Biology
Rohan set up an experiment with germinating bean seeds. He fixed the seeds on a wire mesh with moist sawdust placed below them. At the start, the radicles grow downward and the plumules upward. After a few days though, he noticed that the radicles began bending towards the moist sawdust instead of simply going straight down.
(a) Name two types of tropic movements shown by the radicles in this experiment.
(b) What stimuli are responsible for these movements?
(c) Which one of the stimuli mentioned by you above in (b) is more effective for the growth of the radicles in this experiment ?
(d) Why do the plumules continue to grow upwards even after the radicles bend ?
Chemical Coordination in Plants
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Answer
(a) Two types of tropic movements shown by the radicles in this experiment are geotropism and hydrotropism.
Reason — At first, the radicles grow downward due to positive geotropism. Later, they bend towards the moist sawdust due to positive hydrotropism.
(b) Stimuli responsible for these movements are gravity and moisture.
Reason — Geotropism is a response to gravity and Hydrotropism is a response to moisture/water.
(c) Moisture is more effective for the growth of the radicles in this experiment.
Reason — Since the radicles bend towards the moist sawdust instead of continuing straight downward, moisture has a stronger effect than gravity in this setup.
(d) The plumules continue to grow upwards because they are negatively geotropic, that is, they grow in the direction opposite to gravity.
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Related Questions
The diagram given alongside shows a type of tropism. Study the same and answer the questions that follow:
(a) Name and define the type of tropism shown in the diagram.
(b) Label the guidelines (1) to (4).
(c) Name two effective stimulants that help in the growth of part (2).
(d) Name two groups of plants where part (2) grows towards gametophyte with the help of the stimulants mentioned in (c).
Study the diagrams given below and answer the following questions.
(a) Name the structures shown as X and Y in the figures (A) and (B), respectively.
(b) Write the functions performed by the structures X and Y.
(c) Name the phenomenon depicted and define it.
(d) How do the structures X and Y differ from each other?
(e) Give examples of the plants which show the said phenomenon.
Given below are the figures showing some kinds of tropic movements in plants. Study the same and answer the following questions:
(a) Which one of these figures is correct? Give reason in support of your answer.
(b) Name the kind of movements shown by the root system and the shoot system. Define each.
(c) What are the two stimuli which affect root system and shoot system positively ? Name them.
(d) Which of the following stimuli affect the growth of root strongly?
- Gravity
- Water
(e) Draw a neat and labelled diagram of the longitudinal section of a pistil showing chemotropism in an angiospermic plant.
The figure given below depicts a kind of tropic movement in plants. Study the same and answer the following questions.
(a) What kind of a movement is shown in figure. Define it.
(b) How does this movement differ from geotropism?
(c) Name the stimulus responsible for thigmotropism. Give one example of a plant showing thigmotropism.
(d) Name one stimulus which gives a positive response for the roots but negative response for the shoot.
(e) Draw a neat and labelled diagram of the part of plant showing leaf tendril. Name the plant.