二氧化碳濃度和氮肥對樟樹苗木生長與光合作用之影響

Effects of Carbon Dioxide and Nitrogen on the Growth and Photosynthesis of Cinnamomum Camphor Seedlings

樟樹苗木在常態與提高二氧化碳濃度（350, 700 μL L-1）及不同氮肥（112, 224, 448,　896 ppm）施用下，經12 週之培育後，顯示生長在常態二氧化碳濃度下之樟樹苗，以施用如Hoagland solution 之224 ppm 氮肥者最適合，太低或太高皆不宜。至於生長在提高二氧化碳濃度者，則顯現出隨施用濃度的增加而增加，以896 ppm 有顯著的促進效果。此結果顯示生長在提高二氧化碳濃度下，供應超過Hoagland solution 之標準氮肥濃度，非但不會抑制生長，反具促進效果。生長於700 μL L-1之二氧化碳濃度者，則隨氮肥濃度的增加而增加葉片數量及總葉面積，惟對單葉葉面積則顯現不出差異，顯然總葉面積的增加是因為葉片數目增加的結果。在乾物量方面，生長於高二氧化碳濃度者皆較高，且氮肥用量越高差異越大。在提高二氧化碳濃度下且供應足夠之氮肥，不只增加全株之乾物量且會有較多之光合產物分配至根部。提高二氧化碳濃度會使比葉面積下降，表示可增加葉片厚度。氮肥濃度與二氧化碳濃度無論對比葉面積或葉重比皆未見交感效應。在350 μL L-1二氧化碳濃度下測定光合作用，在提高二氧化碳濃度下生長之樟樹苗木，必需提高氮肥濃度才能與生長於大氣二氧化碳濃度者有相同的光合作用能力。 Seedlings of Cinnamomum camphora were exposed to both ambient(350±20 μL L-1) and enriched 700±30 μL L-1 levels of CO2 in combination with four nitrogen concentrations (112、224、448 and 896 ppm) for12 weeks. Seedling growth in enriched CO2 were increased when nitrogen levels were increased from 112 to 896 ppm, however seedling growth in ambient CO2 was inhibited by 896 ppm NResearch fertilizer after 12 weeks. There were more leaf numbers and total leaf area of seedlings grown in elevated CO2 concentration than in ambient concentration. The increment of total leaf area came from leaf numbers because the single leaf area was not different from those two seedlings grown in ambient and enriched CO2 concentrations. Not only the dry weight of seedlings grown in elevated CO2 concentration is higher than that in ambient concentration but also more photosynthates were allocated to root. The higher leaf thickness was found in seedlings grown in elevated CO2 concentration than in ambient condition for they had a lower specific leaf area. Photosynthetic rates of seedlings grown in elevated CO2 concentration were increased significantly only under the nitrogen supplement did not limited.

Seedlings of Cinnamomum camphora were exposed to both ambient（350±20 μL L-1） and enriched 700±30 μL L-1 levels of CO2 in combination with four nitrogen concentrations (112、224、448 and 896 ppm) for12 weeks. Seedling growth in enriched CO2 were increased when nitrogen levels were increased from 112 to 896 ppm, however seedling growth in ambient CO2 was inhibited by 896 ppm NResearch fertilizer after 12 weeks. There were more leaf numbers and total leaf area of seedlings grown in elevated CO2 concentration than in ambient concentration. The increment of total leaf area came from leaf numbers because the single leaf area was not different from those two seedlings grown in ambient and enriched CO2 concentrations. Not only the dry weight of seedlings grown in elevated CO2 concentration is higher than that in ambient concentration but also more photosynthates were allocated to root. The higher leaf thickness was found in seedlings grown in elevated CO2 concentration than in ambient condition for they had a lower specific leaf area. Photosynthetic rates of seedlings grown in elevated CO2 concentration were increased significantly only under the nitrogen supplement did not limited.