用英语描写一种植物《英语》

Lightning helps provide our daily need of the element nitrogen. Nitrogen is the third most abundant element in the human body, and it must be renewed continually.We are actually surrounded by nitrogen, since it comprises 78 percent of the earth's atmosphere. However, we cannot use the nitrogen in this molecular, gaseous form; nitrogen gas has a strong covalent bond that our bodies cannot break down. Instead, nitrogen must first be taken up by plants as part of the food chain.There are two major ways in which nitrogen becomes part of vegetation. First, certain plants are able to absorb or "fix" nitrogen through their root systems. These plants are called legumes and include clover and peas. Legumes are distinguished by nitrogen-fixing bacteria that live inside their root nodules. These bacteria change the N2 form of atmospheric nitrogen into nitrate, NO3 : N2 + 3O2 ---> 2NO3In the nitrate, form the legumes, as well as other plants, can utilize the needed nitrogen.Through a diet that includes either these plants directly or the products from grazing animals we make the nitrogen available to our bodies.The second major way by which nitrogen is transformed into a usable form is by lightning. The great electrical energy of lightning is easily able to convert N2 to NO3.