Cytokinin biochemistry in relation to leaf senescence. VI. Effect of nitrogenous nutrients on cytokinin levels and senescence of tobacco leaves |
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Authors: | Santokh Singh D S Letham Xue-dong Zhang L M S Palni |
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Institution: | Plant Cell Biology Group, Research School of Biological Sciences, The Australian National Univ., GPO Box 475, Canberra City, ACT 2601, Australia |
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Abstract: | The effect of nitrogenous nutrients on endogeneous cytokinins and senescence of tobacco leaves was investigated. Ammonium nitrate was the most effective in retarding senescence and its activity was attributed principally to NH4+ ions. Repeated applications or a continuous supply of ammonium nitrate was required for maximal retardation of tobacco leaf senescence. Ammonium nitrate solution supplied via the petioles reduced the senescence retarding effect of dihydrozeatin applied directly to the laminae of detached tobacco leaves. Ammonium nitrate also elevated the endogenous levels of cytokinins (especially zeatin and dihydrozeatin) particularly in growing tobacco leaves excised from near the apex of the plant. Ammonium nitrate induced retardation of leaf senescence may be mediated at least partly by its effect on foliar cytokinin content. |
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Keywords: | Cytokinins leaf senescence nitrogenous nutrients radioimmunoassay |
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