Which of the following correctly places in order the steps that occur as dehydration develops in a plant during photosynthesis?

• A. Photosynthetic rate increases → Stomata open → CO\(_2\) uptake increases → Photorespiration decreases
• B. Stomata close → CO\(_2\) uptake increases → Photosynthetic rate increases → Photorespiration decreases
• C. Stomata open → CO\(_2\) uptake decreases → Photosynthetic rate drops → Photorespiration increases
• D. Stomata close → CO\(_2\) uptake decreases → Photosynthetic rate drops → Photorespiration increases

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the context of the problem. Dehydration in plants occurs when water availability decreases, leading to physiological changes that impact photosynthesis and related processes.
2. Step 2: Recall the role of stomata in plants. Stomata are small openings on the surface of leaves that regulate gas exchange, including the uptake of CO\(_2\) and the release of water vapor. When a plant experiences dehydration, stomata typically close to conserve water.
3. Step 3: Analyze the impact of stomatal closure. When stomata close, CO\(_2\) uptake decreases because the plant can no longer efficiently exchange gases with the environment. This reduction in CO\(_2\) availability limits the photosynthetic rate.
4. Step 4: Connect the decrease in photosynthetic rate to photorespiration. As photosynthesis slows down due to reduced CO\(_2\) uptake, oxygen becomes more competitive for the enzyme RuBisCO, leading to an increase in photorespiration. Photorespiration is a process that consumes energy and reduces the efficiency of photosynthesis.
5. Step 5: Verify the sequence of events. The correct order is: Stomata close → CO\(_2\) uptake decreases → Photosynthetic rate drops → Photorespiration increases. This sequence aligns with the physiological responses of plants to dehydration during photosynthesis.