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Etude du système racinaire de l'Eucalyptus en plantation tropicale analyse architecturale, croissance et respiration /Thongo M'Bou, Armel Epron, Daniel. Mialoundama, Fidèle. January 2008 (has links) (PDF)
Thèse de doctorat : Biologie végétale et forestière : Nancy 1 : 2008. Thèse de doctorat : Biologie végétale et forestière : Université Marien Ngouabi, Brazzaville : 2008. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre.
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Applicability of best linear unbiased prediction (BLUP) for the selection of ortets in Eucalyptus hybrid populationsHettasch, Marianne Helena. January 2009 (has links)
Thesis (M.Sc.)(Genetics)--University of Pretoria, 2009 / Includes summary. Includes bibliographical references.
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Genetic variability and leaf waxes of some Eucalyptus species with horticultural potential /Wirthensohn, Michelle Gabrielle. January 1998 (has links) (PDF)
Thesis (Ph. D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1999. / Copies of author's previously published articles inserted. Includes bibliographical references (leaves 122-137).
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The actions of, and interactions between, auxins and cytokinins and their effect on in vitro rooting of selected Eucalyptus clones.Nakhooda, Muhammad. January 2011 (has links)
Clonal propagation of Eucalyptus spp. and its hybrids allows for competitiveness in the
commercial forestry industry through the propagation and preservation of superior/elite
genotypes. Vegetative propagation through rooted cuttings is the industry‟s standard
and the choice of clones selected for plantations are determined by their rooting ability.
However, as many potentially valuable genotypes are recalcitrant to adventitious
rooting, micropropagation is the only effective means of propagating them.
Micropropagation results in high plantlet yields, achieved primarily through the
empirical use of the key plant growth regulators (PGRs) cytokinins and auxins, for
shoot and root production, respectively. Their selection for use in vitro is driven by their
effects on percent rooting rather than root quality. Little is known regarding the quality
of the roots of the plantlets ex vitro, but there is some evidence that they are different
from those of seedlings and cuttings. It was therefore hypothesized that the properties of
exogenous PGRs and their interaction with other exogenous and endogenous PGRs,
influenced root development and subsequent root quality. This was tested in vitro using
a good-rooting E. grandis (TAG31) and two poor-rooting E. grandis x nitens hybrid
clones (GN155 and NH58). In the former, the auxins supplied during the pre-rooting
culture stages (multiplication and elongation) were sufficient for 100% rooting in an
auxin-free rooting medium. Different combinations of PGRs in the two pre-rooting
stages, followed by rooting without auxins, revealed a direct relationship between the
stability of the supplied auxin and the rooting ability of TAG31. Gas chromatographymass
spectrometry (GC-MS) analyses indicated that endogenous shoot levels of indole-
3-acetic acid (IAA) influenced graviperception. Also, low IAA content was associated
with atypical starch grain accumulation or its absence from root tips (53.1 nmol IAA gˉ¹
DW compared with 325.7 nmol IAA g-¹ DW in gravisensing roots). The specific roles
of the natural auxins IAA and IBA on root morphogenesis were then investigated using
2,3,5-triiodobenzoic acid (TIBA; inhibits IAA transport), ρ-chlorophenoxyisobutyric
acid (PCIB; inhibits auxin signal transduction), and the auxin antagonist kinetin in the
rooting medium, following root induction. After 3 weeks, the mean root diameter was
significantly reduced from 552.8μm (control) to 129.2μm (with PCIB) and 278.6μm
(with kinetin). TIBA increased root diameter to 833.4μm, decreased Δ root length,
increased root vasculature and resulted in agravitropism. Hence, whereas rooting could
be induced by IBA, IAA was necessary for the maintenance of vascular integrity and
graviperception. This critical role of IAA in root development is of importance as IBA,
owing to its higher stability, has been traditionally relied upon for root induction in the
majority of micropropagation protocols.
The potential of incorporating IAA into the media formulations of in vitro protocols for
poor-rooters that do not respond well to IAA was then investigated, using GN155 and
NH58. While PCIB in the rooting medium of GN155 completely inhibited rooting, the
addition of dihydroxyacetophenone (DHAP), an inhibitor of auxin conjugation, to the
rooting medium, did not significantly increase % rooting in the presence of 0.1 mg 1ˉ¹
IBA (i.e. 50% rooting with 2mM DHAP and IBA, compared with 45% with IBA alone).
The results suggested that the inability of some eucalypts to induce roots easily in vitro
was not due to a deficiency in auxin signal transduction or to auxin conjugation.
Instead, rooting was inhibited by an accumulation of kinetin within shoots during the
pre-rooting culture stages. The endogenous levels of PGRs in shoots of GN155 and
NH58 showed a strong relationship (R² = 0.943) between the shoot kinetin:auxin and
shoot rootability. Substituting kinetin with the relatively less stable natural cytokinin
trans-zeatin in the elongation stage resulted in a significant increase in % rooting in
both clones, from 19% to 45% (GN155) and from 31% to 52% (NH58), with 0.1 mg 1ˉ¹
IAA in the rooting medium. However, omitting all cytokinins from the elongation
medium, resulted in over 95% and 75% rooting of shoots of GN155 and NH58,
respectively, with 0.1 mg 1ˉ¹ IAA.
These results suggest that IAA is a requirement for root development and cannot be
substituted by its analogues in certain root developmental events. Hence, IAA should be
the preferred auxin for eucalypt micropropagation. As fundamental research, the
approach taken in this study circumvents the empirical method used in improving
micropropagation protocols. The importance of the properties and the interactions
between endogenous and exogenous PGRs in regulating root morphogenesis, and the
practical implications of these findings is emphasised. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2011.
