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Apical segments from maize roots of LG 11 and Orla 264 varieties georeacted, at least for the first few hours, only in light, while those of the Anjou 210 variety were georeactive both in light and darkness. The energy charge in the apical end of the two light geo-sensitive (LG and Orla) maize roots significantly increased in the light. In contrast, in Anjou root tips, the energy charge was already high in the dark and did not change significantly after light exposure. The time course of light-induced changes in adenine nucleotide contents in root tips was compared with varietal differences in georeactivity in light and darkness. The present data corroborate the hypothesis that a high energy state in the root tip is a prerequisite for the expression of the root reaction to gravity.

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