초록
질산태질소(窒酸態窒素)를 선택흡수(選擇吸收)하는 담배식물에 대하여 흡수된 $NO_3-N$의 각조직별(各組織別) 이동양상(移動樣相)과 질산환원효소(窒酸還元酵素)의 활성도(活性度)(nitrate reductase activity. NRA)를 조사하고 생육과정(生育過程)에서 출엽(出葉)된 잎들의 질산환원능력(窒酸還元能力)을 비교조사(比較調査)한 결과(結果) 1. 도관조직(導管組織)인 엽맥(葉脈)까지는 함유(含有)된 질소(窒素)의 대부분(大部分)이 $NO_3-N$으로써 무기태질소(無機態窒素)로 엽맥(葉脈)을 통과(通過)하며 엽육(葉肉)에서는 $NO_3-N$이 환원(還元)되어 무기태질소(無機態窒素)가 거의 검출(檢出)되지 않았다. 2. NRA는 성숙(成熟)된 잎에서 가장 왕성하였으며 분열생장중(分裂生長中)인 잎이나 도관조직(導管組織)에서는 환원기능이 매우 낮은 수준에 머물렀다. 3. 하위(下位)의 성숙엽(成熟葉)은 두껍고 수분(水分)을 많이 함유(含有)하였으며 가장 왕성한 질산환원능력(窒酸還元能力)을 보였다. 4. 생장조직(生長組織)으로 유기질소물질(有機窒素物質)을 공급(供給)하기 위하여 유식물(幼植物)때는 소수(小數)의 좁은 잎에서 높은 수준(水準)의 NRA를 유지(維持)했으나 생육(生育)이 진전되어 많은 잎이 착엽(着葉)되면서 상위(上位)쪽의 성숙엽(成熟葉)은 NRA가 낮은 수준에 머물렀다.
Nitrate nitrogen was absorbed dominantly among the inorganic nitrogen nutrients by tobacco plant. Transport and reduction of $NO_3-N$ in plant tissue were the important metabolism for supplying synthetic N compounds to developing tissues during growth period. Under field and environment-controlled condition tobacco plants were grown and seperated to leaf tissues at stalk positions for investigation of nitrogen transport and assimilation ability during period of rapid vegative growth. The results of studies were summarized as follows: 1. $NO_3-N$ absorbed from roots was transported as inorganic nitrogen through the vascular tissue of leaf veins as resulting from the high $NO_3-N$ ratio of the nitrogen content in leaf veins, but these ratios in mesophyll tissue of the same leaf laminae decreased remarkably in disregard of higher accumulation of nitrogen being compared to midvien. 2. Mesophyll tissue of mature leaves appeared higher value of nitrate reductase activity (NRA) comparing with other tissues, stem, leaf vien, and meristmatic tissue at emergence point with young leaves. 3. Matured leaves at lower position being reducing nitrate nitrogen vigorously observed thick laminae and kept high amount of water in them. 4. Mature leaves of young plant reduced $NO_3-N$ vigorously for supply synthetic N compounds to meristmatic tissues at growing point by the reason of narrow and few leaves at young stage, but in advancing growth period NRA of mature leaves along upper position reached to lower value. This appearence attributed to distribution of organic-N compound demanding for growth to increasing numbers of wide leaves.