scispace - formally typeset
Search or ask a question
Topic

Kinetin

About: Kinetin is a research topic. Over the lifetime, 7856 publications have been published within this topic receiving 135550 citations. The topic is also known as: Kinetin.


Papers
More filters
Journal ArticleDOI
12 Nov 1993-Science
TL;DR: In the roots of maize seedlings, Zm-p60.1 was localized to the meristematic cells and may function in vivo to supply the developing maize embryo with active cytokinin.
Abstract: A beta-glucoside encoded by a cloned Zea mays complementary DNA (Zm-p60.1) cleaved the biologically inactive hormone conjugates cytokinin-O-glucosides and kinetin-N3-glucoside, releasing active cytokinin. Tobacco protoplasts that transiently expressed Zm-p60.1 could use the inactive cytokinin glucosides to initiate cell division. The ability of protoplasts to sustain growth in response to cytokinin glucosides persisted indefinitely after the likely disappearance of the expression vector. In the roots of maize seedlings, Zm-p60.1 was localized to the meristematic cells and may function in vivo to supply the developing maize embryo with active cytokinin.

345 citations

Journal ArticleDOI
TL;DR: The ovule's capacity for indoleacetic acidor gibberellic acid-stimulation of fiber development was reduced by high concentrations of kinetin or abscisic acid, which partially reversed the inhibitory effect of phytohormones.
Abstract: Fertilization of cotton ovules was prevented by removal of styles and stamens on the morning of anthesis. Forty-eight hr later ovaries were harvested and ovules were aseptically transferred to liquid culture medium supplemented with various plant growth substances. In the absence of phytohormones, ovules browned and failed to increase in size or produce fibers. Indoleacetic acid and gibberellic acid provided for ovule growth and fiber development. Kinetin provided for ovule growth only. The ovule's capacity for indoleacetic acidor gibberellic acid-stimulation of fiber development was reduced by high concentrations of kinetin or abscisic acid. Low concentrations of kinetin partially reversed the inhibitory effect of

333 citations

Journal ArticleDOI
TL;DR: During the last 4 years, several chemical substances have been shown to retard senescence of leaf blades, and in this respect the compounds would atppear to substitute either directly or indirectly for the unknown so-called root factors.
Abstract: The chemical changes that occur in leaves as they grow old have been well characterized for many species. The endogenous factors which control and regulate these changes in plant cells remain, to a great extent, obscure, and the problem of why the cell eventually dies is yet unsolved. A normal feature of the ageing leaf blade is a continuous decline in protein level (1). The most rapid fall occurs during senescence and is associated with irreversible yellowing, loss of chlorophyll, and the eventual death of the organ. When a mature leaf is excised from the plant and the petiole kept in water, these same symptoms of senescence occur and, provided the petiole does not form roots, the protein content of the blade may fall to less than half the original value within a few days. If, however, the petiole forms roots, the behavior of the excised leaf is quite different. It will remain green and photosynthetically active, increasing in dry weight and total protein for periods extending, in some cases, to several years (2), much longer, in fact, than the leaf would survive in situ. The factors responsible for senescence and the decline of total protein in the leaf are not fully understood. Experiments with excised leaves have shown that the decrease in protein content of the blade is not necessarily due to a lack of carbohydrate, nitrogen, or other nutrients (14, 4) or to an inability of the cells themselves to synthesize amino acids (13) but is due, rather, to a failing ability to incorporate these amino acids into protein (11). Provided the leaf has a growing root system, the incorporation of amino acids proceeds normally, and it seems logical to assume that the roots metabolize and supply the blade with certain factors necessary for the continued synthesis of protein. During the last 4 years, several chemical substances have been shown to retard senescence of leaf blades, and in this respect the compounds would atppear to substitute either directly or indirectly for the unknown so-called root factors. In 1957, Person, Samborski, and Forsyth (10) demonstrated that both chlorophyll degradation and protein loss in detached wheat leaves are retarded if the blades are floated on solutions of benzimidazole at 50 mg/liter. In the same year, Richmond and Lang (12) showed that similar effects could be obtained if excised leaves of Xanthium are kept with their petioles dipping into solutions of kinetin at 5 mg/liter. Mothes and Engelbrecht (5) sprayed solutions of kinetin directly onto leaves of Nicotiana and reported (1959) that the retention of chlorophyll is localized to the areas of the blade to which kinetin is supplied. They found that labelled amino acids migrate to, and accumulate in, the treated parts of tobacco leaves, and they suggest that kinetin retards leaf senescence by causing the treated areas to act as loci for the accumulation of metabolites (5, 6). Extensive investigations have shown that both protein synthesis and ribonucleic acid synthesis is stimulated in kinetin-treated parts of tobacco leaves. (15). Mothes and Engelbrecht (7) conclude, however, that "accumulation, . . . is not the consequence of synthesis, but mass synthesis of protein, for example, is the consequence of an accumulation of amino acids." In 1959, (8) it was demonstrated that a number of auxins are markedly effective in retarding the senescence of attached or detached autumn leaves of Prunus serrulata-senriko. Where ethanolic solutions of esters of 2,4-dichlorophenoxyacetic acid are applied to the blades, the cells retain their green color for some 10 to 20 days longer than those in the surrounding untreated parts of the blade, or in the control leaves. The retention of green color in the treated areas is associated with an actively photosynthetic chlorophyll and, a maintenance of the initial protein level (9). Attempts to retard senescence by various treatments with kinetin proved unsuccessful in this species. Precise information is still meagre concerning the part played by either auxins or kinins in the retardation of the biochemical changes associated with senescence but it is clear that they must exert a control through some fundamental cellular processes. In this paper are described some effects of one kinin, kinetin, upon the metabolism of protein and nucleic acids during the senescence of excised leaves of Xanthium pennsylvanicum. The results provide evidence that kinetin may control senescence in these 1 Received Jan. 15, 1962. 2 Present address: Agricultural Research Council Unit of Experimental Agronomy, Department of Agriculture, Oxford.

304 citations

Journal ArticleDOI
TL;DR: The senescence of oat leaves has been studied by following the loss of chlorophyll and protein and the increase of alpha-amino nitrogen, after detachment and darkening, and 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.
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.

274 citations


Network Information
Related Topics (5)
Shoot
32.1K papers, 693.3K citations
90% related
Auxin
10.7K papers, 502.6K citations
88% related
Germination
51.9K papers, 877.9K citations
87% related
Seedling
28.6K papers, 478.2K citations
84% related
Abscisic acid
12.8K papers, 587K citations
84% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023115
2022243
2021139
2020137
2019156
2018189