). Leaves were collected from the third node of the first basal branch of the plants, fixed in FAA50 and stored in 70% ethanol 7 and 15 DAA. Cross section of the intermediate region was stained with astra blue and basic fuchsia and installed on permanent slides to measure thickness, of the palisade (PPA) and spongy (PLA) parenchyma, epidermis of the adaxial (EAD) and abaxial (EAB) sides, as well as the proportion of each tissue area using software "Image-Pro Plus". From the 5th DAA, leaf wilt, chlorosis and curling were observed in the plant apices sprayed with 17.8 and 345.6 g a.e. ha¹ of glyphosate. The plants subjected to 24% of the rate attained 58.75% toxicity 30 DAA, presenting abnormal branch, which was not observed under lower concentrations. Twelve and 345.6 g i.a. ha¹ of glyphosate caused necrotic area, hyperplasia of the chlorophyllic parenchyma and epidermis cells, 7 and 15 DAA. In response to the injuries, cell proliferation forming a homogeneous scar tissue and accumulation of phenolic compounds in the affected areas was verified. Blade thickness and PPA subjected to 345.6 g a.e. ha-1 of glyphosate increased 7 DAA, while PLA and EAD showed increased thickness only 15 DAA at the same rate. The sub doses of 172.8 and 345.6 g a.e. ha-1 of glyphosate led to an increase in blade thickness and PPA 15 DAA. The increase in blade thickness is a result of expansion of the palisade parenchyma cell, which may be related to a specific response of the plants to leaf area loss, as well as to synthesis of secondary compounds such as cellulases, due to glyphosate action.
Eucalyptus spp.; anatomy; simulated drift
