Plants’ essential chemical elements Every garden center and hardware Approximate composition of elements necessary for plant growth store sells fertilizer guaranteed to “feed” plants. In a strict sense, we can’t feed plants. Food contains an energy source. Green plants capture solar energy and make their own food through photosynthesis! Photosynthesis and other metabolic processes require chemical elements in appropriate doses for plants to survive and thrive. We can help, directly or indirectly, to provide plants these essential chemical elements. Back in 325 B.C., Aristotle taught that all earthly things were composed of four elements: earth, air, fire, and water. That remained the dominant view for many centuries. In the 1830s and 1840s, scientists -- such as the pioneering agricultural chemist J. von Liebig -- hotly debated the question of “What do plants need to grow?” Soil, mild temperatures, sunlight, and water were easy answers that roughly corresponded to Aristotle’s elements. But why did manure and compost Astrophysics tells us that virtually all provide natural fertility. increase growth? Was there some vital chemical elements were formed in the However, the carbon contained in force in organic matter that nurtured aftermath of the Big Bang or in the organic matter is not directly taken up plants? thermonuclear heat of stars as they by plants. Through the 1880s, the This concept of vitalism was burn or explode. The essential elements scientist A.B. Frank described the discredited by the new agricultural can vary widely in the quantities critical role of mycorrhizae in plant chemists. They determined that required to support survival and nutrition, especially for trees. inorganic mineral elements were growth. The relative amounts that are Mycorrhizae (Greek for “fungus- essential for plant life. Their arguments needed can be compared by weight or roots”) are symbiotic organs containing were so convincing that the concept of by the number of atoms (table, above). plant roots and one or more species a vital life force became a discredited from a broad array of fungi. The plant superstition. Plant nutrition could be Essential elements for growth. The feeds sugar to the fungus while the reduced to a recipe of sterile elements. elements in greatest abundance in fungus enhances the uptake of essential plants are the raw materials for elements -- particularly P and N. These Origin of elements. What is an photosynthesis. Photosynthesis uses beneficial infections may also increase element? Chemically, an element is a light energy to split apart the oxygen resistance to drought and some plant pure substance composed of atoms that and hydrogen of water and to split diseases. all have the same number of protons in apart the carbon and oxygen from This nutritional role of mycorrhizae the nucleus. That number is the carbon dioxide taken from the and of free-living communities of “atomic number” and specifies the atmosphere. Photosynthesis then fungi, bacteria, and other element’s position in the periodic table. releases the oxygen from carbon microorganisms is sometimes hidden, The atomic nucleus also contains dioxide back into the atmosphere and largely due to disruption of the natural neutrons. For each element, the sum of recombines the remaining elements to soil environment and through the numbers of protons and neutrons is form sugar. Sugar is the starting inhibition due to heavy applications of the approximate atomic weight. material for all processes in plants that chemical fertilizer -- particularly of P Depending on the definition, 16 out of require energy. Also, the bulk of a and N. These non-target consequences the 94 naturally occurring elements are plant is made of sugar polymers (e.g. of common cultural practices in plant generally considered essential for the cellulose and starch) or compounds care are just beginning to get the depth growth of plants. Where do these derived from sugar (e.g. lignin). Soil and breadth of attention that they elements really come from, before they organic matter is largely cellulose and warrant. Ongoing research seeks to are bagged and boxed for sale? lignin which is critically important for identify what we can do to restore and soil moisture retention, aeration, maintain these important relationships. mineral element storage, and to fuel the Products and treatments continue to communities of soil organisms that be developed to restore these communities of microorganisms that chlorosis and necrosis in older leaves benefit plants. Although the treatment as well as rosetting of lateral shoots. thresholds are not always known, the Chlorine is required for target should be clear. Practices that photosynthesis, but in such low increase the natural ability of soil to quantities that deficiencies rarely cycle elements in a form available to occur. plants should be encouraged