Annual Ryegrass Germination Response to Different Temperature Regimes.

Prolonged high temperatures during recent winter months have been associated with an induced second dormancy in annual ryegrass (Lolium multiflorum Lam). Additional information is needed on the effect that prolonged high temperatures have on germination of currently used cultivars. Seed of five annual ryegrass cultivars representing diploids and tetraploids (Prine, TAM TBO, Marshall, Chipola, and 'early' variety) were exposed to five alternating (10⁄15, 10⁄25, 15/20, 15/25, and 20/25°C) and three constant (10/10, 15/15, and 20/20°C) temperature regimes treatments. Mean germination rate (days), germination lag (days to first seed germination), germination period (days between first seed germinated and total seed germination), speed of seed germination (proportion of seed germinated), mean of optima, and maximum germination rate were evaluated. Four replicates of 30 seeds were allocated per Petri dish for seed germination count, and were sterilized prior to exposure to treatments.  Petri dishes were arranged in a randomized complete block design in a climate controlled incubator. Germination was determined when radicle appearance occurred. Preliminary results showed no cultivar differences. However, strong treatment effects were shown on all response variables.