Many plant seeds do not respond to ethylene promotive effects
Ethylene is known to promote seed germination. However, seeds of many plants do not respond to the gas and some of the promotive effects are small (1). The most thoroughly studied system is the lettuce "seed" (botanically an achene). Lettuce seed germination is due to the growth or cell expansion of the hypocotyl region which forces the radical through the micropyle. When sufficient phytochrome is present in the far red absorbing form (Pfr) and the temperature is less than 20°C, lettuce seeds germinate within 24 hours following imbibition. When the temperature is raised to 30°C germination of the seeds is inhibited. This effect is called thermal dormancy, but thermal inhibition is a better terra since embryos germinate if the endosperm is removed or punctured. Lettuce seed germination is a simple and rapid way of measuring ethylene action. Other than the fact that ethylene promotes germination, little is known concerning the role, mechanism, or site of action of the gas. The experiments described here were designed to evaluate the role of inhibitors of ethylene action during germination. The inhibitors evaluated in this study included: DIHB (3,5-diiodo-4- hydroxybenzoic acid), STS (silver thiosulfate), C02, NBA (2,5-norbornadiene), and MCEB (5-methyl-7-chloro-4-ethoxy-carbonyl-methoxy-2,l,3- benzothiadiazole).
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Keywords: Ethylene Inhibitors