Appropriate concentrations of ethephon can improve the drought tolerance of turfgrasses， but the specific mechanism of action remains unclear. As an osmotic regulator， proline plays an important role in plant responses to stress. In this study， Kentucky bluegrass （Poa pratensis） and perennial ryegrass （Lolium perenne） were used as materials. We examined the effects of ethephon on physiological indices of turfgrasses in response to drought stress， analyzed changes in the expression of genes related to proline biosynthesis and catabolism， and explored the role of proline in ethephon-improved drought resistance of turfgrasses. The results showed that ethephon alleviated the decrease of relative water content and the increase of electrolyte leakage of turfgrass leaves induced by drought stress， thus contributing to improved drought tolerance. Under drought stress， proline content increased in the two Poa pratensis cultivars， whereas the changes were inconsistent among Lolium perenne cultivars. Ethephon treatment down-regulated the expression of Proline Dehydrogenase （Pro DH） gene in Poa pratensis under drought stress， thereby inhibiting proline degradation. In conclusion， promoting proline accumulation by suppressing the expression of the Pro DH gene might be one of the mechanisms by which ethephon improves drought tolerance in Poa pratensis.

Ethephon  /  Turfgrass  /  Proline  /  Drought stress  /  Gene expression