Amelioration of Salt Stress in Grapevines Based on Use of Both Resistant Rootstocks and Exogenous Silicon

Abstract

Salt stress was induced on grape vines with 100 mM NaCl and amelioration was evaluated by irrigating with 100 mM NaCl plus 2.0 mM K ₂SiO ₃·9H ₂O for 30 days. The three cultivars tested included ‘Cabernet Sauvignon’, the rootstock ‘5BB’, and ‘Cabernet Sauvignon’ grafted onto ‘5BB’. Plant daily height increment and the dry weight of the whole plant were significantly suppressed by NaCl. Na ⁺and Cl ^-accumulation (AIR) was significantly increased by salt stress, with an AIR order: leaves > stems > roots. The total N and P concentrations were significantly reduced by NaCl stress. The K ⁺concentration in the roots and the stems was also significantly decreased by salt stress, however it was significantly increased in the leaves. For all cultivars, Tr, Gs, Ciand Pnwere significantly reduced by NaCl, except Ci for ‘5BB’. The palisade and spongy leaf tissue thickness was significantly reduced by salt treatments. The order of salt stress tolerance was ‘5BB’ rootstock > grafted plants > ‘Cabernet Sauvignon’. Exogenously applied silicon significantly restored plant growth by 15.4 to 37.2% and 7.9 to 14.0% for the plant daily increment and the dry weight of the whole plants, respectively. Na ⁺and Cl ^-accumulation was also suppressed by 8.0 to 53.8% and 20.1 to 47.5%, respectively. In most cases the N and P concentrations were significantly increased, and leaf K+ concentration was significantly decreased in the NaCl + Si treatment compared with the NaCl treatment, suggesting that both potassium and silicon are involved in ameliorating the adverse saline effects. Amelioration by exogenous silicon was further evidenced by enhanced photosynthetic indexes and leaf anatomy. Considering the extent of salt stress injury and restoration by exogenous silicon, the effective silicon restoration for the three cultivars was: ‘5BB’ rootstock > grafted plants > ‘Cabernet Sauvignon’. Ten of the 16 studied variables, including the daily height increment, dry weight, Na ⁺, Cl ^-, N, K ⁺, Na ⁺/K ⁺, Tr, Gs, and the leaf spongy tissue thickness, responded positively to both NaCl stress and exogenously applied silicon, suggesting that these parameters may be reliably used in future studies.