The rhizosphere pH change of Pinus koraiensis seedlings as affected by N sources of different levels and its effect on the availability and uptake of Fe, Mn, Cu and Zn

Dark brown forest soil was collected from the upper 20 cm soil layer in Changbai Mountain Research Station of Ecosystem, Chinese Academy of Sciences. The soil was amended with two different forms of nitrogen fertilizers: NO3- as Ca(NO3)2, NH4+ as NH4Cl at the concentrations of 50, 100, 200 and 400 mgkg-1 respectively. The experiment was carried out with 2-yr-old Pinus koraiensis seedlings in pot. The pH change of rhizosphere soil and the contents of available Fe, Mn, Cu, and Zn in soil and leaves were analyzed. The result indicated that the addition of NH4--N decreased the rhizosphere pH value, while the addition of NO3--N increased the rhizosphere pH value in contrast with the control treatment. The direction and extent of the pH change mainly depended on N source and its concentrations applied. The rhizosphere pH change had a remarkable influence on the availability of the micronutrients in the rhizosphere, and thereafter affected the nutrient uptake by the seedlings. The contents of available mineral nutrients had a negative correlation with the pH value in the rhizosphere soil. The contents of available mineral nutrients in leaves were positively correlated to the levels of the available nutrients in the rhizosphere soils.

一株耐低温反硝化聚磷菌的筛选及其特性研究

通过吸磷试验、硝酸盐还原产气试验及异染颗粒和PHB颗粒染色辅助检验，并采用模拟自然降温方式，从稳定运行的厌氧／缺氧SBR反应器中分离筛选出在低温下（8℃）仍具有高效能的一株反硝化聚磷菌H16。经鉴定，H16属于假单胞菌属（Pseudomonos）。在低温下，探讨了pH值、微量元素对菌株的生长及除磷效能的影响，结果表明，菌株H16生长最适pH为7～8，除磷反应的最佳pH值为7；微量元素的缺乏对H16的生长和除磷效能都有一定的不良影响。同时测定了H16的生长曲线。