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In succulent plants the stomata open in night and close in day. Which among the following would be best hypothesis to explain the mechanism of stomatal action in night only?
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Increase in \(\mathrm{CO}_2\) concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in \(\mathrm{K}^{+}\)transport.
In CAM plants stomata open at night. In these plants night acidification occurs. i.e., malic acid is synthesised during night due to incomplete oxidation of carbohydrates.
In night, $2 \mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6+3 \mathrm{O}_2 \rightarrow 3 \mathrm{C}_4 \mathrm{H}_6 \mathrm{O}_5+3 \mathrm{H}_2 \mathrm{O}$ (malic acid)
$\downarrow$ leads to opening of stomata At night malic acid formed in guard cells dissociates into $\mathrm{H}^{+}$and malate ions. $\mathrm{K}^{+}$ion exchange from subsidiary cells with $\mathrm{H}^{+}$ions. Thus due to accumulation of $\mathrm{K}^{+}$ions osmotic pressure of guard cells increases, endosmosis occurs anDguard cells become turgid due to which stomata opens. The malic acid at day time breaks into $\mathrm{CO}_2$ and pyruvic acid thus increasing the concentration of $\mathrm{CO}_2$ in mesophyll cells. This is utilised in Calvin cycle to form sugar which is finally converted into starch.
In night, $2 \mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6+3 \mathrm{O}_2 \rightarrow 3 \mathrm{C}_4 \mathrm{H}_6 \mathrm{O}_5+3 \mathrm{H}_2 \mathrm{O}$ (malic acid)
$\downarrow$ leads to opening of stomata At night malic acid formed in guard cells dissociates into $\mathrm{H}^{+}$and malate ions. $\mathrm{K}^{+}$ion exchange from subsidiary cells with $\mathrm{H}^{+}$ions. Thus due to accumulation of $\mathrm{K}^{+}$ions osmotic pressure of guard cells increases, endosmosis occurs anDguard cells become turgid due to which stomata opens. The malic acid at day time breaks into $\mathrm{CO}_2$ and pyruvic acid thus increasing the concentration of $\mathrm{CO}_2$ in mesophyll cells. This is utilised in Calvin cycle to form sugar which is finally converted into starch.
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