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Seedling Growth of Smooth Bromegrass Measured in Five Environments¹

Nine cultivars of smooth bromegrass (Bromus inermis Leyss.) were grown in four controlled environments in the greenhouse and growth room and one field environment. The four controlled environments were high light and high temperature, high light and low temperature, low light and high temperature, and low light and low temperature. Each environment was planted as complete blocks with nine cultivars assigned at random into each of the four blocks. Four harvests at 1-week intervals were sampled at random within each cultivar with the first harvest commencing at the two-leaf stage. The studies were confined to seedlings sampled within 2 months of seeding

Significant differences in tiller number, leaf number and area, seedling dry weight, specific leaf weight (SLW), shoot to root ratio (S/R), relative growth rate (RGR), net assimilation rate (NAR), and leaf area ratio (LAR) were found among bromegrass cultivars and environments. ‘Carlton’ and ‘Manchar’ generally produced the largest number of leaves and tillers, largest leaf area, greatest seedling dry weight, and greatest RGR and NAR among the nine cultivars. ‘Blair’ and ‘Lyon’, in most cases, were the poorest entries.

Sed weight was correlated positively with leaf number (0.28 to 0.65), leaf area (0.48 to 0.78), and seedling dry weight (0.38 to 0.79) but was correlated negatively with SLW (—0.15 to —0.67) in all growth stages and environments. The results suggested that increasing seedling vigor at the early growth stage in smooth bromegrass can be achieved by screening breeding material on the basis of seed weight. Furthermore, the correlations between RGR and NAR were highly significant (in most cases, r > 0.90) and persisted throughout the environments studied indicating that cultivar differences in RGR were attributed more to NAR than LAR. Selection for high NAR at the later seedling growth stages (2 months old or more) is suggested as an important parameter in improvement of smooth bromegrass

Key Words: Cultivars • Seed weight • Seedling vigor • Relative growth rate • Net assimiliation rate • Leaf area ratio

² Alfalfa breeder, graduate research assistant, and Chairman, Plant Science Dep., Univ. of Alberta.

Received for publication September 27, 1977.