Question

What are the examples of C3 and C4 plants?

Answer 1

Hint: C3 carbon fixation is the most common of the three metabolic pathways for carbon fixation in photosynthesis along with C4 and CAM. Plants exhibiting C3 fixation (C3 plants) thrive in areas with moderate sunlight and temperature and with the minimum carbon dioxide concentration of 200 ppm plus plenty of groundwater. C4 carbon fixation is more common in monocots; $40\%$ in monocots and only $4.5\%$ of dicots.

Complete answer:
Cereals, barley, oats, rice and wheat, alfalfa (lucerne), cotton, Eucalyptus, sunflower, soybeans, sugar beets, potatoes, tobacco, Chlorella, spinach are some examples of plants following the C3 fixation and are called the C3 plants. C4 plants include maize, sugarcane, pearl millet, sorghum, switchgrass, corn and others. Members of the sedge family Cyperaceae and eudicots – including Asteraceae (the daisy family), Brassicaceae (the cabbage family) and Euphorbiaceae (the spurge family) – also use C4 fixation. There are very few known trees that use C4: Paulownia, seven Hawaiian Euphorbia species and a few desert shrubs that reach the size and shape similar to trees with age.

Note:
The main carboxylating enzyme in C3 fixation is RuBisCO. It catalyses two distinct reactions with $CO_2$ (called carboxylation) and with oxygen (called oxygenation), which give rise to the wasteful process of photorespiration. C4 photosynthesis, on the other hand, reduces photorespiration by concentrating $CO_2$ around RuBisCO.