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The effect of genetic improvement, fertilisation, weed control and regeneration method on the establishment and performance of Eucalyptus macarthurii and Eucalyptus nitens.Van den Berg, Gerhardus Johannes. January 2005 (has links)
Eucalyptus grandis was introduced into South Africa in the 19th century, and has since become the most important of the hardwood plantation tree species grown for pulp. Until the late 1980's E. grandis was virtually the only eucalypt species grown. In order to meet the increasing demand for pulpwood in South Africa, forestry companies need to increase their timber output from an existing land base (Brown and Hillis, 1984; Kimmins, 1994 and Little and Gardner, 2003), or alternatively extend the planting of favourable alternative tree species into areas previously considered unsuitable for forestry due to unfavourable climatic conditions. From 1984 the major timber companies expanded their plantation forestry into the colder, frost-prone highland areas of western KwaZulu-Natal, the northeastern Cape and southeastern Mpumalanga Highveld. As E. grandis was not tolerant to severe frost, E. macarthurii amd E. nitens were planted in these areas as alternatives (Schonau and Gardner, 1991). As much of the earlier research had been centered around the development of silvicultural standards for E. grandis, it became necessary to test these for the different eucalypt species. Two trials were therefore established to E. marcarthurii and E. nitens with the following objectives: - to extend current recommendations to include different species, - to determine the degree of interaction between different silvicultural standards (genetic improvement, fertilisation and weed control), - to determine the effects of weeds, fertilisation, genotype and regeneration method (seedling vs coppicing) on the initial and long term growth, uniformity, tree straightness and survival of cold tolerant eucalypts, - cost effectiveness of various methods for re-establishing E. nitens and E. macarthurii. Genetic improvement played an important role in the establishment and initial
growth of E. macarthurii and E. nitens. The improved treatments outperformed
the unimproved treatments in terms of tree growth until canopy closure. At the last measured date when the trees were six years of age, the E. nitens improved
seedlings were still significantly better in terms of basal area when compared to
unimproved seedlings. The initial positive effect of genetic improvement of E.
macarthurii seedling however, was not sustained. Genetic improvement of E.
macarthurii and E. nitens also had a positive effect on tree straightness and
survival when the trees were assessed at five years of age. The genetic
improvement of both species also showed to be a viable option to produce an
optimum timber output at a lower cost when regeneration is carried out by means
of replanting with seedlings.
Fertilisation also showed positive effects in terms of the establishment and initial
growth of E. macarthurii and E. nitens. At six years after planting, the basal area
of E. macarthurii seedlings without fertiliser was still significantly lower than any
one of the other treatments. However, the initial positive effect fertiliser had on
the growth of E. nitens seedlings decreased to a non-significant level at six years
after planting. Fertilisation of E. macarthurii and E. nitens had a positive effect on
tree straightness and survival when the trees were assessed at five years of age.
The fertilisation of E. macarthurii seedlings also produced an adequate amount of
timber at a relatively low cost.
The controlling of weeds did not have an impact on tree performance initially or
after canopy closure for either E. macarthurii or E. nitens. This is due to the lack
of weed growth at these high altitudes at which the sites were planted. Little and
Schumann (1996) found that eucalypts could tolerate an aboveground weed
biomass of up to 2000 kg ha (-1) before there were any severe losses in growth due
to competition. At both these trials, the weed load did not reach these levels in
order to compete with the trees.
No significant interactions between any of the treatments were detected at both
these sites at any stage.
At the last measured date, there were no significant differences in terms of tree
growth between the coppice and seedling treatments for either E. macarthurii or
E. nitens. Regeneration by means of E. macarthurii and E. nitens coppice had a
positive effect on tree straightness and survival when the trees were assessed at
five years of age. Re-establishment by means of coppice for both E. macarthurii
and E. nitens was also shown to be by far the most cost-effective way at present
to produce an adequate amount of timber. Coppicing was shown to be the least
costly way to produce a m2 ha(-1) of timber provided the right species are coppiced,
and optimum density levels are obtained. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.
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Les marsupiaux arboricoles folivores et l'eucalyptus un exemple d'adaptation aux défenses anti-herbivores des plantes /Lemarchand, Marie-Laure Ducos de Lahitte, Jacques January 2008 (has links) (PDF)
Reproduction de : Thèse d'exercice : Médecine vétérinaire : Toulouse 3 : 2008. / Titre provenant de l'écran titre. Bibliogr. p. 61-73.
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Morphological variation in Eucaltptus L'Herit., series : Dumosae / by Peter John LangLang, Peter John January 1983 (has links)
Typescript (photocopy) / Map overlay in end pocket / 427 leaves : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Botany, University of Adelaide, 1984
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Morphological variation in Eucaltptus L'Herit., series : Dumosae /Lang, Peter John. January 1983 (has links) (PDF)
Thesis (Ph.D.) Dept. of Botany, University of Adelaide, 1984. / Typescript (photocopy). Map overlay in end pocket.
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Predictive models for integrated pest management of the leaf beetle Chrysophtharta bimaculata in Eucalyptus nitens plantations in Tasmania /Candy, Steven Gregory. January 2000 (has links)
Thesis (Ph.D.)--University of Tasmania, 2000. / Library has additional copy on microfiche. Library has additional copy on CD-ROM. Includes bibliographical references.
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Increasing line combining ability and gray leaf spot resistance in maize by integrating conventional breeding with DNA marker technologyKiula, Barnabas Anthony. January 2007 (has links)
Thesis (Ph.D.)(Genetics)--University of Pretoria, 2007. / Includes summary. Available on the Internet via the World Wide Web.
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