he has not mentioned that in my recollection. it does make sense, though, appearing to obey nature. there must be a cycle - one of the types and shadows in the bible of people is trees. jesus healed a blind man once and it happened in two stages - the first being where he said he saw people walking about as trees. jude refers to people who twist gods word as fruitless trees, twice dead and uprooted.
the tree draws up moisture and nutrients from the ground in the spring and then reverses the process in the fall. sitting and standing are for the day and lying down is for night. there could be something to it. i know i feel really good squishing the mud along the lake between my toes, but i could not tell you if i am having toxins drawn out or soaking up nutrients and energies. perhaps both at those times.