from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Growth or orientation of a sessile organism, especially a plant, toward or away from the light of the sun.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The property of some plants of turning under the influence of light; either positively (towards the light) or negatively (away from the light)
from the GNU version of the Collaborative International Dictionary of English
- n. The phenomenon of turning toward the light, seen in many leaves and flowers.
from The Century Dictionary and Cyclopedia
- n. In botany, the tendency of growing organs to bend toward or in some cases away from the light, due in the former case to the retarding influence exerted by the light upon their growth on the side of the highest illumination.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. an orienting response to the sun
helio- + tropism (Wiktionary)