Morpho-anatomical and physiological changes in grapevine leaves exposed to atmospheric fluoride and sulfur dioxide pollution

Abstract

A comparative study on the effects of air fluoride and sulphur dioxide pollution on a local vine (Vitis vinefera L.) cultivar "Asli" growing in the vicinity of a factory producing phosphate fertilisers in the southern suburb of Sfax region was investigated. The chemical analysis of both peripheral and central necrotic leaf round slices reveals a preferential accumulation of fluoride, as well as calcium in leaf margins and tips. However, central leaf areas seem to accumulate both sulfur and magnesium. These findings confirm the involvement of these two elements not only in the detoxification of fluoride as CaF2 and MgF2, but also in regulating metabolic pathways. On the other hand, net photosynthesis is maintained at appropriate levels, while 30 to 40% of leaf surface are altered by necrosis. Furthermore, several structural changes are revealed in polluted leaves. Indeed, the decrease of leaf density is due probably to (i) a decrease in intercellular spaces, (ii) a decline of vascular bundles number and (iii) a gradual sclerotization of collenchyma cells occurring jointly with a thickening of their walls.