Weight, morphology, P and starch content, and anaerobic and N metabolism of roots of loblolly pines grown from seed for 2 yr in drained (D), seasonally flooded (SF) and continuosly flooded (CF) soils, with and without P fertilizer (P1 and P0, respectively) were compared. Root development was best in SF and poorest in CF, and was improved by P1 in all water table treatments. Rates of anaerobic metabolism were greatest in root tips from seedlings grown in CF, and root tips of CF-P1 had higher rates of ethanol and malate production than those of CF-P0. Relative contents of glutamic acid, .gamma.-aminobutyric acid, asparagine, and alanine in xylem sap increased with flooding. These findings and other existing knowledge suggest that loblolly pine roots are capable of accelerated glycolysis under anaerobic or waterlogged soil conditions and that some C breakdown processes are shunted from ethanol production to synthesis of nontoxic products. Enhancement of the energy status of pine roots by P may be a factor in the fertilizer responses commonly obtained on wet or poorly drained soils of the southeastern USA coastal plains.