Re: [Aroid-l] Plants cause oxygen deprivation at night???????

From: ExoticRainforest <Steve at ExoticRainforest.com> on 2010.02.16 at 09:14:28 Thank you Walter!  That is the kind of info I need to make a good explanation!  I hope to be able to post a page on my website in the next few weeksexplaining all of this since my little site receives a lot of hits frompeople around the globe looking for answers.  Almost one half millionhits popped up last year so if none of you object I would like to beable to use selected quotes from your responses in that piece. Steve www.ExoticRainforest.com Walter Turner wrote: I can’t add to the ideas Steve Marak presented,but I can try some numbers. I hope the readers of Aroid-L will workthrough my numbers here. It would be bad enough for me to look like anidiot because I overlooked something that changes the results by afactor of a hundred or so, but it would be worse for the wrong resultsto stand without correction.   I asked a friend who did his doctoral work onplant respiration and got the approximation that the emission of CO2 inthe dark is unlikely to exceed 4 micro moles per square meter of leafsurface per second. This is the same as the O2 taken up. Say our plantshave a leaf area of one meter. Let’s say for the sake of argument thatboth upper and lower leaf surfaces emit at that rate, so our plants useup 8 micro moles PER SECOND (please excuse the upper case, but when wethink of a whole night the seconds really add up).   In an 8-hour night, we have the 8 micro moles/sx 3600 s/h x 8 h = 230400 micro moles of oxygen the plants take up.That is only millionths of moles, so it amounts to 0.23 mole. That gotthe number back down in a hurry.   How much oxygen was in the room to start with? A room 4 m x 4 m x 2.4 m has 38.4 cubic metersof air. That is 38400 liters. At room temperature, a mole of gas is about 25liters, so the room has 1536 moles of air. If we say the air in the room is 20 % oxygen,we have 307 moles of oxygen to start with.   How much of the total oxygen in the room didthe plant use? It is 0.23/307 = 0.075 %.   What about our oxygen-starved sleeper? A person breathes out about 900 g CO2 per dayor about 300 g in an 8-hour night. CO2 has a mole weight of 44. 300/44 = 6.8 moles CO2 emitted = moles O2 takenup by a person in the night.   The 6.8 moles of oxygen used by the sleepingperson amounts to only about 6.8/307 = 2.2 % of that available.   How do the plant and the sleeper compare? Theplant uses 0.23/6.8 = 3.4 % as much.   With all the guessing (“approximation” inscience-speak), none of the numbers has any meaning unless it’s roundedoff to only one digit. You can insist that a sleeping person uses lessoxygen than an active one, the room is smaller and the plant larger,but that doesn’t change anything. A good-sized plant surface won’treduce the oxygen content of the room by much more than a tenth of apercent, and that is only about three percent of what the inhabitantuses up.   If the sleeper is oxygen-starved, he or sheprobably isn’t breathing right. It can’t be blamed on the plant. I’veknown people who slept with their heads under the covers. That doesscare me. Walter Turner --------------070806030007020901020009

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