Question

One of the major ways that plants lose water to the environment is by opening their stomatal pores to let CO2 in for photosynthesis, which also results in water loss. The higher the concentration of CO2, the less often a plant has to open its pores to let in CO2. If the growth of a plant is water-limited, and we experimentally increase the concentration of CO2 near the plant, what would we predict would happen to the plant’s growth rate?

a.The plant’s growth rate should increase because it now has more CO2 available to build sugars.
b.The plant’s growth rate will stay the same because it is limited by water, not CO2.
c.The plant’s growth rate will go down because it will open its pores more to let in CO2 and lose water.
d.The plant’s growth rate should increase because it does not have to use as much water to fix CO2.
e.The plant’s growth rate should go down because CO2 will increase the temperature, increasing evaporation.

Answer 1

d. The plant’s growth rate should increase because it does not have to use as much water to fix CO2.

Step-by-step explanation:

Plants lose water through the process of transpiration, mainly when they open stomatal pores for CO2 uptake during photosynthesis. If the growth is water-limited, increasing CO2 concentration near the plant would allow it to photosynthesize with reduced stomatal openings, minimizing water loss.

This is because higher CO2 levels make photosynthesis more efficient, requiring fewer stomatal openings. Option d is the correct choice, as it accurately reflects the expectation that with increased CO2 concentration, the plant's growth rate should rise due to a more water-efficient photosynthesis process.

Higher CO2 enables the plant to fix more carbon with less water usage, promoting growth even in water-limited conditions. The alternative options are not as fitting: b suggests the growth is solely water-limited, c incorrectly predicts a decrease in growth due to increased water loss, and e introduces an unrelated factor (CO2 increasing temperature) that isn't supported by the given information. In summary, the correct prediction is that elevated CO2 would enhance the plant's growth rate by optimizing water use in photosynthesis.