Abstract

Abstract.Trinexapac-ethyl (TE) is a popular plant growth regulator in the turfgrass industry that inhibits gibberellic acid (GA) biosynthesis and effectively reduces leaf elongation and subsequent clipping production. This greenhouse sand culture experiment was conducted to determine effects of TE application on Kentucky bluegrass (PoapratensisL.) responses to salinity stress. The five salinity levels (0, 20, 40, 60 and 80 mmNaCl) were applied in nutrient solutions and TE treatments (0, 1 and 1.7 g·100m^-2) were applied twice at 4 weeks intervals. Under non-saline condition and low level salinity condition, application of TE at 1 g·100 m^-2(TE₁)increased turf quality (TQ), leaftotal non-structural carbohydrates (TNC) and chlorophyll (Chl) content.In high salinity, TE₁ alleviated the decline in TQ, antioxidant enzyme activities, leaf TNC, Chl and K⁺ content. In addition, treated turf with TE at 1 g·100 m^-2 had lower proline, Na⁺ and malondialdehyde (MDA) content.However, the adverse effects of high salinities were more pronounced when turf was treated by TE at 1.7 g·100 m^-2(TE_1.7),suggesting that effects of TE on salt tolerance varies with its dosages and salinity levels.We concluded that moderate inhibition of gibberellic acid biosynthesis by TE enhances salt tolerance in Kentucky bluegrass and suggest that enhancement is due to the maintenance of antioxidant activities, leading to more root growth and greater levels of TNC and Chl content. Chemical name used: 4-(cyclopropyl-ß-hydroxymethylene)-3, 5-dioxocyclohexanecarboxylicacid ethyl ester (trinexapac-ethyl).