Aspectos fisiológicos e de crescimento em espécies vegetais com potencial extrator de chumbo.

Abstract

For the use of plants as agents for remediation of soils contaminated with lead and other heavy metals (phytoremediation), studies are needed to better understand the mechanisms of tolerance, uptake, translocation and accumulation of heavy metals by plants. For both, the analysis of physiological characteristics, of the phytoextraction and growth-related mechanisms of stress tolerance for metals, becomes an important tool in this study. Thus, we evaluated the potential of sunflower (Helianthus annuus L.), castor bean (Ricinus communis L.), milho (Zea mays L) and vetiver [Vetiveria zizanioides (L.) Nash] as hyperaccumulators of Pb greenhouse and field conditions screenhouse. It was observed that under correction soil contaminated with lead species of maize and vetiver have not had their growth potential and fitoextrator affected, being the same species not observed for castor bean and sunflower demonstrated high sensitivity to the level of soil contamination. From the biochemical point of view, the correction from the contaminated soil had values of chlorophyll a, b and total, statistically superior to castor bean and vetiver species in the analyzed periods, except at 60 days after transplantation for chlorophyll b and total only for the species vetiver, while plants without correction showed decreases in all chlorophyll, and the chlorophyll readings determined by chlorophyll were positively correlated with extractable levels, with good precision and accuracy. In addition, the largest increase in the synthesis of carotenoids indicated that under stress the plants develop alternative routes for energy dissipation in order to avoid problems of photoinhibition and photooxidation. As for the photosynthetic efficiency results showed that imposing 45 days of stress (contaminated with lead) was not able to lead to changes in the photosynthetic apparatus of species, sunflower more efficient in net C02 assimilation and chlorophyll fluorescence maxima than the vetiver. Key work; phytoremediation, heavy metal, pollution.