Question

please answer in a paragraph

11. Aquatic plants and algae carry out photosynthesis using the same light reactions and Calvin cycle as in land plants. Would you expect any of these organisms to also require the CA pathway? Describe the role of the C. pathway in land plants and speculate if this could ever be necessary in an aquatic environment.

Answer 1

Photosynthesis: Gas exchange: As the water gets deeper, the wavelength of light gets shorter until its gone. The red and blue wavelengths are lost, and the green (not so good for photosynthesis) remains. Adaptations include:

Wetland plants often use C4 biochemical pathway of photosynthesis instead of C3.
-C4 provides a possible pathway for recycling CO2 from cell respiration
-plants using C4 have low photorespiration rates and the ability to use even the most
intense sunlight efficiently.
-C4 plants more efficient than C3 plants in rate of carbon fixation and amount of water
used per unit carbon fixed.

Plants identified as having C4 photosynthesis have a C4 metabolic cycle with phosphoenolpyruvate carboxylase as the initial catalyst for fixation of atmospheric CO2, and a C4 acid decarboxylase (NADP-malic enzyme, NAD-malic enzyme, or phosphoenolpyruvate carboxykinase), which releases CO2 for fixation by the C3 cycle. Effective donation of CO2 to Rubisco minimizes competition by O2 and photorespiration, and thus increases photosynthesis under conditions where CO2 is limiting. To achieve this, fixation of atmospheric CO2 in the cytosol by phosphoenolpyruvate carboxylase must be separated from the donation of CO2 to Rubisco by the decarboxylation of C4 acids. In most documented C4 plants, this is accomplished through evolution of various forms of Kranz anatomy, with fixation of atmospheric CO2 in mesophyll cells and donation of CO2 from C4 acids to Rubisco in bundle sheath cells.