Zoysiagrass Water Relations

Development of drought resistant, water-conserving cultivars continues to be an objective of turfgrass breeding programs. This study was conducted to determine for 15 zoysiagrasses [Zoysia japonica Steud., Z. matrella (L.) Merr., and Z. japonica Steud. x Z. tenuifolia Willd.] under greenhouse conditions (i) water relations characteristics, (ii) survival and recovery from extreme water stress, and (iii) the relationship of water relations characteristics to supplemental irrigation requirement determined in field studies. Leaf water potential at zero turgor ([Ψ.sub.L0]) ranged from -1.76 MPa to -2.52 MPa before, and from -2.18 MPa to -2.59 MPa after water stress. Though [Ψ.sub.L0] of genotypes such as Cavalier, El Toro, and Emerald decreased after stress, [Ψ.sub.L0] of genotypes such as Korean Common and DALZ8515 did not change. Osmotic potential at full turgor ([Ψ.sub.Π100]) of genotypes such as DALZ8501 and DALZ8506 was similar or increased after water stress but decreased for genotypes such as Crowne and Korean Common. The [Ψ.sub.L0] and [Ψ.sub.Π100] after stress were negatively correlated with recovery from stress and positively correlated with irrigation requirement. Zoysia genotypes with low relative water content at zero turgor ([RWC.sub.0]), bulk modulus of tissue elasticity ([Epsilon], and apoplastic water fraction (Β) demonstrated poor recovery from stress and required more supplemental irrigation. Cultivars such as Crowne, El Toro, and Palisades had the greatest recovery from stress, the least irrigation requirement, more negative [Ψ.sub.L0] and [Ψ.sub.Π100] and positive [RWC.sub.0], [Epsilon], and Β. This study demonstrates that improvements in biophysical as well as morphological traits should contribute to development of water-conserving Zoysiagrass germplasm.
WATER MANAGEMENT AND CONSERVATION continue to be major emphases of the turfgrass industry and turfgrass breeding programs. Water-use restrictions that limit irrigation of urban and suburban landscapes are commonplace. Therefore, [...]