Human activities such as fossil fuel combustion, nitrogen fertilizer production and cultivation of nitrogen fixing crops are the main sources of reactive n.

人类活动，如燃料燃烧、氮肥生产、固氮植物的培育和畜牧业的集约经营等是引起全球活性氮增加的主要原因。

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There was a negative correlation between the nitrogenase activities of nitrogen fixing bacteria in root and that in leaf and stem.

此外，甘蔗根、茎、叶中固氮菌的固氮酶活性之间关系较为密切，根中固氮菌的固氮酶活性与叶片和茎中的都呈负相关。

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