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प्रश्न
What does a root do in response to gravity? What is this phenomenon known as?
उत्तर
The roots of a plant always grow downwards in response to gravity. This phenomenon is known as geotropism.
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संबंधित प्रश्न
What does a tendril do in response to the touch of a support? What is this phenomenon known as?
Define chemotropism.
Which of the following is a growth movement and which is not?
- Folding up of leaves of sensitive plant on touching with hand.
- Folding up of petals of dandelion flower when light fades.
Why is the folding up of the leaves of a sensitive plant on touching with a finger not a tropism?
What is meant by ‘positive geotropism’ and ‘negative geotropism’? Give one example of each type. Draw a labelled diagram to illustrate your answer, indicating the plant part, which shows positive geotropism, and the plant part, which shows negative geotropism.
P and Q are two types of plants having weak stems which cannot stand upright on their own. The plants P and Q have organs R and S respectively which can grow towards any support which they happen to touch and wind around that support. It is observed that organ R originates from the leaves of the plant whereas organ S originates directly from the stem of the plant.
(a) What is (i) R, and (ii) S?
(b) What is the name of growth movement exhibited by the organs R and S?
(c) Name the stimulus involved in this case.
(d) State whether the behaviour of organs R and S is a tropic movement or a nastic movement.
(e) Name one plant like P and another plant like Q.
Assertion (A): If the plant part moves in the direction of gravity, it is called positive geotropism.
Reason (R): Stem shows positive geotropism.
Write the scientific terms used to represent the following:
Growing of roots towards the gravity.
Some plants like pea plants have tendrils which help them to climb up other plants. Explain how is it done. Name the plant hormone responsible for this movement.
The diagram given alongside shows a type of tropism. Study the same and answer the questions that follow:
- Name and define the type of tropism shown in the diagram.
- Label the guidelines (1) to (4).
- Name two effective stimulants that help in the growth of part (2).
- Name two groups of plants where part (2) grows towards gametophyte with the help of the stimulants mentioned in (c).
