Can we, hence, say that calling the biosynthetic phase as the dark reaction is a misnomer? Discuss this amongst yourselves.
Yes, calling the biosynthetic phase as the dark reaction is a misnomer. The term suggests that these reactions occur in darkness, which is misleading.
The biosynthetic reactions are not directly light driven, but they are dependent on the products of light reactions — namely ATP and NADPH. These products are essential for fixing CO₂ and synthesizing sugars in the stroma. If light becomes unavailable, the biosynthetic process continues for some time using stored ATP and NADPH, but eventually stops when these are depleted.
Therefore, the term "dark reaction" is used only by convention to distinguish these reactions from the light reactions. It should not be construed to mean that they occur in darkness or that they are independent of light.
Explanation
The textbook clearly states that the biosynthetic phase is called 'dark reaction' by convention, but this should not be taken literally. The context explains that these reactions are dependent on ATP and NADPH produced during light reactions. The evidence provided is that when light becomes unavailable, biosynthesis continues for some time and then stops - proving it depends on light reaction products. When light returns, synthesis resumes. This shows the term 'dark reaction' is misleading as it implies the reactions occur in darkness or are light-independent, which is incorrect.