Question

By looking at which internal structure of a plant can you tell whether a plant is C3 or C4? Explain.

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: Unique features of C4 plants
Presence of Kranz anatomy: Special anatomical arrangement of several layers of large bundle sheath cells around the vascular bundles. Bundle sheath cells have: Large number of chloroplasts Thick walls impervious to gaseous exchange No intercellular spaces