Morphological and Physiological Responses of St. Augustine Grass Cultivars to Different Levels of Soil Moisture

Understanding responses of turf grasses to drought stress is important for water resource management to maintain an acceptable level of quality for turfs under prolonged drought conditions. Four cultivars of St. Augustine grass (SA) (Stenotaphrum secundatum [Walt.] Kuntze) were evaluated for morphological and physiological responses to four watering treatments in greenhouse studies. Soil moisture treatments had greater impact on stolon number, photosynthetic rate, and dry matter production than on leaf sheath length and chlorophyll fluorescence. Full irrigation and the 75% field capacity (FC) did not result in significant differences in most of the characteristics, whereas the 25% FC significantly reduced morphological growth, physiological activities, and dry matter production of cultivars. The time when the morphological characteristics started showing differences among the watering treatments varied, with stolon numbers beginning to show response to watering treatments at week 2 (two weeks after watering treatment) and leaf sheath length not differing significantly until week 5 (five weeks after watering treatments). Cultivars differed in response to soil watering treatments among the characteristics. Floratam had the longest stolons, largest leaves, and greatest dry matter accumulation among cultivars across the environments. Raleigh had the lowest dry matter production at all levels of soil moisture but the least reduction of dry matter at 25% FC.