Nitrogen and carbohydrate metabolisms are key factors in maize (Zea mays L.) germination under chromium-induced ROS

Abstract

Heavy metals, such as chromium (Cr), are continuously introduced into the environment through human activities, notably from the excessive use of pesticides, synthetic fertilizers, and irrigation with sewage and industrial wastewater. These substances induce oxidative stress in plants, disrupting crucial morphological and biochemical processes. Seed germination and early plant development are vital stages in the life cycle of plants, heavily reliant on nitrogen metabolism and associated biochemical pathways for energy accumulation. This study aimed to assess the phytotoxic effects of chromium on the growth and biochemical parameters of germinating seedlings from two maize varieties, Pak-Afgoi and Neelem Desi. The findings revealed significant suppression caused by chromium, leading to reduced seed germination rates, embryonic growth, vigor index, and biomass. Nitrogen and protein levels, as well as nitrate reductase activity, were notably affected, with Pak-Afgoi showing lower decreases compared to Neelem. Carbohydrate mobilization and total sugar content also decreased with rising chromium concentrations, although Pak-Afgoi exhibited better nitrogen and carbohydrate utilization rates. Furthermore, oxidative stress markers like hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) indicated damage to growth and biochemical attributes in maize. Interestingly, proline levels increased with higher chromium concentrations, suggesting a protective role in maintaining seedling viability during metabolic disruptions. These results underscore the detrimental impact of chromium on maize growth by altering plant nitrogen and carbohydrate metabolisms and inducing oxidative stress.