Role of ethylene in chlorophyll degradation in radish cotyledons |
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Authors: | Michael Knee |
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Institution: | 1. Department of Horticulture, The Ohio State University, 43210, Columbus, Ohio, USA
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Abstract: | The effect of age of radish seedlings on changes in chlorophyll concentration caused by ethylene was examined. Ethylene was produced at 2–4 nl g?1 h?1 following excision of cotyledons from 5-to 20-day-old seedlings. The youngest cotyledons maintained this rate, whereas ethylene synthesis declined by as much as 80% during a 24-h period in older cotyledons. The youngest cotyledons continued to accumulate chlorophyll in the dark, but after 7 days cotyledons lost chlorophyll and the proportion of chlorophyll lost increased with age. Ethylene promoted, and norbornadiene inhibited, this loss of chlorophyll; in combined treatments the effects of ethylene and norbornadiene were competitive. The maximal rate of chlorophyll loss occurred in 1μl L?1 ethylene; extrapolation of the response to concentration indicated that half-maximum loss would occur at 0.005–0.01 μl L?1 ethylene. In cotyledons from 20-day-old seedlings, chlorophyll degradation occurred mainly after 24 h from excision and transfer to the dark. Chlorophyll degradation during 48 h in the dark was affected by norbornadiene or ethylene applied from 0–24 h or from 24–48 h. |
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