title: Auxin promotes gibberellin biosynthesis in decapitated tobacco plants.
abstract: Excision of the apical bud (decapitation) of tobacco (Nicotiana tabacum L.) plants reduced the endogenous levels of indole-3-acetic acid (IAA), gibberellin A20 (GA20), and GA1 (the bioactive GA), in internode tissue below the excision site. Application of IAA to the stump of decapitated plants dramatically increased GA20 content, to a level 3-fold greater than in intact plants. Gibberellin A1 content was also increased by IAA. Decapitation reduced the conversion of [14C]GA19 to [14C]GA20 and of [14C]GA20 to [14C]GA1, and appeared to promote the deactivation pathway [14C]GA20 to [14C]GA29 to [14C]GA29-catabolite. Application of auxin counteracted these effects, but did not restore the conversion of [14C]GA20 to [14C]GA1 to the level found in intact plants. The results indicate that auxin is necessary for normal GA biosynthesis in stems of tobacco.
authors.affiliation: School of Plant Science, University of Tasmania, GPO Box 252-55, Hobart, Tasmania 7001, Australia.
authors.forename: C M
authors.initials: CM
authors.lastname: Wolbang
authors.forename: J J
authors.initials: JJ
authors.lastname: Ross
mesh_terms: D002250:Carbon Radioisotopes; D005875:Gibberellins / Q000096:biosynthesis*; D007210:Indoleacetic Acids / Q000494:pharmacology*; D010940:Plant Proteins / Q000378:metabolism; D018547:Plant Stems / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D014026:Nicotiana / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D005875:Gibberellins; D007210:Indoleacetic Acids; D010940:Plant Proteins