Silicon alleviates the deleterious salt effect on tomato plant growth by improving plant water status

In order to investigate the role of Si in alleviating the deleterious effects of salinity on tomato plant growth, the tomato cultivar Moneymaker was grown with 0 or 80mM NaCl combined with 0 and 2.5mM Si. Plant growth parameters, salt accumulation in plant tissues and plant water relations were analysed. Si treatment did not alter salt input into the plant or salt distribution between plant organs. There were non-significant differences in plant water uptake, but plant water content in salinised plants supplied with Si was 40% higher than in salinised plants that were not supplied with Si. Plants treated with NaCl alone showed a reduction in plant dry weight and total plant leaf area of 55% and 58%, respectively, while the reduction in plants treated with NaCl plus Si was only 31% and 22%, respectively. Leaf turgor potential and net photosynthesis rates were 42% and 20% higher in salinised plants supplied with Si than in salinised plants that were not supplied with Si. Water use efficiency calculated from instantaneous gas exchange parameters and as the ratio between plant dry matter and plant water uptake were, respectively, 17% and 16% higher in salinised plants supplied with Si. It can be concluded that Si improves the water storage within plant tissues, which allows a higher growth rate that, in turn, contributes to salt dilution into the plant, mitigating salt toxicity effects.