Bending of shoot of a plant towards light can be referred to as
- A.photonasty
- B.positive phototropism
- C.negative phototropism
- D.photoperiodism
Correct answer
Explanation
The correct answer is B, positive phototropism. A shoot growing towards the light is moving in the direction of the stimulus, which makes it a positive tropism.
A tropism is a directional growth movement in response to a stimulus; 'photo' means light. When light falls on one side of a shoot, the hormone auxin moves to the shaded side and makes those cells grow longer, so the shoot bends towards the light. Roots usually show the opposite, negative phototropism, while they grow towards gravity and water.
A is wrong: photonasty is a non-directional movement caused by light, such as flowers opening and closing with day and night.
C is wrong: negative phototropism means growing away from light, as roots do.
D is wrong: photoperiodism is a plant's response to the length of day and night, which controls flowering, not bending.
Exam tip: shoot = positive phototropism and negative geotropism; root = negative phototropism and positive geotropism; auxin causes the bending.
Practice Questions
View allQuartz is extensively used as a piezoelectric material. It contains
- A.Hg
- B.Si
- C.Ti
- D.Sn
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Read the full explanation →Epidermal cells of plant roots increase their absorption surface by having
- A.Scales
- B.Root hairs
- C.Endodermis
- D.Stomata
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Read the full explanation →Which of the following organisms belongs to Coelenterata (Cnidaria)?
- A.Planaria and liverfluke
- B.Sea urchin and sea cucumber
- C.Hydra and sea anemone
- D.Euplectella and sycon
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Read the full explanation →Recently, there was a growing awareness in our country about the importance of Himalayan nettle (Girardinia diversifolia) because it is found to be a sustainable source of
- A.anti-malarial drug
- B.biodiesel
- C.pulp for paper industry
- D.textile fibre
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Read the full explanation →Which of the following statements are correct regarding the general difference between plant and animal cells ? 1. Plant cells have cellulose cell walls whilst animal cells do not. 2. Plant cells do not have plasma membrane unlike animal cells which do. 3. Mature plant cell has one large vacuole whilst animal cell has many small vacuoles. Select the correct answer using the code given below:
- A.1 and 2 only
- B.2 and 3 only
- C.1 and 3 only
- D.1,2 and 3
Show answer
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