They play a role as trace elements. A lot of these elements are blocking in nature: other parts of the organism's metabolism are a function of the availability

They play a role as trace elements. A lot of these elements are blocking in nature: other parts of the organism's metabolism are a function of the availability of trace elements. As an example, Molybdenum was found to put a ceiling on CO2 uptake in certain Orchidaceae. So if you run an orchid nursery and want to reduce your IV-to-flower time by providing more CO2 you need to also provide adequate amounts of trace elements. You could compare it to adding Iodium to table salt in order to keep the population's fertility high.