Photosynthesis in Higher Plants Test - 7

Energy produced during light reaction is transferred to dark reaction in form of ATP to fix the carbon dioxide in form of glucose.

In C₄ plants, Carbon dioxide is fixed in malic acid with the help of enzyme phosphoenel pyruvate (PEP). Malic acid is a four carbon compound that later change into oxyloacetic acid.

In the leaves of C₄ plants such as maize, sorghum we can observe the Kranz anatomy.

The presence of the bundle sheath would help you identifythe C₄ plants.This pathway that has been named the Hatch and Slack Pathway, is again a cyclic process.

Chloroplast dimorphism is a characteristic feature of C₄ plants. These plants contain two kinds of chloroplast in their leaves, bundles sheath cells contain chloroplast in which grana is absent and mesophyll cells without stroma.

Mesophyll cells contain peroxisomes where formation of glycoxylate is formed from glycolate during Hatch and Slack cycle of carbon fixation.

Plants that are adapted to dry tropical regions have theC₄ pathway Though these plants have the C₄ oxaloacetic acid as the first CO₂ fixation product they use the C₃ pathway or the Calvin cycle as the main biosynthetic pathway.

Pigment of Photosystem I occurs in stromal thylokoids and non-appressed parts of granal thylakoids. PS-I absorbs light of wavelength of less than 780 nm.

During fixation of carbon dioxide in C₄ cycle, the enzyme required is PEP carboxylase. These enzyme become active only when concentration of carbon dioxide gas more.