Effects of soil microorganisms on the growth and on the nitrogen and phosphorus absorption by rice seedlings

Abstract

The growth and the nitrogen and phosphorus absorption by rice seedlings were examined under sterile and non-sterile conditions. Sterile seedlings were cultured aseptically for 2 weeks in a sterilized nutrient solutions, a half of which were inoculated with 10-4 diluted paddy soil suspension. In addition a short-term 32p absorption experiment was carried out using rice seedlings precultured in the same way as above in a phosphate-free nutrient solution. Microorganisms retarded the growth of the seedlings, especially root elongation. However, in the presence of microorganisms the roots became thicker and they formed laterals and root hairs close to their tips. More nitrogen was absorbed by the sterile plants at 25 and 50 ppm of nitrogen, whereas more by the inoculated plants at 100 and 200 ppm. As regard to phosphorus absorption, the sterile plants absorbed more phosphorus at phosphorus levels ranging from 5 to 50 ppm. A short-term experiment with 32p revealed that the sterile plants absorbed more phosphorus at the lowest concentration examined (0.01 ppm P), whereas at other concentrations (0.1-25 ppm P) no difference was detected between the sterile and the inoculated plants. The distribution pattern of absorbed nitrogen or phosphorus in the whole plant was not affected by microorganisms at any concentration tested. The growth pattern of root affected by microorganisms in the rhizosphere, especially on the rhizoplane, was suggested to be an important factor to determine the phosphorus absorption in rice plants. © 1978 Taylor & Francis Group, LLC.