Physiological Responses to Soil Drying by Warm-season Turfgrass Species

A study describing the overall physiological responses to drought and exploring the underlying mechanisms in multiple turfgrass species and genotypes is needed to make improvements in breeding for turfgrass species that are tolerant to water-limiting conditions. The objective of this study was to compare the differential canopy and physiological responses of 14 genotypes of warm-season turfgrasses during a controlled water withdrawal experiment in a greenhouse. Fourteen genotypes from St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntz], Japanese lawngrass (Zoysia japonica Steud.), manillagrass [Zoysia matrella (L.) Merr.], and bermudagrass [Cynodon dactylon (L.) Pers.] were planted in acrylic tubes. Their responses in transpiration, gas exchange rate, and leaf firing to fraction of transpirable soil water were characterized through threshold and midpoint values. Threshold and midpoint variables are promising traits that can be exploited to breed for improved drought responses. Bermudagrass had the lowest threshold for leaf firing compared with other species, indicating that the initiation of leaf firing happened later in the drying cycle. This response may be associated with a lower threshold for relative gas exchange rate. ‘Zeon’ manilagrass exhibited better drought tolerance, which was indicated by its lower midpoint for leaf firing and similar characteristics in transpiration and gas exchange rates compared with ‘Taccoa Green’ manilagrass. Further study is needed to elucidate the underlying mechanism of leaf senescence delay in Zeon. No consistent drought mechanisms were found to be universal among the four warm-season species, suggesting that there are likely several different mechanisms that may be species dependent.