NEET Questions Solved

NEET - 2017

With reference to factors affecting the rate of photosynthesis, which of the following statements is not correct?

(1) Light saturation for CO2 -fixation occurs at 10% of full sunlight.

(2) Increasing atmospheric CO2 concentration upto 0.05% can enhance CO2 -fixation rate

(3) C3 -plants respond to higher temperature with enhanced photosynthesis, while C4 -plants have much lower temperature optimum.

(4) Tomato is greenhouse crop, which can be grown in CO2 -enriched amosphere for higher yield. 

(3) In C4 -plants, the initial fixation of CO2 occurs in mesophyll cells. The primary acceptor of CO2 is Phosphoenol Pyruvate (PEP). It combines with CO2 in the presence of enzyme PEP carboxylase to form the first stable product, i.e., oxaloacetic Acid (OAA). C3 plants lack PEPcaboxylase enzyme. They posses RuBisCO enzyme. This enzyme can work as both carboxylase (fixation of CO2) and oxygenase (fixation of O2). RuBisCO has much greater affinity for CO2 than for O2 and the binding is competitive. At higher temperature, its ffinity for CO2 decrease and it works as oxygenase.

Therefore, at higher temperature photosynthesis decrease in C3 -plants, while in C4 -plants increases. 

Difficulty Level:

  • 10%
  • 16%
  • 66%
  • 10%