Eficiência fotossintética de Canavalia rosea (Sw.) DC. e Eugenia astringens Cambess expostas à rejeito de mineração

Abstract

The plants in Restinga are adapted to environments with high temperature and salinity. However, any anthropogenic factor can influence the maintenance of homeostasis and survival of these plants. The rupture of the Fundão dam, in Mariana-MG, impacted all living beings that, directly or indirectly, came into contact with the mud containing mining waste. In this sense, the objective of this study was to evaluate the photochemical response of Canavalia rosea (Sw.) DC. and Eugenia astringens Cambess to the tailings, in Herbácea and Arbustiva phytophysiognomies, respectively, in Restingas de Linhares and São Mateus, in the north of the state of Espírito Santo. Two assessments were carried out in 2019: one in the rainy season and another in the dry season. Soil and leaves were collected for quantification of trace elements and, using the chlorophyll a transient fluorescence technique, the effect of these elements on the photochemical stage of photosynthesis of these plants was evaluated. Trace elements were detected in the soil and in the leaves of the plants, as well as the influence of trace elements in the leaves during the photochemical step of photosynthesis. In C. rosea, the parameters that correspond to energy absorption, capture, reduction and dissipation were changed in the presence of Lead (Pb), Cobalt (Co), Copper (Cu) and Nickel (Ni). Tin (Sn) caused an increase in the initial fluorescence (F0) and decreased the efficiency of reduction of electron acceptors of photosystem I (δR0). In E. astringens, Cadmium (Cd) and Lead (Pb) increased energy dissipation (DI0/RC) and Cadmium (Cd), Cobalt (Co), Iron (Fe) and Lead (Pb) reduced the efficiency of electron transport at 30 msec (F5). The disrupts of components of the electron transport chain was observed in both species, in the two periods evaluated, which indicated the negative effect of trace elements on the electron transport chain. Thus, the extent of damage to these elements in the photochemical step of photosynthesis ranged from the malfunction of the center of evolution of oxygen and connectivity of the components of photosystem II to the oxidation of the final electron acceptors of photosystem I. Such results suggest that the trace elements are impacting vegetation and interfering with the functioning of the plant's photochemical apparatus.