SALINITY TOLERANCE MECHANISMS OF 6 C(4) TURFGRASSES

Physiological responses to salinity and relative salt tolerance of six C4 turfgrasses were investigated. Grasses were grown in solution cult ure containing 1, 100, 200, 300, and 400 mM NaCl. Salinity tolerance w as assessed according to reduction in relative shoot growth and turf q uality with increased salinity. Manilagrass cv. Matrella (FC13521) (Zo ysia matrella (L.) Merr.), seashore paspalum (Hawaii selection) (Paspa lum vaginatum Swartz), and St. Augustinegrass (Hawaii selection) (Sten otaphrum secundatum Walt.) were tolerant, shoot growth being reduced 5 0% at almost-equal-to mM salinity. Bermudagrass cv. Tifway (Cynodon da ctylon x C. transvaalensis Burtt-Davey) was intermediate in tolerance, shoot growth being reduced 50% at almost-equal-to 270 mM salinity. Ja panese lawngrass cv. Korean common (Zoysia japonica Steud) was salt-se nsitive, while centipedegrass (common) (Eremochloa ophiuroides (Munro) Hack.) was very salt-sensitive, with total shoot mortality occurring at almost-equal-to 230 and 170 mm salinity, respectively. Salinity tol erance was associated with exclusion of Na+ and Cl- from shoots, a pro cess aided by leaf salt glands in manilagrass and bermudagrass. Shoot Na+ and Cl- levels were high at low (100 to 200 mM) salinity in centip edegrass and Japanese lawngrass resulting in leaf burn and shoot dieba ck. Levels of glycinebetaine and proline, proposed cytoplasmic compati ble solutes, increased with increased salinity in the shoots of all gr asses except centipedegrass, with tissue water levels reaching 107 and 96 mm at 400 mm salinity in bermudagrass and manilagrass, respectivel y. Glycinebetaine and proline may make a significant contribution to c ytoplasmic osmotic adjustment under salinity in all grasses except cen tipedegrass.