Effect of Trinexapac-Ethyl on the Quality and Physiological Constituents of Perennial Ryegrass (Lolium perenne L.) in the Salinity Conditions

Turf is one of the most important ground covers and it is one of the main elements of urban landscape design. Plant growth regulators، such as growth inhibitors، are widely used in turfgrass management to suppress shoot growth and inflorescences production. This experiment was conducted to determine the interactive effects of trinexapac-ethyl (TE) and salinity on the growth، visual quality، and chemical constituents of perennial ryegrass (Lolium perenne L.). Plants were grown hydroponically under four levels of salinity (1. 5 (control)، 2. 5، 5. 0 and 7. 5 dS/m) and three levels of trinexapac-ethyl (0، 0. 02، and 0. 04 g/m2). The results showed that growth rate of perennial ryegrass decreased significantly with both trinexapac-ethyl and salinity treatments، although the differences in growth rate were not significant between trinexapac-ethyl treatments at 0. 02 and 0. 04 g a. i. /m2 application rates. Root penetration depth، fresh and dry weights increased by trinexapac-ethyl، while salinity decreased them. The results showed that total chlorophyll، chlorophyll a، chlorophyll b، and proline concentrations increased by application of trinexapac-ethyl، while TE had no significant effect on the carotenoid content. Salinity treatment decreased total chlorophyll، chlorophyll a، chlorophyll b، and carotenoid content، but increased proline concentration. Overall، it can be suggested that for improving the tolerance of perennial ryegrass to salinity up to 2. 5 dS/m and reduced mowing frequency، the turf should be sprayed monthly with TE at 0. 02 g/m2.