Advertisements
Advertisements
Question
Explain the mechanism of closing and opening of the stomata.
Advertisements
Solution
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.
RELATED QUESTIONS
Which one of the following is a characteristic NOT related with the suitability of the roots for absorbing water?
What part is played by the following in the uptake of water into the root hair?
The cell wall
Mention whether the following statement is true (T) or false (F) and give explanation in support of your answer.
Dry seeds when submerged in water swell up due to endosmosis.
The diagram below represents a layer of epidermal cells showing a fully grown root hair. Study the diagram and answer the questions that follow:
The root hair cell is in a turgid state. Name and explain the process that caused this state.
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.
Given below is the diagram of a cell as seen under the microscope after having been placed in a solution:
(i) What is the technical term used for the state/condition of the cell given above?
(ii) Give the technical term for the solution in which the cell was placed.
(iii) Name the parts numbered 1 to 4.
(iv) Is the cell given above a plant cell or an animal cell ? Give two reasons in support of your answer as evident from the diagram.
(v) What would you do to bring this cell back to its original condition?
Name the following:
Water is absorbed from the soil by which part.
Identify the zone in wbkh root hair occurs.
