Hi Aatish! I enjoyed it quite a bit. The fibers on the bottom of the leaf may not be significant -- perhaps they are vestigial and only the upper ones provide an advantage.
Alternatively, heavy rain and wind can flip leaves upside down, blow plants over, and splash dirt and water up onto the underside of the leaves, so maybe it is an advantage for the whole leaf to shed water.
Sweet. Hi! This is an odd place to bump into you. :)
I agree with your thoughts that this could be a consequence of coating the top surface in the waxy needles. However, I think it's actually somewhat unusual for a leaf to be superhydrophobic on the top and bottom, so I was wondering if there was some specific advantage to this leaf. Also, the needles on the under-side seemed far more dense than those on top, which was interesting.
Alternatively, heavy rain and wind can flip leaves upside down, blow plants over, and splash dirt and water up onto the underside of the leaves, so maybe it is an advantage for the whole leaf to shed water.