Silicon-mediated growth, physiological, biochemical and root alterations to confer drought and nickel stress tolerance in Maize (Zea mays L.)

Abstract

Abstract Purpose Abiotic stresses are the leading environmental factors which adversely affect plant growth and development particularly drought and nickel stress. Maize is susceptible to drought and nickel stress from germination to final kernel development stage. The purpose of the current study was to evaluate the role of silicon to improve drought and nickel stress tolerance in maize.Methods Different treatments of the study were i) two drought stress levels (100% field capacity and 60% field capacity) ii) nickel stress (100 mg/kg) and iii) combined stress (drought and nickel stress) were used along with two levels of silicon applications, i) control and ii) 50 mg/kg).Results The result showed that silicon had significant effects on plant growth attributes, including Plant height, Leaf area and Leaf dry weight, stem fresh weight and stem dry weight. Plant height reduced up to 24% under drought stress, and 13% under nickel stress. While silicon application mitigated the adverse effects of these stresses and increased the shoot length upto 35%. Leaf water potential decreased under drought 25% and nickel stress 11% and combined stress showed 53% reduction as compared with control, but silicon application significantly improved the leaf water potential up to 12%. Gas Exchange Parameters i.e, photosynthetic rate, transpiration rate, stomatal conductance and respiration rate were significantly reduced under stress conditions. photosynthetic rate showed more reduction in combined stress (drought and nickel stress). as compared with the control (no stress). Silicon application @ 50 mg/kg improved the gas exchange parameters, protein contents, chlorophyll a and b under stress and non-stress conditions. Chlorophyll a and b increased up to 21% and 32% respectively as compared to control (no silicon application). The H2O2 values increased under the drought and nickel stress conditions and decreased in control-no stress. Drought and nickel stress decreased the levels of the catalase (CAT), peroxide dismutase (POD) and superoxide dismutase (SOD). Soil application of silicon 50 mg/kg improved the values of SOD, POD and CAT.Conclusions In crux, the present investigation suggested that silicon application @ 50 mg/kg mitigated the harmful effects of drought and nickel alone and in combination by improving morpho-physiological, biochemical and antioxidant defense in maize. Si-applied plants significantly improved growth and stronger resistance to stress, which was linked to maintaining plant water status and photosynthetic pigments, lower oxidative damage, and higher activities of antioxidant enzymes under drought and nickel stress.