Abstract
In higher plants, it has been known that roots and shoots show positive and negative gravitropism, respectively. However, whether leaves show gravitropism or not is unclear.
To examine the gravitropism of leaves, we analyzed the motion of rosette leaves of Arabidopsis thaliana after changing the direction of gravity. Under continuous light, direction of the expansion of rosette leaves was dependent on the shoot axis, whereas leaves moved in short time in gravity-dependent manner under dark, suggesting the interaction of light signal and gravity on the direction of leaf expansion. In petiole, amyloplasts, which are believed to act statolithe for gravity, were found only in the basal end of a particular cell layer, and sedimented according to the direction of gravity. Based on these data, nature of gravitropism in leaves will be discussed.
