No description available.

No description available.

No description available.

Clonal propagation of Betula pendula and Pinus sylvestris using stem cuttings and tissue culture was studied. Cuttings of both species rooted with a high level of success and rooted cuttings showed high levels of survival. Single-internode cuttings, with one axillary bud and leaf, were most successful with Betula pendula. particularly if such cuttings were collected from elongating shoots. Pinus sylvestris cuttings were also successful if collected from elongating shoots. Although exogenous auxin increased speed of rooting and number of roots formed by cuttings it had little effect on the number of cuttings which formed roots and the subsequent survival of these rooted cuttings. Growth and biomass distribution of rooted cuttings of Betula pendula and Pinus sylvestris was similar to that of seedlings. Successful propagation of both species depended on ortets being in a "juvenile" phase of growth. An attempt to produce "juvenile" cutting material from "adult" genotypes of Betula pendula was made by inducing the formation of epicormic shoots. Although these shoots had "juvenile" morphology, and cuttings derived from these shoots had similar rooting characteristics to cuttings taken from young seedlings, cuttings collected from epicormic shoots demonstrated plagiotropic growth of shoots in comparison with the orthotropic habit of cuttings taken from young seedlings. These results suggest that only partial rejuvenation occurred. Methods of enhancing the yield of cuttings from young seedling ortets of Betula pendula and Pinus sylvestris are discussed. A method to propagate Betula pendula by callus culture was developed. Callus nodules, initiated from stem internodes, were induced to undergo morphogenesis with the development of shoots. Although only half of the cultured nodules regenerated shoots, "morphogenic" nodules formed an average of 100 shoots of 4mm in length or greater when subcultured on a medium with BAP (benzylaminopurine) and NAA (napthaleneacetic acid). Other growth substances tested were less successful or unsuccessful at regenerating shoots. These shoots readily rooted outwith aseptic culture in an intermittent spray unit. Level of rooting and survival of rooted shoots was very high. Successfulb morphogenesis depended on the culture of "juvenile" tissues. Rate of growth of tissue-culture plants was the same as genetically similar seedlings, however tissue-culture plants were found to have slightly thinner stems after one season of growth. A cytological investigation of tissue-culture plants revealed the presence of polyploids which were identified through chromosome counts as allotetraploids with 4n=56 chromosomes in comparison with the normal diploid 2n=28 karyotype. These allotetraploids were readily identified by their unusual leaf morphology and very slow growth. No other ploidy levels were found. The frequency of occurrence of these allotetraploids varied with the type of auxin incorporated in the culture medium. NAA was associated with a level of tetraploidy of 11.0 percent whereas IBA (indolebutyric acid) was associated with a level of 3.8 percent. BAP was used in combination with both these auxins. The higher level of tetraploidy, associated with NAA, was more than compensated by a greatly enhanced level of shoot regeneration on callus nodules cultured on a medium with this auxin in comparison with nodules cultured on a medium with IBA. Presence of allotetraploids was of little concern because of their ease of identification and low level of occurrence. Vegetative material taken from genotypes of Betula pendula greater than one year old developed callus tissues but this callus showed little capacity to undergo morphogenesis. A few shoots did develop from callus initiated from shoot internodes collected from a four-year-old genotype. Only one of these shoots formed roots. Study of this plantlet suggested that it was not "juvenile" although its origins were adventitious.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. Includes bibliographical references (leaves 195-210).

No description available.

