Date of Award

2004

Document Type

Restricted Thesis

Terms of Use

© 2004 Seeta A. Sistla. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts

Department

Biology Department

First Advisor

Mark Jacobs

Abstract

When vascular bundles are broken, plants undergo a process of polar cellular re-differentiation that is hypothesized to be induced by a build up of the plant hormone indole-3- acetic-acid (IAA, or auxin). Previous studies have documented the influence of locally increased auxin concentrations on the position of newly formed vascular tissue, suggesting that a positive feedback mechanism drives auxin conductivity along a preferred localized transport route that subsequently differentiates into vascular tissue. Auxin directs cellular re-differentiation by moving in an apical to basipetal direction around the wound in a concentration-dependent manner. Wounding can initiate glycosidase action and increase biosynthesis of the phenolic compounds in non-injured adjacent cells, rapidly increasing the concentration of free flavonoids. The wounding effect putatively causes the partial inhibition of the cellular efflux component of polar auxin transport (PAT) through the influence of PAT inhibitor (PATI) flavonoids. This build up of flavonoids (such as quercetin) is theoretically highly adaptive, serving to direct re-differentiation by increasing auxin concentration around the wound while not affecting auxin transport elsewhere. This research focuses on changes in the extent of re-differentiation of parenchyma cells to xylem cells around a vascular injury in Coleus blumei, following the exogenous application of a synthetic or natural PATIs or non-PATIs to the site of the wound. I t was found that the application of the PATI quercetin to the vascular wound increases the extent of re-differentiation over a restricted time course that is not apparent in any other PATIs or non- PATIs treatments. These results provide preliminary evidence of a specific developmental phenomenon whereby the inhibition of auxin transport by flavonoids may be physiologically significant to the plant.

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