Phototropism
/foh-TOT-roh-pizm/🔬 Anatomy●● Intermediate
Also known as: light response, heliotropism
The growth response of a plant to light direction. Positive phototropism (growth toward light) occurs in stems and is mediated by the plant hormone auxin, which accumulates on the shaded side, causing cells there to elongate faster. Negative phototropism (growth away from light) occurs in some roots. Phototropism explains why houseplants lean toward windows and why seedlings grow toward artificial lights. Regular rotation prevents lopsided growth.
Etymology
Greek phōs (light) + tropos (turning)
Example
“Rotate your houseplants a quarter turn each week to prevent phototropism from causing them to lean toward the window.”