system
Given the following post, respond as if you're commenting on Reddit:
human
If it was inside a vacuum, what exactly would happen to a tree and how long would it take for it to die?
gpt
Plants exchange a lot of water with their environment. It is chemically consumed by photosynthesis and the constant upward flow from the roots to the crown helps transport nutrients.

The rate of evaporation is controlled by thousands of valved openings called stroma on the surface of each leaf. If the tree detects that it is losing water too fast, the valves close.

These valves were never designed for the vacuum of space though (low pressure will lead to evaporation and sublimation), and the underlying leaf is not equipped for extreme temperatures and unfiltered ultraviolet radiation. The leaves will probably wilt almost immediately.

Bark has the characteristics of a decent space suit. It is strong, mostly watertight, and has some insulating ability. The cambium (the living layer under the bark but above the wood) would be viable for a while until it either boils in the sun or freezes solid. Actually, some species don't mind being frozen for a while so chucking it into deep interstellar space where it is too cold for water to sublimate much might fail to kill it. 

Radiation damage would accrue over days or months as your oak drifts among the stars.