Germination and seedling growth of prairie grass, tall fescue and Italian ryegrass at different temperatures

Abstract

We measured the effects of temperature on the germination, emergence and growth during early tillering of Italian ryegrass (Lolium multiflorum), prairie grass (Bromus catharticus) and tall fescue (Festuca arundinacea). Radicle emergence (the percentage of seeds with emerged radicles) and 'field' emergence (the percentage of seeds with shoots > 1 cm long) were reduced at 35¦C (constant, all lines), or 30/25¦C (12/12 h, prairie grass and Tama Italian ryegrass only). All lines took longer to germinate at 15 and 10¦C (constant) than at higher temperatures, and final percentage germination of tall fescue lines was lower at 10¦C (constant) than at other temperatures. Italian ryegrass had the fastest shoot extension, and consequently the fastest 'field' emergence. Seed respiration rates were higher in fescue than in the other lines at 4 days from imbibition, and rates rose in all lines at 8 days. Over the first 20 days after sowing, growth rates were closely related (r = 0.87-0.99) to weights of seed and caryopses, when account was taken of perenniality (which was associated with relatively slow growth) and polyploidy (which was associated with growth faster than might be expected from seed size alone), and a multivariate relationship including temperature was developed (R2 = 0.88). Growth rates of shoots at 20 days after sowing were ranked Tama Italian ryegrass > prairie grass > Ucivex Italian ryegrass > tall fescue, and 24/19 > 21/16 > 18/13 > 30/25 > 15/10¦C. Growth during tillering, up to 42 days after emergence, was ranked Italian ryegrass > prairie > tall fescue and 21/16 = 18/13 > 24/19 = 15/1O¦C. Relative growth rates and relative rates of tillering were independent of temperature in Italian ryegrass, but were lower at 15/10 and 24/19 than at 21/16 and 18/13¦C in prairie grass and tall fescue. Prairie grass had higher yield per tiller but lower tiller numbers than Italian ryegrass; tall fescue had both lower yield per tiller and lower tiller number. Italian ryegrass was therefore the species best adapted to variations in environment and competition at sowing.