Influence of Oxygen Gas on Developed Plants
The most evident effect of oxygen gas on developed plants is to elicit the production of carbon dioxide from the combination of this oxygen with the plants’ own carbon. At night, leaves “inspire” atmospheric oxygen and partly replace it by “expiring” carbon dioxide, whereas during the daytime the reverse occurs, and overall the atmosphere in a closed spbaace remains about constant in volume. If the leaves are very thick, however, as in cactus, they absorb the oxygen without releasing carbon dioxide. The production of carbon dioxide gives back to plants a substance that they can decompose and thereby regain the carbon that they had lost. The formation of carbon dioxide from atmospheric oxygen and plant carbon was confirmed for leaves of 57 species.
Oxygen is essential to plant growth and development. For example, germinating seeds require it; roots need it and die if put in nitrogen, hydrogen, or, especially, carbon dioxide, even if the shoot is exposed to air and light; and shoots survive in oxygen-free environments only if their green parts are exposed to light, allowing them to break down carbon dioxide that they have formed from their own internal oxygen and carbon, thereby producing and releasing enough oxygen to sustain themselves. Plant parts that are growing or otherwise physiologically active require more oxygen than do less active parts. The oxygen inspired cannot be recovered by an air pump. In non-green plant parts, the carbon dioxide produced by the combination of atmospheric oxygen with plant carbon probably ascends with the sap to be decomposed by the leaves rather than being fixed directly in the absorbing organ.