Ethephon Seed Treatment Enhanced Drought-Stress Tolerance of Kentucky Bluegrass Seedlings.

Ethephon (2-chloroethyl phosphonic acid, an ethylene-releasing compound) has been as a plant growth regulator in turfgrass managemnet. The aim of the study was to assess the effects of ethephon (ETH) seed treatment on drought tolerance of Kentucky bluegrass seedlings. Seeds of two Kentucky bluegrass cultivars, Midnight and Nuglade, were exposed to ETH treatment (4 g seeds immersed by 100 mL of 150 mg/L ethephon solution for 24 h) and control (immersed by the same amount of distilled water for 24 h), respectively. Then the seeds were subject to Hydroponic conditions to allow leaf growing to about 13 cm long. Seedlings were then exposed to two water stress treatments: control (half-strength Hoagland¡¯s solution) and PEG treatments [half-strength Hoagland¡¯s solution plus PEG 6000 (30%)]. The most noticeable effect of ETH seed treatment was an increase in the length and numbers of roots in both cultivars. In addition, ETH treated plants exhibited better turf performance under PEG induced water stress illustrated by higher levels of relative water content and lower levels of lipid peroxidation as well as electrolyte leakage. Compared to control plants, ETH treated plants maintained higher levels of antioxidant enzyme activity, proline content, soluble protein content and root viability relative to the control at 10 day of drought stress. The results suggest that ETH treatment may improve drought tolerance of Kentucky bluegrass seedlings.