Verbeek-Boasson, Rosalinda

English

SUMMARY AND CONCLUSIONS 1. The greening and the growth of chloroplasts as induced by light has been investigated in leaf discs from etiolated tobacco leaves in sterile culture. 2.On a medium containing salts after Murashige and Skoog plus sucrose, chlorophyll synthesis proceeds very slowly during the first day after the transfer from darkness to light. Thereafter the rate of chlorophyll synthesis increases considerably. The chlorophyll content reaches its maximum after 4-6 days in the light. 3.In whole leaves in sterile culture chlorophyll synthesis progresses in about the same pattern and at the same rate as in leaf discs. 4.When etiolated intact plants were illuminated, chlorophyll synthesis started immediately at a high rate, and continued at a much higher rate than in the isolated leaves and discs. Moreover, in whole plants the chlorophyll content reached a much higher final value. Glucose, fructose, various vitamins, inositol, auxin, kinetin and gibberellin failed to bring the rate of chlorophyll synthesis in leaf discs on the level of that in the whole plant. 5.During the light-induced development of the etiolated tissue on standard medium the number of plastids per cell increases considerably. 6.The number of chloroplasts per cell has also been determined in barley and oats. In these species light-induced greening is not accompanied by plastid replication..

ARTS repository - University of Groningen

   University of GroningenChloroplast replication and growth in tobaccoVerbeek-Boasson, RosalindaIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1969Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Verbeek-Boasson, R. (1969). Chloroplast replication and growth in tobacco. [s.n.].CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 21-06-202264 SUMMARY AND CONCLUSIONS 1. The greening and the growth of chloroplasts as induced by light has been investigated in leaf discs from etiolated tobacco leaves in sterile culture. 2. On a medium containing salts after Murashige and Skoog plus sucrose, chlorophyll synthests proceeds very slowly during the first day after the transfer from darkness to light. Thereafter the rate of chlorophyll synthesis increases considerably. The chlorophyll content reaches its maximum after 4-6 days in the light. 3. In whole leaves in sterile culture chlorophyll synthesis progresses in about the same pattern and at the same rate as in leaf discs. 4. When etiolated intact plants were illum:inated, chlorophyll synthesis started immediately at a high rate, and continued at a much higher rate than in the isolated leaves and discs. Moreover, in whole plants the chlorophyll c0i!tent reached a much higher final value. Glucose, fructose, various vita­m:ins, inositol, auxin, kinetin and gibberellin failed to bring the rate of chloro­phyll synthesis in leaf discs on the level of that in the whole plant. 5. During the light:induced development of the etiolated tissue on stand­ard medium the number of plastids per ceU increases considerably. 6. The number of chloroplasts per ceU has also been determ:ined in barley and oats. In these species light-induced greening is not accompanied by pIastid replication. 7. 5-Fluorouridine (FUDR) has no effect on the number of cells per Ieaf disc, nor on the size of the cells. 8. FUDR inhibits both chlorophyll synthesis and the growth in diameter of the plastids. It does not inhibit the increase in chloroplast number per cell on standard medium. ft bas no effect at all on ehlorophyll synthesis in bean, and only a very slight inhibitory effect on barley. 9. FUDR has no effect on the ultrastructure of the chloroplasts. 10. The inhibiting effect of FUDR is reversed by thym:idine but not by uridine. 11. Leaf dis cs treated with FUDR for 4 days and exposed to 3 H-thymidine after this, inco-rporated the thymidine into the eytoplasm of all cells, and into occasional nuclei. Most of the label disappeared after treatment with DNA-ase. 12. When leaf discs were treated with kinetin during a period of 7 days in darkness and 7 days in the light, the number of cells per disc i& not affected, but the eells become very large and eontain large numbers of chloroplasts. ; induced by light has :aves in sterile culture. ld Skoog plus sucrose, te first day after the chlorophyll synthesis ,es its maximum after ,ynthesis progresses in iscs. chlorophyll synthesis much higher rate than plants the chlorophyll fructose, various vita­ring the rate of chloro­hole plant. iolated tissue on stand­nsiderably. n determined in badey not accompanied by te number of celIs per the growth in diameter 'roplast number per cell phyll synthesis in bean, chloroplasts. thymidine but not by posed to 3 H -thymidine sm of all celJs, and into ~atment with DNA-ase. ing a period of 7 days per disc is not affected, 1mbers of chloroplasts. FUDR inbibits the expansion of the cells to some extent and completely abo­lishes the extra increase in chloroplast number per cell. 13. Nalidixic acid had about the same effect as FUDR on chloroplast ultrastructure, chloroplast numbers per ceH, chloroplast size and chlorophyll synthesis. 14. lt is concluded that the ra te of chlorophyll synthesis in tobacco is dependent on the quantity of functional DNA. 15. It is concluded that the increase in chloroplast size depends on the amount of functional DNA. 16. It is suggested that under normal circumstances the maximum num­ber of chloroplasts in the cell is limited by cell size, and that the effect of kinetin and auxin on tbis number is brought about by an increase in cel! size. 17. 1 t is suggested that chloroplasts contain more than one copy of their DNA, and that when they divide in the presence of FUDR the number of copies per plastid is reduced, causing these plastids to remain smaller than plastids with the normal number of copies, because.of a gene-do sage effect. 65 

Chloroplast replication and growth in tobacco

https://pure.rug.nl/ws/files/14412836/Verbeek-Boasson_R..pdf

Chloroplast replication and growth in tobacco

Abstract

Similar works

Full text

Available Versions

ARTS repository - University of Groningen