Plants produce CO2 as well, photosynthesis is only used to produce sugars, normal respiration (I.e. sugars + O2 = energy + CO2), is used by plants to consume those sugars.
Only a plant cells containing chlorophyll and exposed to sunlight will photosynthesise. Notably at night there isn’t much sunlight, so normal respiration dominates a plants gas conversion processes, and results in them producing net CO2.
Based on the graphs in the blog post, I assume GP is placing the CO2 production on plants because it the CO2 levels peak at night, then return to normal every morning.
Yep, I've noticed this as well with my cannabis grow tent. At an 18/6 lighting schedule, it's noticeable that CO2 grows up to 800ppm in the tent at the end of the fake-night cycle.
Only a plant cells containing chlorophyll and exposed to sunlight will photosynthesise. Notably at night there isn’t much sunlight, so normal respiration dominates a plants gas conversion processes, and results in them producing net CO2.
Based on the graphs in the blog post, I assume GP is placing the CO2 production on plants because it the CO2 levels peak at night, then return to normal every morning.