plagiotropism

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Growth of a plant part at an oblique angle to a stimulus, such as gravity.

from The Century Dictionary.

• noun In botany, oblique geotropism; a turning by which the organs of certain plants have their long axes more or less divergent from the vertical—that is, across the direction of gravitation or of the ray of light. Compare or-thotropism.