Question

when stomata are open, co₂ can diffuse into a photosynthesizing leaf down its concentration gradient. what keeps the concentration of co₂ in the leaf low, so diffusion occurs efficiently?
○ co₂ does not pass through lipid bilayers readily, so the rate of diffusion is always low.
○ in leaf cells, co₂ is being used rapidly in the reaction catalyzed by rubisco.
○ co₂ concentrations in the atmosphere around the leaf are actually very low, at only about 0.04% of the molecules in air.
as the diagram shows, water vapor (h₂o) exits the stomata down its concentration gradient because the interior of a cell usually contains much more water than the surrounding air. the loss of water increases the fitness of the plant, meaning that water loss when the stomata are open directly benefits the plants ability to survive and produce offspring.
○ true
○ false

Explanation:

• For the first question: In leaf cells, \(CO_2\) is used in the Calvin cycle (catalyzed by rubisco), which keeps its concentration low. \(CO_2\) can pass through lipid bilayers (it's non - polar). The low atmospheric \(CO_2\) concentration (0.04%) is not the reason for low leaf \(CO_2\) concentration as diffusion is from high to low.
• For the second question: Water loss (transpiration) helps in nutrient uptake (as water is a solvent for nutrients in the soil solution and the transpiration stream moves nutrients up the plant) and cooling (evaporative cooling), which benefits the plant's survival and reproduction (fitness).

Answer:

• First question: In leaf cells, \(CO_2\) is being used rapidly in the reaction catalyzed by rubisco.
• Second question: True.