Effect of stabilization time and soil chromium concentration on Sesbania virgata growth and metal tolerance

Abstract

Sesbania virgata is a pioneer shrub from the Fabaceae family, native to riparianenvironments in northeast of Argentina, southern of Brazil and Uruguay. In peri-urbanriparian soils, metal contamination is a frequent problem, being its bioavailability partlydetermined by the stabilization time and frequency of contamination events. The effectof time elapsed between chromium (Cr) soil enrichment and plant seeding and Cr doseson S. virgata tolerance and metal absorption were evaluated. Treatments weredeveloped by adding Cr (80-400 ppm) to the soil and allowing two days or fifteenmonths to elapse before sowing, and a control treatment without Cr addition. After 150days from seeding, bioaccumulation and translocation factors, growth parameters (drybiomass and its aerial/radical allocation pattern, stem length and its elongation rate),morphological parameters (root volume and leaf area), and physiological parameters(chlorophyll content) of the specimens were determined. The emergence of S. virgatawas inhibited since 150 ppm when Cr was added to the soil two days before seeding,with Cr accumulation in roots starting at 80 ppm (17.4 ± 2.5 mg∙kg -1 ). Under 15 monthsof metal stabilization, S. virgata plants survived across the entire range of Cr dosestested, with accumulation in roots since 100 ppm (35.5 ± 0.2 mg∙kg -1 ) and metaltranslocation to aerial tissues only under 400 ppm. The results obtained showed that S.virgata did not have high BCF and TF values, suggesting that it cannot be classified asbioaccumulator of Cr under the tested conditions. However, its presence in environments contaminated with Cr can be beneficial, as it helps to stabilize the metal in the soil.