Drought Effects on Water Relations of Three Cultivated Grasses

Abstract

Water is the predominant environmental factor controlling yield of forages in the northern Great Plains. This study was conducted to compare the effects of contrasting soil water regimes on the water relations of smooth bromegrass (Bromus inermis Leyss.), crested wheatgrass [Agropyron cristatum (L.) Beauv. ssp. pectinatum (Bieb.) Travel.], and Altai wildrye [Leymus angustus (Trin.) Pilger]. The grasses were grown on deep black soil (Melfort silt)' clay, Typic Cryoboroll) under two soil water regimes: DRY plots were covered by rain‐out shelters beginning at the end of May and IRR plots were watered when soil water potential averaged −0.07 MPa. Measurements of soil water potential (ψs), leaf water potential (ψ/L), osmotic potential (ψ,), and relative water content (RWC) were taken periodically during first and second growths in 1983 and 1984. Crested wheatgrass (CWg) generally had lower ψL and RWC than smooth bromegrass or Altai wildrye. At a specific ψs, ψL of CWg was 0.3 to 0.7 MPa lower than that of Br, possibly resulting from small xylem vessels in CWg. Osmotic adjustment in CWg and smooth bromegrass was similar, but CWg lost more water for a change in pressure potential(ψp), which helped it maintain ψp. Differences in water relations reflected growth patterns and drought resistance strategies previously reported for these species.