Gravity is perceived by the cell, possibly by the sinking of \____________. This mechanical signal is transduced into a physiological signal in the gravity-sensing cell, and then the signal is sent to other cells, with the hormone auxin playing a role. Differential cell \___________ occurs, affecting cells in the "up" and "down" sides of the root or shoot and causing it to curve in the appropriate direction. Roots are positivelygravitrophic, while shoots are negatively so.