Physiological responses of spinach leaves to low oxygen conditions: a very preliminary study

The study of anoxia tolerance has been generally performed on roots rather than on leaves. We are investigating the physiologycal effects on spinach leaves of root anoxia. Ethanol concentration does not show a significant variation after the onset of anoxic condition, nor any increase for all the 12h long experiment; on the contrary, a higher accumulation (up to 0,2 mg/g FW) of lactate occurs. The anoxic stress determines an early 4-fold increase of ADH activity, then it assesses about 2 times higher than control for the rest of the treatment. LDH activity rises only a little under anoxia. It seems not to be a tight correlation between enzymes activity and their own metabolites: the release of volatile end-products of anaerobic metabolism via the shoot, and the so high ADH activity, should have contributed most to ethanol accumulation in leaves. We wonder if the diffusion through the leaf tissue might be responsible of the low ethanol concentration measured. We are working on the isolation of ADH and LDH genes, and related coding sequences, in order to verify at molecular level the regulation of the protein synthesis under anoxic and hypoxic stress.