Of Plant Growth in Oxygen-Free Environments

Abstract

Plants can survive without oxygen in their atmospheres only if they have enough area of green tissue to produce free oxygen through the decomposition of the carbon dioxide that they form entirely from their own tissues. Oxygen seems to aid photosynthetic assimilation of carbon dioxide. Thus, in environments lacking oxygen, the elaboration of a certain amount of oxygen appears necessary for the decomposition of a certain amount of carbon dioxide. If the oxygen is removed as it is formed, plant growth is arrested. Seeds will not germinate in oxygen-free environments, and newly germinated seeds, before they have developed green parts, will die in these environments. Plants do not assimilate nitrogen, hydrogen, or carbon monoxide gases. They survive in these gases as they do in a vacuum, by means of the oxygen released by their leaves, and they can do so only if they are not in direct sunlight. The amount of oxygen needed to sustain a plant's life is small; more is needed for growth. Carbon dioxide always becomes harmful to plants if it is present in amounts too large for them to decompose. Excess carbon dioxide is more harmful to plants in an atmosphere of nitrogen than in one of ordinary air. In pure hydrogen gas, the carbon dioxide formed by the leaf from its own substance is decomposed by the hydrogen, with production of water and carbon monoxide gas. In an atmosphere of carbon monoxide, green plants, in the sun, do not decompose this gas but do add oxygen.