台灣常見數種作物、野草及林木之光合作用特性

Photosynthetic Characteristics of Several Crops, Wild Grasses and Woody Plants Grown in Taiwan

為瞭解台灣常見之林木、C3型作物、C4型作物及C4型野草等光合作用之特性，選用台灣常見的林木，包括常綠針葉樹－－紅檜（Chamaecyparis formasana）等17種。C3型作物－－番茄（Lycopersicon esculentum）等16種。C4型作物－－高粱（Sorghum bicolor）等11種，C4型野草－－鋪地草（Pannicum repens）等6種為材料。以上材料均種植於盆中，待植物生長繁茂後，以完全展開之最上位著生葉為對象，測定其最大光合速率，葉片導度及葉綠素含量，並探討藉較易測得之葉片導度（leaf conductance）及葉綠素含量，推估光合速率及其生態地位之可行性。茲將結果摘述於下：不同供試植物間其在飽和光度下之光合速率（Pmax）的差異相當大，林木為4-21µmol CO2 m-2s-1，C3型作物為10-23µmol CO2 m-2s-1，其平均值約為林木之1.8倍，C4型作物之Pmax最高，其平均值較C3型作物約高1.5倍，較林木高約3倍，C4型野草則較C4型作物低約10%。Pmax與光飽和點間之關係呈現極顯著及顯著正相關，依其相關可分為C3型、C4型植物兩群（相關係數分別為r = 0.872, P<0.001, r = 0.781, P<0.05）。在光飽和點相同時，C4型植物之Pmax較C3型植物平均約高出1.3倍，表示C4型植物具有高光飽和點及高光合成能力之特性。Pmax與葉片導度之關係呈極顯著正相關，其相關亦可分為C3型植物及C4型植物兩群（相關係數分別為r = 0.914, P<0.001, r = 0.738, P<0.01）。在相同葉片導度時，C4型植物較C3型植物之Pmax平均約大1.6倍。至於Pmax與葉綠素含量之關係，當葉綠素含量在2-10 mg dm-2之範圍內，C4型植物之Pmax與葉綠素含量呈顯著正相關，C3型作物與先驅樹種，其Pmax雖亦隨葉綠素含量之增加而增加，但其斜率遠小於C4型植物（l<3.425），而其他屬中生之C3型林木雖然其Pmax有隨葉綠素含量增加而升高之勢，但已趨於平緩，屬陰生樹種之鴨腳木，其葉綠素含量雖較高，但其Pmax卻仍低，與其分布之生態環境有關。從以上結果得知可由葉片導度推估植物之光合速率，而且依葉片導度及葉綠素含量與光合速率間之相關，可推估不同植物在生態上之地位。 17 widespread species of Taiwan woody plants such as Chamaecyparis formasana, 16 species or C3 crops i.e., Lycopersicon esculentum etc., 11 species of C4 crops i.e., Sorghum bicolor etc., 6 species of C4 wild grasses i.e., Pannicum repens etc., were selected as raw materials for the investigation of the photosynthetic characteristics of common wood species, C3 crops, C4 crops and C4 wild grasses. All vegetations were grown in controlled pols. We measured the maximum photosynthetic rate(Pmax). leaf conductance(gs) and chlorophyll content in the upper fully expanded leaves for each nourishing vegetation. We deduced the feasibility of the photosynthetic rate and its ecological niche by the above data as well. The experimental results are as follows: The photosynthetic rates differ significantly between plant sources under the illumination of saturated light i.e., 4-21µmol CO2 m-2s-1 for woody plants. 10-23µmol CO2 m-2s-1 for C3 crops, of which average is 1.8 times woody plants. C4 crops have the highest values, of which average is 1.5 times C3 crops, and 3 time woody plants. 10% lower of C4 wild grasses when comparing to C4 crops. There is a remarkably positive relationship between Pmax and light saturated point According to this relationship, the plant types can be classified as C3 and C4 plants, respectively (ANCOVA, correlation coefficient r=0.872. P<0.001; r=0.781. P<0.05). Pnmx value of C4 plants is 1.3 fold greater than C3 plants at the same light saturated point. It accounts for the higher light saturated point and photosynthesis capacity. There is significant correlation(r= 0.914. P<0.001. r=0.738. P<0.01) between Pmax and gs for C3 and C4 plants. C4 plant is 1.6 fold greater than C3 plant at the same gs. Significant correlation between chlorophyll content and Pmax has been shown for C4 plant. while the chlorophyll content is in the range 2-10 mg dm-2. Although a he Pmax value of C3 plant increases with the chlorophyll content, its s lope in a correlation figure is less than C4 plant (1 < 3.425). Furthermore, neutral woody species’ Pmax values increased with chlorophyll content, but they gave the level-off tendency after all. However. Shefflera octophylla-one kind of shade species with higher chlorophyll content gave lower Pmax value, which seemed relating 10 its ecological system. By using the measured data such as the gs to deduce the photosynthetic rate, the dependable gs and chlorophyll content relating to photosynthetic rate, the ecological niche of various plants can be predicted.

17 widespread species of Taiwan woody plants such as Chamaecyparis formasana, 16 species or C3 crops i.e., Lycopersicon esculentum etc., 11 species of C4 crops i.e., Sorghum bicolor etc., 6 species of C4 wild grasses i.e., Pannicum repens etc., were selected as raw materials for the investigation of the photosynthetic characteristics of common wood species, C3 crops, C4 crops and C4 wild grasses. All vegetations were grown in controlled pols. We measured the maximum photosynthetic rate(Pmax). leaf conductance(gs) and chlorophyll content in the upper fully expanded leaves for each nourishing vegetation. We deduced the feasibility of the photosynthetic rate and its ecological niche by the above data as well. The experimental results are as follows: The photosynthetic rates differ significantly between plant sources under the illumination of saturated light i.e., 4-21µmol CO2 m-2s-1 for woody plants. 10-23µmol CO2 m-2s-1 for C3 crops, of which average is 1.8 times woody plants. C4 crops have the highest values, of which average is 1.5 times C3 crops, and 3 time woody plants. 10% lower of C4 wild grasses when comparing to C4 crops. There is a remarkably positive relationship between Pmax and light saturated point According to this relationship, the plant types can be classified as C3 and C4 plants, respectively (ANCOVA, correlation coefficient r=0.872. P<0.001; r=0.781. P<0.05). Pnmx value of C4 plants is 1.3 fold greater than C3 plants at the same light saturated point. It accounts for the higher light saturated point and photosynthesis capacity. There is significant correlation(r= 0.914. P<0.001. r=0.738. P<0.01) between Pmax and gs for C3 and C4 plants. C4 plant is 1.6 fold greater than C3 plant at the same gs. Significant correlation between chlorophyll content and Pmax has been shown for C4 plant. while the chlorophyll content is in the range 2-10 mg dm-2. Although a he Pmax value of C3 plant increases with the chlorophyll content, its s lope in a correlation figure is less than C4 plant (1 < 3.425). Furthermore, neutral woody species’ Pmax values increased with chlorophyll content, but they gave the level-off tendency after all. However. Shefflera octophylla-one kind of shade species with higher chlorophyll content gave lower Pmax value, which seemed relating 10 its ecological system. By using the measured data such as the gs to deduce the photosynthetic rate, the dependable gs and chlorophyll content relating to photosynthetic rate, the ecological niche of various plants can be predicted.