University Of Tasmania
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The use of gibberellin mutants to explore the role of microtubules in stem elongation

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posted on 2023-05-26, 20:50 authored by Kitchener, Anne Elizabeth
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.


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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). Thesis (Ph.D.)--University of Tasmania, 1995. Includes bibliographical references (p. 131-161)

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