Amyloplast movement in living statocytes

Much evidence implicates amyloplast movement in plant graviperception. How this signal is transduced into a differential growth response is not known. Studies using fixed tissue are useful for deriving mean sedimentation rates, but cannot yield data on: the movement of individual amyloplasts, the role of cytoplasmic streaming, and the initial dynamic events occurring during the presentation time. These limitations were overcome by examining living tissue sections with a horizontally mounted microscope connected to a video camera and recorder. The kinetics of the early response to reorientation are consistent with the hypothesis that amyloplasts act by contact with a sensitive surface near the lower wall and indicate that cytoplasmic streaming provides an important vector in amyloplast redistribution in response to gravity.