Question

Which of the following statements about dark reactions is correct?

• A. They occur in darkness
• B. They are not light dependent
• C. They are dependent upon the products synthesised during light reactions
• D. All of these

Answer 1

Answer: (C)

Biosynthetic phase (Dark or Blackman's reaction) catalyses the assimilation of $C{O}_2$ to carbohydrates. These reactions occur in stroma or matrix of chloroplasts and all the enzymes required for the processes are present in the stroma/ matrix of chloroplasts. These reactions do not require light, instead assimilatory power ($ATP$ and $NADPH$) produced during photochemical (light) phase is used in fixation and reduction of $C{O}_2$. However, this should not be construed to mean that they occur in darkness or that they are not light dependent.