Salinity Tolerance Mechanisms of Six C4 Turfgrasses

Abstract

Physiological responses to salinity and relative salt tolerance of six C4 turfgrasses were investigated. Grasses were grown in solution culture containing 1, 100, 200, 300, and 400 mm NaCl. Salinity tolerance was assessed according to reduction in relative shoot growth and turf quality with increased salinity. Manilagrass cv. Matrella (FC13521) (Zoysia matrella (L.) Merr.), seashore paspalum (Hawaii selection) (Paspalum vaginatum Swartz), and St. Augustinegrass (Hawaii selection) (Stenotaphrum secundatum Walt.) were tolerant, shoot growth being reduced 50% at ≈400 mm salinity. Bermudagrass cv. Tifway (Cynodon dactylon × C. transvaalensis Burtt-Davey) was intermediate in tolerance, shoot growth being reduced 50% at ≈270 mm salinity. Japanese lawngrass cv. Korean common (Zoysia japonica Steud) was salt-sensitive, while centipedegrass (common) (Eremochloa ophiuroides (Munro) Hack.) was very salt-sensitive, with total shoot mortality occurring at ≈230 and 170 mm salinity, respectively. Salinity tolerance was associated with exclusion of Na+ and Cl- from shoots, a process aided by leaf salt glands in manilagrass and bermudagrass. Shoot Na+ and Cl- levels were high at low (100 to 200 mm) salinity in centipedegrass and Japanese lawngrass resulting in leaf burn and shoot die-back. Levels of glycinebetaine and proline, proposed cytoplasmic compatible solutes, increased with increased salinity in the shoots of all grasses except centipedegrass, with tissue water levels reaching 107 and 96 mm at 400 mm salinity in bermudagrass and manilagrass, respectively. Glycinebetaine and proline may make a significant contribution to cytoplasmic osmotic adjustment under salinity in all grasses except centipedegrass.