I ran a similar experiment at home, albeit with a fern rather than potatoes and without simulating martian light.
My fern started to perish (and it was a well established plant). The biggest problem I'm facing at the moment is that Mars is extremely nitrogen deficient.
It seems that this short story was originally published in an old science fiction magazine (that my local library doesn't stock). Was wondering if it also made its way into a compilation of some sort. Google hasn't turned up anything for me yet.
Can you imagine if someone told Asimov that his story "Buy Jupiter" would be mistaken for a "link" to buy a copy of his work, by someone reading on an international network of computers that have access to all of the information in the world - and were so overrun with advertising that his own title was mistaken for one. Given "Buy Jupiter's" plot summary - https://en.wikipedia.org/wiki/Buy_Jupiter [1] - this is extremely apropos!! Some things never change :)
[1] WHICH I'M LINKING ON A FREAKING ENCYCLOPEDIA GALACTICA THAT CONTAINS IN EVERY LANGUAGE ALL OF THE GENERAL KNOWLEDGE OF THE WORLD (WIKIPEDIA).
It'd be interesting to measure the gas composition inside the chamber --- although I suspect the bodging together a gas spectrometer is going to be a bit problematic.
This all at at one atmosphere, though, isn't it? I see you have a vacuum pump, but that enclosure doesn't look like it'd be safe to evacuate. I'd like to try low pressures. Intuitively I'd expect hard-skinned plants like cactuses to cope better --- but intuition is frequently wrong. Another interesting thing to try would be to use one atmosphere of absolute pressure but have accurate partial pressures of carbon dioxide and nitrogen to simulate the Martian atmosphere...
Yeah one atmosphere, but with the same atmospheric mix as what is on Mars. I was trying to simulate compressing the Martian atmosphere into a pressurised and thermally insulated greenhouse.
My enclosure is only good down to about 0.8 atmospheres, below that the big rubber seal around the door starts to leak. The vacuum pump is used when mixing the atmospheric composition.
Figure the first martian plants would live in a pressurised, insulated greenhouse. There are some neat passively heated designs around.
I think my next experiments will be with legumes trying to fix nitrogen and improve the soil. The way I see it, pressure, warmth and light are all problems for which we have existing solutions. The real question is can we get stuff to grow without importing tons of fertiliser?
Using a well established plant might be worse than using a young one. They grow into the situation they find and adapt. If your plant is used to standard house plant conditions it might be harder compared to one used to bad soil and little water. But probably you already took that into consideration?