Control of cell division in the filamentous green alga Zygnema Item Type text; Thesis-Reproduction (electronic) Authors Staker, Robert Dale, 1945- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 25/09/2021 05:42:58 Link to Item http://hdl.handle.net/10150/318132 CONTROL OF CELL DIVISION IN THE FILAMENTOUS, GREEN ALGA ZYGNEMA by Robert Dale Staker A Thesis Submitted to the Faculty of the DEPARTMENT OF BIOLOGICAL SCIENCES In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE WITH A MAJOR IN BOTANY In the Graduate College THE UNIVERSITY OF ARIZONA 1 9 7 S STATEMENT BY AUTHOR This thesis has been submitted in partial fulfill­ ment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library, Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below: Robert W. Hoshaw Professor of Biological Sciences ACKNOWLEDGMENTS The author wishes t:o express special! appreciation to Dr» Robert W » Hoshaw for.his many suggestions and guidance durihg the research of the problem and the writing of this manuscript<, The author wishes to extend his gratitude to Dr0 Robert Mellor for his criticism and suggestions» A special thanks is extended to Dr» Willard Van Asdall for his time in reading and criticizing this thesiso I am indebted to Dr„ James Rosowski for his suggestion of the subject matter and for his helpful suggestions and techniques throughout this: study 0 iii TABLE OF CONTENTS •' Page LIST OF ILLUSTRATIONS o , . , = 0 . „ . .0 o 0 = v LIST- OF TABLES © o o o o o o o o o o o o.o o o o o ' vxi. ABSTRACT O O O O O O O 0 O O O O O O 0 0 0 0 O 0 0 VLl J» INTRODUCTION O O O O O O O O O O O. O O O 0 0 0 0 0 1 REVIEW OF LITERATURE « o . 0 » . a « > = «, » = 4 MATERIALS AND METHODS . ».•»; , , » o 0 • « » „ . ' 9 Experimental Organism «, » ' , e 0- « « » • «• 9 Medium and Inoculation « , » „ . o a. oooo « 10 Growth Conditions , « = 6 , a o . o o » o o » 10 Harvesting and Fixation 0 # «. 0 o « a 0 ■ a -o « 12 Mordanting and Staining » , = « » « * , , v 13 Counting. Mitotic Divisions o Vo , ,'a 14 Stages of Cell Division Defined » o o o ? 0 e 14 Prophase o ©. o * o o o o o o .o * o o o o .15 Me tap ha s e a © © o » o .o o o o o o ©o © © 15 Anaphase © © © © o © ©' © © © © © © © © © .15 Telophase © ©.© © © © .© o © o o © © o © © 15 . Quantity of Cell Division © © © © © © © © © © 15 OBSERVATIONS AND RESULTS © © , © © © © © © , = © © 17 Optimum Temperature for Growth © © © © © © © ©. 17 Optimum Light Intensity for Growth © © © .© © © 17 12 s12 hr Light-Dark Cycle © © © © © « © © © © 20 Mitotic Times and Average Percentage © © . © © 20 4 i20 hr Light-Dark Cycle © © © © © © © © © © © 26 10:14 hr Light-Dark Cycle V © © © © © © © © © 26 Continuous Low Light © © © © © © © © © © © © © 26 An Attempt to Quantify Mitosis .© © © © © © © © 27 DISCUSSION A N D •CONCLUSIONS © © © © © © © © © © © © . 31 SUMMARY © a © © © o © ©o© © © © © © © © © o © © © a 37 LITERATURE CITED © « © © © © © V © © ©. © © V V © © 41 iv LIST OF ILLUSTRATIONS Figure - Page 1o Growth of Zygnema plotted as a function of temperatureo Five plates were grown at, each temperature 0 0 0 „ „ 0 0 0 6 0 # o : 13 2S Grovrth of Zygnema plotted as a function of light intensity „ 0 V 0 0 » 0 „ 0 V . 0 „ 19 3<> Histogram showing, the pattern of cell division in Zygnema sp8 when grown on a 12 $12 hr light-dark cycle, at 20 X 1 C with a light intensity of 400-500 ft-c for two weeks 0 „ 0 » , 0 0 0 0 0 0 22 40 i Analysis of Figo 3 with percent of each phase of mitosis during the 7 Pil to the 1 AM division period 0 0 » ;• , 0 0 „ . • ; 23 5V Pattern of cell division of Zvanema sp0 grown.on 12$12 light-dark cycle at 400- 500 ft-c for 2 weeks and then subjected to.a 4 $20 hr light-dark cycle for 5 days0 The temperature was 20 t 1 C 0 0 , e „ „ 0 0 ; 24 6v- Histogram.showing the pattern of cell division in Zygnema spa grown on a 10:14 hr light-dark cycle at 20 t 1 at a light intensity of 400-500 ft-c for .2 weeks o @ o 0 0 » o @ 0 0 @ @ @ @ ® 0 0 0 & ■ 23 7» : The pattern of cell division found in Zygnema grown for 2 weeks under 9 stand­ ard conditions9 and then subjected to continuous low light intensity of 40 ft-c (24:0 hr light-dark cycle) for a period of 5 days »• . , .. , »• . » e , . 