School of Botany - Theses

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Studies on the flagella and cytoskeleton of pleurochrysis carterae (prymnesiophycae) and mallomonas splendens (synurophyceae)

Beech, Peter Luke. (University of Melbourne, 1989)

The flagellar apparatus of motile, coccolith-bearing cells of Pleurochrysis carterae (Braarud & Fagerlund) Christensen (Prymnesiophyceae) and that of Mallomonas splendens (G.S.West) Playfair (Synurophyceae) are described at interphase and during cell division. The interphase arrangement of the flagellar apparatus in Pleurochrysis carterae is similar to that in Pleurochrysis sp. (Inouye & Pienaar 1985) but I report new information on microtubular root 1 (R1) and describe in detail the transition region of the flagellar axoneme. The basal body of the longer flagellum is shown to be that which is associated with R1. A distinctive membrane decoration is noted on specific areas of the peripheral endoplasmic reticulum (PER) and I discuss the role of the PER in scale secretion and endocytosis. The basal bodies of P. carterae duplicate before mitosis and the crystalline roots (CRs), which arise from R1 and root 2 (R2), disassemble at prophase as their component microtubules elongate towards the future spindle poles. By late prometaphase the basal bodies have segregated semi-conservatively and each pair displays diminutive flagellar roots for the future daughter cells. The two parental basal bodies now bear R1s, indicating that the basal body that produced a short flagellum in the parental cell has transformed into one that will produce a long flagellum in the daughter. All flagellar roots assume their interphase appearance by early cytokinesis. Amputation of the flagella of P. carterae results in their immediate regeneration according to deceleratory kinetics. In the presence of 1?g/ml cycloheximide flagella regenerate to only c. half-length. Immunofluorescence microscopy shows that CRs diminish in size as flagella regenerate and, in the presence of cycloheximide, are depleted when flagella cease to elongate. These data indicate that a pool of presynthesized precursors is available for flagellar regeneration in P. carterae and that part of this pool consists of tubulin from the CRs. Cells of Mallomonas splendens bear a single emergent flagellum (F1) and a non-functional basal body (F2). Direct observations on dividing cells show that the FIs of daughter cells arise from newly formed basal bodies as the parental F1 retracts and thereby transforms into a new F2; the parental F2 remains as such for successive generations. These results are confirmed with thin-sections. The flagellar apparatus of M. splendens at interphase displays numerous features that are novel in the Synurophyceae: the basal bodies are surrounded by a distinctive fibrous capsule; this is continuous with a thick, fibrous band that constitutes the anterior portion of the rhizoplast; the posterior of the rhizoplast forms a cone of numerous, striated straps over the nuclear apex; a single (three-membered) microtubular root (R1) is present which forms a loop around the basal bodies and descends to terminate on the rhizoplast near the nuclear apex; the descending portion of R1 has at least two orientations with respect to the basal bodies. The development of these structures is described from dividing cells. The R1s and rhizoplasts for daughter cells are formed de novo in association with new basal bodies at early mitosis as the parental structures disassemble. The new rhizoplasts are the organizing centres for the mitotic spindle. Mitosis in M. splendens is compared to that in the Chrysophyceae. The final chapter deals with the deployment of the four posterior bristles in M. splendens. Bristles articulate at their flexed basal ends, via an attached fibrillar complex, on specialized body scales (base-plate scales). Bristles are formed independently of their base-plate scales and I describe how they are united outside the cell. Mature posterior bristles are secreted onto the plasma membrane at late interphase and then extruded, basal ends first, from beneath the layer of body scales. Once bristles are fully extruded they are drawn back to the posterior apex of the cell with their basal ends leading - thus a 180� reorientation of the bristles has been effected outside the cell. A cytoplasmic protuberance which contains at least one microtubule accompanies the bristles throughout this reorientation and I propose that it is intimately involved. The fibrillar complex is formed in situ on the bristles and appears to mediate the deployment of bristles onto new base-plate scales.
Aspects of the water relations of eucalyptus behriana F. muell. and E. microcarpa (maiden) maiden near Melton, Victoria

Myers, Bronwyn Anne. (University of Melbourne, 1985)
Studies on the distribution and cycling of nitrogen in forests

Baker, Thomas Grant, 1955- (University of Melbourne, 1982)
A taxonomic study of the genus Nostoc in Antarctica

Garrick, Russell. (University of Melbourne, 1981)

