Prevention of Action of Far-Red-Absorbing Phytochrome in Rumex crispus L. Seeds by Ethanol

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Abstract
Phytochrome-enhanced germination of curled dock (R. crispus L.) seeds is further stimulated by pretreatments in solutions of 0.5-2 M methanol and 0.03 to .gtoreq. 0.3 M 2-propanol during a 2-day 20.degree. C imhibition. Similar pretreatments in 0.1 M ethanol, acetaldehyde and n-propanol inhibit phytochrome-enhanced germination. If exposure to ethanol is delayed until 16 h after a red irradiation, seeds escape the ethanol inhibition indicating a mechanism other than toxicity. The rate of escape from ethanol inhibition roughly parallels the escape from phytochrome control in seeds held in water only, indicating possible ethanol effects on phytochrome. Ethanol pretreatment prevents the far-red absorbing form of phytochrome (Pfr) from acting but does not accelerate dark decay or prevent transformation. Ethanol inhibition may be prevented if ethanol pretreatment is at 10.degree. C instead of 20.degree. C, or may be overcome by transferring ethanol-pretreated seeds to 10.degree. C in water. Similarly, ethanol inhibition can be overcome by a 2-h 40.degree. C temperature shift concluding the pretreatment. The ethanol causes perturbations at a membrane which prevent Pfr from acting.