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Sugar Unloading in Roots of Ricinus communis L. I. The Characteristics of Enzymes Concerned with Sucrose Catabolism and a Comparison of Their Distribution in Root and Shoot Tissues

S. Chapleo and J. L. Hall
The New Phytologist
Vol. 111, No. 3 (Mar., 1989), pp. 369-379
Published by: Wiley on behalf of the New Phytologist Trust
Stable URL: http://www.jstor.org/stable/2557231
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Sugar Unloading in Roots of Ricinus communis L. I. The Characteristics of Enzymes Concerned with Sucrose Catabolism and a Comparison of Their Distribution in Root and Shoot Tissues
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Abstract

Acid invertase (EC 3.2.1.26) is present in soluble and insoluble preparations from root and shoot tissue of Ricinus communis L. Greatest activity is found in expanding tissue, whilst very low activity is found in vascular and in phloem-enriched tissue from stem internodes. In most tissues less than 20% of the total acid invertase activity is insoluble, the exception being extrafloral nectaries where 65-82% is insoluble. The activity of sucrose synthase (EC 2.4.1.13) is low in leaves and apical regions of the primary root; the root stele contains greater activity than the cortex. Considerable diel variations in leaf carbohydrate content were demonstrated and the results suggest that variations for the young sink leaves might be out of phase with those of source leaves by as much as one photoperiod. The results are discussed in relation to the metabolism and transport of sucrose, particularly in roots.

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