Avon Valley Railway - Fighting the Nimby-Graffiti

[nickt]

I seem to recal an old wifes tale ( and my biology teacher , and he was an old woman) that with photosynthesis a plant gives out oxygen during daylight hours and "eats" co2 to produce chlorofil ( the green gunge in leaves), but, at night the process opposes ie oxygen used and co2 emmited hence in hospitals flowers were removed from bedsides at night.