Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2005
Publication Date: 1/1/2006
Citation: Chao, W.S., Serpe, M.D., Anderson, J.V., Gesch, R.W., Horvath, D.P. 2006. Sugars, hormones, and environment affect the dormancy status in underground adventitious buds of leafy spurge (Euphorbia esula). Weed Science. 54(1):59-68. Interpretive Summary: We have examined growth of root buds in leafy spurge (Euphorbia esula L.) in response to sugars, growth regulators, and paclobutrazol (a gibberellic acid biosynthesis inhibitor) using a hydroponic system. The results showed that sucrose, glucose, auxin (indole 3-acetic acid, 1-naphthaleneacetic acid), abscisic acid, cytokinin (6-benzylaminopurine), and paclobutrazol caused repression of root bud growth. In contrast, gibberellic acid promoted root bud growth; in addition, gibberellic acid and sugar were functionally antagonistic. We have also examined seasonal effects on the development of innate dormancy to root buds of leafy spurge. The results showed that root buds developed the strongest dormancy in October or November. This type of innate dormancy persisted until first freezing occurred in November to early December.
Technical Abstract: Leafy spurge is a deep-rooted perennial weed that propagates vegetatively from an abundance of underground adventitious buds located on roots and crown (root and crown buds). Signals from both leaves and apical or axillary meristems are known to inhibit root bud growth. To increase our understanding of how carbohydrates and growth regulators affect root bud growth, decapitated leafy spurge plants were hydroponically treated with glucose, sucrose, gibberellic acid (GA), abscisic acid (ABA), indole 3-acetic acid (IAA), 1-naphthaleneacetic acid (NAA), 6-benzylaminopurine (BA), and a GA biosynthesis inhibitor, paclobutrazol. Both glucose and sucrose caused suppression of root bud growth at concentrations of 30 mM. BA, ABA, IAA, NAA, and paclobutrazol inhibited root bud growth at concentrations as low as 1 µM, 2 µM, 100 µM, 1 µM, and 16 µM, respectively. GA at 30 µM promoted root bud growth in the absence or presence of paclobutrazol at 16 µM. GA as low as 15 µM increased bud growth when decapitated plants were treated with different GA concentrations in 30 mM sucrose. Cellular sugar and starch levels in root buds were also determined at various times after decapitation. Buds of intact plants contained the highest levels of sucrose and starch compared to buds harvested 1, 3, and 5 d after decapitation. To determine how seasonal changes affect root bud dormancy, growth from root buds of field-grown plants were monitored over several years. Root buds of field-grown leafy spurge had the highest level of innate dormancy from October to November which persisted until a prolonged period of freezing occurred in November or early December. Our data support the hypothesis that carbohydrates may be involved in regulating dormancy status in root buds of leafy spurge. Nomenclature: Euphorbia esula L., leafy spurge, EPHES. Keywords: Charbohydrates; dormancy; hormones; underground adventitious buds.