Evaluation of techniques to break seed dormancy in Redroot pigweed (Amaranthus retroflexus)

If we understand factors that trigger seed dormancy release, then we can accurately predict whether the seed will remain dormant or germinate out of the seed bank. With regards to annual weed species, detailed understanding of what breaks seed dormancy is therefore critical for determining how many weed seeds will germinate into problematic weeds. To investigate the breaking of dormancy in weed seeds, we conducted an experiment with Redroot pigweed (Amaranthus retroflexus). Dormant seeds were treated with cold stratification (4 °C for 30 days), application of gibberellic acid (at 500, 1000, 1500, and 2000 parts per million) or ultrasound (for 10, 20, 30, and 40 minutes), soaking in hot water (90 °C for 3, 5, 7 and 10 minutes) or 98% sulfuric acid (for 1, 2 and 3 minutes) to determine which treatment most effectively broke dormancy. The results showed that Redroot pigweed seed dormancy was effectively broken by cold stratification, gibberellic acid, or ultrasound. Short treatments with hot water had minimal effect while longer times or treatment with sulfuric acid eliminated seed germination. In addition to germination percentage, germination rate, plumule length, radicle length, seedling length, seedling dry weight, and seed vigor index were also measured; similarly application of gibberellic acid had the most significant effect on these parameters. The results of this study add to our understanding of what processes effectively or ineffectively break Redroot pigweed seed dormancy and promote growth.