Leaf and stem anatomical characterization of Euphorbia hirta L., a tolerant species to glyphosate.

Euphorbia hirta L. is a weed species that is tolerant to the most used herbicide in agriculture, glyphosate. The anatomical characteristics of plants influence the processes of absorption and translocation of herbicides. The objective of this work was to characterize the anatomy of the aerial vegetative axis (leaves and stem) of E. hirta, to support the establishment of strategies for better control of this species with herbicides. The plants were grown in a greenhouse under controlled conditions. When they reached sizes between 8 and 12 cm, samples of stems and leaves were collected, fixed in FAA 50, and stored in 70% ethanol. Subsequently, the samples were processed following usual light microscopy techniques. In cross-section, the stem of E. hirta has a circular shape. The leaf epidermis is uniseriate composed of isodiametric cells of compact arrangement and with the presence of multicellular trichomes and anthocyanin. As for the morphometric parameters evaluated, the young leaves have a lower thickness in the abaxial epidermis. Based on the anatomical characteristics observed in E. hirta, the main barriers that can act in the absorption of herbicides are the high hairiness and the high content of anthocyanin in the epidermal cells.