Twenty-five commercially available turfgrass cultivars were evaluated for cumulative evapotranspiration (ETcum) attributes under progressive water stress for 0 to 21 and 0 to 24 days using the gravimetric mass balance method in two greenhouse studies. At the end of the water-stress treatment, the cultivars were scored visually for their green appearance on a 0 (no green) to 10 (100% green) scale. The Gompertz nonlinear model gave a best fit to ETcum vs. days adjusted for pan evaporation variation in the greenhouse compared with monomolecular and logistic nonlinear regression models. Two ETcum attributes—maximum evapotranspiration rates (ETmax) and inflection time (ti) (the time when the change in ET becomes zero)—were estimated for each cultivar using the Gompertz model. Based on final ETcum, ETmax, ti, and greenness score, `Bristol', `Challenger', and `Wabash' Kentucky bluegrass (Poa pratensis L.); `Shademaster' creeping fescue (Festuca rubra L.); `FRT-30149' fine fescue (F. rubra L.); and `Aurora' hard fescue (F. ovina var. duriuscula L. Koch.) were identified as low water-use cultivars.
George C.J. Fernandez and Belinda Love
Belinda Love, Wayne S Johnson, and George C.J. Fernandez
Germination of purple sage [Salvia dorrii (Kellogg) Abrams] seed was evaluated under 21 temperature combinations (day temperatures from 5 to 30C and night temperatures from 5 to 30C) in two experiments: 1) cool-moist stratification; and 2) sandpaper scarification, leaching with water, or gibberellic acid (GA3). The quadratic responses of weighted germination percentage (WGP), a combined index of germination percentage and speed of germination, were significant (P ≤ 0.05) for all treatments. The interaction of day and night temperatures was significant (P ≤ 0.05) only for the 2-week stratification treatments and for the Expt. 2 control. Stratification increased WGP over the control. Optimal WGP for all stratification treatments ranged from 46% to 51%. Optimal WGP was the same for both GA3 treatments. Optimal WGP for 0.29 mmol GA3 occurred at 16C night temperature and 22C day temperature, and for the 1.44 mmol GA3 treatment at 18C night and at 30C day temperature.