Document Detail

Changes in ABA turnover and sensitivity that accompany dormancy termination of yellow-cedar (Chamaecyparis nootkatensis) seeds.
MedLine Citation:
PMID:  11741045     Owner:  NLM     Status:  MEDLINE    
Yellow-cedar (Chamaecyparis nootkatensis [D. Don] Spach) seeds exhibit prolonged coat-imposed dormancy following their dispersal from the parent plant. Analyses were undertaken using S-(+)-[(3)H] abscisic acid (ABA) to monitor the capacity of embryos to metabolize ABA following their isolation from seeds subjected to various dormancy-breaking and control treatments. Radiolabelled phaseic acid (PA) and dihydrophaseic acid (DPA) were detected in embryos and, to a greater extent in the surrounding media, by 48 h regardless of whether the embryos had been excised from seed previously subjected to only a 3 d soak or to a full dormancy-breaking treatment. Of the two enantiomers of ABA, only the natural S-(+)-ABA effectively inhibited germination of isolated embryos. A metabolism-resistant synthetic ABA analogue S-[8',8',8',9',9',9']-hexadeuteroabscisic acid, S-(+)-d6-ABA, consistently slowed the germination rate of excised embryos to a greater extent than that caused by natural S-(+)-ABA. The deuterium-labelled ring methyl groups of the analogue made it more resistant to oxidation by yellow-cedar embryos and thus rendered the analogue more persistent and possessing greater activity. With increasing time of exposure to moist chilling, yellow-cedar embryos became increasingly insensitive to both ABA and to the analogue. Subjecting seed to chemical treatments (GA(3) in combination with 1-propanol) prior to moist chilling strongly enhanced the germinability of whole seeds. This treatment also had a relatively greater impact on ABA metabolism than did moist chilling alone, as indicated by a greater capacity of S-(+)-d6-ABA to inhibit the germination of embryos as compared to S-(+)-ABA. Moist chilling was most critical for reduced ABA sensitivity of embryos. A change in the embryo's ability to metabolize ABA and reduced embryo sensitivity to ABA are two factors associated with dormancy termination of whole seeds of yellow cedar; a change in only one of these factors is insufficient to elicit high germinability.
Nancy Schmitz; Suzanne R Abrams; Allison R Kermode
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of experimental botany     Volume:  53     ISSN:  0022-0957     ISO Abbreviation:  J. Exp. Bot.     Publication Date:  2002 Jan 
Date Detail:
Created Date:  2001-12-13     Completed Date:  2002-04-08     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9882906     Medline TA:  J Exp Bot     Country:  England    
Other Details:
Languages:  eng     Pagination:  89-101     Citation Subset:  IM    
Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada.
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MeSH Terms
1-Propanol / pharmacology
Abscisic Acid / chemistry,  metabolism*,  pharmacology
Chamaecyparis / drug effects,  physiology*
Dose-Response Relationship, Drug
Germination / drug effects
Gibberellins / pharmacology
Seeds / drug effects,  physiology
Time Factors
Reg. No./Substance:
0/Gibberellins; 21293-29-8/Abscisic Acid; 71-23-8/1-Propanol; 77-06-5/gibberellic acid; 7782-39-0/Deuterium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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