Physiological and Biochemical Disruption of Maize (Zea mays L.) under Zinc Sulphide-induced Stress

Zinc sulphide (ZnS) application can influence plant growth, with effects varying by concentration and plant variety. This study evaluated the impact of ZnS on two maize (Zea mays L.) cultivars, AS-5277 and 30-K08, focusing on biomass production, photosynthetic pigments, and biochemical traits. Five ZnS concentrations (0.1–0.3 g/100 ml, denoted T1–T5) were applied, compared to a control. Growth parameters (plant height, root length, fresh and dry weight, moisture content, leaf width) and photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoids) were measured, alongside flavonoid, sugar, and phenol content. Lower ZnS concentrations (T1: 0.1 g/100 ml, T2: 0.15 g/100 ml, T3: 0.2 g/100 ml) significantly enhanced plant height, root length, fresh and dry weight, and leaf width in both varieties, with AS-5277 showing greater improvements than 30-K08. Chlorophyll a, chlorophyll b, and carotenoid contents increased at lower concentrations, peaking at T3, but declined at higher concentrations (T4: 0.25 g/100 ml, T5: 0.3 g/100 ml). Similarly, flavonoid, sugar, and phenol contents increased at lower concentrations, with AS-5277 exhibiting more pronounced enhancements. Higher ZnS levels inhibited growth, reduced pigment levels, and lowered biochemical contents, indicating toxicity. These findings underscore ZnS’s dual role as a beneficial micronutrient at low doses and a toxicant at high doses, with varietal differences in response. Optimizing ZnS application rates is crucial to enhance maize growth and biochemical activity while minimizing toxicity risks.