title: Abscisic acid in the thermoinhibition of lettuce seed germination and enhancement of its catabolism by gibberellin.
abstract: Germination of lettuce (Lactuca sativa L. cv. 'Grand Rapids') seeds was inhibited at high temperatures (thermoinhibition). Thermoinhibition at 28 degrees C was prevented by the application of fluridone, an inhibitor of abscisic acid (ABA) biosynthesis. At 33 degrees C, the sensitivity of the seeds to ABA increased, and fluridone on its own was no longer effective. However, a combined application of fluridone and gibberellic acid (GA3) was able to restore the germination. Exogenous GA3 lowered endogenous ABA content in the seeds, enhancing catabolism of ABA and export of the catabolites from the intact seeds. The fluridone application also decreased the ABA content. Consequently, the combined application of fluridone and GA3 decreased the ABA content to a sufficiently low level to allow germination at 33 degrees C. There was no significant temperature-dependent change in endogenous GA1 contents. It is concluded that ABA is an important factor in the regulation of thermoinhibition of lettuce seed germination, and that GA affects the temperature responsiveness of the seeds through ABA metabolism.
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 981-8555, Japan.
authors.forename: Takeru
authors.initials: T
authors.lastname: Gonai
authors.forename: Shusuke
authors.initials: S
authors.lastname: Kawahara
authors.forename: Makoto
authors.initials: M
authors.lastname: Tougou
authors.forename: Shigeru
authors.initials: S
authors.lastname: Satoh
authors.forename: Teruyoshi
authors.initials: T
authors.lastname: Hashiba
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Hirai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawaide
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Toshihito
authors.initials: T
authors.lastname: Yoshioka
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D018525:Germination / Q000187:drug effects / Q000502:physiology; D005875:Gibberellins / Q000378:metabolism / Q000494:pharmacology*; D018545:Lactuca / Q000187:drug effects / Q000254:growth & development*; D010937:Plant Growth Regulators / Q000494:pharmacology*; D011728:Pyridones / Q000494:pharmacology; D012639:Seeds / Q000187:drug effects / Q000254:growth & development*; D013696:Temperature
chemical_list: D004338:Drug Combinations; D005875:Gibberellins; D010937:Plant Growth Regulators; D011728:Pyridones; C013351:fluridone; D000040:Abscisic Acid; C007842:gibberellic acid