Plants require iron (Fe) and copper (Cu) at low concentrations for metabolic functions; however, excess soil Fe and Cu can cause toxicity and affect plant development. The objective of this study was to assess the effects of soil Cu and Fe concentrations on seedling emergence, as well as on the metabolism of the main reserve compounds and the biomass in roots, stems, leaves, and cotyledons of Canavalia ensiformis. A greenhouse experiment was conducted in a completely randomized design; the Cu and Fe treatments in the soil were: (control, 50, 150, 250 and 350 mg dm^-3) over a period of 10 days. Seedling emergence was not affected by the evaluated treatments; however, the results showed an increase in the emergence speed index (EVI) for the Fe treatment at a dose of 150 mg dm^-3 of soil compared to 350 mg dm^-3 of soil. Treatment with Cu at a dose of 350 mg dm^-3 of soil reduced root length. Cu treatments reduced root dry mass. Fe treatments affected the content of soluble amino acids in the stems, leaves and cotyledons, as well as the total soluble proteins in the cotyledons and the carbohydrate content in the leaves. Cu treatments increased protein and carbohydrate content in leaves and starch content in cotyledons. High concentrations of Cu and Fe modify the production of nitrogenous compounds in the plant and reduce root biomass.

Copper (Cu) is a naturally occurring element in soils, and at adequate concentrations, it is essential for plant survival. However, excessive Cu can lead to contamination, impairing soil quality and affecting the development of living organisms. The present study aimed to evaluate the physiological responses of Stizolobium aterrimum plants grown in soils contaminated with increasing doses of copper. The experiment was conducted in a greenhouse under controlled temperature conditions. Five treatments were applied (0, 30, 60, 240, and 480 mg dm⁻³). After 51 days of cultivation, the plants were harvested, and their tissues were separated into leaves, roots, and nodules. Nitrogen compounds were extracted, and the contents of total soluble amino acids, ureides, and soluble proteins were quantified. The activity of the nitrogenase enzyme was analyzed in vivo. The results indicate that Stizolobium aterrimum is partially tolerant to copper contamination, exhibiting adequate growth and metabolism in the presence of moderate Cu concentrations. However, increasing Cu levels in the soil reduce fresh biomass production and lead to higher copper accumulation in the root system. High soil Cu concentrations also affect the absorption of other nutrients, in addition to copper itself. Cu doses around 240 mg dm³ can already be considered toxic.

High boron (B) concentrations in the soil can cause toxic effects to plants, so herbaceous cotton (Gossypium hirsutum latifolium Hucth) is a crop sensitive to such stress. Thus, this study aimed to evaluate the emergence, partitioning, and allocation of metabolic compounds of two herbaceous cotton cultivars subjected to B treatments. The experiment was carried out in a greenhouse, under a completely randomized design in a 2 × 4 factorial scheme, using two cultivars and four concentrations of B in the form of boric acid: 0.5 (control), 30, 60, and 120 mg dm⁻³ B. The increase in the concentration of B in the soil generated a significant toxic effect on the growth and biomass of the cotton plant. Cultivar 1—TMG 50 WS3 obtained greater emergence and shoot growth, while cultivar 2—FM 911 GLTP invested in roots; however, in both cultivars, B remained accumulated in the shoot. There was an increase in amino acids in the roots and a decrease in proteins and phenolic compounds in leaves and cotyledons. It was concluded that the seedlings presented satisfactory emergence up to 60 mg dm⁻³ B, and that among the cultivars there are distinct responses to B application.

The accumulation of heavy metals, such as lead (Pb), causes environmental degradation, affecting human health and plant metabolism. Pb can alter plant physiological processes, including photosynthesis, influencing the structure of chloroplasts and leaf tissues. The present study aimed to evaluate the effect of increasing lead concentrations in soil on gas exchange, photosynthetic pigments, and the anatomy of leaf tissues in Inga vera subsp. affinis and Inga laurina. The experiment was conducted in a greenhouse using a randomized block design in a 2 × 6 factorial scheme, with Pb concentrations of 0, 100, 200, 300, 400, and 500 mg dm⁻³. I. vera subsp. affinis and I. laurina maintained stable photosynthetic parameters even under high Pb concentrations. Regarding photosynthetic pigments, I. vera subsp. affinis exhibited high levels of chlorophyll a and b, even at the highest Pb concentration. Additionally, I. laurina showed a greater accumulation of carotenoids and phenolic compounds at higher Pb doses. In leaf tissues, Pb did not alter thickness. These results suggest that both species possess adaptation mechanisms to heavy metal stress, enabling the maintenance of photosynthetic activity and ensuring the completion of their life cycle under adverse conditions.

Plants need boron (B) in low concentrations to carry out structural and metabolic functions. However, excess B in the soil can cause problems in plant emergence and development. This study aimed to evaluate the emergence responses and production of nitrogen compounds of herbaceous cotton (Gossypium hirsutum L.R. latifolium Hutch) germinated in soil with high concentrations of B. The experiment was carried out in a greenhouse, under a completely randomized design, using different concentrations of B, at concentrations 0.5 (control), 30, 60, and 120 mg B dm^-3 soil. Plants were cultivated for 15 days, for evaluation of emergence parameters, and reserves partition and allocation. There was a significant effect of the B application on the emergence velocity index (EVI), emergence percentage, and shoot length. We observed a decrease in the shoot dry mass production and a significant increase in photosynthetic pigments; the concentrations of total soluble amino acids in stems, leaves, and cotyledons, as well as the concentrations of total soluble protein in cotyledons and the concentrations of starch present in all organs, were affected. G. hirsutum showed signs of phytotoxicity in the treatment of 120 mg B dm^-3, for all evaluated parameters.

Heavy metal contamination represents a significant environmental challenge, requiring sustainable strategies for the recovery of degraded soils. Phytoremediation has emerged as a promising alternative, especially when associated with plant growth-promoting microorganisms. In this context, Bacillus subtilis presents significant biotechnological potential due to its ability to promote plant growth, modulate stress responses, and interact with metals in the soil. Recent studies demonstrate that this bacterium can reduce the toxicity of elements such as, cadmium, lead, and copper through mechanisms such as, biosorption, production of chelating metabolites, and induction of antioxidant systems in plants. Furthermore, its resistance to adverse conditions favors its application in contaminated environments. Thus, the association between plants and B. subtilis constitutes an efficient and ecologically viable approach for the remediation of impacted soils.