I'm trying to remember about how plants that are phototropic (+ or -) move. Are they using cellular turgor (sp?) pressure? For example when my Phalenopsis grow leaves, the new leaf is very phototropic, I must rotate the plant every 2-3 days to try and keep the leaves facing up (purely for personal esthetic reasons). Once fully grown the leaf is no longer phototropic, why is that? Some plants actually follow the sun on a daily basis, are they using the same mechanics?