Plant graviperception and gravitropism: a newcomer's view.

Gravitropism is an adaptable mechanism corresponding to the directed growth by which plants orient in response to the gravity vector. The overall process is generally divided into three distinct stages: graviperception, gravitransduction, and asymmetric growth response. The phenomenology of these different steps has been described by using refined cell biology approaches combined with formal and molecular genetics. To date, it clearly appears that the cellular organization plays crucial roles in gravisensing and that gravitropism is genetically different between organs. Moreover, while interfering with other physical or chemical stimuli and sharing probably some common intermediary steps in the transduction pathway, gravity has its own perception and transduction systems. The intimate mechanisms involved in these processes have to be unveiled at the molecular level and their biological relevance addressed at the cellular and whole plant levels under normal and microgravitational conditions. gravitropism: a newcomer's view.