During night times stomata remain closed.Then how do the plants respire?
CO2 can still diffuse out of plant tissue when stomata are closed at night plus plants can reduce their metabolism to reduce the rate of respiration during the night.
1) They do not need to respire during night as there is no light, i.e. no photosynthesis.
2) see CAM plants http://en.wikipedia.org/wiki/Crassulace … metabolism
I’m sorry but plants still respire during the night. Their cells are still doing things other than photosynthesizing that require energy.
What makes you think that the stomates are closed throughout the night?
They may not be open throughout, but they don’t need to be, any more than your mouth has to be open all the time for your respiratory needs.
Night is also the best time to recharge the interior with carbon dioxide with minimized water loss.