Cells, especially plant cells can withstand much more than 1 Bar of pressure difference. A plant will not start to boil in a vacuum, contrary to other comments. Every land organism has gone though a great deal of evolution to make sure it doesn't loose to much (or any) water though evaporation on its surface.

However plants require on pressure and evaporation to pull water from the roots to the leaves. It will loose its water through its stromata in the leaves a loot more than normal. If the roots are in water it will be ok, just dry out the ground realy quickly.

Most likely the leaves will die fairly quickly, followed by the roots. The cambium of a woody plant will probably not even notice the vacuum for a few months. Just like in winter it will basically hibernate beneath the bark and form new sprouts once it is in atmosphere again.

You will probably have to cut away some dead wood to expose the living cambium and initiate regrowth of roots and new sprouts but a tree will be able to regrow after being in a vacuum for a (relatively) long ass time. Think of a tree stump getting new sprouts around the outer edge a year after it was cut down.

No idea about radiation and heat though. If it is floating in direkt sunlight its probably fucked after a few days.