Comparative drought resistance mechanisms of eleven major warm-season turfgrasses

Abstract

Comparative drought resistances of eleven major warm-season turfgrasses were evaluated in the field after withholding irrigation. The relative importance of the drought avoidance and tolerance mechanisms was also investigated. For the plant evaluations, visual leaf rolling and firing, leaf water potential, and visual shoot recovery were measured in the field, greenhouse, and controlled environment growth chamber studies. Both the rooting potential and stomatal characteristics were investigated in separate studies to assess their contributions to the drought avoidance of each species. Proline and abscisic acid (ABA) changes were measured during progressive water stress to determine their association with drought resistance. From the field shoot recovery data, it was found that 'Meyer' and 'Emerald' zoysiagrasses (Zoysia sp.), 'Arizona Common', 'Tifgreen', and 'Texturf 10' bermudagrasses (Cynodon sp.), and 'Georgia Common' centipedegrass [Eremochola ophiuroides (Munro.) Hack.] possessed good drought resistance, whereas 'Texas Common' St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] and 'Tifway' bermudagrass [Cynodon dactylon (L.) pers. x C. transvaalensis Davy] possessed poor drought resistance. 'Texas Common' buffalograss [Buchloe dactyloides (Nutt.) Engelm.], 'Pensacola' bahiagrass (Paspalum notatum Flugge.), and 'Adalayd' seashore paspalum (Paspalum vaginatum Swartz) ranked in the intermediate range. Bermudagrass and seashore paspalum had good drought avoidance, whereas zoysiagrass, St. Augustinegrass, and buffalograss had poor drought avoidance. Zoysiagrass and St. Augustinegrass had good drought tolerance, whereas bermudagrass had poor drought tolerance. Bahiagrass possessed medium drought tolerance mainly due to a dormancy mechanism. An extensive root system, such as deep rooting, high root dry weight, and large number of roots, and good stomatal characteristics, such as early closure and/or wax-covered stomata contributed to the drought avoidance mechanism. The relative importance of each component varied among species. There were significant correlations between shoot recovery which represents drought resistance and plant parameters such as leaf rolling (r=-$0.59), leaf firing (r=-$0.84), canopy-air temperature differential (r=-0.64), and leaf water potential (r=0.54) under water stress. Thus, these parameters are potential techniques for drought resistance prediction in warm-season turfgrasses.