Succulents have their stomata closed during the day time. How do they get `CO_(2)` for photosynthesis?

Explanation

Succulents (e.g. Bryophyllum, Kalanchoe, Sedum, Calcycinum, etc). Are xerophytes and grow under semi-arid conditons. They have their stomata closed during the day time and open at night (in dark). This helps these plants to conserve their water content which otherwise would be lost under extremely dry conditons. These plants fix atmospheric `CO_(2)` into organic acids (such as malic acid, oxalo acetic acid, etc.) at night when the stomata are open. Conversions of `CO_(2)` into organic acids is called acidification. The fixed `CO_(2)` is released during the day by the process of deacidification which is used in photosynthesis.