水筆仔苗木於不同鹽度處理下光合誘導反應之探討

A study on photosynthetic induction of Kandelia obovata seedlings under different salinity treatments……Ching-Wen Wang, Shau-Lian Wong,

本研究以倒卵葉水筆仔（Kandelia obovata Sheue, Liu & Yong）為對象，以5種鹽度處理後量測其氣體交換與葉綠素螢光參數，探討其光合作用之光誘導（photoinduction）特性。結果顯示倒卵葉水筆仔生理表現在10-30‰鹽度範圍較佳，其光合光誘導特性為：1.光照時間：光照初期的30 min內，光合作用速率較低，氣孔亦同，此時段吸收之輻射能量（radiation energy）以非光化學消散（nonphotochemical quenching, NPQ）為主要路徑，本階段屬非氣孔性因素，光照持續到30-90 min時，光合作用速率才逐步提升，此時氣孔開度亦同步提升，吸收之輻射能量流向以光化學消散為主，本時期屬氣孔因素|2.光照強度：在低光源（0-800µmol photon m-2 s-1）時，倒卵葉水筆仔的光合生理行為以非光化學消散為策略，待光量達800-2,000µmol photon m-2 s-1階段時，仍持續調升非光化學消散，呈現隨著光度增強不斷調節的機制，且於光量>1,500µmol photon m-2 s-1階段時，光合作用速率有下降的現象，顯示倒卵葉水筆仔為適應光環境動態變化所做的生理調節|3.依輻射能量利用分析結果，顯示倒卵葉水筆仔生理表現在10-30‰鹽度範圍較佳，其光誘導機制是為適應生長環境鹽度及光量動態變化，發展出光保護（photoprotection）型態的光合生理行為。

In this study, Kandelia obovata seedlings were used to measure the gas exchange and chlorophyll fluorescence parameters of K. obovata under five salt gradients treatments to evaluate the photoinductive characteristic of photosynthesis. The results showed that photoinductive characteristics of the K. obovata seedlings were affected by the irradiation time and intensity. 1. Irradiation time: In the first 30 minutes of irradiation, the photosynthesis rate and stomata were not activated. The radiation energy absorbed in this period was mainly dissipated by non-photochemical quenching. This stage was affected by non-stomatal factors. When the irradiation lasted for 30-90 minutes, the photosynthesis rate gradually increased. At this time, the opening of the stomata also increased synchronously. The absorbed radiation energy was processed mainly by photochemical quenching. This stage was affected by the stomatal factor. 2. Irradiation intensity: Under variable irradiation sources (0-2,000µmol photon m-2 s-1) , the photosynthetic physiological responses of K. obovata was mainly processed by a non-photochemical quenching strategy, which showed a mechanism that continuously adjusted as the irradiation intensity increased. At irradiation above 1,500µmol photon m-2 s-1, the rate of photosynthesis decreased. This response indicated that the physiological regulation of K. obovata adapted to the dynamic changes of the light environment. 3. The results of the radiation energy utilization analysis showed that the K. obovata was suitable for growing in the salinity range between 10‰to 30‰. The photoinductive mechanism was adjusted to adapt to the salinity of the growing environment and the dynamic changes of irradiation, and developed photosynthetic physiological behaviors of photoprotection accordingly.