Zoysiagrass water relations

Development of drought resistant, water-conserving cultivars continues to b e an objective of turfgrass breeding programs. This study was conducted to determine for 25 zoysiagrasses [Zoysia japonica Steud,, Z, matrella (L,) Me rr., and Z. japonica Steud, x Z, tenuifolia Willd,] under greenhouse condit ions (i) water relations characteristics, (ii) survival and recovery from e xtreme water stress, and (iii) the relationship of water relations characte ristics to supplemental irrigation requirement determined in field studies. Leaf water potential at zero turgor (psi (L0)) ranged from -1.76 MPa to -2 .52 MPa before, and from -2.18 MPa to -2.59 MPa after water stress. Though psi (L0) of genotypes such as Cavalier, El Toro, and Emerald decreased afte r stress, psi (L0) of genotypes such as Korean Common and DALZ8515 did not change. Osmotic potential at full turgor (psi (pi 100)) of genotypes such a s DALZ8501 and DALZ8506 was similar or increased after water stress but dec reased for genotypes such as Crowne and Korean Common. The psi (L0) and psi (pi 100) after stress were negatively correlated with recovery from stress and positively correlated with irrigation requirement, Zoysia genotypes wi th low relative water content at zero turgor (RWC0), bulk modulus of tissue elasticity (epsilon), and apoplastic wafer fraction (beta) demonstrated po or recovery from stress and required more supplemental irrigation. Cultivar s such as Crowne, El Toro, and Palisades had the greatest recovery from str ess, the least irrigation requirement, more negative psi (L0) and psi (pi 1 00) and positive RWC0, epsilon, and beta. This study demonstrates that impr ovements in biophysical as well as morphological traits should contribute t o development of water-conserving Zoysiagrass germplasm.