Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow. Ancient fossil records show some pretty fascinating facts about how both plants and insects responded to changing levels of atmospheric oxygen, fossil records show dragonfly relatives with wingspans of up to three feet during times of very high oxygen concentrations. Cockroaches stayed the same size but the hollow tracheal tubes that carried oxygen through their bodies got smaller, allowing the insects to invest resources in other dimensions.
The stomata, valve-like structures on plant leaves that open and close to regulate air movement into plant tissues decreased in number when co2 levels were exceptionally high but returned to higher, normal ranges of when co2 levels decreased. Carbon dioxide is often a limiting factor in plant growth -- it makes sense that plants would try to increase ways to capture that gas when supplies are low. Co2 plus water in the presence of sunlight is the formula for photosynthesis.