As the requirements for more efficient and economical crop production
emerge, so the need for a better understanding of plant growth and development
is felt. It is especially the need to understand means by which man
may influence growth and development in order to achieve greater productivity,
that requires attention. Observation and analysis of plant growth and the
concomitant study of plant components, organs and chemicals, provides one of
the research oriented approaches to gaining an understanding of the mechanism
of growth control.
Ultimately, the extent of reproductive growth (fruiting) or the bearing capacity
in all plants is governed by the volume and area of vegetative growth
and the supply of substances required for growth produced by those vegetative
organs. Productivity then, is governed by the efficiency of conversion of
solar energy to chemical energy and by the relative ability to store this
energy. Plant shoots play a fundamental role in both assimilation and storage
of carbohydrates.
Given the same growing conditions, similar plants sometimes exhibit different
rates of growth. For example, ontogenetically juvenile plants exhibit differences
in form and vigour in comparison with ontogenetically adult plants.
Although the genotype of such adult and juvenile plants may vary only in expression
and not in constitution, there does appear to be some property in
juvenile plants which induces the characteristic enhanced vegetative vigour.
It is this property, amongst many others, which needs to be better understood,
for it is a potential means of gaining greater yields from plants
without alterations being made to the environment.
A high degree of organisation of growth processes must exist to account for
the orderly development of plants. A few organic compounds that influence
certain biochemical and physiological reactions have been isolated from the As the requirements for more efficient and economical crop production
emerge, so the need for a better understanding of plant growth and development
is felt. It is especially the need to understand means by which man
may influence growth and development in order to achieve greater productivity,
that requires attention. Observation and analysis of plant growth and the
concomitant study of plant components, organs and chemicals, provides one of
the research oriented approaches to gaining an understanding of the mechanism
of growth control.
Ultimately, the extent of reproductive growth (fruiting) or the bearing capacity
in all plants is governed by the volume and area of vegetative growth
and the supply of substances required for growth produced by those vegetative
organs. Productivity then, is governed by the efficiency of conversion of
solar energy to chemical energy and by the relative ability to store this
energy. Plant shoots playa fundamental role in both assimilation and storage
of carbohydrates.
Given the same growing conditions, similar plants sometimes exhibit different
rates of growth. For example, ontogenetically juvenile plants exhibit differences
in form and vigour in comparison with ontogenetically adult plants.
Although the genotype of such adult and juvenile plants may vary only in expression
and not in constitution, there does appear to be some property in
juvenile plants which induces the characteristic enhanced vegetative vigour.
It is this property, amongst many others, which needs to be better understood,
for it is a potential means of gaining greater yields from plants
without alterations being made to the environment.
A high degree of organisation of growth processes must exist to account for
the orderly development of plants. A few organic compounds that influence
certain biochemical and physiological reactions have been isolated from the wide array of organic and inorganic substances found in plant extracts.
A growing body of evidence suggests that such growth regulatory compounds
are ubiquitous in plants; are active at exceedingly low concentrations and
are under genetic control. Plant hormones are almost certainly involved in
directing or regulating plant growth and development.
The subject of the present research concerns the characterization of differences
in shoot growth of juvenile and adult phases of a commercial Citrus
cultivar and an investigation of the possible role which plant hormones may
play in such differences. In add i tion to a comprehensive literature survey,
three separate sets of experiments were conducted. In the first, an analysis
of the components and parameters of the difference in vegetative shoot growth
of adult and juvenile scions was carried out. Anatomical and ultrastructural
comparisons were also made. In the second set of experiments the endogenous
levels of gibberellins, cytokini ns and inhibitors of buds and other tissues,
which might playa role in the regulation of shoot flush growth, were examined.
Specific extractions were performed and appropriate bioassay techniques were
employed for the three hormone classes investigated. In the final set of experiments
the effects of synthetic plant growth regulators on shoot flush
growth were monitored. The growth regulators were applied by means of trunk
injections or as droplets on shoot terminal buds.
These experiments were planned and executed with the above mentioned concepts
and ideals in mind. The objective of the project was to contribute in some
measure to the knowledge which will allow better use to be made of available
natural resources. / Thesis (Ph.D.)-University of Natal, Pietermartizburg, 1982.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/11038 |
| Date | January 1982 |
| Creators | Hendry, Nigel S. |
| Contributors | Van Staden, Johannes. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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