Background : Heat stress induced from high temperature are known to crucially affecting on physiological properties and yield in Cnidium officinale. Methods and Results : The effect of foliar application of mixture including a urea, ascorbic acid and calcium chloride on high temperature injury of Cnidium officinale. Photosynthesis and leaf temperature in Cnidium officinale were investigated after cultivating for 24 hours at 35℃. Net photosyntheis rate, transpiration was measured at 1,000 μmol m-2 s-1 of photon flux density and leaf temperature was analyzed by thermal image. Net photosyntheis rate, stomatal conductance and transpiration rate in mixture traetment were 2 times of higher than in control. Water use efficience was not different significantly. Leaf temperature was lower in mixture treatment (25.3℃) than in control (29.0℃). Conclusion : This result show that foliar application of urea, ascorbic acid and calcium chloride was reducing a high temperature injury through a improving photosynthetical capacity and decreasing leaf temperature of Cnidium officinale.

Background : Management of air temperature are known to primarily affecting on physiological properties and yield in plant. Methods and Results : The effect of air temperature on characteristics of photosynthesis and chlorophyll fluorescence in Cnidium officinal were investigated using growth chamber after cultivating for 24 hours under controlled condition. Net photosyntheis rate, transpiration was measured at 1,000 μmol m-2 s-1 of photon flux density and chlorophyll fluorescence was analyzed by OJIP method. Net photosyntheis rate was highest in treatment of 25℃. Although transpiration rate was lowest, water use efficience was also in treatment of 25℃. Stomatal conductance was mainly influenced from ambient climatric factors such as vapor pressure deficit. As results of chlorophyll fluorescence by OJIP analysis, maximum quantum yield (Fv/Fm) of photosystem II (PSII), PIabs and the relative activities per reaction center such as ABS/RC, DIo/RC were not changed at air temperature. Therefore, elevated air temperatue during short term influence the dark reaction in photosystem through controlling a water use efficience and transpiration. Conclusion : This result show that 25℃ of air temperature may be a adequate temperature to improving the efficiency of photosynthesis in Cnidium officinale.