Urea is the most widely used N fertilizer because of its high N content and low cost . Upon application to soil urea is rapidly hydrolyzed by urea enzymes to form ammonia the accumulation of excess ammonia can result in toxicity to dry direct-seeded rice .

尿素因含氮量高、价格低廉在我国应用广泛，尿素施于土壤后会迅速被土壤 脲酶水解从而形成氨，而过量氨的积累会对旱直播水稻 幼苗产生毒害作用。

Moreover compared with urea CRNF increased the activities of active oxygen scavenging enzymes such as SOD and POD and decreased the accumulation amount of MDA in the functional leaves during rice leaf aging .

此外，施用控释 氮肥能显著地提高生育中、后期功能叶中的SOD、POD等活性氧清除 酶的活性，降低功能叶中的丙二醛含量。

The Relation of Nitric Oxide Synthesis and Urea Cycle Enzymes

一氧化氮合成与 尿素循环 酶的关系：瓜氨酸&一氧化氮循环

Urea are secreted from saliva and gingival crevicular fluid continuously and rapidly broken down by urease enzymes of oral microflora to ammonia and carbonhydrate .

从唾液和龈沟液中持续分泌的 尿素被口腔细菌 尿素酶快速分解产生氨和二氧化碳。

This paper is concerned with the effect of excessive amount of urea on the activities of some enzymes of the TCA and glyoxylic acid cycles .

本文进一步从离体 酶 系探索过量 尿素对热带假丝酵母在烃类氧化过程中有关三羧酸循环，乙醛酸循环，呼吸链，ω和β氧化等几个 关键 酶活力的消长关系。