Question

C3 pathway is found in?
A) Pea
B) Maize
C) Onion
D) All the above

Answer 1

Hint: Along with C4 and CAM, C3 carbon fixation is the most common of three metabolic routes for carbon fixation in photosynthesis. Through the following reaction, carbon dioxide and ribulose bisphosphate (RuBP, a 5-carbon sugar) are converted into two molecules of 3-phosphoglycerate:

Complete answer:
Melvin Calvin, Andrew Benson, and James Bassham were the first to discover this response in 1950. The Calvin–Benson cycle begins with C3 carbon fixation, which occurs in all plants. Carbon dioxide is taken out of malate and into this process in C4 and CAM plants rather than straight from the air.
Plants that rely only on C3 fixation (C3 plants) thrive in locations with moderate sunshine intensity, moderate temperatures, carbon dioxide concentrations of 200 ppm or higher,[ and abundant groundwater. C3 plants, which evolved throughout the Mesozoic and Paleozoic epochs, predate C4 plants and account for around 95% of all plant biomass on Earth, including essential food crops like rice, wheat, soybeans, and barley.
Transpiration allows C3 plants to lose up to 97 percent of the water they take up through their roots. C3 plants close their stomata to limit water loss in dry conditions, but this also prevents $CO_2$ from entering the leaves, lowering the $CO_2$ concentration in the leaves. As a result, the $CO_2$:$O_2$ ratio falls, and photorespiration rises. C4 and CAM plants have evolved to thrive in hot, dry environments, and they can thus outcompete C3 plants in these conditions.

So, the correct answer is option (A), C3 pathway is found in pea.

Note:
During carbon dioxide fixation, the majority of plants make a 3-carbon acid termed 3-phosphoglyceric acid (PGA) as a primary product. The C3 pathway, often known as the Calvin cycle, is one example of such a pathway. Carboxylation is the first of three stages in the Calvin Cycle.