Plants in pair

Previously, humans did not know that plants too have male and female gender distinctions. Botany states that every plant has a male and female gender. Even the plants that are unisexual have distinct elements of both male and female.

But this fact is mentioned in the following quoted verse of the Holy Qur’an:

“And (He it is) Who sends down rain from the sky and thereby We bring forth various kinds of vegetation in pairs.”

[Al Qur’an 20:53]

Who could have know this when the Holy Qur'an was revealed?