Abstract
To determine the selectivity of movement of amino acids from source leaves to sink tissues in soybeans (Glycine max [L.] Merr. `Wells'), 14C-labeled serine, leucine, or lysine was applied to an abraded spot on a fully expanded trifoliolate leaflet, and an immature sink leaf three nodes above was monitored with a GM tube for arrival of radioactivity. Comparisons were made with 14C-sucrose and 14CO2 assimilates. Radioactivity was detected in the sink leaf for all compounds applied to the source leaflet. A heat girdle at the source leaf petiole essentially blocked movement of applied compounds, suggesting phloem transport. Transport velocities were similar (ranged from 0.75 to 1.06 cm/min), but mass transfer rates for sucrose were much higher than those for amino acids. Hence, the quantity of amino acids entering the phloem was much smaller than that of sucrose. Extraction of source, path, and sink tissues at the conclusion of the experiments revealed that 80 to 90% of the radioactivity remained in the source leaflet. Serine was partially metabolized in the transport path, whereas lysine and leucine were not. Although serine is found in greater quantities than leucine and lysine in the source leaf and path of soybeans, applied leucine and lysine were transported at comparable velocities and in only slightly lower quantities than was applied serine. Thus, no selective barrier against entry of these amino acids into the phloem exists.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bach M. K., Magee W. E., Burris R. H. Translocation of Photosynthetic Products to Soybean Nodules and Their Role in Nitrogen Fixation. Plant Physiol. 1958 Mar;33(2):118–124. doi: 10.1104/pp.33.2.118. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Cataldo D. A., Christy A. L., Coulson C. L. Solution-Flow in the Phloem: II. Phloem Transport of THO in Beta vulgaris. Plant Physiol. 1972 May;49(5):690–695. doi: 10.1104/pp.49.5.690. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Chopowick R. E., Forward D. F. Translocation of Radioactive Carbon after the Application of C-Alanine and CO(2) to Sunflower Leaves. Plant Physiol. 1974 Jan;53(1):21–27. doi: 10.1104/pp.53.1.21. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Clauss H., Mortimer D. C., Gorham P. R. Time-course Study of Translocation of Products of Photosynthesis in Soybean Plants. Plant Physiol. 1964 Mar;39(2):269–273. doi: 10.1104/pp.39.2.269. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Fisher D. B. Kinetics of C-14 translocation in soybean: I. Kinetics in the stem. Plant Physiol. 1970 Feb;45(2):107–113. doi: 10.1104/pp.45.2.107. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Geiger D. R., Sovonick S. A., Shock T. L., Fellows R. J. Role of free space in translocation in sugar beet. Plant Physiol. 1974 Dec;54(6):892–898. doi: 10.1104/pp.54.6.892. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Heathcote J. G., Haworth C. An improved technique for the analysis of amino acids and related compounds on thin layers of cellulose. II. The quantitative determination of amino acids in protein hydrolysates. J Chromatogr. 1969 Aug 5;43(1):84–92. doi: 10.1016/s0021-9673(00)99169-6. [DOI] [PubMed] [Google Scholar]
- Joy K. W., Antcliff A. J. Translocation of amino acids in sugar beet. Nature. 1966 Jul 9;211(5045):210–211. doi: 10.1038/211210a0. [DOI] [PubMed] [Google Scholar]
- NELSON C. D., PERKINS H. J., GORHAM P. R. Note on a rapid translocation of photosynthetically assimilated C14 out of the primary leaf of the young soybean plant. Can J Biochem Physiol. 1958 Dec;36(12):1277–1279. [PubMed] [Google Scholar]
- Sovonick S. A., Geiger D. R., Fellows R. J. Evidence for active Phloem loading in the minor veins of sugar beet. Plant Physiol. 1974 Dec;54(6):886–891. doi: 10.1104/pp.54.6.886. [DOI] [PMC free article] [PubMed] [Google Scholar]