Soil contamination by trace elements is a worldwide concern that can result from several sources, such as mining, smelting, car traffic exhaust, agriculture plant protection products such as fungicides, and fertilizers. Among the metals involved, copper can cause alterations in the photosynthetic, respiratory, and enzymatic processes of plants, leading to reduced growth of roots and shoots. An alternative to dealing with metals present in the soil is phytoremediation, which consists of using plants to extract or stabilize these elements. The leguminous Crotalaria juncea is widely used as a green manure and may be advantageous due to its capacity for biological nitrogen fixation and biomass accumulation. This research aimed to evaluate the growth and physiological behaviour of C. juncea in copper-contaminated soil and its potential use as a phytoremediation plant. For the fresh and dry mass of shoots and roots, compared with 30 mg.dm⁻³ of Cu, there was a decrease in values with the increase in concentrations up to a dose of 480 mg.dm⁻³. The roots were less sensitive to increased Cu concentrations than the shoots. The tolerance index decreased as copper concentrations in the soil increased. From 60 mg.dm⁻³, its vegetative growth decreased, but C. Juncea was able to tolerate and accumulate copper in the root system, presenting high potential as a phytostabilizing species.

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.

Brazilian soils are predominantly rich in aluminum, which becomes mobile at pH < 5, affecting sensitive plants; however, some species have developed aluminum tolerance mechanisms. The purpose of this study was to compare the physiological responses of Crotalaria genus species, family Fabaceae, which have the ability to associate with nitrogen-fixing bacteria under the influence of Al³⁺ in the soil. The soil used was Oxisol; the experimental design was in randomized blocks in a factorial scheme (2 × 3): soil factor (available toxic aluminum content; correction of dolomitic limestone—MgCO₃) and species factor (C. juncea; C. spectabilis; C. ochroleuca); cultivated within 43, 53, and 53 days, respectively, with five replications; 30 experimental samples. Mass and length, pigments, gas exchange, and changes in nitrogen metabolism were evaluated. C. juncea showed a higher concentration of amino acids in the leaves, internal carbon, and stomatal conductance in soil with Al³⁺, as well as higher production of ureides, allantoinic acid, allantoic acid, proteins, and amino acids in the nodules, with 78% of the Al³⁺ accumulation occurring in the roots. C. ochroleuca demonstrated greater shoot length and nodule number production in limed soil; in soil with Al³⁺, it showed a 91% increase in chlorophyll a content and 93% in carotenoids. C. spectabilis showed a 93% increase in ureide production in the leaves in soil with Al³⁺.

Zinc (Zn) is an essential micronutrient in the plant life cycle, playing catalytic, structural, and regulatory roles in various physiological processes. However, when present in excess, Zn becomes a potentially toxic element (PTE), causing adverse effects ranging from impaired seed germination to inhibited plant growth and development. Understanding plant responses to increasing Zn concentrations in the soil is fundamental for the recovery of degraded areas and for assessing phytoremediation potential. This study aimed to evaluate the effects of different Zn concentrations on the emergence of Moringa oleifera Lam. seedlings, comparing the responses to two Zn sources in the soil: zinc chloride (ZnCl₂) and zinc sulfate (ZnSO₄). The experiment was conducted in a greenhouse under a completely randomized factorial design with four replicates. Treatments consisted of six Zn concentrations: 0 (control), 100, 200, 300, 400, and 500 mg Zn dm^-3 of soil, for both sources. After a 30-day stabilization period (days after element application, DAE), M. oleifera seeds were sown and maintained for 15 days, after which emergence and biometric parameters were evaluated. Data were subjected to analysis of variance, and when significant differences were detected, the Scott-Knott test at a 5% significance level was applied to compare treatments and sources. High Zn concentrations (400 and 500 mg Zn dm^-3 of soil) negatively affected seedling emergence, regardless of the Zn source. ZnSO₄ proved to be the more phytotoxic source, significantly reducing both the emergence percentage and speed, as well as biomass accumulation in the seedlings.

Micronutrients when present in high concentrations can become toxic to plants. Nickel exemplifies this phenomenon, having been considered essential for higher plants since the 1980s. Despite its beneficial effects on seed germination, growth and photosynthesis, an excess of Ni triggers the production of reactive oxygen species, thus exerting harmful effects on physiological and biochemical processes. The literature on this element exists mainly in narrative form, lacking scoping and systematic reviews and meta-analyses, which are crucial for understanding the progression of research in this field over the decades and for conceiving new directions of investigation. To begin to fill this gap, our scoping review, conducted using the PRISMA protocol, aims to outline the plant species under study, methodologies employed, and physiological markers used by peer-reviewed articles published from 2013 to 2022 focusing on the Fabaceae family, taking into account their diversity, economic, social importance and potential for use in phytoremediation programs. Our key findings indicate that Glycine max emerges as the most extensively studied species within the Fabaceae family. Research efforts predominantly target biotic stress, fertilization, and toxicity as primary objectives. However, categories covering physiological data such as nodules, biological nitrogen fixation, carbon metabolism, and gas exchange were underrepresented in the literature.