Item – Theses Canada

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OCLC number
29314579
Author
Liu, Jin-Hao,1959-
Title
Hormonal controls of adventitious root initiation in hypocotyls of Helianthus annuus seedlings.
Degree
Ph. D. -- University of Calgary, 1991
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, 1992.
Description
2 microfiches.
Notes
University Microfilms order no. UMI00322807.
Includes bibliographical references.
Abstract
A system for studying the initiation of adventitious root formation (ARF) in hypocotyls of derooted seedlings of sunflower (Helianthus annuus L.) is described. It was found that pH of the test solutions and any gravistimulation of cuttings affected ARF. Removal of original root system of the seedlings elicited changes in the levels of endogenous plant hormones and ARF in the basal portion (rooting zone, or RZ) of hypocotyls. Before the excision of original roots, endogenous indole-3-acetic acid (IAA) level in the RZ was higher than that in the non-rooting zone (NRZ) (apical portion of hypocotyls). After the excision of original roots the quantity of IAA decreased in the RZ, but increased steadily in the NRZ. A transient increase in ethylene production in the RZ occurred following root removal, peaking at 3 h. This increase in ethylene production was absent in the NRZ. Exogenous auxins applied during the early and critical stages of ARF enhanced ARF. When the inhibitors of auxin transport were applied to the hypocotyl just below cotyledons, the number of root primordia was reduced. If the source of endogenous auxin was removed by decapitation (removal of cotyledons and apical bud), the number of root primordia decreased dramatically. The inhibitors of ethylene biosynthesis/action reduced ARF in non-decapitated cuttings. Ethylene-releasing compounds enhanced endogenous ethylene production and rooting and they counteracted the effect of ethylene inhibitors. If the source of endogenous auxin was removed by decapitation, ethylene-releasing compounds showed no promotive effect on ARF, but they enhanced auxin action. Surgical removal of a part of hypocotyl tissues showed that ARF occurred only in the regions where auxin could accumulate although the excision of the tissues might also enhance ethylene biosynthesis in other regions. Ethylene had no effect on auxin transport and metabolism in the hypocotyls, and thus it cannot stimulate rooting via the alteration of auxin level and distribution along the hypocotyls. Exogenous auxins stimulated ethylene production in the RZ, thus ethylene may have a promotive feedback effect on the stimulation of ARF by auxin. (Abstract shortened by UMI.)
Subject
Sunflowers Seedlings.
Biosynthesis.
Tournesols Plants.
Biosynthèse.
ISBN
0315711205
9780315711204