This thesis provides written descriptions and illustrations of Antarctic specimens of Nostoc from both field and cultured material. The aims of the project were to provide the first detailed morphological descriptions of Nostoc from Antarctica and to assess the three different taxonomic approaches currently in use for this genus and for blue-green algae in general. Eight samples of field material are shown to consist of colonies of just two distinctly different structures. Clonal cultures obtained from all of these are described in detail using defined, standardized culture conditions. Five morphologically distinct strains have been recognized from these eight samples. Additionally two distinct strains, previously isolated from field material of unrecorded morphology, have been incorporated into the study. Detailed observations on the morphology and life-cycles displayed by cultures have been made over a 12 week period. Seven genetically distinct strains are distinguished, essentially by plant-mass appearance, although microscopic characters are of importance in some. Two basic types of life-cycle are elucidated, one of which differs from those previously described in the literature. A key is presented which allows the identification of Nostoc strains in culture using these characters. An attempt is made to identify the isolates, and the field material from which they were derived, using three taxonomic approaches. The classical system (Geitler, 1932) is useful only on the field material which is assigned either to N. commune Vauch. or as being close to N. sphaericum Vauch. and N. fuscescens Fritsch. The revised classical system proposed by Drouet (1978) identifies all field and culture material as N. commune (Vauch.) Drouet. Some close correlations are made between cultured strains and those examined in culture by Kantz and Bold (1969). It is concluded that none of these three taxonomic approaches is without its problems and shortcomings and presently no correlation can be made between them. A programme for future work is suggested which might be able to overcome these difficulties and which would lead to an even greater understanding of the important Antarctic genus, Nostoc.
The effects of sewage effluent on the macrophytes off Werribee, Port Phillip Bay

Brown, V. B. (Victoria Bayley) (University of Melbourne, 1980)
The estimation of indole-3-acetic acid

Blaz�, Kevin L. (University of Melbourne, 1979)

This project evolved from a consideration of polarity in the embryo of the brown alga, Hormosira banksii. It was hypothesized that uneven distribution of auxin due to unilateral illumination led to the protrusion of the rhizoid on the dark side of the zygote. It was intended to test this hypothesis by supplying the zygotes with labelled indole-3-acetic acid and, after incubation in this medium, examine the zygotes using micro-autoradiography. The concentration of indole-3-acetic acid in the cell had to be determined in order that the radioactive compound could be supplied to the zygotes at physiological concentrations. This required the review and selection of extraction, purification and assay methods. The literature review encompasses examples of most of the types of methods in current use. Since the various methods of bioassay have many advantages, limitations and equipment requirements in common, only two methods are described. As the same can be said for other types of methods, these are not considered in detail. The literature review is directed at the researcher seeking a method for the assay of auxin, and, to this end, key references are cited to enable the worker to gain more information. On consideration of the equipment available, the method using the fluorescence of 2-methyl indole-?-pyrone appeared the most suitable. For purification, chromatography using a column of polystyrene resin seemed feasible. Finally, methanol, a widely-used solvent, was selected for extraction. The assay method was examined first, as the quality of extraction and purification could then be determined using the assay. Similarly, the purification was examined prior to the method of extraction. In assessing the capabilities of the methods, many problems were encountered - some peculiar to the equipment used, but several fundemental problems related to the techniques themselves. In fact, considering the findings of this work, it is apparent that the methods of auxin-assay warrant reappraisal with particular respect to losses.
Pollen-wall proteins and breeding systems of plants

Vithanage, H. I. M. V. (University of Melbourne, 1978)

Quatitative cytochemical methods have been developed to estimate changes during development in the pollen-wall proteins. Acid phosphatase was used as a marker for intine proteins, and non specific esterase for the exine proteins. In marrow-stem kale, Brassica oleracea and ryegrass, Lolium perenne the intine enzyme showed two peaks of accumulation during development, the first corresponding to its synthesis and incorporation in the intine, and the second to accumulation in the pollen cytoplasm at maturity. In contrast, the exine enzyme showed a single peak at pollen maturation. This was correlated with dissolution of the tapetum and consequent loss of its very high esterase activity, coincident with the accumulation of esterase in the exine cavities. In sunflower, Helianthus annuus acid phosphatase and esterase were detected in both exine and intine sites during pollen development. Acid phosphatase was associated with the nexine at pre-vacuolate period with high levels in the tapetum. At mid-vacuolate period the tapetum became plasmodial and enzyme activity was detected around the exine surface and was transferred to the exine cavities by the end of the vacuolate period. Esterase activity was associated with the exine at pre-vacuolate period; subsequently during the vacuolate period, activity was present in the intine, and in the cytoplasm at maturity. Two peaks of accumulation were detected, closely resembling those for the intine marker enzyme in Brassica and Lolium. The developmental cytochemistry of the stigma of Helianthus, Lolium and Secale has been investigated with a view to understanding the nature of selfincompatibility, the site of tube arrest and the route of pollen tube penetration. The callose rejection response in pollen and stigma that has been established for Cosmos and various Crucifers have been found in Helianthus. The rejection reaction is found to occur in the pollen grain and pollen tubes of grasses. The callose produced in germinating self pollen of the grass, Secale cereale has been isolated by a degredative physicochemical procedure. Partial acid hydrolysis, enzyme hydrolysis, sugar analysis and methylation analysis have shown that the material is a 1,3-?-linked glucan; however some evidence points to the presence of 1,4-?-linkages in addition.
Collected papers submitted for the degree of Doctor of Science in the University of Melbourne

Neales, Tom Finnis. (University of Melbourne, 1978)

