Effects of accelerated aging on italian ryegrass (Lolium multiflorum) seed germination

Authors: Williams, Robert; Bartholomew, Paul

Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 1/17/2008
Publication Date: 2/4/2008
Citation: Williams, R.D., Bartholomew, P.W. 2008. Effects of accelerated aging on italian ryegrass (Lolium multiflorum) seed germination [abstract]. Proceedings of Southern Weed Science Society, January 28-30, 2008, Jacksonville, FL. 61:190.

Interpretive Summary: Abstract only

Technical Abstract: Italian ryegrass (Lolium multiflorum) is a productive, high quality cool-season forage that is overseeded in warm-season pastures for winter and early spring grazing. However, in some pastures and croplands it can be a serious weed. Italian ryegrass does not form an extensive seed bank and the seed persists less than 3 years when seed are on or near the soil surface. For Italian ryegrass to be persistent in a pasture it must successfully reseed itself, or rely on an ephemeral seed bank with aging seed. The question arises as to the germinability and seedling vigor of aged seed, and the subsequent effect on reestablishment of an annual grass. Seed in the soil or on the soil surface may go through several hydration-dehydration cycles before seed germination occurs. Even dormant seed will imbibe water when available and dry as the soil becomes drier. Earlier we have shown that this hydration-dehydration cycle "ages" seed, thereby affecting subsequent germination and/or vigor. This conditioning of seed can also be achieved through 'accelerated aging.' Accelerated aging [subjecting seed to high temperature (41 °C) and high humidity (100%)] reduces germination and seedling vigor. Germination of unaged ryegrass seed and of seed aged for 3 days was between 80 and 95%, whereas the germination of seed aged for 5 day was 60%. Accelerated aging also reduced germination of ryegrass seed subjected to moisture stress. After 7 days, seed germination at -8 bars for control, 3-day and 5-day aged seed was 80%, 40% and 0%, respectively. Accelerated aging for 3 or 5 days reduced seedling growth at 3 and 6 weeks after planting. After 6 weeks total seedling dry weight was reduced by 24% with 5 days of accelerated aging. These results indicated that seed artificially aged lose viability and vigor, have delayed or reduced germination, and the seedlings have less vigor than non-aged seed. Further work is necessary to relate accelerated aging of seed to the natural aging of seed under field conditions.