Ooh, cool! I’ve often wondered about the composition of the gas inside a pepper, and pondered experiments to measure it. My main hypotheses were that it would be mostly air, that it would be higher in oxygen, or that it would be higher in carbon dioxide.
Still, given that plant cells are cemented together you’d need a structure that allowed air in, or a puncture. In any case the secondary question was
And if pumpkins follow green peppers as hollow fruit then the answer is that minimally most if not all of it is produced by respiration of the cells of the fruit or possibly some commensurate organism contribution.
I wonder if there is some tendency to a pressure differential inside to outside of hollow fruit? If so which direction?
Someone with an air compressor needs to test this. I think the corky plate on the base will prove to be slightly porous to air. As regards cells being cemented together, sure, but the internal structure of a pumpkin is not a monolithic block of material - it’s composed of packed fibres.
I don’t have a reputation to even bet on this, so I might just be completely wrong. I can test the air tightness of a pepper right now by just gently squeezing one in a bowl of water. Back in a moment…
OK, for a pepper, gentle non-damaging squeezing underwater caused bubbles to emerge from a tiny, neat hole at the blossom end that I have never noticed before on a pepper, but assume is an anatomical feature. I only have the one fruit in the house at the moment, so it may be too early to generalise.
Science!
Update: I looked at a selection of different peppers in the supermarket today; they all appear to have that little hole at the blossom end. I’m sort of surprised this isn’t exploited by insects.
That same spot on a fig is exploited by wasps.