Leaf Discs Take In Oxygen In The Dark - Why?

[macpark]

My daughter needs help with an IGCSE biology question!
Obviously, in the dark photosynthesis cannot occur as there is no light.
Plants do use oxygen too, through the hairs on the roots, which is why a water logged plant dies because the roots cannot get enough oxygen from their surroundings. Why does this apply to discs of leaves which, in this experiment, were cut from young orange tree leaves.

[LazyGun]

Ermm - Plants also respire too, and require Oxygen. During the day, when photosynthesis is active, they produce more O2 through the process of photosynthesis than their own metabolic process actually needs, and so the excess O2 is dissipated via leaves, bark, and roots into the atmosphere.

During the night,photosynthesis shuts down because they are not receiving the photons from the sun. However, the plants still have a metabolic requirement for O2, which is obtained via the process of gaseous diffusion across all parts of the plant, but especially the leaves.

The net balance of O2 is that, even taking into account their oxygen requirement during the hours of night, they still "exhale" more O2 than they require........

http://wiki.answers.com/Q/Why_do_plants_take_in_oxygen_and_release_CO2_at_night

[wildwood]

^^ Isn't that why they (used to) remove flowers from the hospital ward/room at night?

[Peter Pedant]

because the plants use up the oxygen and hence suffocate the patients. ?

Reminds me of the killer wall-paper that was in Napoleon's room ( @ Longwood on St Helena - it had scheele's green on it/in it and this was converted to AsH3 by the damp atmosphere)

[woofgang]

no wildwood, seriously its because the staff used to knock the vases over at night, the oxygen use thing is a story.....

[Old_Geezer]

Couldn't they employ less clumsy staff ?

[woofgang]

lol OG

[LazyGun]

That plants respire and use O2 is not a story; That flowers and plants were banned from wards because this might suffocate or deprive patients of O2 is :)

Others have talked about the possibility of Hospital Acquired Infections from flowers and the water in the vases; But there has never been a recorded instance of this happening.

As Woofgang says, the reason that wards have banned flowers is the management of those flowers on the ward, and the potential for spills, breakages, cleanups, getting rid of the flowers etc.

Interesting article from NHS choices on this ;

http://www.nhs.uk/news/2009/12December/Pages/Hospital-flowers-not-harmful.aspx