Question

Different types of photosynthesis occur depending on the environmental conditions and the type of plant. Which type of photosynthesis occurs in plants in hot dry conditions?
I. ${C_3}$photosynthesis
II. ${C_4}$ photosynthesis
III. CAM Photosynthesis

A. I only
B. II only
C. III only
D. I and II only
E. II and III only

Answer 1

Hint: ${C_3},{C_4}$ and CAM pathways are the adaptations that permit several plant species to lessen photorespiration in them. These pathways function in a way that RuBisCO grabs large concentrations of carbon dioxide and prevents it from binding with oxygen.

Complete answer:
Photosynthesis is the process of capturing light energy and transforming it into chemical energy. Green plants use light energy and convert carbon dioxide and water into glucose. Oxygen is produced as a by -product. It regulates the proper balancing between oxygen and carbon dioxide in the atmosphere.
${C_3}$ pathway: It is the most typical among the three pathways used for carbon fixation. It takes place in all the plants following photosynthesis. Here ribulose bisphosphate, carbon dioxide and water react to form two molecules of $3$-phosphoglycerate. The plants following this cycle are Xerophytic, Mesophytic and Hydrophytic. The suitable temperature for photosynthesis is $15 - 25$ degrees. The number of NADPH and ATP molecules needed to release glucose are NADPH-$12$ and ATP-$18$
Examples include: Rice, sunflower and cotton
${C_4}$pathway: It is known as the Hatch-Slack pathway which involves the primary step in removing carbon from the $C{O_2}$ to utilise in sugar and various molecules. It is found in tropical plants. The term ${C_4}$ signifies the four carbon molecules which are the initial product of this pathway. The photorespiration procedure is not seen much. The first product released is oxaloacetate. The suitable temperature for photosynthesis is around $30 - 40$ degree. The number of NADPH and ATP molecules needed to release glucose are NADPH-$12$ and ATP-30
Examples- Sugarcane,maize ,sorghum
CAM pathway: is the third carbon fixation method used by plants. Crassulacean acid metabolism(CAM) is used by the plants where the stomata remains closed during the day time to lessen evapotranspiration. But it opens during the night time to gather carbon dioxide,allowing it to scatter in mesophyll cells. Xerophytic plants follow this type of cycle. The suitable temperature for photosynthesis is around $40$ degree. The number of NADPH and ATP molecules needed to release glucose are NADPH-$12$ and ATP-$39$.

Hence, the correct answer is option (E).

Note: The difference between ${C_3}$ and ${C_4}$ plant is photorespiration. Plants undergo photorespiration also called the ${C_2}$ cycle while ${C_4}$ does not due to the presence of kranz anatomy. The CAM plants can survive in arid conditions where loss of water is the primary step.