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Ch. 39 - Plant Responses to Internal and External Signals
Campbell - Campbell Biology 11th Edition
Urry11th EditionCampbell BiologyISBN: 9789357423311Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoUrry 11th EditionCh. 39 - Plant Responses to Internal and External SignalsProblema 2
Capitolo 39, Problema 2

Auxin enhances cell elongation in all of these ways except:
a. Increased uptake of solutes
b. Gene activation
c. Acid-induced denaturation of cell wall proteins
d. Cell wall loosening

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Understand the role of auxin in plant growth: Auxin is a plant hormone that plays a crucial role in the regulation of plant growth and development, particularly in cell elongation.
Review how auxin affects cell elongation: Auxin promotes cell elongation by increasing the plasticity of the cell wall, allowing cells to expand.
Examine each option to determine how auxin influences cell elongation: Consider how auxin might increase solute uptake, activate genes, induce acidification, or loosen cell walls.
Analyze option (a): Increased uptake of solutes can lead to water entering the cell, causing it to expand. Auxin can facilitate this process.
Analyze option (c): Acid-induced denaturation of cell wall proteins is not a typical mechanism of auxin action. Instead, auxin promotes cell wall loosening through acid growth hypothesis, which involves the activation of enzymes that modify the cell wall structure, not denaturation.

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Auxin and Cell Elongation

Auxin is a plant hormone that plays a crucial role in the regulation of plant growth and development, particularly in cell elongation. It promotes cell elongation by increasing the plasticity of the cell wall, allowing cells to expand. This process is essential for plant growth, especially in stems and roots, where auxin concentration can influence the direction and rate of growth.
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Auxin

Acid Growth Hypothesis

The acid growth hypothesis explains how auxin facilitates cell elongation by promoting the acidification of the cell wall. Auxin stimulates proton pumps in the plasma membrane, which lower the pH in the cell wall region. This acidic environment activates enzymes that loosen the cell wall structure, making it more extensible and allowing cells to elongate as they take up water.
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Acids

Gene Activation by Auxin

Auxin influences gene expression by activating specific genes that are involved in cell growth and development. This hormone can bind to receptor proteins, leading to the degradation of repressor proteins and the activation of transcription factors. These transcription factors then initiate the expression of genes that contribute to cell wall modification, solute uptake, and other processes necessary for cell elongation.
Video consigliato:
10:46
Auxin
Pratica correlata
Domanda del libro di testo

The hormone that helps plants respond to drought is:

a. Auxin

b. Abscisic acid

c. Cytokinin

d. Ethylene

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Domanda del libro di testo

Charles and Francis Darwin discovered that

a. Auxin is responsible for phototropic curvature

b. Red light is most effective in shoot phototropism

c. Light destroys auxin

d. Light is perceived by the tips of coleoptiles

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Domanda del libro di testo

How may a plant respond to severe heat stress?

a. By reorienting leaves to increase evaporative cooling

b. By creating air tubes for ventilation

c. By producing heat-shock proteins, which may protect the plant's proteins from denaturing

d. By increasing the proportion of unsaturated fatty acids in cell membranes, reducing their fluidity

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Domanda del libro di testo

The signaling molecule for flowering might be released earlier than usual in a long-day plant exposed to flashes of:

a. Far-red light during the night

b. Red light during the night

c. Red light followed by far-red light during the night.

d. Far-red light during the day

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