Responses of tropical legumes to nickel stress: impacts on growth, foliar structure, and nitrogen metabolism

Abstract

Nickel, although an essential micronutrient at low concentrations, can exert detrimental effects on plant growth and development when present in excess, particularly due to anthropogenic activities like industrial processes. Leguminous plants, including Calopogonium mucunoides (Calopo) and Canavalia ensiformis (Jack bean), renowned for their nitrogen-fixing symbioses with rhizobia and their potential to enhance soil fertility, were investigated for their differential responses to moderate Ni stress. This study examined the impact of Ni on biomass production, Ni accumulation, leaf anatomy, and nitrogen metabolism in these legumes. Results demonstrated contrasting responses: Jack bean exhibited higher Ni accumulation in both leaves and roots, concomitant with enhanced growth and pronounced anatomical modifications, suggesting greater tolerance. In contrast, Calopo displayed significant alterations in root protein and amino acid content. Principal component analysis corroborated these findings, highlighting distinct acclimatization strategies employed by each species. This research provides valuable insights into the complex impact of Ni on plant biodiversity, emphasizing the importance of investigating understudied species to comprehend the diverse physiological responses to trace element stress.