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प्रश्न
What is meant by positive tropism and negative tropism? Explain with examples.
उत्तर
If the movement of the response is towards the stimulus, it is known as positive tropism; whereas if the movement of the response is in the direction opposite to the stimulus, it is is known as negative tropism.
The movement of roots towards the pull of gravity is an example of positive geotropism, whereas the movement of plant stem in the direction opposite to the pull of gravity is an example of negative geotropism.
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संबंधित प्रश्न
Where is the auxin hormone made in a plant stem?
What happens to the moonflower
- during the daytime, and
- at night?
What is this phenomenon known as?
Name the five types of tropisms.
How are tropic movements helpful to plants? Explain with an example.
One of the following plant hormones is responsible for the phenomenon of phototropism in plants. This is :
(a) gibberellin
(b) eltroxin
(c) cytokinin
(d) auxin
There are three plants A, B and C. The flowers of plant A open their petals in bright light during the day but close them when it gets dark at night. On the other hand, the flowers of plant B open their petals at night but close them during the day when there is bright light. The leaves of plant C fold up and droop when touched with fingers or any other solid object.
- Name the phenomenon shown by the flowers of (i) plant A and (ii) plant B.
- Name one flower each which behaves like the flower of (i) plant A and (ii) plant B.
- Name the phenomenon exhibited by the leaves of plant C.
- Name a plant whose leaves behave like those of plant C.
- Which plant/plants exhibit the phenomenon based on growth movements?
A potted plant having straight parts A and B was placed horizontally on its side as shown in Figure (i). After a few days, it was observed that parts A and B of the plant acquired new positions as shown in Figure (ii).
- Name the phenomenon exhibited by the position of plant parts A and B in Figure (ii).
- Name the stimulus (other than sunlight) which causes plant part A to grow and bend upwards, and plant part B to bend downwards.
Which flowering plant shows a photo nasty just opposite to that of a Dandelion?
Why do stems show positive phototropism?
Given below are the figures showing some kinds of tropic movements in plants. Study the same and answer the following questions:
- Which one of these figures is correct? Give reason in support of your answer.
- Name the kinds of movements shown by the root system and shoot system. Define each.
- What are the two stimuli which affect root system and shoot system positively? Name them.
- Which of the following stimuli affects the growth of the root strongly?
- Gravity
- Water
- Draw a neat and labelled diagram of the longitudinal section of a pistil showing chemotropism in an angiospermic plant.
