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प्रश्न
Explain the mechanism of closing and opening of the stomata.
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.
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संबंधित प्रश्न
The phenomenon of loss of water through a cut stem or injured part of plant is called ___________.
State whether the following statement is true or false. Rewrite the false statement correctly.
Water absorption mainly occurs through the root-hair.
Concentration of mineral nutrient elements is higher inside the root hairs than in the surrounding soil. How do roots take them in from the soil?
Choose the correct answer:
Wilting of plants occurs when ____________
Name the following:
The solution outside the cell having lower solute concentration than the fluids.
Column ‘II’ is a list of items related to ideas in Column ‘I’. Match the term in Column ‘II’ with a suitable idea given in Column ‘I’.
| Column I | Column II |
| (i) Diffusion | (a) The exit or flow of water from the cell to the outer environment. |
| (ii) Xylem | (b) The shrinkage of protoplasm when the cell is kept in a hypertonic solution. |
| (iii) Root pressure | (c) The tissue through which water and mineral salts move upward in a plant. |
| (iv) Isotonic solution | (d) Two solutions which have equal osmotic pressure. |
| (v) Exosmosis | (e) The process by which the molecules of perfume spread in the room when the bottle is open. |
| (vi) Osmosis | (f) The process by which roots absorb water from the soil. |
| (vii) Plasmolysis | (g) The pressure by which water rises up to some feet in a lofty tree. |
| (viii) Hypotonic solution | (h) The concentration of the solution when lower than that of the cell sap. |
Multiple Choice Question:
Water will be absorbed by the root hairs when:
Multiple Choice Question:
The most widely accepted theory for ascent of sap is ______.
Plasma Membrane is ______.
Give other name of epidermal cells in roots of plants.
