[reg45]

Yes, it is correct that plants do not consume oxygen. However, they do consume carbon dioxide and the amount of CO₂ is also diminished at higher altitudes. In fact, the effect of altitude on CO₂ is actually greater than on O₂ because CO₂ is denser than O₂.

[alexander_busek]

In fact, plants both PRODUCE oxygen (when the sun is shining, thus allowing them to perform photosynthesis and take CO2 and H2O and create glucose while simultaneously releasing oxygen into the atmosphere) and CONSUME oxygen (at night, when they take that glucose they stored up during the day and combine it with oxygen taken from the atmosphere to release ENERGY to power their metabolisms - while releasing CO2 as a waste product).

A plant kept under a belljar (otherwise sealed off from the environment) will do just fine as long as it gets enough sunlight (and starts with enough soil and water). It will produce oxygen during the day and consume that very same oxygen during the night. (I realize that this is a simplification.)

The only reason we have a net PLUS of oxygen in our atmosphere is because - can you guess? - the SINK of the biomass in the plants, themselves. When that biomass dies and is allowed to decay, it will "take up" all of the free oxygen that it once generated in life. The only way to maintain a net plus is to remove the biomass from the biosphere - e.g., to prevent it from rotting, by fossilizing it.

Your biology lesson for today.

Regards,