Suscetibilidade do capim-colonião e de cultivares de milho ao flúor

Abstract

A emissão de fluoretos à atmosfera oriunda da produção de superfosfatos e de cerâmica tem causado preocupação pelo efeito tóxico às plantas, contudo são poucos os estudos desenvolvidos acerca do problema com espécie de interesse econômico agrícola. Desenvolveu-se o estudo para avaliar o efeito do flúor (F) atmosférico em plantas de capim-colonião e de cultivares de milho, utilizando como referência espécies bioindicadoras do tipo sensível e tolerante. As plantas foram expostas à contaminação pelo F atmosférico por curtos períodos durante 32 dias em sistema de nebulização com 0,16 mol L -1 de ácido fluorídrico no ambiente interno de uma câmara (~0,20 mmol m -3 de F), havendo um controle não exposto, com quatro repetições. A exposição das plantas ao F causou aumento da concentração do elemento nas folhas até 60 mg kg -1 para o capim-colonião, e entre 100 mg kg -1 nas folhas novas e 170 mg kg -1 nas folhas velhas para quatro cultivares de milho, o que demonstrou o efeito cumulativo do elemento no ambiente. Sintomas visuais da toxicidade foram observados nas plantas e se caracterizaram pela ocorrência de cloroses e necroses na lâmina foliar. O capim-colonião é uma espécie bastante sensível ao poluente no ar. As cultivares de milho DKB 390 e Ômega 8315 também são mais sensíveis ao F quando comparadas às AG7088 e 2B707. Os teores de clorofila a nas plantas foram mais afetados pelo F em relação aos teores de clorofila b.Palavras-chave: Panicum maximum Jacq.; Zea mays L.; bioindicadoras; fitotoxicidade; clorofila. Susceptibility of guineagrass and corn varieties to fluoride AbstractThe emission of fluorides to the atmosphere arising from the production of superphosphate and ceramics has caused concern because of toxic effects on plants. However, few studies have been developed about fluoride (F) pollution with agricultural crops. A study evaluated the effect of atmospheric F in guinea grass and maize plants, using reference bioindicator plants of the type sensitive and tolerant. The plants were exposed to atmospheric contamination by F for short periods during 32 days in a misting system delivering 0.16 mol L -1 of hydrofluoric acid inside a chamber (~ 0.20 mmol m -3 of F). Unexposed plants (control) were also evaluated, with four replications. Exposure of plants to F caused an increase in leaf fluoride concentration up to 60 mg kg -1 for guinea grass and 100 mg kg -1 in the new leaves and 170 mg kg -1 in the old leaves for four varieties of maize, which demonstrated the cumulative effect of the element in the environment. Visual symptoms of toxicity were observed in plants and characterized by occurrence of chlorosis and necrosis on leaf blades. The guinea grass proved to be a species very sensitive to air pollution. The maize varieties DKB 390 and Omega 8315 were more sensitive to F when compared to the AG7088 and 2B707 ones. Chlorophyll a in plants was more affected by the F in relation to the contents of chlorophyll b.

Beneficial use of a by-product from the phosphate fertilizer industry in tropical soils: effects on soil properties and maize and soybean growth

“…We found fluorine levels in maize plants lower than those reported by Fortes et al (2003), who described fluorine toxicity in maize plants near a ceramic industry, and lower than those found by Domingues et al (2011), who studied the susceptibility of guinea grass and maize varieties to fluoride. Our reported values were also smaller than those observed by Haidouti et al (1993), who studied fluorine levels on plants growing near an Al industry in Greece.…”

Fluoride Exposure Compromises Gas Exchange of Plants

“…During the F exposures, when the visual symptoms become more pronounced in the leaves, A decrease probably due to more severe structural and ultrastructural damage and change of biochemical and photochemical phases of photosynthesis [26,27]. This was caused by F accumulation in chloroplasts, reduction in g s or changes in photosynthetic enzyme activity and loss of chlorophyll a [8,28]. The data [29] also demonstrated A increase for two pine species, under low HF concentrations in the environment, while there had been no structural and ultrastructural damage to the needles; however, photosynthesis declined as F concentrations were higher, and was also associated with more severe damage to plants.…”

“…In the chloroplasts, F affects enzymes, such as ATP synthase, ribulose bisphosphate carboxy lase-oxygenase and sucrose synthase, which have their activity reduced [6]. The chlorophyll content is also decreased and the photosynthetic system of plants is impaired, which results in a decrease in CO 2 assimilation and production [7,8]. In Brazil, this problem began to be studied in 1990, due to the losses recorded on soybean production in the state of Minas Gerais [9] and in forest trees [10,11] located in areas adjacent to the Cubatão industrial hub-SP.…”

“…In Brazil, this problem began to be studied in 1990, due to the losses recorded on soybean production in the state of Minas Gerais [9] and in forest trees [10,11] located in areas adjacent to the Cubatão industrial hub-SP. These studies expanded the knowledge on the Atlantic Forest biome [12], as well as on fruit crops and forages as bioindicators of environmental pollution [8,13]. Despite the importance of the subject, there is only limited information on the response of agricultural perennial species of economic interest and (sub) tropical origin to the atmospheric F pollution [14].…”

Effects of Fluoride on Respiration and Photosynthesis in Plants: An Overview

“…The chlorophyll content is also decreased and the photosynthetic system of plants is impaired. Ultimately, these caused to decrease the CO 2 assimilation and production [40,41].…”