Efeitos fisiológicos da contaminação por ferro em Phaseolus vulgaris e Zea mays

Abstract

Understanding the toxic effects of iron on plant physiological processes appears as an important tool for promoting actions that aim to enhance agricultural production in areas under the influence of mining activities or whose environmental characteristics favor the bioavailability of the metal. The objective of this work is to verify the physiological alterations in the germination and growth of common bean (P. vulgaris) and mayze (Z. mays) submitted to planting under high iron conditions. The plants were submitted to concentrations of 1, 4, and 8 mM of iron in the forms of Fe-EDTA, Ferrous Sulfate (Fe +2), and P. vulgaris underwent complementary treatment with Iron Chloride (Fe+3) at the same concentrations as the other sources. The seeds were germinated in a germination chamber B.O.D., using a constant temperature of 25 ºC and a photoperiod of 12h/12h. The analyzed variables were the germination percentage (%G), germination speed index. Plants were grown in 0.5L polyethylene pots in an inert substrate, fed Hoagland's solution at half ionic strength and pH 5.0 and the following variables were analyzed: Leaf area, stem length, root length, dry mass, quantification of chloroplast pigments, analysis of chlorophyll fluorescence. The activity of the antioxidant enzymes SOD, CAT, POX was verified for the young seedlings. Iron stress did not change the germination of the evaluated species, however it affected the initial growth and biomass allocation at concentrations of 4 mM and 8 mM for the different sources of Fe. The species P. vulgaris did not show variations in the levels of chloroplast pigments. between treatments, however, in Z. mays the pigments varied in relation to the control in all treatments. The pollutant did not affect the integrity of the photosynthetic process of the evaluated species. The action of antioxidant enzymes was not observed in P. vulgaris, and the use of non-enzymatic routes to combat ROS is characteristic of the species, whereas Z. mays showed POX action in the Fe+2 treatment. Thus, it can be concluded that Fe concentrations above 4 mM generate changes in the growth of the evaluated cultivars.