The release of oxygen might be helpful to some.
Oxygen is nothing special. If higher oxygen levels promoted healing and immunity, they could just add it to hospital air from tanks.
Pollen? Not to many allergy sufferers.
I think pollen allergies are misunderstood. People who are sensitized to pollen by underexposure are probably more vulnerable to viruses as well.
Seeing plants chopped down, subdued and subjected to an early death could seriously sadden people....which, I suppose would add to more tears at the funeral. (As could the pollen)
I agree that it's sad to see plants cut and killed, and it's a waste when the same plants could go on living and flowering for longer. Some flowers can be cut without hurting the plant/tree, if it is done right.
I think the best thing is when hospitals/nursing homes/etc. have living trees and gardens built into their architecture. Those that don't should add them.
But I think more pollen exposure could be good, even if people have to go through some allergic reactions to build up immunity. "No pain no gain," as they say, but more research should be done on otherwise healthy allergy sufferers to see how their immune systems, mucus membranes, etc. change after systematic exposure to pollen lessens their allergic reaction to it.
I think that pollen could help strengthen immune systems and mucus membranes and neutralize viruses by sticking to them and preventing them from sticking to and infecting cells.
I'm not sure exactly how to research this, but you could probably examine mucus membranes to see how they interact with viruses as well as pollen and other particles, such as industrial dusts and other air-pollution.
We see all these photos of coronavirus now, and pollen looks similar, but we could be learning more about how these microscopic particles function and interact in the various environments they inhabit, such as our mucus membranes.