인산결핍 조건하에서 질소고정식물체내의 Ureide 분배

Ureide Distribution in Nitrogen Fixing Soybean Plant under External Phosphorus Limitation

인산 결핍이 질소고정식물체의 Ureide 농도 및 분배에 미치는 영향을 살펴보고자 Bradyrhizobium japonicum MN 110을 접종한 대두 식물체를 1.0 mM-P(대조구) 및 0.05 mM-P(결핍구)를 함유한 무질소 영양액을 처리, 재배하여 이식 28, 35,42, 49일 후 수확하였다. 3주의 실험기간중 건물량은 대조구의 경우 8.9배, 결점구의 경우 2.7배 증가하였다. 인산 결핍구에서 식물체의 전질소 및 인산의 함량은 이식 후 28일에 각각 80%,40%,49일에 각각 93%, 84% 감소하였으며 뿌리 및 근류보다 잎과 줄기의 질소 농도가 크게 감소하였다. 인산 결핍은 잎과 줄기의 수용태 및 ureide태 질소 농도를 감소시켰으나 뿌리의 경우 영향을 받지 않았으며 인산결점구의 경우 전체 수용태 및 ureide태 질소의 함량중 뿌리 함유량 비율이 대조구에 비하여 증가하였다. 이러한 결과는 인산 결핍이 근류의 질소고정뿐만 아니라 고정질소의 상향 이동도 저해함을 나타낸다.

Soybean plants inoculated Bradrhizobium japonicum MN 110 were grown in outdoor perlite pots with nitrogen free nutrient solution containing 1.0 mM-P(control) and 0.05 mM-P(stress) and harvested at 28, 35, 42 and 49 days after transplanting (DAT) to examine the effect of phosphorus deficiency on ureide concentration of and distribution to diffrent plant organ in nitrogen fixing soybean plant during the vegetative growth. Total dry mass of control plants increased 8.9 fold and that of phosphorus deficient plant increased 2.7 fold during the experimental period. Phosphorus deficiency reduced total phosphorus and nitrogen accumulation by 80%,40% respectively, at 28 DAT and 93%, 84%, respectively, at 49 DAT. Nitrogen concentration was reduced by phosphorus deficiency in all tissues with leaf and stem tissues affected to a greater degree than nodule and root tissues at every sampling date. Phosphorus deficiency significantly reduced soluble reduced-N and ureide-N concentration in leaf and stem but did not affect those in root. The proportion of soluble reduced-N in leaf was reduced from 60% to 50% but increased from 10% to 20% in the roots. The proportion of ureide-N in leaf of control plants was higher than that in phosphorus deficient plants, whereas, roots of phosphorus deficient plants contained a higher propotion of ureide-N than those of control plants. These indicated that phosphorus deficiency not only inhibit nitrogen fixation of nodules but also restrict the translocation of fixed nitrogen out of the root system into the xylem.(Received April 4, 1997; accepted May 2, 1997)