EFFECTS OF ANOXIA ON WHEAT SEEDLINGS .1. INTERACTION BETWEEN ANOXIA AND OTHER ENVIRONMENTAL-FACTORS

Anoxia was imposed on 4-6-d-old, intact wheat seedlings, after the roots had first been exposed for 1 d to O2 concentrations between 0.016 and 0.06 mol m-3. Apices of the main axis of the seminal roots were considered to have tolerated anoxia if elongation occurred after return from anoxia to air, hereafter called 'retention of elongation potential'. During anoxia, elongation potential was retained longer in roots of intact seedlings than in 0-5 mm excised root tips supplied with 50 mol m-3 glucose. In intact seedlings, elongation potential was retained longer at 15-degrees-C than at 25-degrees-C, and at pH 5.0 and 6.0 than at pH 4.0. These differences between treatments were maintained in the presence of exogenous glucose, and glucose supply prolonged the retention of elongation potential in all anoxic treatments. Elongation potential was retained much longer at very low O2 concentrations (0.006 to 0.01 mol m-3) than under anoxia; this was established at pH 4.0. Anoxia inhibited the transport of sugars from the shoots and/or endosperm to the root by 79-97%, as assessed from experiments with roots of intact plants exposed to anoxia at pH 6.0 and 15-degrees-C. Overall, the results demonstrate: (i) that the occurrence of adverse effects of anoxia during waterlogging in the field may interact with other environmental factors and (ii) that there are pronounced difficulties integrating data on tolerance to anoxia obtained in different laboratories.