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Science & Technology General Science
Q.

Consider the following statements:

1. Exchange of gases in plants occurs not only across the surface of leaves but also across the surface of stems and roots.

2. Plant close its pores known as the Stomata, when they do not need carbon dioxide for photosynthesis.

3. Guard cells present in plants are responsible for controlling the movement of water in them. 

Which of the statements given above is/are correct?
Explanation:

ANSWER: (D)

  • Stomata are tiny pores present on the surface of the leaves. Massive amounts of gaseous exchange take place in the leaves through these pores for the purpose of photosynthesis. But it is important to note here that exchange of gases occurs across the surface of stems, roots and leaves as well. (Thus, Statement 1 is correct)
  • Since large amounts of water can also be lost through these stomata, the plant closes these pores when it does not need carbon dioxide for photosynthesis. (Thus, Statement 2 is correct)
  • The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly, the pore closes if the guard cells shrink.

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