The effect of
anoxia on the energy economy of root cells was studied by measuring heat production,
ethanol and
ATP production, K(+) fluxes and electrical activity in two Vitis species, V. riparia and V. rupestris, that differ in their tolerance to
anoxia.
Anoxia triggered a marked decrease of metabolic activity (measured by microcalorimetry) and of
ATP levels in both species. In V. riparia after the first 2 h of
anoxia, the decrease in the rate of heat production was not associated with a further significant decrease in
ATP content, whereas in V. rupestris the
ATP level continued to decrease until very low values were reached. The concomitant increase in the rate of
ethanol production did not compensate for the decreased aerobic
ATP supply. In V. rupestris,
anoxia typically led to energy deficit and
ATP imbalance, together with the subsequent disruption of ion homeostasis and cell death. In V. riparia, the strong decrease in K(+) membrane permeability together with the fast down-regulation of the electrical signals allowed the cells to avoid severe ion imbalances during prolonged anoxic episodes.