text: Some species of Cuscuta use a type of this process that assesses the low red/far red ratios transmitted by their prey, while other species exhibit a form responsive to VOCs.
full_question: Some species of Cuscuta use a type of this process that assesses the low red/far red ratios transmitted by their prey, while other species exhibit a form responsive to VOCs. A type of this phenomenon is mediated by statoliths. Cholodny and Went modeled this process in coleoptiles, similar to an experiment by the Darwins. This phenomenon is contrasted with nastic movements. The touch-sensitive, or "thigmo-", type of this phenomenon occurs in tendrils. Some forms of this process involve asymmetric distribution of auxin, which inhibits cell expansion on the lower side of a root in a type sensitive to gravity. For 10 points, name this process in which plants directionally grow or turn in response to a stimulus such as light.
first_sentence: Some species of Cuscuta use a type of this process that assesses the low red/far red ratios transmitted by their prey, while other species exhibit a form responsive to VOCs.
raw_answer: tropism [or phototropism; or gravitropism; or chemotropism; or thigmotropism; prompt on directional growth until it is read]