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.
https://reprage.com/post/marsarium-9
https://www.reddit.com/r/Colonizemars/comments/5vi52v/inspir...
[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...
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?