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प्रश्न
Explain the mechanism of closing and opening of the stomata.
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उत्तर
The closing and opening of the stomata depends on the turgidity of the guard cells. Each guard
cell has a thicker wall on the side facing the stoma and a thin wall on the opposite side. Guard cells contain chloroplasts. As a result of the synthesis of glucose during photosynthesis and some other chemical changes, the osmotic pressure of the contents of the guard cells increases and they absorb more water from the neighbouring cells, thus becoming turgid. Due to turgor, the guard cells become more arched outwards and the aperture between them widens, thereby opening the stoma.
At night or when there is shortage of water in the leaf, the guard cells turn flaccid and their inner rigid walls become straight, thus closing the stomatal aperture.
संबंधित प्रश्न
The phenomenon of loss of water through a cut stem or injured part of plant is called ___________.
Three plants (a), (b) and (c) were placed in beakers containing coloured water. The water in each beaker was covered with a layer of oil. The leaves were removed from plant (b), while plant (c) was exposed to strong light.
(i) In which plant, (a), (b) or (c) would the water move up the fastest?
(ii) In which plant (a), (b) or (c), would the water move up slowly?
(iii) Why was the water covered with a layer of oil?
(iv) What is being investigated by this experiment?
The diagram below represents a layer of epidermal cells showing a fully grown root hair. Study the diagram and answer the questions that follow:
Draw a diagram of the above root hair cell as it would appear when a concentrated solution of fertilizers is added near it.
Draw a diagram of the root hair cell as it would appear when a concentrated solution of fertilizers is added near it.
The below figure shows a root hair:
(i) Label the parts 1 to 4.
(ii) What is the role of part 4?
(iii) Why is the root hair one-celled?
(iv) What will happen to the root hair if some fertilizer is added to the soil near the root hair?
A thin strip of epidermal cells from the fleshy scales of an onion bulb was examined in a drop of water, under a microscope. All the epidermal cells looked alike and the figure alongside represents one of them. The thin strip was then transferred to a drop of strong sugar solution and re-examined under the microscope after about five minutes.
(i) Make a sketch of one of the epidermal cells, as it might appear after immersion in a strong sugar solution. Label any two parts which have undergone a change.
(ii) Give the scientific term for the change shown in Q.(i) above.
(iii) What would you do to bring this cell back to its original condition?
(iv) Give the scientific term used for the recovery of the cell as a result of the step taken in Q.(iii) above.
Write a note on the morphological structure of the root.
Identify the part of the plants which is responsible for maximum absorption of water.
Roots of the plants absorb water from the soil through the process of ____________.
