title: Changes in gibberellin A(1) levels and response during de-etiolation of pea seedlings.
abstract: The level of gibberellin A(1) (GA(1)) in shoots of pea (Pisum sativum) dropped rapidly during the first 24 h of de-etiolation. The level then increased between 1 and 5 d after transfer to white light. Comparison of the metabolism of [(13)C(3)H] GA(20) suggested that the initial drop in GA(1) after transfer is mediated by a light-induced increase in the 2beta-hydroxylation of GA(1) to GA(8). A comparison of the elongation response to GA(1) at early and late stages of de-etiolation provided strong evidence for a change in GA(1) response during de-etiolation, coinciding with the return of GA(1) levels to the normal, homeostatic levels found in light- and dark-grown plants. The emerging picture of the control of shoot elongation by light involves an initial inhibition of elongation by a light-induced decrease in GA(1) levels, with continued inhibition mediated by a light-induced change in the plant's response to the endogenous level of GA(1). Hence the plant uses a change in hormone level to respond to a change in the environment, but over time, homeostasis returns the level of the hormone to normal once the ongoing change in environment is accommodated by a change in the response of the plant to the hormone.
authors.affiliation: School of Plant Science, University of Tasmania, G.P.O. Box 252C, Hobart, Tasmania 7001, Australia.
authors.forename: D P
authors.initials: DP
authors.lastname: O'Neill
authors.forename: J J
authors.initials: JJ
authors.lastname: Ross
authors.forename: J B
authors.initials: JB
authors.lastname: Reid
mesh_terms: D005875:Gibberellins / Q000378:metabolism*; D008027:Light; D018532:Pisum sativum / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D063245:Plant Development; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D010944:Plants / Q000378:metabolism / Q000528:radiation effects
chemical_list: D005875:Gibberellins