Effect of the light on adenine nucleotide content of georeacting maize roots

Apical segments from maize roots of LG 11 and Orla 264 varietiesgeoreacted, at least for the first few hours, only in light,while those of the Anjou 210 variety were georeactive both inlight and darkness. The energy charge in the apical end of thetwo light geo-sensitive (LG and Orla) maize roots significantlyincreased in the light. In contrast, in Anjou root tips, theenergy charge was already high in the dark and did not changesignificantly after light exposure. The time course of light-inducedchanges in adenine nucleotide contents in root tips was comparedwith varietal differences in georeactivity in light and darkness.The present data corroborate the hypothesis that a high energystate in the root tip is a prerequisite for the expression ofthe root reaction to gravity. (Received October 17, 1978; )