Effects of summer drought and strong light stress on Kentucky bluegrass in Shanghai

Kentucky bluegrass (Poa pratensis) is an important cool-season turf grass, which can remain green in wet and cool areas year-round. However, it is difficult for it to survive in summer in Shanghai. In this study, eight Kentucky bluegrass cultivars with different summer stress tolerance were processed in the field under four stress treatments: drought / bright light, drought / shade, water / bright light, and water / shade. The results showed that leaf water content declined with the decrease in soil water content. When the leaf water content was less than 70%, the plants displayed obvious injuries. Drought caused more damage to plants than did intense light / UV, and intense light / UV exposure in dry conditions aggravated the damage to plants. There was no significant difference in drought and intense light / UV tolerance among the grass types, and these types could be maintained in good condition if given sufficient supply of water. Therefore, it was speculated that drought was the main abiotic stress factor that caused the difficulty in growing Kentucky bluegrass over the summer in Shanghai, and the reason for the difference in summer tolerance among the types might have been caused by biological stress (such as rust).