Multiple choice

Stomata open during the day time because the guard cells

  1. photosynthesize and produce osmotically active sugars

  2. are thin walled

  3. are bean shaped

  4. have to help in gaseous exchange
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Guard cells contain chloroplasts and photosynthesize during daylight. They produce sugars like glucose, which lowers the guard cell's water potential. Water enters by osmosis, increasing turgor pressure and causing stomata to open. Option A correctly explains the mechanism. Options B and C describe structural features but not the cause of opening. Option D states the purpose, not the cause.

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