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 (Poa pratensis L.) responses to salinity stress. The five salinity levels (0, 20, 40, 60, and 80 mm NaCl) were applied in nutrient solutions and TE treatments (0, 1, and 1.7 g/100 m2) were applied twice at 4-week intervals. Under non-saline conditions and low level salinity conditions, application of TE at 1 g/100 m2 (TE1) increased turf quality (TQ), leaf total 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 m2 had lower proline, Na+, and malondialdehyde (MDA) contents. However, the adverse effects of high salinities were more pronounced when turf was treated by TE at 1.7 g/100 m2 (TE1.7), suggesting that effects of TE on salt tolerance vary with its dosages and salinity levels. We concluded that moderate inhibition of GA biosynthesis by TE enhances salt tolerance in kentucky bluegrass and suggest that enhancement is the result of the maintenance of antioxidant activities, leading to more root growth and greater levels of TNC and Chl content. Chemical names used: 4-(cyclopropyl-β-hydroxymethylene)-3, 5-dioxocyclohexanecarboxylic acid ethyl ester (trinexapac-ethyl).
Masoud Arghavani, Mohsen Kafi, Mesbah Babalar, Roohangiz Naderi, Md. Anamul Hoque and Yoshiyoki Murata
Reza Salehi, Abdolkarim Kashi, Jung-Myung Lee, Mesbah Babalar, Mojtaba Delshad, Sang-Gyu Lee and Yun-Chan Huh
Photosynthetic characteristics, concentrations of mineral elements in xylem sap, and some vegetative traits of ‘Khatooni’ melon were compared with those of melons grafted onto three Cucurbita rootstocks cvs., Ace, Shintozwa, and ShintoHongto, and trained with three methods: T1) no pinching and fruit thinning; T2) pinched to produce two lateral branches; and T3) pinched to two branches and all the flowers and lateral branches from lower nodes thinned. Internal CO2 and water use efficiency varied with rootstocks. Stem diameter of scions, aerial fresh and dry weights, mean fruit weight and yield, electric conductivity, pH, and sap volume per plant of grafted plants were higher in grafted melons than in the nongrafted ones. These traits were unaffected by training methods. Mineral concentrations varied considerably depending on the rootstocks and training methods used. Xylem sap collected from the decapitated stem base of grafted melons trained with T2 and T3 methods contained a higher amount of mineral ions, especially NO3 −, PO4 3−, and K+, than did the sap from own-rooted plants. The increase in the mineral levels in sap resulting from grafting was most apparent in ‘Khatooni’ grafted onto ‘ShintoHongto’ rootstock.