Mark Moccio, age 12, of Niagra Falls, Ont., Canada, for his question:

DOES LIGHTNING ASSIST PLANT GROWTH?

A roaring thunderstorm showers water on the plant world and, strange to say, its flashes of lightning also add a little fertilizer. Plants need air, light and moisture, plus a number of chemical foods  one of which is nitrogen. Lightning processes small helpings of nitrogen into the special chemical compounds that plants can use.

At this moment, an estimated 1,800 thunderstorms are flashing streaks of lightning in scattered spots around the world. Every day, about 44,000 thunderstorms occur around the globe. During an average year, all this lightning adds millions of tons of chemical fertilizer to the soil.

The plant world needs lots of nitrogen among its chemical foods  and nitrogen is the lazy gas that makes up 78% of the air.    However, plants cannot use these free atoms of nitrogen. They must be combined with other atoms into molecules of nitrogen oxides. This chemical process is called nitrogen fixing. When this is done, plants can absorb dissolved nitrate chemicals through their roots.

A flash of lightning is an electrical discharge with enormous energy. As it slices through the damp air of a cloud, its energy unites certain atoms to form molecules. Some of the molecules form other molecules  and the flashing lightning creates a series of chemical changes.

Since nitrogen and oxygen make up most of the air, we can expect compounds of these atoms. Some of these newly made nitrogen oxide chemicals are suitable plant foods. The rain washes them down into the soil, where they provide valuable fertilizer. The plants absorb these vital nitrates through their roots.

Thunderstorms are rather small and widely scattered. The plant world is enormous. No area can count on the lightning to provide enough nitrates to the soil. However, nature has other ways to fix nitrogen for the plant world, and farmers also may add fertilizers that contain usable nitrate compounds.

In the world of nature, the best nitrogen fixers are certain bacteria. They thrive in small nodules on the roots of beans, peas and other members of the legume plant family. When corn and grain crops consume the usable nitrates in the soil, a sensible farmer plants a legume crop  and the bacteria in its roots adds more nitrates. Lightning adds small helpings of this fertilizer here and there. But a crop of legumes adds much more   and just where it is needed.