Question

Source of $C{O}_2$ for photosynthesis during day in CAM plants is

• A. $3--PGA$
• B. malic acid
• C. oxalo-acetic acid
• D. pyruvate

Answer 1

Answer: (B)

In CAM plants (crassulacean acid metabolism), the source of $C{O}_2$ for photosynthetic during the day time is malic acid. In these plants there is no Kranz anatomy, but there occurs dark acidification, i.e. during night malic acid is formed. This malic acid breaks up into $C{O}_2$ and pyruvic acid in day time and $C{O}_2$released is utilized in $C_3$ cycle.