一株玉米一生要吸收200多公斤水,一株向日葵一个夏天也要吸收250公斤水。生产一吨小麦需要1,700吨水,棉花和豆类所需要的水就更多了。那么,作物吸收这么多的水哪儿去了呢?其中绝大部份的水又从这些作物的叶表面上的气孔散失到大气中去了,这叫做植物的蒸腾作用。作物为了正常生长,必须不断地通过根系从土壤中吸水。生长盛期的大豆, A corn to absorb more than 200 kilograms of water throughout his life, a sunflower has to absorb 250 kilograms of water a summer. It takes 1,700 tons of water to produce one ton of wheat, and more for cotton and beans. So where does the crop absorb so much water? Most of the water is lost to the atmosphere from the pores in the leaf surfaces of these crops, which is called the transpiration of plants. In order to grow normally, the crop must constantly absorb water from the soil through the root system. Growing soybean,