Effects of iron and copper on emergence and physiology of Canavalia ensiformis (l.) DC

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.