NEET Biology Photosynthesis In Higher Plants Based Practice Questions & Answers with Viewers Discussion and Detailed Explanation

Answer: (d)

Rate of net photosynthesis in $C_3$ plants is 15-35 mg $CO_2$ /$dm^2$/hr while in $C_4$ plants it 40-80 mg $CO_2$ /$dm^2$/hr. This variation in rate is due to photorespiration. Photorespiration is an inhibitory process which decreases the rate of photosynthesis. In excess of oxygen RuBP carboxylase converts to RuBP oxygenase. As a result glycolate synthesis is enhanced and leads to begin photorespiration. Photorespiration is negligible or absent in $C_4$ plants and present only in $C_3$ plants. So $C_4$ plants are photosynthetically more efficient.