Mecanismos fisiológicos de ilex paraguariensis a. St.-Hil. exposta a diferentes concentrações de cádmio

Abstract

The expansion of agribusiness activities has caused a number of environmental damages. In this sense, we can highlight soil contamination by heavy metals (such as cadmium, lead, and arsenic), originating from pesticides and fertilizers used by this sector. These contaminants represent a great danger to the health of all living beings, as they accumulate in the soil and enter the food chain. This study sought to investigate the physiological mechanisms of the species Ilex paraguariensis when exposed to different concentrations of cadmium in the soil, to evaluate its tolerance capacity and its potential use as a phytoremediation strategy. The specific objectives included the analysis of general physiological responses (biomass, height, root length, leaf area and chlorophyll content) and photosynthetic responses (CO₂ assimilation rate, carboxylation efficiency, water use efficiency, stomatal conductance, and photosystem II efficiency). The results indicated that exposure to cadmium at moderate concentrations (1.5, 3 mg Kg-1) was not only tolerated by the species, but also promoted positive effects on some physiological variables, such as a significant increase in photosynthetic efficiency (Y`), electron transport rate (ETR), net photosynthetic rate (A), water use efficiency (WUE), and the A/Ci ratio. These effects suggest the occurrence of a hormetic response. However, exposure to higher concentrations of Cd (6 mgKg-¹) triggered a reduction in performance in some of these variables, indicating a tolerance limit for this species. In general, the results indicate that the species Ilex paraguariensis presents physiological defense mechanisms that enable its acclimation when subjected to moderate stresses caused by cadmium. The analysis also suggests that the beneficial effects observed at lower concentrations of Cd may represent an adaptive potential for the eventual application of the species in phytoremediation processes.