Avaliação dos parâmetros de crescimento, área foliar e clorofila de Mentha crispa L. cultivada em solo contaminado com Cd e Zn

Abstract

Some anthropic activities accumulate heavy metals in the environment, such as Zinc (Zn) and Cadmium (Cd). For soil decontamination, it is necessary to apply remediation techniques, such as phytoremediation, which uses contamination-tolerant plants to promote the removal of these metals from the soil. Thus, the present work aimed to evaluate the tolerance of Mentha crispa L. cultivated in an Oxisol contaminated simultaneously with Cd and Zn. Tolerance was evaluated through growth parameters (height, number of shoots and leaves), leaf area, and chlorophyll concentration. Cultivation lasted 115 days in soil contaminated with increasing concentrations of Zn and Cd (treatments from C1 to C7) and control treatment (without the addition of metals). Every 15 days, growth parameters, chlorophyll concentration, and leaf area were measured. Plants cultivated in treatments C6 and C7 with concentrations of metals above the Maximum Adsorption Capacity (MAC) of the soil did not resist the toxicity of metals and died, being removed from the experiment. The control treatment (C0) showed better growth parameters such as height and number of leaves and shoots. In the treatments from C1 to C4, below the CMA, in which metal concentrations are already considered high, the plant was very tolerant, with a slight reduction in height, number of shoots, and leaves. Treatment C5, which corresponds to CMA, reduced by 38.33%, 71.32%, and 33.82% for height, number of buds, and leaves, respectively, compared to C0, being the parameter with less development, which may indicate metal toxicity. Regarding the concentration of chlorophyll and leaf area, the values obtained did not show anomalies when comparing the treatments from C1 to C5 with the control treatment C0. Roots showed greater length and biomass reductions relative to the increase in metal concentration in the soil. There was also a decrease in shoot biomass for treatments with higher metal contents in the soil, C3 (158.59 g), C4 (142.49 g), and C5 (97.88 g). Therefore, this work concludes that the Mentha crispa L. plant appears to be tolerant when cultivated in an Oxisol contaminated simultaneously with the metals Cd and Zn up to concentrations that correspond to the AMC of the soil. This plant can be indicated for evaluation of the phytoremediation process.