Changing tenses when referring to facts

I have a question that is sort of a follow-up to something I asked previously ().

If you're referring to a fact that is still true in the present day, is it OK to switch to present tense in a subordinate clause after a main clause that is in the past tense? Here's the example I'm working with:

"The professor discovered that the rare plant possesses healing properties, which can be used in a variety of skin treatments."

As long as the plant still currently possesses healing properties and always will, is the switch to present tense correct here? Or do you think the following works better:

"The professor discovered that the rare plant possessed healing properties, which could be used in a variety of skin treatments."

I can't decide. the second example sounds slightly better to my ear but, logically, I think the first example must be correct.

Thank you to answers.