Abstract: A study has been undertaken to explore the effect of silicon supply on the salt tolerance of two varieties of tall fescue (Festuca arundinacea), XD and K31. XD has stronger resistance to salinization than K31. A pot experiment was conducted to investigate the effect of silicon on the plants’ morphological indexes and protective enzyme activities under different salinization conditions. The results showed that plant height, tillers, leaf number, leaf length, leaf width, the aboveground biomass and water content of K31 and XD presented a decreasing trend with increases in salinity. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) firstly increased and then decreased with rising salinity. The activity of protective enzymes in XD and K31 peaked when salt concentrations were 150 and 100 mmol·L^-1. Silicon supplies significantly increased the tillers, leaf numbers, leaf length, plant height, aboveground biomass and water content, as well as SOD, POD and CAT activities, but the response of the two kinds of tall fescue varied under different salt concentrations. Silicon supplies significantly increased the tillers and leaf numbers of XD when salinity was below or at 50 mmol·L^-1, but they did not affect K31. However, the leaf length, plant height, aboveground biomass, SOD and CAT activities of XD significantly increased when salinity was below or at 100 mmol·L^-1. Silicon supplies also significantly increased the leaf length, plant height and aboveground biomass, SOD, POD and CAT activities of K31 when salt concentration was 150 and 200 mmol·L^-1. These results indicate that silicon supplies could enhance the salt resistance of both kinds of tall fescue and that the extent of enhancement varies with salt concentration and the degree of tall fescue resistance. Under higher salinization conditions, the improving effect of silicon supply on salt tolerance was stronger in tall fescue with weak salt tolerance. These results show that it is possible to expand the adaptive range of tall fescue by supplying silicon.

Key words: tall fescue, salinity, silicon, morphological parameter, protective enzyme