水稻为三碳植物，其伴生性恶性杂草稗草为四碳植物。
Rice is C_3 plant and its companion, noxious weed barnyardgrass is C_4 plant.
他们没告诉你的第三件事：动物食品比植物食品有更高的碳足迹。
What they don't tell you: It's true that animal products tend to have much higher carbon footprint than food produced from plants.
因为空气中二氧化碳的密度只有万分之三，所以聚集在植物内部的碳是从周围极大体积的空气中得来的。
The concentration of carbon dioxide in the air being only 0.03 percent; carbon is amassed into the compass of the plant form a large volume of air.
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