Question

Are aquatic plants C₃ or C₄?

Answer 1

C₃ plants:

1. In C₃ plants, the first product of CO₂ fixation is 3-phosphoglyceric acid (a three-carbon compound).
2. These plants are mostly found in temperate regions. Example: rice, barley.

C₄ plants:

1. In C₄ plants, the first product of CO₂ fixation is oxaloacetic acid (a four-carbon compound).
2. C₄ plants are mostly found in tropical areas. They possess a distinct type of leaf anatomy called ‘Kranz’ anatomy in which the mesophyll cells form a cluster around the bundle-sheath cells. Example: maize, sorghum.

Aquatic plants:

1. Aquatic plants are mostly C₄ plants since the amount of dissolved CO₂ is low in aquatic habitats.
2. These plants have two CO₂ acceptors (phosphoenolpyruvate and ribulose bisphosphate) and fix CO₂ much faster in comparison to C₃ plants.
3. They also exhibit a higher photosynthesis rate. Example: Udotea flabellum.