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Aspects of the physiological and chemical control of adventitious root formation in Eucalyptus nitens (Deane & Maiden) Maiden

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Luckman, G (1996) Aspects of the physiological and chemical control of adventitious root formation in Eucalyptus nitens (Deane & Maiden) Maiden. PhD thesis, University of Tasmania.

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Abstract

Eucalyptus nitens is an important species in plantation forests in Tasmania
and is becoming important in other cool temperate regions of the world.
Reliable initiation of roots in cuttings is needed, to enhance forest productivity
through the establishment of clonal plantations.
Adventitious root initiation is dependent on the re-polarisation of cells to form a
new root meristem. Failure to initiate roots may be due to the inability of the
plant to undergo re-polarisation of cells to form a new meristem. The research
undertaken has been directed at the manipulation of some of the factors that
are implicated in the establishment of cellular polarity in plants. Several new
techniques for enhancing root initiation have been investigated and shown to
promote root formation in cuttings of E. nitens. The principle conclusions of
the research are outlined below.
It was demonstrated that a high proportion of E. nitens seedlings have the
ability to initiate adventitious roots in cuttings collected from very young
seedlings. This ability is lost quickly as the plant ages. The loss of rooting
ability does not appear to be related to any specific changes in the stem
morphology. Histological examination demonstrated that the loss of rooting
ability is not correlated with the formation of structural barriers within the
stem or callus. Root primordium formation appears to occur in regions of
undifferentiated callus in most cuttings but can also occur directly from the
cambium, with little or no intervening callus phase.
Root initiation was found to be sensitive to the timing and method of auxin
applications. It was possible to increase the proportion of cuttings that initiate
roots by delaying the application of auxin until several weeks after the cuttings
were first placed on the mist-bed. Calcium ions are part of the mechanism by
which auxin signals are translated into cellular actions. Attempts to increase
the rate of root initiation in cuttings by altering calcium levels in the
surrounding medium were inconclusive.
Electric potential differences are known to play a role in the establishment of
cellular polarity and in organogenesis from callus. It was demonstrated that
low voltage electric currents could be used to stimulate root initiation in some cuttings. It was hypothesised that cuttings with substantial basal callus would
be most receptive to this treatment, but this was found not to be the case. The
experiments using electric currents were difficult to replicate and were subject
to unexplained variation in results. Further development of the technique is
required to quantify the effects of such currents and to identify the mode of
action.
Stigmasterol and vitamin D were demonstrated to act as auxin synergists in
the promotion of root initiation in cuttings and also to stimulate the growth of
tissue cultures. ATPase extracts were prepared to investigate whether the
action of sterol potentiation of auxin is associated with changes in membrane
bound I-1+-ATPase activity.
The treatment of cuttings with G compounds, as a method of promoting root
initiation, was investigated. G compounds are a group of naturally occurring
chemicals found in some eucalypt species and are known to inhibit and to boost
root initiation in some species. In cuttings of E. nitens, they were found to
have no significant effects on root initiation.
The results obtained are discussed in terms of the role that the treatments
might play in root morphogenesis through the re-polarisation of cells to create a
new axis. The results support the general hypothesis that treatments aimed at
enhancing the development of cellular polarity are useful in stimulating root
initiation in cuttings. Some suggestions are made for future research, to
develop these initial findings into practical treatments for the propagation of
E. nitens.

Item Type: Thesis (PhD)
Keywords: Eucalyptus, Eucalyptus
Copyright Holders: The Author
Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1997. Includes bibliographical references (leaves 231-249)

Date Deposited: 19 Dec 2014 02:35
Last Modified: 10 May 2017 02:50
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