IB Biology Topic C3.1.21 Promotion of Cell Growth by Auxin Revision Notes (HL)

IB Biology Topic C3.1.21 Promotion of Cell Growth by Auxin Revision Notes (HL) | RevisionDojo

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Auxin Promotes Cell Growth by Acidifying and Loosening the Cell Wall

Auxin is a key phytohormone that regulates plant growth and development.
One of its most important roles is promoting cell elongation, which underlies phototropism, gravitropism and apical dominance.
It does this by acidifying the cell wall, loosening it so the cell can expand under turgor pressure.

Common Mistake

Auxin does not directly push the plant toward light.
It increases growth on one side, and that uneven growth produces the bend.

The Acid-Growth Hypothesis Explains How Auxin Loosens the Wall

Auxin triggers hydrogen ion (H+) secretion into the apoplast, the space outside the membrane but within the cell wall.
This acidifies the cell wall, weakening the cross-links between cellulose molecules.
The loosened wall lets the cell expand under turgor pressure.

Note

This mechanism is called the acid-growth hypothesis.

Step by Step: From Auxin to Elongation

Auxin activation

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Auxin Promotes Cell Growth by Acidifying and Loosening the Cell Wall

Auxin is a key phytohormone that regulates plant growth and development.
One of its most important roles is promoting cell elongation, which underlies phototropism, gravitropism and apical dominance.
It does this by acidifying the cell wall, loosening it so the cell can expand under turgor pressure.

Common Mistake

Auxin does not directly push the plant toward light.
It increases growth on one side, and that uneven growth produces the bend.

The Acid-Growth Hypothesis Explains How Auxin Loosens the Wall

Auxin triggers hydrogen ion (H+) secretion into the apoplast, the space outside the membrane but within the cell wall.
This acidifies the cell wall, weakening the cross-links between cellulose molecules.
The loosened wall lets the cell expand under turgor pressure.

Note

This mechanism is called the acid-growth hypothesis.

Step by Step: From Auxin to Elongation

Auxin activation

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic C3.1.21: Promotion of Cell Growth by Auxin Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Auxin Promotes Cell Growth by Acidifying and Loosening the Cell Wall

The Acid-Growth Hypothesis Explains How Auxin Loosens the Wall

Step by Step: From Auxin to Elongation

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Auxin Promotes Cell Growth by Acidifying and Loosening the Cell Wall

The Acid-Growth Hypothesis Explains How Auxin Loosens the Wall

Step by Step: From Auxin to Elongation

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account