Abstract
Tobacco plant(8-leaf seedlings) were grown on water culture fertilized with different N sources ($NO_3-N$, $NH_4-N$, $NO_3+NH_4-N$) during 15 days. Daily uptake of nutrients and inorganic constituents in plants were investigated in relation to growth responses of them. 1. Nitrate-fed plant showed higher daily uptake of inorganic cations than those in other treatments, and reached about two times higher uptake of nitrogen and three times more uptake of cations (K, Ca, Mg). Potassium was preferentially uptaken at a very fast rate from the beginning after treatment. Also $NO_3-N$ tended to be taken up selectively by the plant from the mixture of nitrate and $NH_4-N$. 2. The initial pH (pH 6.0) of culture medium drastically changed into acid (pH 4.0) in the $NH_4-N$ medium, but into slightly higher (pH 6.4) in the nitrate when measured after exposure of 24 hours. The mixture also tended to show an acidity but much weaker than $NH_4-N$ solution. 3. Nitrate-fed plant had a normal growth pattern but $NH_4-N$ fed plant almost stopped growing. Those plants containing both nitrate and ammonium N were also showed very poor growth.
질소원(窒素源)을 달리한 배양액(培養液)으로 담배식물의 양분흡수와 생육반응을 조사한 결과 1. $NO_3-N$ 배양액에서 자란식물은 양분 흡수가 크게 촉진되었다. $NH_4-N$ 배양액에서 자란식물보다 $NO_3-N$의 흡수로 무기양(無機陽)이온의 흡수가 현저하게 증가되었고 그중 K의 흡수가 가장컷으며 처리직후부터 빠른 흡수속도로 총질소(總窒素)는 2배(倍), K, Ca, Mg는 모두 3배 이상 높았다. 그리고 $NO_3+NH_4$ 혼합배양액(混合培養液)에서는 $NO_3-N$ 선택흡수(選擇吸收)되는 경향을 보였다. 2. 담배식물이 자란 배양액의 산도(酸度)는 질소원별로 상이(相異)하여 $NO_3-N$ 배양액은 알카리쪽으로 미미하게 변하지만 $NH_4-N$ 배양액에서 산성(酸性)쪽으로 큰 변화를 나타냈고 $NO_3+NH_4$ 혼합액(混合液)도 산성(酸性)쪽으로 변하지만 $NH_4-N$단독배양액보다는 크지 않았다. 3. 담배식물의 생육반응은 $NO_3-N$ 배양액에서 가장 양호하게 나타났으나 $NH_4{^+}$을 함유한 배양액에서는 생육이 부진하였으며 특히 $NH_4-N$ 단독배양액에서는 생육이 거의 정지되었다.