A common event during in vitro morphogenesis (either embryogenesis or shoot organogenesis) is the ability of somatic cells within the explants to de-differentiate and acquire “meristematic identity”. The developmental program of such meristematic cells can then be re-routed to form shoots or embryos depending on the imposed culture environment. The objective of this research is to investigate how the altered expression of Brassica genes regulating meristematic activity in vivo affects in vitro morphogenesis. It is predicted that ectopic expression of positive regulators of the shoot apical meristem, SHOOT MERISTEMLESS (STM) and ZWILLE (ZLL) which increase the pool of meristematic cells within the apical meristem, has a beneficial effect on somatic embryogenesis and shoot organogenesis. Conversely the over-expression of CLAVATA1 (CLV1), a negative regulator which depletes the pool of meristematic cells, should inhibit both processes. Over-expression of the Brassica STM in Arabidopsis enhanced the production of somatic embryos and shoots in vitro possibly by reducing the requirement of the tissue for exogenous auxin, which is the inductive signal for the production of embryogenic and organogenic cells. This was also accompanied by profound alterations in gene expression patterns affecting components of DNA methylation and glutathione metabolism, which are beneficial for embryo formation. The introduction of STM also enhanced Arabidopsis shoot organogenesis through profound transcriptional changes in cytokinin signalling. While the ectopic expression of the Brassica CLV1 inhibited both somatic embryogenesis and shoot organogenesis, the expression of ZLL had no effects on the production of somatic embryos but encouraged the formation of shoots. Taken together these results suggest the existence of similar genetic mechanisms regulating the formation of meristem cells in vivo and embryogenic/organogenic cells in vitro.

A common event during in vitro morphogenesis (either embryogenesis or shoot organogenesis) is the ability of somatic cells within the explants to de-differentiate and acquire “meristematic identity”. The developmental program of such meristematic cells can then be re-routed to form shoots or embryos depending on the imposed culture environment. The objective of this research is to investigate how the altered expression of Brassica genes regulating meristematic activity in vivo affects in vitro morphogenesis. It is predicted that ectopic expression of positive regulators of the shoot apical meristem, SHOOT MERISTEMLESS (STM) and ZWILLE (ZLL) which increase the pool of meristematic cells within the apical meristem, has a beneficial effect on somatic embryogenesis and shoot organogenesis. Conversely the over-expression of CLAVATA1 (CLV1), a negative regulator which depletes the pool of meristematic cells, should inhibit both processes. Over-expression of the Brassica STM in Arabidopsis enhanced the production of somatic embryos and shoots in vitro possibly by reducing the requirement of the tissue for exogenous auxin, which is the inductive signal for the production of embryogenic and organogenic cells. This was also accompanied by profound alterations in gene expression patterns affecting components of DNA methylation and glutathione metabolism, which are beneficial for embryo formation. The introduction of STM also enhanced Arabidopsis shoot organogenesis through profound transcriptional changes in cytokinin signalling. While the ectopic expression of the Brassica CLV1 inhibited both somatic embryogenesis and shoot organogenesis, the expression of ZLL had no effects on the production of somatic embryos but encouraged the formation of shoots. Taken together these results suggest the existence of similar genetic mechanisms regulating the formation of meristem cells in vivo and embryogenic/organogenic cells in vitro.

Shoot dieback of lodgepole pine in the British Isles has been a long standing problem, but it was not known whether or not a pathogen was involved. During 1980--1982, a shoot dieback disease of lodgepole, similar to those previously observed at different places, was studied at the Glengarry and Eilanreach forests in the northwest of Scotland. Dieback symptoms and stages in their development were investigated. A thorough review of the literature on dieback disease of lodgepole pine indicated that different disease symptoms were involved in the present outbreaks. A hitherto undescribed fungus, Ramichloridium pini de Hoog & Rahman was found to be closely associated with the early stages of discolouration of the buds and shoots of lodgepole pine while Sclerophoma pythiophila (Cda.) Hohn was most prevalent on healthy and dead tissues. A new modified Czapek Dox Agar medium has been found to suppress S. pythiophila significantly while allowing normal growth of R. pini at about 15°C, which is the optimum temperature for the latter. A method of mass production of inoculum was devised. For germination of the conidia of R. pini free water is not essential. Good germination of conidia and elongation of germ tubes occurred on undetached flushing needle sheaths and bud scales. Extensive artificial inoculations have firmly established that R. pini is the primary pathogen of the present shoot dieback disease of lodgepole pine. Most successful infections were obtained from inoculations carried out in May and June. By October, shoots became resistant to infection. Plants of the Central Nass River provenance were more resistant to R. pini than those from Long Beach, Washington. It has been shown that conidia produced on needle fascicle scars could provide natural inoculum. The infection period lay between mid April to mid May or up to early June at Eilanreach in 1981.

Thesis (B.S.) Summa Cum Laude--Butler University, 2009. / Includes bibliographical references (leaves 30-31).