KVPY Sample Paper KVPY Stream-SX Model Paper-21

  • question_answer
    Which of the following in guard cell is responsible for opening of stomata?

    A) Decrease in \[C{{O}_{2}}\]concentration and more \[{{H}^{+}}\]ion concentration

    B) Decrease in \[C{{O}_{2}}\]concentration and less \[{{H}^{+}}\] ion concentration

    C) Increase in \[C{{O}_{2}}\]concentration and more \[{{H}^{+}}\]ion concentration

    D) More free \[{{H}^{+}}\]ions and less \[C{{l}^{-}}\]ions

    Correct Answer: B

    Solution :

    Decrease in \[C{{O}_{2}}\]concentration and less \[{{H}^{+}}\]on concentration is responsible for the opening of stomata.
    According to active \[{{K}^{+}}\] transport theory (Levitt), rise in pH of the guard cells (due to increased concentration of \[{{H}^{+}}\]present) pauses hydrolysis of starch into phosphoenol pyruvate, which further combines with \[C{{O}_{2}}\]present in guard cells to form oxalic acid which gets changed to malic acid.
    \[{{H}^{+}}\] ions pass out of the guard cells in exchange of \[{{K}^{+}}\] ions that react with malate inside guard cells. This leads to absorption of water from adjacent cells, which increases the turgor of guard cells and causes opening of stomata.

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