Question

The saturation point for plants (A) and plants (B) is

• A.
• B.
• C.
• D.

Answer 1

Answer: (B)

Photosynthesis is affected by several internal factors as well as external environmental factors.
The internal factors affecting rate of photosynthesis are
(a) number, size, age and orientation of leaves
(b) amount of chlorophyll
(c) rate of translocation of food etc.
The internal factors are mostly genetic.
(iii) The external factors affecting rate of photosynthesis are
(a) availability of light
(b) temperature
(c) CO2 concentration
(d) soil water

Effect of carbondioxide- (i) Carbon dioxide is the major limiting factor for photosynthesis.
(ii) The CO2 concentration is very low in the atmosphere; between 0.03 and 0.04% (300 - 400 ppm).
(iii) This concentration of CO2 is far below the optimum requirement of photosynthesis.
(iv) The minimum CO2 concentration below which there is no net absorption of CO2and the rate of photosynthesis is equal to rate of respiration is called
compensation point.
(v) The maximum CO2 concentration at which photosynthesis takes place but beyond which photosynthesis takes place is called saturation point.
(vi) Very high concentration of carbon dioxide causes closure of stomata. As a result rate of photosynthesis decreases.
C3 plant saturation point is 450ppm and for C4 plant is 360ppm.