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Item A study of the growth of axillary buds in angiosperms : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Botany at Massey University(Massey University, 1991) Jowett, David FrankA description of the growth of axillary buds in the period before bud break was made in a number of angiosperms. This entailed a study of the growth of buds at representative locations in a plant as well as at different stages in the plant's growth. A number of different patterns of axillary bud development were found to exist. A way of assessing the significance of the differences between patterns was found. This involved comparing the observations with the theoretical possibilities which existed. A loose classification of the patterns was then constructed using the theoretical possibilities as a basis. An analysis of the data for each species was carried out to see if a cause for the cessation of bud growth could be determined. This analysis pointed towards the existence, in a large number of species, of a correlation between growth in an axillary bud and growth in surrounding tissues, particularly the expanding subtending leaf. One species - Salix fragilis - was chosen as the subject for a particularly detailed analysis. A clear correlation was established between growth in an axillary bud and growth in the stem in the immediate vicinity of the bud as well as in its subtending leaf. A number of experiments aimed at finding out the nature of a correlation between growth in an axillary bud and its subtending leaf were carried out with this species. These demonstrated that removal of a subtending leaf at an early stage in its growth had a significant depressing effect on axillary bud growth. This depressing effect was most pronounced during the period of most rapid growth in the axillary bud and its subtending leaf. The data from the general survey of over thirty plant species and the experiments with Salix jragilis seem to support the notion that the process of axillary bud growth - as opposed to that of lateral shoot outgrowth from axillary buds - is affected more by conditions within the growing stem than by influences exerted by the stem apex.Item Investigations of some floral vascular systems with particular reference to interpretations involved in the Gonophyll theory : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Botany at Massey University(Massey University, 1969) Skipworth, John PeytonThroughout the history of Plant Science, the Angiosperm flower has provided botanists with one of their most intriguing structural entities. The number of theories which have been advanced to account for the origin of the flower and for the nature of its component appendages are multitudinous and in large part unproven. In 1960 the British botanist Melville propounded a new theory, the Gonophyll theory, and this has excited considerable interest among floral morphologists. The basic tenets of Melville's interpretation were based on the course taken by vascular bundles, and in an arena still bedevilled by conflicting opinion, the lucid presentation of the Gonophyll theory carried some conviction. The present writer was at the time pursuing an interest in the development of the patterns displayed by vascular tissue in vegetative shoots and did in fact demonstrate an instance in which there was considerable change in vascular pattern during the period of primary trace development (Skipworth 1962). In addition, Tepfer (1953) had reported an instance where some alteration in vasculature of a fertile shoot did take place during the time between anthesis and fruit maturity. From these two reports emanated the suspicion that when they first appear, the strands comprising the vascular system of flowers may not display the relationships apparent at floral maturity.Item Male cone development in Pinus radiata : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology at Massey University, Palmerston North, New Zealand(Massey University, 1995) Wang, Yunqiu; Wang, YunqiuLight microscopy and transmission electron microscopy were used to investigate the morphological, anatomical changes and the timing of these changes during male cone development of Pinus radiata growing in the central part of the North Island, New Zealand. The timing of developmental events, including the initiation of the male cone primordia, the onset of meiosis of pollen mother cells and the formation of pollen grains were recorded. Their relationship with environmental factors in comparison with pine species growing in the Northern Hemisphere was discussed. Some significant morphological aspects of male cone buds, microsporophylls and structural/ultrastructural changes of microsporangia, tapetal cells and pollen mother cells during the meiotic processes in particular, were reported in the morphological and anatomical study. In correlation with these structural/ultrastructrual changes, the soluble protein content, banding patterns of the total soluble protein, banding patterns of four isoenzymes during male cone development were studied by SDS-PAGE and isoelectric focusing techniques. Seven soluble protein species were detected by SDS-PAGE closely related to the different developmental stages of the male cone, and one of them with a molecular mass of 20.5 KD in particular was found to be a potential male cone tissue specific gene expression product. Acid phosphatase, esterase, malate dehydrogenase and peroxidase were studied during male cone development, using isoelectric focusing methodology. Variations in banding patterns of the enzyme activity and number of isoforms of each enzyme in relation to the different developmental stages of the male cone were revealed. A number of isoforms of these four isoenzymes were found to be unique to specific developmental stages. A search for floral-specific genes controlling floral developmental events was attempted. MADS-box DNA sequences belonging to a homeotic gene family controlling floral development in higher plants are reported for the first time in the genus Pinus in this study. The MADS box gene AGAMOUS from Arabidopsis thaliana was used as a probe to hybridise with genomic DNA of P. radiata. The tentative evidence of hybridisations was obtained in Southern blots, suggesting the possible existence of MADS box related DNA sequences in P. radiata. PCR technique was subsequently used to clone these sequences from genomic DNA of radiata pine to confirm the result obtained from Southern blot study. PCR with two degenerate primers targeted to highly conserved regions within the MADS- box resulted in the amplification of a 78 bp DNA sequence. These PCR amplified pine DNA sequences were subcloned in M13 and were sequenced by the dideoxy protocol. The analysis of these DNA sequence data and the amino acid sequences deduced from these DNA sequences showed that these DNA sequences can be divided into three groups, probably belonging to three MADS-box genes of Pinus radiata. Two DNA sequence groups are most likely to be the conserved regions of pine MADS-box genes, controlling the late steps of "floral" development which are homologous to class C genes determining the identity of male floral parts (stamens) and female parts (carpels) in angiosperms. One DNA sequence group is speculated to be the conserved region of pine MADS-box gene controlling the earlier steps of floral development, analogous to class B genes controlling petal and stamen development in angiosperms