Question

what are the constraints upon C4 photosythesis in a dynamic light environment compared with C3 species?

Answer 1

C4 plants does not have the same ability to acclimate low light, temperature variation or elevated carbon dioxide as of C3 plants. This makes C4 plants limited to certain regions.

The main constraint is the C4 plants use fluctuating light less efficiently than C3 plants.

When leaf gas exchange plant growth and dry matter carbon isotope discrimination is measured to infer co2 bundle sheath leakiness is observed in C4 plants. The growth of all species was reduced by Dynamic Light, only small changes in steady state gas exchange characteristics was observed more in C4 plants than in C3 species.

Dynamic light leads to imbalances in the coordination of C4 and C3 cycles by increasing leakiness and decreasing the quantum efficiency of photosynthesis.

Hence inability of C4 plants to efficiently utilize fluctuating light contribute their absence in forest environment.

Apart from Dynamic light, Drought also contributes constraints in photosynthesis pathway of C4 plants.

Under well watered conditions photosythetic rates were significantly higher in C4 plants than in C3. During drought decrease in CO2 assimilation results in low electron transport rates and photochemical efficiency. This suggests high metabolic sensitivity of photosynthesis in severe drought seen in c4 plants suggest an inherent characteristic of C4 pathway than C3. This could also be a reason why C4 species are less abundant in arid regions.