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Abstract

Nickel (Ni) contamination of agricultural soils is a serious issue that disrupts physiological and biochemical plant functions and hence crop production. Maize (Zea mays L.) was used to evaluate the possible stress relieving effects of the rhizospheric fungus Aspergillus terreus caused by Ni. Ni was tested to be intolerant of rhizospheric fungi at different concentrations (50, 100 and 200 ppm). The experiment on pots was completed in a greenhouse environment with four treatments of control, fungus inoculation, nickel stress (100 ppm), and nickel + fungus with completely randomized design (CRD). Stress by nickel led to massive reduction in root length (95%), shoot length (73%), fresh (98%), and dry weight (99%). Photosynthetic pigments too were reduced: chlorophyll a (26%), chlorophyll b (21%), carotenoids (86%) and xanthophylls (67%). In contrast, A. terreus inoculation enhanced plant growth parameters and restored physiological balance under nickel stress. Chlorophyll a and b increased by 12% and 19%, carotenoids by 74%, and xanthophylls by 52% upon fungal inoculation. Nickel stress also elevated flavonoid and phenolic contents by 89% and 84%, respectively, indicating oxidative stress activation. Fungal inoculation reduced these stress markers by 87% and 86%, respectively, while proline and lipid contents were also reduced by 47% and 32% upon inoculation. Sugar content, severely reduced by Ni stress (97%), was recovered by 94% following A. terreus inoculation. These findings indicate that Aspergillus terreus is an effective biological agent for mitigating nickel toxicity in maize.

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