Question

in c₃ plants the conservation of water promotes __. a shift to c₄ photosynthesis the opening of stomata photorespiration photosynthesis the light reactions submit request answer part b in c₄ and cam plants carbon dioxide is fixed in the __ of mesophyll cells. stroma thylakoids cytoplasm grana stomata

Explanation:

• For the first question: In \(C_3\) plants, when water is conserved (e.g., stomata close to reduce water loss), the concentration of \(CO_2\) in the leaf decreases. Rubisco (the enzyme in the Calvin cycle) can then bind to \(O_2\) instead of \(CO_2\) (a process called photorespiration). \(C_3\) plants cannot shift to \(C_4\) photosynthesis as they lack the specific Kranz anatomy of \(C_4\) plants. Closing stomata would not promote the opening of stomata. Photorespiration reduces the efficiency of photosynthesis (so photosynthesis is not promoted), and the light reactions are not directly promoted by water conservation in this context.
• For the second question: In \(C_4\) plants, \(CO_2\) is first fixed in the mesophyll cells in the cytoplasm (using PEP carboxylase) to form a 4 - carbon compound. In CAM plants, \(CO_2\) is also initially fixed in the cytoplasm (at night) using PEP carboxylase. The stroma is where the Calvin cycle (a part of \(C_3\) photosynthesis) occurs. Thylakoids and grana are related to the light - dependent reactions (not the initial \(CO_2\) fixation in \(C_4\) and CAM). Stomata are for gas exchange, not \(CO_2\) fixation.

Answer:

• First question: photorespiration
• Second question: cytoplasm