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During 24 hours there is a time in i.e. twilight when plants neither give oxygen nor carbon dioxide why is it so?

This also suggests that neither of the two vital processes i.e. respiration or photosynthesis is being carried out.

Well, during twilight there is not enough sunlight so photosynthesis may slow down or even cease but what about respiration?

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    $\begingroup$ Plants do have mitochondria and therefore their cells undergo respiration. $\endgroup$ – user560 Jul 2 '13 at 4:24
  • $\begingroup$ @leonardo Then after the completion of Kreb's cycle carbon dioxide should be released but during twilight neither is oxygen released nor is carbon dioxide.. and i am not able to understand why.. $\endgroup$ – user3800 Jul 2 '13 at 4:55
  • $\begingroup$ @AanalDesai do you have a credible reference for this?.. "Then after the completion of Kreb's cycle carbon dioxide should be released but during twilight neither is oxygen released nor is carbon dioxide" $\endgroup$ – rg255 Jul 2 '13 at 7:09
  • $\begingroup$ @GruffinEvo7 I am quite sure that during twilight neither oxygen nor carbon dioxide is released but the thought of compensation point just flashesd my mind maybe it could be the reason for no release of oxygen or carbon dioxide.... $\endgroup$ – user3800 Jul 2 '13 at 14:32
  • $\begingroup$ Plants collect energy (from light, through photosynthesis) to do use of it, just like any other living system do. To use that energy, plants require to do respiration. $\endgroup$ – Always Confused Oct 25 '19 at 4:27
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You haven't directed us to any evidence for your assertion, so it is difficult to evaluate.

I'm not a plant physiologist, so I will argue from first principles:

photosynthesis consumes CO2 and produces O2:

6CO2 +6H2O -> C6H12O6 + 6O2

respiration consumes O2 and produces CO2:

C6H12O6 + 6O2 -> 6CO2 +6H2O

Plants do both of these things at the same time for at least part of the day. During the day, in a growing plant, photosynthesis will exceed respiration: a lot of the fixed carbon is fed into anabolic processes to produce "plant stuff"; polysaccharides, proteins, nucleic acids. This means that the plant will be a net producer of O2 and a net consumer of CO2. At night there is, of course, no photosynthesis and respiration will dominate and the plant will be a net producer of CO2 and a net consumer of O2.

At certain times of the day, twilight for example, there will be a transition between these two states, and the plant will pass through a state where there will be no net flux in either of the gases.

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  • $\begingroup$ Well, Could it be due to compensation point that neither oxygen nor carbon dioxide is released? $\endgroup$ – user3800 Jul 2 '13 at 14:31
  • $\begingroup$ Just looked at "compensation point" on Wikipedia. Yes that is exactly what I had deduced must happen. Like I said I'm not a plant phyiologist. Was your question meant to go beyond this idea? $\endgroup$ – Alan Boyd Jul 2 '13 at 14:38
  • $\begingroup$ No, it answered my question. $\endgroup$ – user3800 Jul 2 '13 at 14:42

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