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Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892

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BuyFindarrow_forward

Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892
Textbook Problem

A characteristic of auxin (IAA) transport is:

a. IAA moves by polar transport from the base of a tissue to its apex.

b. IAA moves laterally from a shaded to an illuminated side of a plant.

c. IAA enters a plant cell in the form of IAAH, an uncharged molecule that can diffuse across cell membranes.

d. IAA exits one cell and enters the next by means of transporter proteins clustered at both the apical and basal ends of the cells.

e. All of the above are characteristics of auxin transport in different types of cells.

Summary Introduction

Introduction:

Auxin is a phytohormone responsible for stimulating the division and elongation of cells. It is also involved in root initiation and bud formation. It is also responsible for the production of other phytohormones when working in harmony with cytokinin. This hormone is synthesized in developing leaves, apical meristem, and developing an embryo. It affects the growing tissues present in all parts of the plant.

Explanation

Justification/ Explanation for the correct answer:

Option (c) is given as: IAA enters a plant cell in the form of IAAH, an uncharged molecule that can diffuse across the cell membrane. The studies of auxin transport show that hormone enters the apex of a cell in its hydrogen attached form. This hydrogen attached form is produced when hydrogen attaches to IAA in the cell wall. The hydrogen is then removed in the cytoplasm to release IAA and hydrogen ion.

The attachment of hydrogen to auxin facilitates the motion of the hormone. This helps in the diffusion of IAA through the transport protein present in the cell wall. Thus, the transport of auxin from one cell to another takes place without the help of any transporter proteins or channels because it is present in the hydrogen attached form. Hence, option (a) is correct.

Explanation for the incorrect answers:

Option (a) is given as: IAA moves by polar transportation from the base of the tissue to its apex. Though IAA moves by a mechanism called polar transport the movement is from top to bottom and not bottom to top...

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