We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
A young friend recently asked, while on a lovely July walk, how plants got the energy to grow. It is high school bio, but I forgot some of it. I recalled the rough outlines of the Calvin Cycle, then began wondering whether plants had mitochondria because they use solar energy. Well, plant cells are eukaryotes just as are animals, so of course they have mitochondria.
For photosynthesis, they don't need mitochondria much. Light waves provide the energy to split water into the Hs and the O, and to attach those Hs to ADP onto ATP - the main energy source of most living things. Thus oxygen is produced by plants from water.
The second step of photosynthesis is to use the ATP to produce glucose (sugar) from CO2. Technically, triose phosphates are produced, which the cell combines to construct glucose. Simple sugar is the main building block for plant structure (eg cellulose, etc).
That whole thing is called the Calvin Cycle and it is one fancy mini-machine.
However, for night functioning and for extra needs, plants can also burn sugar (that's called respiration) just as animal cells do. Mitochondria do that job. In the respiration of plants and animals, glucose is metabolized to CO2 and water to produce ATP - the energy for cell life and growth. Thus plants are CO2 emitters and oxygen emitters.
Animal life requires plants, but not vice versa. Only plants can produce glucose which is the building block for many things including carbs.
I will not get into the topic of how plants and animals construct proteins now. It is all a miracle.
Animal life requires plants....
Except the grass we grow to feed the cows looks a whole lot better than the grass that didn't have their poop returned.
The corn silage we produce is worth much more than the stuff only grown with commercial fertilizer.
God created everything in six miraculous days. The big banger evo folk religion is far more than merely an insult. Evos are like mice living inside a piano; the mice think it's the strings that make the beautiful music.
Actually, plants are not CO2 emitters, only O2. The absorb CO2.
Also, if you think the Calvin cycle is amazing - dig into the Krebs Cycle. That is downright byzantine. My high-school biology teacher made us work through that for a couple weeks.
Without mitochondria, seeds wouldn't germinate. There would be no ability for plants to go dormant in winter (deciduous plants, for example) and come back in the spring. You're right, it is high school biology, but it is fun to contemplate such things in our moments of leisure.