Subject: How does oxygen enter the leaves of a plant at night?

The guard cells photosynthesis during the day to produce sugars so that 
the water would enter the cells by osmosis and cause it to become turgid 
and pull the stoma open. However, at night, the guard cell become flaccid 
and the stoma closes. How then does oxygen enter the plant?

I have considered the possiblility of the plant producing excess oxygen 
during the day and storing it at night for use. However, during the day 
when the plant produces oxygen during photosynethesis, the oxygen would 
diffuses out of the leaf due to a diffusion gradient as atmospheric air 
contains less oxygen than in the leaf. How then does the plant " store" 
oxygen and how does oxygen enter the plant at night?

Re: How does oxygen enter the leaves of a plant at night?