29 80 , The relati bus hip found in Zygnema when grown for 2 weeks under 9 standard . conditions9 arid then inoculated on plates subjected to continuous darkness (0:24 hr light-dark cycle) for 5, days 0 e 0 „ 30 v L 1ST OF ILLUSTRATIONS-- - Continued Figure Page 9 o Controlled groxsrth environment in which cultures of Zv^nema were grown 0 « , .« « 0 '«' 39 10 o Petri plates shox«7ing the growth; of Zyanema after 14 days of 12:12 hr light-dark cycle? 400-500 ft-c and 20 i1 C o „ , , o 0 0 0 39 11 o Diagram showing the .Zvanema cell in prophase , stage of cell division. Nuclear membrane . has. dissolved and chromatin material has thickened .o o o o o » o e o oo^o o o o.o o o 40 12o Diagram of the metaphase cell in Zvahema ■ with chromosomes kt equator 0 0 0 , 0 «• * » 0 40 - 13 o Anaphase cell, in Zvanema with chromatids f migrating toward cell pole „ 0 , «; #• • o 0 « » . 40 14, Diagram of telophase cell with nuclear membrane reappearing, cytokinesis nearing completion * • , , , ., . .o .» . , , 40. LIST OF WBLES Table 10 Composition of the gro^Tth medium used m this study @ o o o-o.o o o o o o o © 2o' Stages of mitosis and their distributions0 Data from the 12 :12 hr light-dark. experiment using ’standard conditions’0 vii ABSTRACT During the present investigation some of the variables that "affect cell division in the greena filamen­ tous alga ZyRnema were studied0 This alga was grown on a defined medium in axenic culture under a controlled environmento Various parameters that influence the growth of Z y g n e m a and to an extent mitotic division^ were controlled to determine some of the optimum growth requirements of this alga. An attempt;was made to determine the minimum amount of light required to synchronize cell division. Also it was confirmed that cell division occurs during the dark cycle of a diurnal light-dark cycle„ with most pf the cells dividing during the first 5 or 6 hr after the onset of darkness, A study of mitotic times was made with methods used by other workers, Since no cell division was found when Zygnema was grown under continuous low light intensity conditions s it is concluded that cell division in this genus is exogenously or environmentally controlled. viii INTRODUCTION Rhythmic processes of many organisms appear to be under the control: of an "unacquired character/' some­ times called a biological clock, Zeitgeber, or cue, that is synchronized with some external environmental factor0 Rhythmic activities in organisms are sometimes referred to as endogenous if they occur independently of environ­ mental influences and exogenous if they occur as a direct result of environmental influences (Sweeney and Hastings„ 1962)o A classical example of an endogenous rhythm is that of luminescence in Gonyaulax, a unicellular marine , dinoflagellate (Sweeney and Hastings» 1958*)V' ■ Among the grpen algae which have been investigated for 24-hr rhythms of mitosis, the following are reported to exhibit peaks in the dark portion of the light-dark cycles Closteriunu Cosmarlum, Hvdrodictvonfl UlothrixV Staurdstrum, ' ' ’ " ' ' 1 MouReotia «■■■, SpiroRvra; and Zygnema (Leedale, 1959) 0 The rhythm was reported to be exogenous in these genera, , mitosis occurring at any time of the clock merely by adjust­ ing the time of the dark period in a growth cabinet» How­ ever, Leedale has presented no data on which this statement is based» Evidence that at least one of these algae, Zy&nema, does not show an endogenous circadian rhythm lies in the ■: ' . • ■ i : - : • ■ . 2 fact that cell division in this alga does not occur in continuous darkp as is the case with luminescence in Gonyaulaxo Although cell division occurs in Zygnema during the dark portion of the 12 s12 hr light-dark cycle* it is thought to be a light-dependent event (Rosowski p 1969)0 Most researchers in this field have found that the mitotic peaks occur during the dark period of the circadian light-dark cycle» but certain algae under special conditions show a peak in the light period0 Among these algae are Stigeoclonium and Draparnaldia (Brandham and Godwardp 1965), However, in the case of these two algaep the investigators show background mitosis (about !%)» indicating a certain degree of asynchrony or, as it is .