The two major themes of this thesis of published work reflect my interest in the function of the trace element boron in plant nutrition and also my later, and present, involvement with the whole-plant aspects of photosynthesis and carbon nutrition, including that of crop species. In the 1950's there was,in Australia, great interest in the plant physiology of the plant trace elements - Mn, Zn, Cu, Mo and B. This interest derived from the findings of the 1940's that the correction of trace element deficiencies (in plants, cattle and sheep) increased agricultural production in existing pastoral areas, and also allowed hitherto unproductive regions to be cultivated (see, Anderson, 1971 and Underwood, 1962). My interest in the function of boron in plant nutrition originated under these influences in 1956, when I arrived in Melbourne University on an appointment whose brief was to teach plant and crop physiology to Agricultural Science students. This research interest widened in the early 1960 ' s in include aspects of the photosythetic and gas-exchange behaviour of leaves and intact plants. This was prompted by several influences including an interest in the physiological aspects of crop production and plant adaptation, the horizons that were opened by Gaastra's (1959) pioneering paper, and the availability of infrared absorption instruments (IRGAs) that allowed the accurate and instantaneous measurement of carbon dioxide and water vapour in an air stream. These involvements were much stimulated by the, initially apparently disparate, work of the 1960's on the physiology and biochemistry of photosynthesis in which some intellectual coherence was achieved in 1969-1970. This was the realisation that there existed in plants at least three distinct 'modes' of photosynthesis - C^, C4 and CAM (see: Bj�rkmann, 1973). My continuing association with Agricultural Science, and with its students and problems, also lead to work in crop physiology, mainly using the ideas and techniques associated with the investigation of photosynthesis and growth.
The ecology of amsinckia (amsinckia spp.) in wheat crops in Victoria

Friend, Douglas Aristides (University of Melbourne, 1977)

Amsinckia hispida, A. lycopsoides and A. intermedia are serious annual weeds of wheat crops in Victoria. Studies of cytology, seed germination, reproductive development, growth physiology, and competitive ability in relation to wheat were undertaken to elucidate the biological and ecological characteristics of Amsinckia that contribute to the success of these species as weeds. The most widespread species in Victoria is A. hispida, which was used in all the experimental studies. Observations in the field included all three species. Chromosome counts indicated the close relationship between A. hispida, a native of South America, and the other two North American species. All present similar problems as weeds. Germination was found to be regulated by a primary dormancy, which confined germination during after-ripening to low-temperatures (<10�C) and short photoperiods (darkness to 8 hr). In the field germination occurred as a flush, the magnitude of which depended on the timing and amount of rainfall, and the depth of burial. Seed produced in the previous spring, lying on or close to the soil surface, gave high germination percentages from the autumn to early winter. Ungerminated buried seed developed a light requirement for germination, which may be satisfied by cultivation. Seed held in the dark for 56 days at temperatures of 15� and 25�C developed a secondary dormancy, which greatly restricted germination under normally favourable conditions. These regulatory mechanisms would serve to confine germination to the normal growing season for Amsinckia, while providing several strategies for coping with adverse seasonal conditions as well as periodic cultivation. Reproductive development to flower initiation was retarded by increase in temperature from 10* to 20�C, whereas subsequent development was hastened by the same temperature increase. Increase in photoperiod from 8 to 16 hr greatly hastened development to flowering. Environmental regulation of development ensures that Amsinckia plants complete their life cycle before unfavourable conditions ensue in the late spring, irrespective of the time of germination, while balancing vegetative growth for maximum effectiveness in competition with reproductive growth for maximum seed production. Vegetative growth was characterized by a high relative growth rate (c. 0.18 mg mg-1 day-1) under moderate temperatures (15-20�C and high irradiance (no shade), associated with a high net assimilation rate (0.4-0.5 mg cm-2 day-1 ) and a high leaf area ratio (0.3-0.4 cm2 mg-1). A temperature optimum for growth in the range 15-20�C found in Amsinckia, is amongst the lowest reported for a temperate species. Potential seed production was extremely high - up to 2,000 seeds per plant in sward conditions. In competition with wheat, Amsinckia depended on its ability to respond rapidly to changes in the aerial and soil environments, in order that it maintain its share of light, nutrients and moisture. A reduction in irradiance elicited increases in leaf angle, leaf and stem lengths, specific leaf area, and shoot to root ratio. A reduction in the supply of soil nutrients resulted in a decrease in the shoot to root ratio. Where there was intense competition for both light and nutrients Amsinckia shoot dry weight was reduced by about 30%. Reductions in the yield of wheat resulting from competition from Amsinckia may be associated with a reduced supply of light,nutrients and/or moisture, but the results suggest that competition for soil moisture may have the greatest effect on wheat yields. The results have important implications on methods used to control Amsinckia. The possibility of reducing the effectiveness of Amsinckia by encouraging competition from wheat in the crop is stressed.
The decline in productivity of second rotation pinus radiata (D. Don.) plantations in Southeast South Australia

Friedel, Margaret Hilda. (University of Melbourne, 1972)

School of Botany - Theses

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