I was looking for a percentage - e.g. at night plants release on average
20% (carbon dioxide) of the amount of oxygen that they released during the
day.

"monique" schreef
That is going to depend on the species, the growing conditions (light,
moisture, temperature, etc.) Many factors affect metabolism, and I'm not
sure there's a constant percentage.

M. Reed

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Not to mention differences in day length!
PvR