Nitrogen fixed by legume root nodules accounts for 40% of total biological nitrogen fixation.

豆科植物的根瘤固氮占生物固氮总量的40%。

youdao

Some of them, such as nitrogen, oxygen, argon, neon, and so on, may be regarded as permanent atmospheric components that remain in fixed proportions to the total gas volume.

其中一些气体，如，氮，氧，氩， 氖等，作为空气的永久组成成分，总是以固定的比例存在于大气中。

youdao