Pathfinder, Adenocaulon Bicolor

Day 225: Pathfinder is a plant familiar to hikers in the Pacific Northwest even if they don't know what it's called or why it earned that name. Also known as Trail Plant, Adenocaulon bicolor's leaves are green on the upper surface, but silvery-grey on the underside. The stems are quite resilient and flexible, and when something (human or animal) passes through a group of the plants, it is easy to see the route they took from the turned-over leaves. This much is common knowledge, but a larger question arises: what evolutionary advantage does this give the plant? I like to ask the hard questions, so I turned to Arnie first, and then went prowling in the depths of obscure research papers to see if I could find the answer. In so doing, I learned that Pathfinder is a "sun-fleck" species (a fact I had not known previously, and should have observed). It lives where illumination comes as brief packets of light which only penetrate the upper canopy sporadically throughout the day, the plant returned to shadow as the sun passes through its arc above the trees. The silvery underside is due to certain types of crystalline structures within the cells. These serve to back-scatter the light into the plant's internal cell layers, increasing its ability to photosynthesize. I was unable to locate information regarding what type of crystals these might be, although in some other silvery-blotched plants, the colouration is due to calcium oxalate, but nothing I read referred to it as being contained in Adenocaulon.

During my reading, Arnie had answered my email, and his response prompted me to share what I had discovered. He said, "The truthful answer is, 'I don’t know.'  I thought about making up a good story, but inspiration is letting me down this morning." I probably would have bought it, too. I mean, he is the expert.