Silicon Supply Improves Leaf Gas Exchange, Antioxidant Defense System and Growth in <i>Saccharum officinarum</i> Responsive to Water Limitation

Silicon (Si) is not categorized as a biologically essential element for plants, yet a great number of scientific reports have shown its significant effects in various crop plants and environmental variables. Plant Si plays biologically active role in plant life cycle, and the significant impact depends on its bioaccumulation in plant tissues or parts. In particular, it has been investigated for its involvement in limited irrigation management. Therefore, this experiment was conducted to examine the effect of Si application in eco-physiological, enzymatic and non-enzymatic activities of sugarcane plants against water stress. Four irrigation levels, i.e., normal (100–95% of soil moisture), 80–75, 55–50, and 35–30% of soil moisture were treated for the sugarcane cultivar GT 42 plants supplied with 0, 100, 200, 300, 400 and 500 mg Si L⁻¹ and exposed for 60 days after Si application. Under stress, reduction in plant length (~26–67%), leaf area-expansion (~7–51%), relative water content (~18–57%), leaf greenness (~12–35%), photosynthetic pigments (~12–67%), physiological responses such as photosynthesis (22–63%), stomatal conductance (~25–61%), and transpiration rate (~32–63%), and biomass production were observed in the plants without Si application. The drought condition also inhibited the activities of antioxidant enzymes like catalase (~10–52%), peroxidase (ca. 4–35), superoxide dismutase (10–44%) and enhanced proline (~73–410%), and malondialdehyde content (ca. 15–158%), respectively. However, addition of Si ameliorated drought induced damage in sugarcane plants. The findings suggest that the active involvement of Si in sugarcane responsive to water stress ranges from plant performance and physiological processes, to antioxidant defense systems.