Leaf conductance (g), net photosynthetic carbon fixation rate (Pyi), leaf protein concentration and ribulose-l,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity were examined in baldcypress {Taxodium distichum L.) seedlings subjected to rhizosphere hypoxia. Seedlings grown in nutrient solution were treated with either air or N2. Changes in g. Pyj, leaf protein concentrations and RuBPCO activity in response to the treatments were measured at 12, 24, and 48 h. In a second experiment, similar measurements were conducted on plants grown in soil medium under either flooded or drained conditions over a period of 28 d. Under rhizosphere hypoxia, both g and Pyj were reduced significantly at 24 and 48 h as compared to control plants while there were no significant differences in leaf protein concentrations between treatments. RuBPCO activity, however, was reduced significantly (27 % reduction) at 48 h. In flooding experiment, g and decreased on days 3, 5, and 10 significantly. RuBPCO activity was significantly lower in flooded plants as compared to control (aerated) plants on day 3 and 5 following initiation of flooding. bi this experiment, g and began to improve after day 10, to as much as 97 and 87 % of control by day 28, respectively. RuBPCO activity which had decreased significantly by day 3, remained significantly lower on day 5 and slightly (but not significantly) lower than in control plants during the remainder of the experiment. Present data support the hypothesis that in baldcypress seedlings, reduced RuBPCO activity is among the early signals of flood-stress contributing to the loss of leaf Pyj. In addition, plant acclimated to the stress conditions during the long-term experiment indicating that some flood-tolerant tree species such as baldcypress may occupy wet sites due to such capabilities.