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Abstract

Six single gene mutants of garden pea (Pisum sativum L.) were utilised to further
examine the control of internode elongation. These short mutants could be divided into
two types; GA-synthesis (1s, le), and GA-response ( 1k, lka, lkb, 1w) types. They
were compared with the parental wild-type cv. Torsdag in an analysis of the changes
in orientation of cortical microtubules in expanding dark-grown internode tissue with
distance from the apical hook. Immunofluorescence analysis of FITC-labelled cortical
microtubules in tangential sections of epidermal cells and longitudinal sections of
subepidermal cortical cells of the mutants and wild-type plants revealed a shift away
from the wild-type microtubule arrangement toward less transverse microtubule arrays
in the mutants. This lower average microtubule orientation (resulting from a reduced
proportion of cells with predominantly transverse microtubule arrangement) correlated
with decreases in the rate and distribution of extension growth along internode 3 of
dark-grown mutants, providing additional circumstantial support for the role of
transverse microtubule orientation in extension growth.
Analysis of microtubule arrangement and growth profiles of the GA-synthesis
mutants, le and is, revealed overall reductions in average microtubule orientation and
rate and distribution of growth in comparison to wild-type plants. These changes
correspond to the mutants' reduced endogenous GA1 content and implicate GA1 in the
microtubule-mediated regulation of both rate and distribution of extension growth
along the epicotyl. Exogenous application of GA1 to GA-synthesis mutants resulted in
a shift in average microtubule orientation toward the wild-type arrangement, and a
corresponding increase in internode length, substantiating a role for GA1 in
microtubule-mediated extension growth.
Average microtubule orientation in le and ls was never as transverse as in the wildtype,
and transverseness of the array decreased more rapidly than in the wild-type over
the same length of epicotyl, implicating GA1 in both the initial organization of
microtubules and the maintenance of stability of transverse arrays.

Item Type:	Thesis - PhD
Authors/Creators:	Kitchener, Anne Elizabeth
Keywords:	Stems (Botany), Growth (Plants), Plants
Copyright Holders:	The Author
Copyright Information:	Copyright 1994 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:	Thesis (Ph.D.)--University of Tasmania, 1995. Includes bibliographical references (p. 131-161)
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