Abstract
The senescence of oat leaves has been studied by following the loss of chlorophyll and protein and the increase of α-amino nitrogen, after detachment and darkening. Protein synthesis and the amounts of proteolytic enzymes in the leaves have been determined directly. The process of senescence is shown to be a sequential one in which protein synthesis,most probably the formation of a proteolytic enzyme with l-serine in its active center, is of prime importance. The evidence is as follows. Firstly, l-serine specifically enhances senescence, especially in presence of kinetin. Secondly, cycloheximide, which inhibits protein synthesis in other systems, delays senescence and prevents the serine enhancement. Although requiring higher concentrations, cycloheximide can be as effective as kinetin in inhibiting senescence. It is shown directly that cycloheximide prevents protein synthesis in oat leaves under the same conditions as when it prevents senescence. Thirdly, leaves have been shown to contain two proteinases, with pH optima at 3 and 7.5, whose activity increases during senescence, even though the total leaf protein is decreasing. The amounts of both these enzymes present after 3 days are clearly increased by serine, and are greatly decreased by cycloheximide or by kinetin. The role of kinetin in delaying senescence thus may rest on its ability to suppress protease formation.
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Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Anderson J. W., Rowan K. S. The effect of 6-furfurylaminopurine on senescence in tobacco-leaf tissue after harvest. Biochem J. 1966 Feb;98(2):401–404. doi: 10.1042/bj0980401. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ellis R. J., Macdonald I. R. Specificity of cycloheximide in higher plant systems. Plant Physiol. 1970 Aug;46(2):227–232. doi: 10.1104/pp.46.2.227. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LOWRY O. H., ROSEBROUGH N. J., FARR A. L., RANDALL R. J. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed] [Google Scholar]
- Ross C. Influence of cycloheximide (Actidione) upon pyrimidine nucleotide metabolism and rna synthesis in cocklebur leaf discs. Biochim Biophys Acta. 1968 Aug 23;166(1):40–47. doi: 10.1016/0005-2787(68)90488-7. [DOI] [PubMed] [Google Scholar]
- Shibaoka H., Thimann K. V. Antagonisms between Kinetin and Amino Acids: Experiments on the Mode of Action of Cytokinins. Plant Physiol. 1970 Aug;46(2):212–220. doi: 10.1104/pp.46.2.212. [DOI] [PMC free article] [PubMed] [Google Scholar]