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

Abstract

By identifying the factors that initiate seed dormancy release, we can reliably predict whether a seed will remain dormant within or exit the seed bank and become a seedling. With regard to annual weed species, assessing which factors efficiently break seed dormancy is critical for estimating the number of weed seeds that will develop into problematic weeds. To better understand dormancy breaking in 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), ultrasound (for 10, 20, 30, and 40 min), soaking in hot water (90°C for 3, 5, 7, and 10 min), and 98% sulfuric acid (for 1, 2, and 3 min). The results showed that Redroot pigweed seed dormancy was effectively broken by cold stratification, gibberellic acid, and ultrasound. Short treatments with hot water had minimal effect while longer times or treatment with sulfuric acid stopped 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 knowledge of what processes effectively or ineffectively break Redroot pigweed seed dormancy and promote growth.

Keywords: dormancy breaking; germination; seed treatments; ultrasonic waves.

FIGURE 1

Effect of various treatments on the germination parameters of Redroot pigweed seed monitored for 14 days after no treatment (Control), or treatment by cold stratification (Chilling), application of gibberellic acid at 500, 1000, 1500, and 2000 parts per million, ultrasound treatment for 10, 20, 30, or 40 min, pretreatment with hot water for 3, 5, 7, or 10 min or sulfuric acid for 3, 5, or 7 min. Fifty seeds were used for each technical replicate. Data shown represent averages and standard deviation for three technical replicates for each treatment. Means followed by the same letters do not have a significant difference from each other based LSD multiple range test at the 5% level.

FIGURE 2

Effect of various treatments on the seedling parameters of plumule length, radicle length, or seedling length (which is the sum of the plumule, seed, and radicle) of Redroot pigweed seed 14 days after no treatment (Control), or treatment by cold stratification (Chilling), application of gibberellic acid at 500, 1000, 1500, and 2000 parts per million, ultrasound treatment for 10, 20, 30, or 40 min, pretreatment with hot water for 3, 5, 7, or 10 min, or sulfuric acid for 3, 5, or 7 min. Fifty seeds were used for each technical replicate. Data shown represent averages and standard deviation for three technical replicates for each treatment. Means followed by the same letters do not have a significant difference from each other based LSD multiple range test at the 5% level.

FIGURE 3

Pearson's correlation coefficients (n = 51) among seven quantitative traits on Redroot pigweed. The correlation coefficients were significant at the statistical probability level of 1%. GP, percent germination; GR, germination rate; PL, plumule length; RL, radicle length; SDW, seedling dry weight; SL, seedling length; SVI, seed vigor index.