Question

Describe the effects of an increase in oxygen pressure on the dark reactions of photosynthesis.

Short answer

An increase in oxygen pressure on the dark reactions of photosynthesis decreases carbon fixation.

Step-by-step solution

Definition of dark reaction

Thelight-dependent reaction and the light-independent reaction are two types of reactions that convert light energy to chemical energy. Calvin's cycle, also known as the CBB (Calvin-BensonBassham) cycle, is a series of processes that take place in the stroma of the chloroplast. It is also known as the dark reaction because it is a light-independent reaction.

Effects of the increase in oxygen pressure on the dark reactions

The ambient carbon dioxide is fixed with Ribulose 1,5-bisphosphate to form two three-carbon molecules in Calvin's cycle. To make another sugar, one of the three-carbon compounds is reduced. RuBisCo catalyzes a reaction between carbon dioxide and Ribulose 1,5 -bisphosphate (RuBP), forming a six-carbon compound that is then instantly converted into two three-carbon compounds and 3-phosphoglyceric acid in the first step of Calvin's cycle (3-PGA). Carbon fixation is the name for this process.

That’s why when the oxygenase activity of RuBP carboxylase-oxygenase increases, the efficiency of fixation may decrease.