Zoysiagrass is a warm-season grass that is relatively resistant to cold and drought stresses. This grass is grown in temperate regions. Available water resources for irrigation of the grass in the recent years has been declining. Different management methods for water requirement of the grass have been used. The use of plant growth regulators has also been used in the management of this grass in this study. This study evaluated the effects of Trinexapac-ethyl on the physiological characters of this grass conducted in a factorial experiment in a completely randomized design with three replications. Rhizomes of 5 cultivars of Zoysiagrass ( Zoysia matrella ) were planted in pots with 20 cm diameter in the greenhouse at Isfahan University of Technology (IUT). Treatments included withholding irrigation and spraying ethyl without Trinexapac-Ethyl (drought stress + TE) two weeks prior to the stress period with the Trinexapac-ethyl concentration in spray (1.95 ml L-1). The results showed that shoot soluble sugar content and relative water content increased by Trinexapac-Ethyl application. Proline content also increased by Trinexapac-ethyl treatment. However, no significant difference was observed under drought stress without Trinexapac-ethyl. The chlorophyll and carotenoid contents increased by Trinexapac-ethyl treatment. During the drought stress period, ion leakage increased without Trinexapac-Ethyl. But, drought stress + TE treatment decreased ion leakage in all the varieties of Zoysia matrella . Catalase enzyme activity in drought + TE treatment also increased. The highest sugar content, proline, chlorophyll, and carotenoid in cultivars 3 and 14 of the Zoysia matrella were obtained by TE applications under drought stress condition. These cultivars also had higher catalase activity, but the others showed no significant differences. Also, cultivar 14 had more catalase enzyme activity with significant difference compared with other cultivars. Generally, Trinexapac-ethyl increased soluble sugars, chlorophyll content, carotenoids, enzyme activity reduced plant height, and improved the quality of the grasses. Finall, Trinexapac-ethyl had a significant role in reducing drought stress. Key words : catalase enzyme. Trinexapac-ethyl. Proline. Zoysiagrass
