低光培育之羅漢松屬苗木的氣體交換與葉綠素螢光特性

Characteristics of gas exchange and chlorophyll fluorescence of four Podocarpus species seedlings grown in low light environment

桃實百日青、叢花百日青、蘭嶼羅漢松及羅漢松在海拔與地理分布具明顯之差別。本研究目的在分析此四種葉形相似的羅漢松屬苗木，培育於5%相對光度之氣體交換與葉綠素螢光特性對光誘導的反應，以及其葉片色素與可溶性蛋白質含量，以了解四種苗木於林下低光環境生理反應之差異。結果顯示，四種苗木之光量子收率、光補償點、光飽和點、暗呼吸作用速率及葉綠素a/b 等，在樹種間無顯著差異。而飽和光合作用速率於樹種間有顯著差異，氣孔導度與光合作用速率間呈負相關、且Ci/Ca大於0.74，氣體交換之生理調適策略保守，氣孔非光合作用之限制因子。桃實百日青之光化學能力與rubisco活性低，但類胡蘿蔔素含量高，使其具非光化學消散能力應付可能出現的高光；叢花百日青葉綠素含量高、光合速率高，其特性與遺傳適應有關；蘭嶼羅漢松光化學能力高、非光化學消散低，而色素與可溶性蛋白質含量最低，但單位葉綠素之類胡蘿蔔素含量高，且光合速率高，推測其以最低之資源配置達生存目的。羅漢松之ETR高、光化學分配比例（P）高，非光化學消散可適度調節，色素與可溶性蛋白質含量均介於其他三者之間，可能有較佳之生理調節能力。因此，四種羅漢松屬苗木均具耐陰性，光合作用受非氣孔因素影響，其生理反應之調節方式略有差異。 Podocarpus nakaii (Pn), Podocarpus fasciculus (Pf), Podocarpus costalis (Pc), and Podocarpus macrophyllus (Pm) are distributed different altitudes and regions. The purpose of this study was to investigate the characteristics of gas exchange, chlorophyll fluorescence and the content of pigment and soluble protein in the four Podocarpus species seedlings with similar foliage form, and grown under 5% relative light intensity. Results were showed no differences in quantum yield of photosynthesis, light compensation point, light saturation point, dark respiration, and chl a/b for all species. Light-saturated photosynthetic rate was differences significantly among species. There was negative correlation between photosynthetic rate and stomatal conductance (gs), and Ci/Ca was greater than 0.74. Adjustment strategies of gas exchange were conservative. gs was not the limiting factor of photosynthesis. Pn was lower photochemical capacity and rubisco activity, greater carotenoids content, coped sudden light through nonphotochemical quenching. Pf was greater chlorophyll content, higher photosynthetic rate, related to genetic adaption. Pc was greater photochemical capacity, less non-photochemical quenching, the least content of pigment and soluble protein, greater ratio of caro/chl a+b, to survival using less resource. Pm was greater ETR and P, appropriately adjusted non-photochemical quenching, medium content of pigment and soluble protein, could be better physiological regulation. The results showed that photosynthesis were affected by non-stomatal factors, shade-tolerant for all species, and physiological adjustments were slightly different.