Question

By looking at a plant externally can you tell whether a plant is C3 or C4? Why and how?

Answer 1

Part 1: Introduction to C3 plants
The plants which use C3 carbon fixation pathway and the first product of carbon dioxide fixation is a 3-carbon organic compound, 3-phosphoglycerate, are termed as C3 plants. Examples include oat, wheat, soyabean, tobacco etc.

Part 2: Introduction to C4 plants
The plants in which the first product of carbon dioxide fixation is a 4-carbon organic compound, oxaloacetate, are termed as C4 plants. Examples include maize, sugarcane, Sorghum, Amaranthus etc.

Part 3: Identification of plants externally
It is not possible to identify externally whether a plant is C3 or C4. Though C4 plants are generally found mostly in tropical areas but there is no external feature that can distinguish between C3 and C4 plants.