Responses of Cherrybark Oak Seedlings to Short-Term Flooding

Effects of short-term flooding on water status, stomatal conductance and net photosynthesis of cherrybark oak ( Quercus falcata var. pagodaefolia Ell.) seedlings were studied under controlled environment conditions. Flooding for 6 days induced significant stomatal closure, reduced transpiration, and reduced net photosynthesis. The response to flooding was almost immediate with maximum and average daily values of transpiration, stomatal conductance, and net photosynthesis reduced sharply within one day following flooding. Average diurnal stomatal conductance declined from 0.44 cm s -1 to 0.32 cm s -1 at 24 hours and to 0.23 cm s -1 at 48 hours after flooding began, while average diurnal net photosynthesis was reduced from 6.85 mg CO 2 dm -2 h -1 to 3.07 and 0.86 mg CO 2 dm -2 h -1 at 24 and 48 hours after flooding, respectively. Low levels of stomatal conductance and net photosynthesis continued throughout the entire experiment and average daily net photosynthesis fell below zero for the fourth through sixth days of flooding. Leaf xylem pressure potential measurements, however, suggested that water deficits did not develop as a result of flooding. The recovery of stomatal functioning during the 3 days after termination of flooding was relatively slow. Rapid stomatal closure and significant declines in net photosynthesis are probably important factors contributing to the intolerance of cherrybark oak seedlings to flooding. Forest Sci. 31:760-771.