title: Introduction:  an overview of gravity sensing, perception, and signal transduction in animals and plants.
abstract: The antiquity of biological sensitivity and response to gravity can be traced through the ubiquity of morphology, mechanisms, and cellular events in gravity sensing biological systems in the most diverse species of both plants and animals.  Further, when we examine organisms at the cellular level to elucidate the molecular mechanism by which a gravitational signal is transduced into a biochemical response, the distinction between plants and animals becomes blurred.
authors.affiliation: Life Sciences Division, NASA Headquarters, Washington, DC 20546.
authors.forename: T W
authors.initials: TW
authors.lastname: Halstead
mesh_terms: D000818:Animals; D006112:Gravitation; D018522:Gravitropism / Q000502:physiology; D018466:Gravity Sensing / Q000502:physiology*; D010037:Otolithic Membrane / Q000502:physiology; D018521:Plant Physiological Phenomena; D018087:Plastids / Q000502:physiology; D012679:Sense Organs / Q000166:cytology / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*