INTRODUCTION

Those who answer gardening questions from the general public will tell you that surprising numbers of people have a basic misconception about plants. The belief that plants build themselves from the soil is widespread even today, more than 300 years after proof showing this not to be so. Why such a belief still exists is puzzling. Consider the common practice of removing lawn clippings. If grass was simply built from soil, a lawn from which kilograms of clippings were removed during the growing season for the past dozen years would resemble a sunken garden, but it does not. Something additional to soil must go into building a plant.

PHOTOSYNTHESIS: THE KEY

We now understand that plants construct themselves from carbon dioxide (CO2), water, and minerals with the aid of light energy. What plants make by this photosynthesis (putting together by light) is an endless supply of carbohydrates: sugars, starch, and cellulose.

Other green organisms can also photosynthesize

Plants are not the only organisms able to photosynthesize. Our oceans, lakes, and rivers are populated by a wide array of green organisms such as those algae which appear as green scum on ponds and lakes; the larger green, brown, and red algae, the seaweeds, found on or near seashores; and other microscopic organisms, the phytoplankton (certain bacteria, diatoms, dinoflagellates, and the smallest algae), which are especially abundant in our oceans.