ATP involvement in plant tissue responses to low temperature

The effects of chilling and freezing temperature on membrane permeability and ATP content were studied in the leaves of cucumber (Cucumis sativus L.) and winter rape (Brassica napus L. var. oleifera L.) leaves, grown at different temperatures. In the winter rape leaves, the endogenous ATP content was modified by application of dinitrophenol (DNP) solutions of different concentrations. The low temperature‐induced changes in membrane permeability (as monitored by the conductivity method) were found to be associated with ATP decrease, both in the chilling‐sensitive and chilling‐resistant (subjected to freezing) plants. In tissues showing reversible injuries, changes in ATP content preceded those in membrane permeability and the adenylate energy charge was affected slightly. In tissues showing irreversible membrane damage, the ATP content was always below 0.4 μmol (g dry weight)−1 and the adenylate energy charge was near 0.5. DNP treatment increased freezing sensitivity of winter rape leaves. In the cold‐hardened winter rape leaves, however, freezing and thawing did not significantly affect ATP content or the energy charge, although the specimen showed a rather large increase in membrane permeability. In these leaves ATP content recovered about 20 h after a freezing and thawing treatment. It is proposed that a decrease in ATP supply might be the primary reason for the membrane leakiness at low temperature, both in chilling‐sensitive and chilling‐resistant (subjected to freezing) plants. The conclusion is, however, not true for the cold‐acclimated, frostadapted cells.