Abscisic acid in the thermoinhibition of lettuce seed germination and enhancement of its catabolism by gibberellin.
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.
Gonai
Takeru
T
Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 981-8555, Japan.
Kawahara
Shusuke
S
Tougou
Makoto
M
Satoh
Shigeru
S
Hashiba
Teruyoshi
T
Hirai
Nobuhiro
N
Kawaide
Hiroshi
H
Kamiya
Yuji
Y
Yoshioka
Toshihito
T
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
D004338:Drug Combinations; D005875:Gibberellins; D010937:Plant Growth Regulators; D011728:Pyridones; C013351:fluridone; D000040:Abscisic Acid; C007842:gibberellic acid