倒卵葉水筆仔與紅海欖苗木於高鹽度和淹水處理下光合作用之探討

Study on Photosynthesis of Kandelia obovata and Rhizophora stylosa Seedlings under High Salinity and Flooding Treatments

本研究量測倒卵葉水筆仔 （Kandelia obovata Sheue, Liu & Yong） 與紅海欖 （Rhizophora stylosa, Griffith） 在10與40‰ 鹽度與淹水處理後其葉片之氣體交換與葉綠素螢光參數，探討其 光合作用特性。結果顯示倒卵葉水筆仔光合作用速率受到光照時間影響，光照初期的30 分鐘 內，光合作用速率幾乎未啟動，氣孔導度亦低，此時段吸收之能量以熱消散為主要路徑，光 照持續30分鐘後，光合作用速率才逐漸增加，吸收之能量仍以熱消散為主，熱消散比例並沒 有隨著光合作用速率上升而下降，呈現隨著光照時間延長而向上調節，這現象顯示倒卵葉水 筆仔因應光環境動態變化所做的生理調節；倒卵葉水筆仔在淹水處理下光化學效能加強，且 能減少照光後光抑制的比例與提高（qE+qT）/NPQ比值，與未淹水處理者呈現顯著差異，顯示 水筆仔在40‰ 鹽度下能適應淹水環境，相對調升光保護的能力，表示其能適應間歇性淹水、 且具光保護機制。而紅海欖在40‰ 鹽度下栽植時，無論淹水或沒淹水，光合作用速率和光化 學消散效率都很低，吸收之能量以熱消散為主要路徑，且有顯著之光抑制現象，顯示紅海欖 不耐40‰ 之鹽度處理。

Kandelia obovata and Rhizophora stylosa were used as study materials in this study. The gas exchange and chlorophyll fluorescence parameters were measured under salinity (10‰ and 40‰) and flooding treatments to explore the photosynthetic characteristics. The results show that the photosynthesis rate of the Kandelia obovata varied with the duration of irradiation. During the initial 30 minutes of irradiation, the photosynthetic rate was almost not activated, and the stomatal conductance was also low. The energy absorbed by its leaves during this period is processed mainly through heat dissipation. After 30 minutes of irradiation, the photosynthetic rate gradually increased, but most of absorbed energy was still dissipated through heat. This phenomenon suggests that Kandelia obovata adjusts the physiological behavior in response to the dynamic changes of the irradiation. In response to flooding, K. obovate develops positive energy utilization and photoprotection patterns. Kandelia obovata is more suitable for growing in environment with intermittent flooding. Rhizophora stylosa cultured at 40‰ of salinity under flooding or no flooding treatments had low photosynthetic rate, low photochemical quenching and the energy absorbed was dissipated mainly through heat. Severe photoinhibiton was also found in Rhizophora stylosa cultured at 40‰ of salinity. The results suggest that R. stylosa is not resistant to flooding under 40‰ of salinity.