Photosynthesis Idea

1) For I. nobilis, the majority of mature leaves appear functionally dead. The leaves are completely covered in epiphylls and discolored where the lamina does poke through. Jim talked about this at some point with respect to big fat Garcinia leaves at Fortuna. Why don't the trees drop these leaves? Are these leaves serving as a storage reserve of nutrients? Or is there more photosynthesis occurring than I would suspect? I should look into papers that compare the photosynthetic rate of young versus old leaves. Maybe it could be an interesting side project to test this on one of my species across soil environments -- I would hypothesize that the relative difference in photosynthetic rates between young and old leaves would be greater on more infertile soils where there is a greater advantage in maintaining a photosynthetically dead nutrient reservoir. Also, I should consider focusing my defoliation on newer leaves, because removing the old leaves might not evoke a re-foliation response if these leaves are not contributing carbon to the plant.