It is one of nature's great ironies that the availability of nitrogen in the soil frequently sets an upper limit on plant growth even though the plants' leaves are bathed in a sea of nitrogen gas.
下述情形真可謂是自然界的一個(gè)莫大諷刺：土壤中所能獲得的氮肥量往往對植物的生長構(gòu)成了一個(gè)上限，雖然植物的葉子被沐浴在一片氮?dú)獾暮Ｑ笾小?