A follow up question for What is the method to produce food within a volcano caldera?
How can a plant harness magma's heat to "photosynthesize"? It is very different from an animal, which can move freely. The plant should have a different mechanism to harness the heat, then store the harnessed energy. Bonus points to answers that can reasonably provide how and where (in the plant, I suppose?) to store that energy. I don't know if "starch stockpiling" will be applicable to this plant.
Of course, the plant is fire and heat-resistant in all parts due to the iron-carbon composite (or whatever, but it is basically a fireproof mostly-carbon based).
My initial idea is to have roots that stretch to magma in one side, and to water or cooler earth on another side (I read somewhere that you must use alternating hot and cool parts to harness energy from geothermal, but that's as far as I understand).
This question graduated from the Sandbox.