Where are auxins synthesized? How do they promote phototropism?
Where are auxins synthesized? How do they promote phototropism?
Auxins are synthesized at the shoot tips (growing tips of the plant).
When light falls on one side of the plant, auxin diffuses towards the shady side (the side away from light). The high concentration of auxin on the shady side stimulates the cells in that region to grow longer than the cells on the illuminated side. As a result, the shoot bends towards the light, exhibiting phototropism.
Marking Scheme
- 11 mark for stating that auxins are synthesized at the shoot tips.
- 21 mark for explaining the diffusion of auxin to the shady side and subsequent cell elongation causing bending towards light.
Hint
Auxins are made at the growing tips. They prefer the shade and cause cells on that side to grow longer.
Quick Oral Answer
Auxins are synthesized at the shoot tips. They promote phototropism by diffusing to the shaded side of the stem, causing the cells there to elongate more than those on the lighted side, which makes the stem bend towards the light.
Analysis & Explanation
Auxin is a plant hormone synthesized at the growing tips of shoots. It is highly sensitive to light and tends to accumulate on the side of the shoot that is in the shade. Since auxin promotes cell elongation, the cells on the shaded side grow faster and longer than those on the sunny side, causing the stem to curve or bend towards the light source. This directional growth movement in response to light is called phototropism.
Common Mistakes
- 1Writing that auxins are synthesized in roots to promote phototropism (roots show negative phototropism).
- 2Stating that auxins accumulate on the light-facing side instead of the shady side.
Interesting Facts
Auxins were the first class of plant hormones to be discovered. Charles Darwin and his son Francis studied their effects on phototropism using canary grass coleoptiles.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2024?
This question carries 2 marks in the CBSE Class 10 Science 2024 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Control and Coordination" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Coordination in Plants" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2024 paper?
This is a Very Short Answer question from Section B in the CBSE Class 10 Science 2024 paper.