IB Biology Topic C3.1.18 Positive Phototropism Revision Notes (HL)

IB Biology Topic C3.1.18 Positive Phototropism Revision Notes (HL) | RevisionDojo

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Positive Phototropism Directs Plant Shoots Toward Light Sources

A seedling on a windowsill bends toward the light.
This curvature is not random: it is a precise response called positive phototropism, the growth of shoots toward a light source.

Definition

Phototropism

Phototropism is the growth response of a plant towards or away from light.

Light Detection and Auxin Redistribution Drive the Bending

Detecting the light
1. The shoot tip contains light-sensitive pigments that detect the direction of light.
2. When light comes from one side, the pigments sense the imbalance.
Redistributing the auxin
1. Auxin is made in the shoot tip and moved to the shaded side of the shoot.
2. This uneven distribution is set up by auxin efflux carriers that actively transport auxin across cells (covered in detail in C3.1.20).

Definition

Auxin

Auxin is a phytohormone that regulates growth by promoting cell elongation.

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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

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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 nisi ut aliquip ex ea commodo consequat.

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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Positive Phototropism Directs Plant Shoots Toward Light Sources

A seedling on a windowsill bends toward the light.
This curvature is not random: it is a precise response called positive phototropism, the growth of shoots toward a light source.

Definition

Phototropism

Phototropism is the growth response of a plant towards or away from light.

Light Detection and Auxin Redistribution Drive the Bending

Detecting the light
1. The shoot tip contains light-sensitive pigments that detect the direction of light.
2. When light comes from one side, the pigments sense the imbalance.
Redistributing the auxin
1. Auxin is made in the shoot tip and moved to the shaded side of the shoot.
2. This uneven distribution is set up by auxin efflux carriers that actively transport auxin across cells (covered in detail in C3.1.20).

Definition

Auxin

Auxin is a phytohormone that regulates growth by promoting cell elongation.

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.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic C3.1.18: Positive Phototropism Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Positive Phototropism Directs Plant Shoots Toward Light Sources

Light Detection and Auxin Redistribution Drive the Bending

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

Positive Phototropism Directs Plant Shoots Toward Light Sources

Light Detection and Auxin Redistribution Drive the Bending

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