四年级英语手抄报小短文30字 Normally,trees are the best defence against pollution;but when it's too hot outside,the trees'own self-defence mechanism may actually make things worse. 正常情况下，树木是抵御污染的最佳卫士，但是当外界温度过高时，树木自身的防御机制实际上可能会令污染状况恶化。 Trees produce natural chemicals,called isoprene and terpene,that are thought to protect their leaves from too much heat and sunlight.When the chemicals react with nitrogen oxide--found in pollution from cars--they form ozone,a much bigger health threat to humans and animals. 树木分泌的天然化学物质异戊二烯和萜烯被认为可保护树叶免受过多热量和阳光的伤害。然后，当这些化学物质与氮氧化合物（存在于汽车排放的废气中）发生化学反应时，就会形成臭氧，这会对人类和动物的健康构成更大的威胁。 本文来源：https://www.wddqw.com/doc/3e7c086e383567ec102de2bd960590c69ec3d838.html