I've read that some plant and tree seeds can be cryogenically preserved for years, if not decades. However, I've not read of anyone considering the following theory: Could it be possible that our diverse plant life here was a result of asteroids skimming or impacting Earth-like planets and carrying/depositing their plant seeds on our Earth? If it's possible for seeds to be carried on asteroids and survive the deep cold of space, then the "seeds of life" on our planet are not just microbial.
closed as off-topic by Organic Marble, Brian Tompsett - 汤莱恩, DarkDust, Nathan Tuggy, Mark Omo May 7 '18 at 18:26
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is about other space sciences (physics, weather, astronomy, etc), and does not directly pertain to space exploration as outlined in the help center." – Organic Marble, Brian Tompsett - 汤莱恩, DarkDust, Nathan Tuggy, Mark Omo
In fact some seeds have been viable after tens of thousands of years. Which is pretty close to how long the fastest object to leave our solar system would take to get to the nearest star. Of course it isn't headed that way, and it never came close enough to Earth for anything to transfer, but timing doesn't certainly rule out this idea.
Additionally some algae and other plants have been tested to survive some time in space, though obviously not thousands of years. So the hazards of space also do not yet rule out plants surviving the trip.