Light promotes an increase of cytokinin oxidase/dehydrogenase activity during senescence of barley leaf segments
Copyright © 2010 Elsevier GmbH. All rights reserved.
| Veröffentlicht in: | Journal of plant physiology. - 1979. - 168(2011), 7 vom: 01. Mai, Seite 694-8 |
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| Weitere Verfasser: | , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2011
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| Zugriff auf das übergeordnete Werk: | Journal of plant physiology |
| Schlagworte: | Journal Article Plant Proteins Oxidoreductases EC 1.- cytokinin oxidase EC 1.5.99.12 |
| Zusammenfassung: | Copyright © 2010 Elsevier GmbH. All rights reserved. Following a study of the relationship between cytokinin oxidase/dehydrogenase (CKX) and senescence in darkened barley leaf segments, we have now investigated the influence of light on the in vitro activity of CKX. Seedlings of Hordeum vulgare L. were grown for 8d under a light/dark regime of 18h white light and 6h darkness. Then apical parts of 7cm length were cut from the first foliage leaves and their bases were placed in water. In segments kept in the dark, the CKX activity measured by cleavage of N(6)-(Δ(2)-isopentenyl)adenine rose from 0.1pkat (gFW)(-1) to 0.8pkat (g initial FW)(-1) within the first 4d of incubation. In contrast, in segments kept under the light/dark regime it reached a value of 8.6pkat (g initial FW)(-1) over the same time period. The chlorophyll a content declined slightly slower during light/dark cycling than in darkness. In contrast to segments and isolated laminae, corresponding attached laminae exhibited less CKX activity after 2d under light/dark conditions than after 2d in the dark. The activity in attached laminae of first foliage leaves of plants growing in light/dark cycling increased strongly only when the plants were older than 4 weeks. In line with this, the CKX activity in attached laminae of flag leaves of barley growing in fields increased in a late developmental state. The senescence of darkened isolated laminae of Zea mays L. and Phragmites australis (Cav.) Trin. ex Steudel was associated with an enhancement of CKX activity too. Because in most cases a positive correlation between CKX activity and senescence was found, it is likely that the enzyme promotes senescence by destroying cytokinins, which help to keep Poaceae leaves green. Light may promote not only cytokinin degradation but also the formation of bioactive cytokinins in leaf segments |
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| Beschreibung: | Date Completed 23.06.2011 Date Revised 30.09.2020 published: Print-Electronic Citation Status MEDLINE |
| ISSN: | 1618-1328 |
| DOI: | 10.1016/j.jplph.2010.10.004 |