So where concentrations of these minerals and elements are low, the growth of phytoplankton is diminished. Plants are able to convert no more than about 20 percent of the light energy they receive into photosynthetic materials. Some are even less efficient because of a lack of essential minerals. For example, low phosphorus levels often inhibit the growth of water plants. Despite apparent inefficiencies, though, the earth's plants still produce 328 trillion pounds of organic matter a year.
Plants are the primary food producers in food chains and food webs.
Plant eaters, herbivores, are the primary consumers, which ingest plant material directly. Plants depend on sunlight for energy, which is ultimately converted into essential nutrients for all the consumers in food chains and webs.