Photosynthetic organisms are able to trap the energy of sunl

Photosynthetic organisms are able to trap the energy of sunlight for the synthesis of organic molecules. As usual, the exact photosynthetic mechanism employed has evolved through the interaction of the organism with its environment by natural selection. Read the article The Ecology of Photosynthetic Pathways (http://www.nature.com/scitable/knowledge/library/the-ecology-of-photosynthetic-pathways-15785165) and answer the questions that follow.

1. Why isn’t maximizing gCO₂ by having a large number of open stomata generally a good way of maximizing photosynthesis?

2. Why is it difficult for plants to achieve a high A/E ratio in environments characterized by high temperatures and low humidity? Hint:  A/E = (Ca-Ci)/1.6 (VP_a-VP_i)

A = photosynthetic carbon assimilation

E = transporation rate

1.6 = the ratio of the diffusivity of water to CO₂

C_a = concentration of CO₂ in the air surrounding a leaf, and C_i = CO₂ concentration inside the leaf

VP_a = water vapor pressure of the air outside the leaf, and VP_i= water vapor pressure inside the leaf

3. What do the C3, C4 and CAM photosynthetic pathways all have in common?

4. You have seen how various plants have evolved mechanisms to deal with the problem of photorespiration. Design a mechanism, or suggest an evolutionary design change not yet observed that would overcome the problem of photorespiration.

http://www.nature.com/scitable/knowledge/library/the-ecology-of-photosynthetic-pathways-15785165

Solution

Q 3.What do the C3, C4 and CAM photosynthetic pathways all have in common?

Ans. The CO₂ is fixed by rubisco and made into sugars by Calvin cycle in C₃, C₄ and CAM plants.