Tolerância e resposta bioquímica de Canavalia ensiformis sob estresse por cádmio

Abstract

Soil contamination by cadmium (Cd) represents an important environmental challenge due to its high toxicity, persistence, and negative effects on plants, organisms, and ecosystems. In light of the need for sustainable alternatives for the recovery of degraded areas, this study evaluated the phytoremediation potential of jack bean (Canavalia ensiformis) through morphophysiological and biochemical analyses following exposure to Cd. The experiment was conducted in a greenhouse using pots filled with sterilized sand and four treatments (0, 300, 600, and 900 μmol L⁻¹), applied as a single dose after 36 days of seedling cultivation, ensuring complete root establishment. The plants remained exposed to the metal for 8 days. Growth parameters (shoot height, root length, shoot and root dry mass), Cd concentration in plant tissues, the translocation index (TI), soluble protein concentrations, and the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) in leaves were evaluated. The results indicated no significant differences in morphophysiological characteristics, suggesting initial tolerance to Cd stress during the assessed period, although visual signs of damage were observed at the highest concentrations. Determination of Cd concentrations revealed increasing, dose-dependent accumulation, with a predominance in roots, a pattern consistent with species that act mainly through phytoestabilization. The TI increased with the doses but remained at moderate levels, indicating limited transport of the metal to the shoot. From a biochemical perspective, no statistical differences were observed for soluble protein concentrations or for the activity of SOD and CAT, suggesting that the short exposure period was not sufficient to trigger strong antioxidant responses in the leaves, although variation trends reinforce the onset of defense system activation. The results show that C. ensiformis combines robustness, the ability to accumulate Cd in roots, and maintenance of metabolic functions under moderate stress conditions, demonstrating its potential for phytoremediation, especially in phytoestabilization strategies. It is concluded that the species represents a viable, low-cost, and environmentally appropriate alternative for mitigating Cd-contaminated areas, and future studies are recommended to include longer exposure periods, different soil types, evaluation of additional enzymes, repeated application cycles, and interactions with rhizospheric microorganisms to further improve the understanding of the species’ phytoremediation efficiency.