Elevated chromium stress in soil affects plant growth, yield, and nutritional quality of Cassava (Manihot esculenta Crantz).

Abstract

Chromium (Cr) contamination, a major form of heavy metal (HM) pollution, poses serious risks to plant growth, crop productivity, and food quality. This study investigates the effects of Cr(VI) on cassava (Manihot esculenta Crantz) by growing plants in soils amended with increasing Cr(VI) concentrations (0.1-0.4 g/kg). Plant morphological traits, yield performance, nutrient composition, and Cr(VI) accumulation patterns were assessed in controlled pot experiments. Results showed a dose-dependent decline in growth parameters such as plant height, stem diameter, leaf area, and number of leaves. Yield traits including tuber number, diameter, fresh weight and total yield also declined significantly with higher Cr(VI) levels. Nutritional analysis revealed a sharp reduction in tuber starch content (from 494.66 ± 54.6 µg/g in control to 242.33 ± 30.7 µg/g at 0.4 g/kg Cr). Leaf carbohydrate levels initially increased at 3 months after planting (MAP) but declined at 6 and 9 MAP under continued Cr(VI) stress. Cr(VI) exposure also reduced uptake of key micronutrients (Fe, Cu, Zn, Mn) and macronutrients (P, Ca). Notably, tender leaves accumulated more Cr(VI) than mature leaves, while tuber Cr(VI) levels increased with soil Cr(VI) concentrations, suggesting tissue-specific accumulation and detoxification mechanisms. These findings underline cassava's potential for phyto-remediation and raise concerns for food safety in Cr (VI) contaminated environments.