This work aimed to evaluate the degree of susceptibility and characterize the injuries caused by fluoride in the morphoanatomy of Magnolia ovata. Seedlings were subjected to fluoride simulated rain (10 µg.ml-1 of F-) during 10 consecutive days. In the control treatment, only deionized water was used. Leaves were collected for quantification of fluoride in the dry weight and fixed for light and scanning electron microscopy analyses. The apical leaves presented a small percentage of interveinal and margin necrosis in one or both leaf surfaces and greater fluoride accumulation, in relation to the control, than the basal portion leaves. Micromorphological analyses indicated that the areas apparently healthy of epidermis presented alterations in the external periclinal walls and formation of concave shapes, beyond damaged stomatic ledge, erosion of epicuticular waxes and presence of spores and fungal hyphae. The structural characterization of the injuries showed retraction of the protoplast of the epidermal cells, collapse of the mesophyll and epidermal cells and accumulation of phenolic compounds in cells of the necrotic regions. The micromorphological variations occurred before leaf symptoms, confirming the importance of micromorphology in early diagnosis of the injury. Plants of M. ovata presented few visible symptoms in response to fluoride; however, morphoanatomic responses suggest that this species possesses potential features to be used as a bioindicator.
Fluoride; leaf anatomy; Magnolia ovata
