Silicon-induced increase in chlorophyll is modulated by the leaf water potential in two water-deficient tomato cultivars

This study aims to explain the effects of silicon on chlorophyll and to measure gas exchange and carbohydrate levels in two Lycopersicon esculentum cultivars that are exposed to drought. The experimental design used in this study was a randomised combination of five different water and silicon conditions (control, water deficit + 0.00 micromol Si, water deficit + 0.25 micromol Si, water deficit + 1.00 micromol Si, and water deficit + 1.75 micromol Si) applied to the two cultivars (Super Marmante and Santa Cruz). Gas exchanges, levels of chlorophylls and total soluble carbohydrates were evaluated. Silicon at concentrations of 0.25, 1.00, and 1.75 micromol induced a gradual increase in total chlorophyll levels. A correlation analysis revealed a linear, positive interaction between the leaf water potential and chlorophyll levels (r = 0.71; P less than 0.05). This study confirmed the hypothesis that Si has a beneficial effect with regard to chlorophyll. Under water-deficient conditions, both cultivars showed an increase in the level of chlorophyll a when treated with Si in addition to changes in the total chlorophyll levels. These results were supported by the change in leaf water potential. In addition, a reduction of the effects of water restriction was also observed in the transpiration rate, the stomatal conductance and in the levels of total carbohydrates.