Department of Soil and Environmental Sciences, University of California, Riverside, California 92521.
Appl Environ Microbiol. 1983 Aug;46(2):304-11. doi: 10.1128/aem.46.2.304-311.1983.
Pigeon peas (Cajanus cajan) were grown in large soil columns (90-cm length by 30-cm diameter) and inoculated with four different strains of cowpea rhizobia, which varied with respect to hydrogen uptake activity (Hup). Despite the profuse liberation of H(2) from Hup nodules in vitro, H(2) gas was not detected in any of the soil columns. When H(2) was injected into the columns, the rates of consumption were highest in the treatments (including control) containing Hup nodules (218 and 177 nmol . h . cm) and lowest in the Hup treatments (158, 92, and 64 nmoles . h . cm). In situ H(2) uptake rates in small soil cores at fixed distances from the nodules decreased exponentially with distance from the nodule (R = 0.99). This decrease in H(2) consumption was associated with a similar decrease in numbers of H(2)-oxidizing chemolithotrophic bacteria as determined by the most-probable-number method. On the basis of two equations derived separately upon diffusive theory (Fix's Law) and kinetic theory (Michaelis-Menten), the empirically derived rate constants and coefficients indicated that all of the H(2) emitted from Hup nodules would be consumed by H(2)-oxidizing bacteria within a 3- to 4.5-cm radius of the nodule surface. It is concluded that H(2) is not lost from the soil-plant ecosystem during N(2) fixation in C. cajan but is conserved by H(2)-oxidizing bacteria.
菜豆（Cajanus cajan）在大型土壤柱（90 厘米长×30 厘米直径）中种植，并接种了四种不同的豇豆根瘤菌菌株，这些菌株在氢摄取活性（Hup）方面存在差异。尽管体外从 Hup 根瘤中大量释放出 H2，但在任何土壤柱中都未检测到 H2 气体。当将 H2 注入柱中时，含 Hup 根瘤的处理（包括对照）中 H2 的消耗速率最高（218 和 177 nmol. h. cm），而 Hup 处理中最低（158、92 和 64 nmol. h. cm）。在距根瘤固定距离的小土壤芯中，原位 H2 吸收速率随距根瘤的距离呈指数下降（R = 0.99）。这种 H2 消耗的减少与通过最可能数法确定的 H2 氧化化能自养细菌数量的类似减少有关。基于根据扩散理论（Fix 定律）和动力学理论（Michaelis-Menten）分别推导的两个方程，经验得出的速率常数和系数表明，Hup 根瘤释放的所有 H2 都将在距根瘤表面 3 到 4.5 厘米的半径内被 H2 氧化细菌消耗。结论是，在 C. cajan 中固定 N2 期间，H2 不会从土壤-植物生态系统中损失，而是被 H2 氧化细菌所保留。
