Tall and airy/ short and dense are characteristics associated with sativa/indica but not the defining factors. Leaf stomata are how you determine genus. Stomata are pores on the leaf that open and close. They draw in CO2 while releasing O2 and water vapor. Indica have fewer and smaller stomata to retain water. Sativa have many and larger stomata to expel water. It isn't a better wax coating keeping water out. It is the ability to shed excess water quickly after the rain stops. Towels left in a bucket of water for days will not mold. If you spread one out on a cloths line and wad the other up on the floor which will mold? You need saturation and air over time to grow mold. Remove saturation in a shorter time, mold can't grow.
I grow equatorial sativas. prune for air flow, and grew on the prevailing windward side of hills. Did that for 20 years without any mold issues. The plant that did mold was one I forgot I planted. The suburbs pushed out to me so I moved indoors almost 20 years ago.
Terpenes are essential oils that can be effective against mold and spores. Cannabis stores it's terpenes in the trichomes. When the mold eats into the trichomes they spill open killing the active mold and some of the spores. Great for the plant because it protects the seeds. Saving the plant at the expense of the trichomes kind of defeats our purpose of growing them.
