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The regulation of growth and development in Pisum sativum


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Knowles, Claire Louise 2005 , 'The regulation of growth and development in Pisum sativum', PhD thesis, University of Tasmania.

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Physiological changes within a plant during growth and development are
under strict regulation, permitting an integrated response to multiple
environmental and endogenous stimuli. Amongst these processes are the
hormonal regulation of growth and the transition from a vegetative to
reproductive state. The focus of this research was to investigate two
developmental processes in pea (Pisum sativum): (i) the role of
brassinosteroid (BR) phytohormones and (ii) flowering.
BRs are essential regulators of plant growth and development that affect a
host of molecular, cellular and physiological processes. There is a
comprehensive knowledge of BR synthesis, whilst much less is known about
the physiological and cellular effects of BRs. The promotive effect of BRs on
cell elongation is profound and there is evidence in azuki bean and
Arabidopsis that brassinolide can cause microtubule (MT) realignment and
rescue MT organisation of BR mutants, respectively. This study augments
these findings and has provided novel information on both cortical and
epidermal cells. Immunofluorescence showed significant differences in the
average MT orientation of cortical cells of mutants versus wild types.
Strikingly, these mutants possessed abundant MTs, unlike the BR-deficient
bull-1 mutant in Arabidopsis. Following the application of brassinolide to
intact plants, both epidermal and cortical cells of BR-synthesis mutants lk and
Ikb showed a significant shift in MT orientation towards more transverse,
whereas the BR-receptor mutant, lka, showed a small non-significant
response. Morphological and physiological studies showed that the
photosynthetic abilities of BR mutants could be affected. Although the
stomata of lk were smaller, the stomata of BR mutants were not physically
blocked as in bull of Arabidopsis. Interestingly, the BR mutation was
correlated with a reduced complexity of leaf epidermal cells. To investigate
the elevated cell wall yield threshold of pea BR mutants as a potential
explanation for the mechanism of BR-mediated cell elongation, a pea yieldinlike
gene was cloned. Its expression was strongly regulated during development in lk, Ikb and lka as well as the wild types but no clear effect of
a BR deficiency was observed.
Pea has been frequently employed as a model legume to study flowering
using genetic and physiological approaches, but compared to the detailed
model known for Arabidopsis, there is a deficiency of information about the
molecular regulation of flowering in pea. Combining molecular and
physiological approaches is fundamental for revealing information about the
role and interaction of the rapidly growing number of pea flowering genes.
This study examined the expression patterns of seven flowering-related
genes (COLa, SOC1a, FTL, TFL1aIDET, PIMIAP1, PM6/SEP1/2 and
UNI/LFY) during early development of wild type pea seedlings. This
information was related to parallel physiological experiments. FTL showed
marked up-regulation under long days at the time of floral commitment, while
up-regulation of PIM/AP1 and SEP1/2 occurred several days later. These
results suggest that FTL is a suitable early marker of floral commitment and
may be useful for diagnosing molecular defects in other flowering mutants.

Item Type: Thesis - PhD
Authors/Creators:Knowles, Claire Louise
Keywords: Peas, Brassinosteroids, Plant hormones
Copyright Holders: The Author
Copyright Information:

Copyright 2005 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Available for library use only but NOT for copying until 6 December 2007. After that date, available for use in the Library and copying in accordance with the Copyright Act 1968, as amended. Thesis (PhD)--University of Tasmania, 2006. Includes bibliographical references

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