【摘要】 选取乌心石、肖楠及大叶楠三种台湾中低海拔乡土树种之二年生苗木为供试材料 ,测定植物对主要环境因子变化之反应 ,并特别对经干旱驯化后植物之形态与生理之反应 ,及连续缺水情形下植物叶片萤光测值之变化进行探讨。对不同光度的反应结果得知 ,乌心石及肖楠在光度 30 0 μmol· m- 2 s- 1时 ,其净光合成率仍为光度 70 0 μm ol· m- 2 s- 1时之 96 %及 92 .7% ,显示其较能适应于低光度下 ,较具耐荫性。三种苗木之光合最适温度 ,乌心石与肖楠约为 30℃ ,而大叶楠约为 32℃ ,均属一般热带 C3型植物之特性。经三个月干旱驯化后之苗木树高增量及地径增量均明显低于对照组 ,而肖楠及乌心石驯化组植物根茎比及比叶重亦有明显增加情形 ,表现出形态上适应干旱的现象 ,而较具耐旱性。驯化处理后之苗木在断水过程中均能在较高的水分应力下维持较高的光合成率 ,呈现较强的耐旱性。而肖楠驯化组之气孔导度明显低于对照组 ,显示肖楠对缺水逆境产生适应 ,能避免因过多失水而造成生理障碍。细胞间隙二氧化碳浓度与外界二氧化碳浓度比值 (Ci/Ca)值变化得知 ,三种苗木驯化组测值均小于对照组 ,显示历经驯化后植株有增加其气孔因子影响光合成率的现象。虽然遭遇水分逆境 ,使其光合成率下降 ,但驯化组苗木仍能维持较高的用?更多还原

【Abstract】 Three native trees,Formosan Michelia,Taiwan Incense cedar and Large leaved Nanmu,were chosen to test their physiological responses to different environmental stresses, including drought stress. Responses of photosynthetic gas exchange and chlorophyll fluorescence following drought acclimation were measured to understand the adaptative responses to water stress.According to the photosynthetic responses to irradiance,Formosan Michelia and Taiwan Incense cedar had higher photosynthetic rates at low light intensity than Large leaved Nanmu.In addition, Large leaved Nanmu was more sensitive to light intensity.The photosynthesis optimum temperature was 30℃ for Formosan Michelia and Taiwan Incense cedar and 32℃ for Large leaved Nanmu.After three months of the drought acclimation treatment,trees of Taiwan Incense cedar and Formosan Michelia were better able to acclimate in morphology including height,ground diameter,root shoot ratio and specific leaf weight.During water withholding treatment, acclimated trees that displayed higher photosynthetic capacity under high soil water potential were more drought resistant.The Ci/Ca ratios of acclimated trees were lower than those of controls.This implied that stomatal regulation of photosynthesis in acclimated trees was important in controlling the photosynthetic rate.The leaf conductance of acclimated Taiwan Incense cedar was lower than the controlable which showed a greater adaptive response to water stress.更多还原