What is the purpose of THC to marijuana plants? lt doesn’t kill plant pests. ‘fit the plant produces it for a reason.
I submit that it is to protect against ultraviolet radiation. lt is found more prominently in flowering females because they have a high investment in seed production and they use it to protect against Ultra violet (UV) light. This is why plants produce more THC at higher altitudes and at or near the equator.
If THC is a good UV blocker could sunblockers be formulated using these properties? I can even imagine that the molecule may have some sort of antiaging properties.
THC and the other cannabinoids have quite a few protective qualities. It is a bacteriological and has some anti-fungal action as well. The physical quality of the resin and its placement in glands protruding from the leaf and flower tissue protects acts as fly-paper, capturing some small pests in its stickiness. The cannabinoids have a profound affect on birds and mammals that might eat the substances producing an intoxication that they may not find pleasant.
Although they are not cannabinoids, marijuana’s odor causing substances, mono and di-terpines, also provide marijuana with protection from predators. Some animals find its odor repulsive or learn to associate it with an unpleasant experience.
The quality that you describe, protecting the plant and developing seed from UV light, may also be helpful to the plant. In a controlled experiment, high quality marijuana plants were grown under identical conditions except that some were provided with UV light while others didn’t receive it. The buds from plants receiving the UVB light had higher percentages of THC. This is an indication that the plant is using it as a protectant.
THC or a derivative from its chemistry should be studied to see if it does afford UVB protection and if it is a viable means of providing it.