Green skin is common in science fiction, but what if green skin were not just for aliens? If humans had green skin, what if it permitted us the ability to perform photosynthesis (光合作用), which plants use to live off of (依靠)sunlight?
Let's analyze what science says about it and ask award-winning science-fiction author John Scalzi what he thinks.
Plants can live off of photosynthesis because they grow broad, flat leaves to harvest as much light as possible. They also need less energy because they are far less active than animals.
According to Lindsay Turnbull, a plant ecologist at the University of Oxford, if the skin of a woman were photosynthetic like a leaf, the amount of surface area she had would satisfy only 1% of her daily energy requirements to survive. For a photosynthesizing woman to meet her energy demands, she would need a lot more skin—about a tennis court's worth, Turnbull estimated.
In addition, photosynthesis requires carbon dioxide. Plants have pores (毛孔)that they use to supply the gas to their cells. If photosynthetic humans had chloroplasts (叶绿体), they might need porous skin to let in carbon dioxide, but such pores might let other things take in or leak out—for instance, moisture (水分)—in ways that might prove harmful to the human body.
One might wonder if photosynthetic people might prefer moving to sunny climates. Although such people might receive a small increase from photosynthesis if they moved to a desert area, they would likely base other resource issues to deal with, such as a lack of water, Scalzi said. "There's always going to be trade-offs (平衡)," he noted.
And would photosynthetic humans prefer hole or no clothing to absorb all those rays? In some photosynthetic societies, clothing might become a symbol of the elite—a sign they get enough energy from food and do not need photosynthesis. You can imagine them saying. "I'm rich, so I can cover up." Scalzi said.
So would Scalzi want photosynthetic skin for himself? "Probably not." he said. "I don't see the benefit from it being so great that I would completely change the way I'd look to benefit from it."
