Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 25, 2008
Publication Date: July 1, 2008
Citation: Foley, M.E., Chao, W.S. 2008. Growth regulators and chemicals stimulate germination of leafy spurge (Euphorbia esula) seeds. Weed Science. 56:516-522 Interpretive Summary: Dormancy is a key characteristic of weeds that contributes to their persistence in natural and agroecosystems. Very little baseline information exists on dormancy and germination of leafy spurge seeds. Thus, we surveyed the effect of various growth regulators and chemicals on germination of dormant leafy spurge seeds. Gibberellic acid provided the highest level of germination stimulation and its effect was modulated by an alternating temperature during germination.
Technical Abstract: This study was conducted to survey the effect of various growth regulator and chemical treatments on germination of leafy spurge seeds. Non-treated seeds in this population were nearly fully imbibed in 3 h and display approximately 35% germination in 21 d under the normal alternating temperature of 20:30 C (16:8 h). Ten mM gibberellic acid (GA3) induces 66% germination at constants temperatures of 20 and 30 C. The alternating temperature increased the efficacy of 10 mM GA3 with 94% germination. Non-treated seeds did not germinate at the constant temperatures suggesting that alternating temperature acts via a GA independent pathway. Kinetin at 0.1 to 1 mM was ineffective, but a saturated solution of kinetin induced 73% germination. Ethephon at 0.01 to 1 mM induced 58 to 66% germination, although there was little response to different concentrations. Ethylene gas at 1 ppm stimulated germination to 77%. Germination of seeds incubated continuously in 1 and 10 mM nitrate displayed 38% and 43% germination, respectively. Seeds pulsed for 24 h with 100 mM nitrate displayed 58% germination after 21 d. Potassium phosphate-citrate buffer (pH 3.4) and its individual components induced 60 to 70% germination. Fluridone (10 and 100 µM), 1-naphthaleneacetic acid (NAA) (0.1 to 10 mM), and ethanol (0.2 to 15%) had no effect on germination, but subsequent elongation in the presence of NAA was inhibited due to swelling of the radicle. This research reveals the major effect of alternating temperature and gibberellic acid in germination of dormant leafy spurge seeds.