Silicon-mediated improvement in the salt resistance of wheat (Triticum aestivum) results from increased sodium exclusion and resistance to oxidative stress

Silicon (Si) is reported to reduce the effect of salinity on wheat (Triticum aestivum L.) and other crops. In the present study, Si decreased plant Na⁺ uptake and shoot : root Na⁺ distribution of a salt-resistant as well as a salt-sensitive wheat genotype. Reduced shoot Na⁺ concentration and increased shoot K⁺ : Na⁺ ratio led to improved plant growth. Silicon increased cell-wall Na⁺ binding from 49% in SARC-1 and 37% in 7-Cerros under salinity to 87% in SARC-1 and 79% in 7-Cerros under salinity + silicon. It may also have resulted in decreased potentially toxic leaf sap Na⁺ concentration. The concentration of glutathione, an important antioxidant in plants, was increased due to the addition of Si under saline conditions. The salt-resistant wheat genotype SARC-1 was less Si-responsive in terms of shoot fresh weight, having a 39% increase compared with a 49% increase in 7-Cerros, as well as root fresh weight, having a 12% increase compared with a 22% in 7-Cerros. It is concluded that Si may have improved shoot growth of the salt-resistant as well as the salt-sensitive wheat genotype by decreasing plant Na⁺ uptake and shoot : root Na⁺ distribution as well as by increasing glutathione concentration. Silicon may have also improved in-plant Na⁺ detoxification by increasing cell-wall Na⁺ binding.