Evidence indicates that plants increase the number of stomata in their leaves as atmospheric CO₂ levels decline. Increasing the number of stomata per unit surface area should have the effect of doing which of the following?
1) increasing dehydration of leaf tissues
2) decreasing dehydration of leaf tissues
3) countering the effect of declining CO₂ on photosynthesis
4) reinforcing the effect of declining CO₂ on photosynthesis
5) decreasing the O₂ content of air next to the leaves lower than it would otherwise be
6) increasing the O₂ content of air next to the leaves higher than it would otherwise be

Question

Quizplus · Accepted Answer

Increasing the number of stomata per unit surface area would allow for more effective gas exchange, including the uptake of CO₂ and release of O₂ for photosynthesis. This would counteract the effect of declining atmospheric CO₂ levels on photosynthesis (3), as more stomata would increase the efficiency of CO₂ uptake. However, an increase in stomata may also lead to greater dehydration of leaf tissues (1), as more water vapor can escape through the stomata. To counteract this, plants may also decrease the size of their stomata to reduce water loss. Increasing the number of stomata may have a minor impact on the O₂ content of air next to the leaves (6), but this is not a major effect of stomatal density changes.

Evidence Indicates That Plants Increase the Number of Stomata in Their