二氧化碳與氮養分濃度對樟樹苗木的生長與生理反應之影響

Abstract

本研究旨在探討不同二氧化碳濃度(354.29±12.80 μL L-1, Ambient, A及719.65±28.70 μL L-1, Elevated, E)與不同氮養分濃度(112、224及448 ppm)處理對樟樹(Cinnamomum camphora) 苗木之形質生長、氣體交換、光捕捉能力、非結構性碳水化合物與氮養分於植體之分配、介質的酸鹼值變化與氮養分狀態，以及根部之原生質膜H+-ATP水解酵素在氮養分吸收所扮演之角色等的影響，為期8週。在整個試驗期間，高二氧化碳濃度對苗高淨生長與地際直徑淨生長具有持續且顯著的促進效果，而不同氮養分濃度處理間並無顯著差異。雖然於處理4週後，高二氧化碳濃度與較高氮養分濃度能夠提昇光合作用速率，但各項葉綠素螢光反應參數與葉綠素含量的結果已透露，高二氧化碳濃度對光合作用光反應具有負面影響，此反應會隨著氮養分濃度增加而減緩之。處理8週後，光合作用速率已逐漸適應於高二氧化碳濃度之環境，各項葉綠素螢光反應參數與葉綠素含量與大氣二氧化碳濃度處理者之間無顯著差異。由於碳有往地下部輸送的傾向，有助於地下部吸收氮養分，而原生質膜上H+-ATPase更能促進氮養分的吸收，尤其是NO3-，然其於地上部進行同化作用已有降低而於地下部進行同化作用則有增加的趨勢。由地下部之NO3-及NH4+含量、介質pH與NO3-及NH4+含量的結果推測，地下部吸收氮養分型態的偏好，有由NO3-轉為偏好吸收NH4+的傾向。氮養分供應適度與否，將對生長表現、生理作用、光合作用光反應、碳與氮於地上部與地下部的分配，以及氮養分的吸收等反應於二氧化碳濃度提昇而有正面的效應。

This study investigated the effects of different carbon dioxide concentrations (354.29±12.80 μL L-1, Ambient, A, or 719.65±28.70 μL L-1, Elevated, E) and different nitrogen concentrations (112, 224 or 448 ppm) on growth performances, gas exchange, ability of radiation capture, allocations of non-structural carbohydrates and nitrogen nutrients, situations of pH and nitrogen nutrients, and the role of plasma membrane H+-ATPase played on nitrogen uptake in the soil medium of Cinnamomum camphora seedlings for eight weeks. During entire experimental period, the net height growth and net ground diameter growth were continually and significantly enhanced by elevated carbon dioxide concentration, but have no obviously difference among nitrogen concentrations. Although photosynthetic rate was promoted by elevated carbon dioxide concentration and higher nitrogen concentration after four weeks, the results from chlorophyll fluorescence measurements and chlorophyll contents have demonstrated that the light reaction of photosynthesis has been negatively affected by elevated carbon dioxide concentration. This impact would be weak with nitrogen concentrations increased. After eight weeks, photosynthetic rate has gradually acclimated under elevated carbon dioxide condition. Chlorophyll fluorescence parameters and chlorophyll contents of elevated carbon dioxide treatment have no significantly different from those of ambient treatment. Because of it has a tendency to transport more carbon to the roots, and to improve nitrogen uptake. Plasma membrane H+-ATPase could accelerate nitrogen uptake, especially for nitrate uptake. But nitrate assimilation has a trend to decrease in the shoots and to increase in the roots under elevated carbon dioxide condition. According to the results from nitrate and ammonium contents of roots, pH value and nitrate and ammonium contents of soil medium, I may conjecture that the hobby for nitrogen forms to uptake has changed, from nitrate uptake changed to ammonium uptake. Nitrogen concentration supply adequately or not would have a positive effect on growth performances, physiology, the light reaction of photosynthesis, allocations of carbon and nitrogen between shoots and roots and nitrogen absorption to response carbon dioxide concentration enrichment.