Abstract
The quantity of RNA in the ribosomal fraction of the first leaf of cucumber (Cucumis sativus) increases during growth, reaches a maximum before the final fresh weight is attained, and then decreases. The main changes are in the free ribosome fraction, the quantity of membrane-bound ribosomes remaining about constant. Few 65.5S chloroplast ribosomes are present in small leaves; however, they increase in quantity rapidly during growth and form about half of the ribosomes present in the mature fully green leaf. The cytoplasmic ribosomes have a sedimentation coefficient of 77.6S. Ribonuclease-sensitive polysomes were present in leaves of all ages except possibly the very oldest. The proportion of ribosomes in polysome form decreases during growth and then remains roughly constant during senescence. Following maturation of the leaf, the rate of incorporation of 32P into ribosomal-fraction RNA begins to decline. This decline could account for the loss of ribosomes during the early stages of senescence. The possibility that leaf ribonuclease might be responsible for the final, more rapid loss of RNA, is discussed.
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- Barker G. R., Rieber M. The development of polysomes in the seed of Pisum arvense. Biochem J. 1967 Dec;105(3):1195–1202. doi: 10.1042/bj1051195. [DOI] [PMC free article] [PubMed] [Google Scholar]
- CLARK M. F., MATTHEWS R. E., RALPH R. K. RIBOSOMES AND POLYRIBOSOMES IN BRASSICA PEKINENSIS. Biochim Biophys Acta. 1964 Oct 16;91:289–304. doi: 10.1016/0926-6550(64)90253-1. [DOI] [PubMed] [Google Scholar]
- Loening U. E., Ingle J. Diversity of RNA components in green plant tissues. Nature. 1967 Jul 22;215(5099):363–367. doi: 10.1038/215363a0. [DOI] [PubMed] [Google Scholar]
- Simon E. W. Types of leaf senescence. Symp Soc Exp Biol. 1967;21:215–230. [PubMed] [Google Scholar]
- Srivastava B. I., Atkin R. K. Effect of second-leaf removal or kinetin treatment on the nucleic acid metabolism of senescing first seedling leaf of barley. Biochem J. 1968 Apr;107(3):361–366. doi: 10.1042/bj1070361. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stutz E., Noll H. Characterization of cytoplasmic and chloroplast polysomes in plants: evidence for three classes of ribosomal RNA in nature. Proc Natl Acad Sci U S A. 1967 Mar;57(3):774–781. doi: 10.1073/pnas.57.3.774. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tester C. F., Dure L., 3rd Selective precipitation of monomeric ribosomes by bentonite. Biochem Biophys Res Commun. 1966 May 3;23(3):287–293. doi: 10.1016/0006-291x(66)90543-2. [DOI] [PubMed] [Google Scholar]
- VENABLE J. H., COGGESHALL R. A SIMPLIFIED LEAD CITRATE STAIN FOR USE IN ELECTRON MICROSCOPY. J Cell Biol. 1965 May;25:407–408. doi: 10.1083/jcb.25.2.407. [DOI] [PMC free article] [PubMed] [Google Scholar]
- WETTSTEIN F. O., STAEHELIN T., NOLL H. Ribosomal aggregate engaged in protein synthesis: characterization of the ergosome. Nature. 1963 Feb 2;197:430–435. doi: 10.1038/197430a0. [DOI] [PubMed] [Google Scholar]
- WILSON C. M. Chromatographic separation of ribonucleases in corn. Biochim Biophys Acta. 1963 Feb 26;68:177–184. doi: 10.1016/0006-3002(63)90133-1. [DOI] [PubMed] [Google Scholar]
- Watts R. L., Mathias A. P. The use of bentonite in the isolation of plant polyribosomes. Biochim Biophys Acta. 1967;145(3):828–831. doi: 10.1016/0005-2787(67)90142-6. [DOI] [PubMed] [Google Scholar]
- Wilson S. H., Hoagland M. B. Physiology of rat-liver polysomes. The stability of messenger ribonucleic acid and ribosomes. Biochem J. 1967 May;103(2):556–566. doi: 10.1042/bj1030556. [DOI] [PMC free article] [PubMed] [Google Scholar]