Photosynthetic and Physiological Characteristics of the EvergreenLigustrum japonicumand the DeciduousCornus officinalis

초록

The evergreen, broad-leaved,Ligustrum japonicumand the deciduousCornus officinalisare distributed in the central and southern parts of Korea and are widely used as landscape plants. In this study, we observed changes in the physiological characteristics of the two species across seasons by observing the changes in leaf photosynthesis; chlorophyll fluorescence; chlorophyll, carotenoid, and carbohydrate contents, osmolality and total ions. With a low soil moisture content due to low rainfall in June, the deciduousC. officinalisshowed a 0.3 mmol m(-2) s(-1)stomatal conductance and open stomata allowing for photosynthesis. However, the evergreenL. japonicumshowed a 0 mmol m(-2) s(-1)stomatal conductance and almost completely closed stomata, indicating a high water use efficiency.Cornus officinalisexhibited a higher leaf net photosynthetic rate (P-N), stomatal conductance (gs), transpiration (E), and carbon fixation efficiency (CE) thanL. japonicumin all months except for November at which time its leaves fell from senescence. In winter,L. japonicumshowed a dramatic decrease in its photosynthetic rate andF(v)/F(m)ratio under conditions of lower than average air temperature and soil moisture; furthermore, it showed a high ratio of the photochemical quantum yield Y(NO) and almost no photosynthetic activity despite it having leaves.Ligustrum japonicumappears to be tolerant to water stress and low temperature by a maintenance of osmosis through the increase and accumulation of soluble carbohydrates in winter. In conclusion, the two species showed different physiological characteristics under a water stress environment.

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