RESPOSTAS DE Licania tomentosa E Syzygium malaccense À APLICAÇÃO DE GLIFOSATO

Abstract

The agriculture intensification driven by the agribusiness expansion in Brazil has led to the increasing use of herbicides such as glyphosate. Although effective in weed control, its extensive application has raised concerns about side effects on non-target plant species, especially those located near cultivated areas. In this context, the present study aimed to evaluate the physiological and morpho-anatomical effects of glyphosate on two native tree species widely used in urban afforestation and found in Cerrado ecosystems: Licania tomentosa and Syzygium malaccense, investigating their sensitivity to herbicide and their potential as environmental bioindicators. The experiment was carried out in a greenhouse using healthy seedlings of both species exposed to five increasing doses of glyphosate (0, 25, 50, 75, and 100 g ha⁻¹) in a completely randomized design. The evaluations included biometric analyses (plant height and stem diameter), physiological assessments (gas exchange), and morpho-anatomical analyses of the leaves. For Licania tomentosa, the results showed no visible symptoms of phytotoxicity, but significant internal alterations such as necrosis in idioblasts, loss of chlorophyll parenchyma, and epidermal hyperplasia. Physiologically, reductions were observed in transpiration rate, CO₂ assimilation, and stomatal conductance, along with an increase in internal CO₂ concentration and a decrease in carboxylation efficiency, indicating severe metabolic stress. However, growth variables did not show statistically significant changes. In Syzygium malaccense, no visible phytotoxic symptoms were observed either, but progressive anatomical changes were detected, such as epidermal duplication and necrosis, along with the disappearance of idioblasts containing calcium oxalate crystals. There was a significant reduction in plant height and stem diameter, as well as a negative impact on gas exchange, reflecting impaired photosynthesis. The increase in internal CO₂ suggests failures in photosynthetic biochemical processes, even at reduced herbicide doses. Both species demonstrated sensitivity to glyphosate, evidenced by physiological and structural changes prior to the appearance of visual symptoms. These characteristics highlight the potential of L. tomentosa and S. malaccense as bioindicators of environmental contamination in transitional areas between native vegetation and agricultural fields. The early detection of internal damage reinforces the importance of anatomical and physiological methods in assessing the effects of herbicides on non-target plants, supporting monitoring and conservation strategies.