Stomatal and photosynthetic response of sweet gum (Liquidambarstyraciflua) to flooding

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Abstract
Effects of short-term flooding on stomatal conductance, net photosynthesis and water status of sweet gum seedling were studied under controlled environment conditions. Flooding for 9 days induced partial stomatal closure, resulting in significant declines in transpiration and net photosynthesis. The response to flooding was rapid with an average daily stomatal conductance declining from a preflood level of 0.43 cm .cntdot. s-1 to 0.26 cm .cntdot. s-1 by 24 h after flooding began (40% reduction). The average preflooding daily net photosynthesis was reduced from 13.7 to 10.2 .mu.g CO2 .cntdot. dm-2 (25% reduction) during the same period and the average daily stomatal conductance and net photosynthesis for the 9th day of flooding were reduced by 70 and 77%, respectively, compared with preflood levels. The leaf xylem pressure potential measurements, however, indicate that water deficit did not develop as a result of flooding. Partial stomatal reopening 3 days after termination of flooding was noted with an average daily stomatal conductance approaching 63% of the preflood levels and an averge daily net photosynthesis reaching 46% of its preflood levels. Maintenance of positive net photosynthesis throughout the flooding, and partial stomatal and photosynthetic recovery following drainage may account for the tolerance of sweet gum seedings to short-term flooding.