本研究以三年生無患子（Sapindus mukorossi）實生苗為材料，藉控制不同土壤含 水率（Relative soil water contents, RWC）模擬水分充足（31.32 %）、暫時凋萎點（12.97 %）及永久凋萎點（4.96 %）等三種土壤水分狀況作幼苗生長及光合作用特性的研究。試 驗期間三種處理苗木全數存活，缺水的苗木生長較差，但根莖葉生物量分配無顯著變化， 另表現出羽狀複葉之小葉對天頂夾角顯著增加。內部變化則有葉綠素含量顯著上升、構成 類囊體之醣脂質單半乳糖二苷脂（MGDG）減少及雙半乳糖二苷脂（DGDG）增加；生理 方面發現各處理間的葉綠素螢光之Fv/Fm值無顯著變化，均維持在0.82左右，但非光化學 消散（NPQ）則顯著上升；光合氣體交換速率測定顯示無患子苗木缺水時光合作用能力及 氣孔導度下降，但光量子收率上升，水分利用率也提高。試驗結果顯示無患子苗木能於嚴 重乾旱時減少水分消耗、保護光合系統並維持生長，其耐旱力強有助於生存於乾旱環境。

This study aimed to explore the photosynthetic physiological properties of threeyear- old Sapindus mukorossi seedlings under three moisture treatments with relative soil water contents (RWC) to simulate degree of drought: sufficient water supply (RWC 31.32 %), temporary wilting point (RWC 12.97 %) and permanent wilting point (RWC 4.96 %). S. mukorossi seedlings could survive on each water treatment, except the increment and pinnule angle. There was no obvious difference in the morphological change and biomass allocation. The internal changes including increased leaf pigments, decreased thylakoid membrane glycolipids monogalactosyldiacylglycerol (MGDG) and increased digalactosyldiacylglycerol (DGDG). The measure of chlorophyll fluorescence showed that Fv/Fm remained around 0.82, without significant differences between all S. mukorossi seedlings, but non-photochemical quenching (NPQ) had significant increase in drought treatment. S. mukorossi seedlings with drought treatment displayed lower photosynthetic capacity and stomatal conductance as displayed by photosynthesis gas exchange, but higher quantum yield and water use efficiency (WUE). The result indicated that S. mukorossi seedlings could reduce water consumption, protect photosynthetic systems and maintain growth under drought deficit.