and Although present in plants in even situations or practices that disturb or smaller quantities, boron deficiencies diminish the processes such as low do occur, resulting in marginal scorch organic matter, heavy fertilization, soil of leaves, dead shoot tips, and compaction, and improper drainage deformation of fruits. should be discouraged. Iron has a key role in the synthesis of chloroplasts, the site of photosynthesis What do essential elements do for within cells, as well as several critical the plant? Nitrogen is the element that respiratory enzymes. Deficiency of Fe is most associated with enhanced plant is extremely common in alkaline soils growth and is a key component of all due to impaired availability at high pH, proteins. Many proteins function as causing interveinal chlorosis and shoot enzymes or biological catalysts, dieback. making plant metabolism possible. Manganese is also required for Plants have very efficient pumps to chlorophyll synthesis and the release of take N from the soil, usually in the oxygen during photosynthesis. form of nitrate, and to bind it to sugar Deficiency of Mn causes chlorosis, fragments to form amino acids, the necrosis, and deformation of leaves. building blocks of proteins. Deficiency Zinc is a structural part of some in N decreases production of enzymes and a cofactor for others. chlorophyll and enzymes, resulting in Deficiency in Zn can reduce internodal decreased photosynthesis, decreased elongation and discolor the lower leaf Healthy, forest-grown oak seedling is growth, and premature senescence. surface to produce “bronzing”. showing extensive connections between Potassium is also critical for Copper is a constituent of several roots and soil organic matter that photosynthesis, cell expansion, and to enzymes. Deficiencies of Cu can cause support soil microorganism diversity regulate the opening and closing of interveinal chlorosis, defoliation, leaf stomates. Deficiency of K leads to mottling, and shoot dieback. chlorosis and scorching of the leaf Although molybdenum is the communities of microorganisms margins. essential element in the lowest sustains living communities of green Calcium interacts with pectin to concentration in plants, Mo is still plants and especially trees. As plant crosslink plant cell walls and to act as a essential for the conversion of nitrate parts are shed and individuals die, the messenger to regulate growth into amino acids in living cells. breakdown of organic matter as well as hormones. Woody stems contain an exudates from living plants fuel even greater proportion of Ca than is Plants as part of natural systems. communities of beneficial shown in the table, which is drawn In nature, plant nutrition is far from the microorganisms. from herbaceous plants. Calcium simple view of roots immersed in a Plant nutrition links the astrophysics deficiency reduces elongation of solution of inorganic chemicals. The of chemical elements to the utilization internodes and overall growth. importance of the living web of plant of solar energy of plants, the capture of A magnesium atom lies in the center nutrition is especially clear with trees carbon from and the release of oxygen of the chlorophyll molecule and also and other perennial woody species that to the atmosphere, and the rich increases the effectiveness of some involve long-term relationships with diversity of soil microorganisms. Of enzymes. Magnesium deficiency often communities of soil organisms course, urban and community appears as chlorosis and scorching including fungi, bacteria, and protozoa. landscapes and the nurseries that serve between leaf veins and premature leaf All of these organisms, directly or them may feel the need to compromise shedding. indirectly, require organic matter in the part of the natural system to support Phosphorous is part of the soil to fuel their metabolism. As with short-term management needs. Still, “backbone” of nucleic acids that carry living roots, these organisms require plants did not develop in sterile genetic information. Phosphorous is the proper combination of air and water laboratories, but in living soil. also a key element in ATP, the primary in the soil for their own respiration. molecule for the transfer of biological Soil compaction and adverse changes (Written by Dr. Kevin T. Smith, US energy. Deficiency in P causes severe in soil chemistry and drainage reduce Forest Service and originally published stunting and reduced flowering and the effectiveness of the microbial in American Nurseryman 206 (10): 10- fruiting. communities to support plant growth. 11, 2007). th Sulfur is a constituent of two The 19 century vitalists held a germ essential amino acids as well as plant of truth in the midst of their vitamins and enzyme cofactors. misunderstanding of plant nutrition. Deficiency of S causes on overall The life force in manure was exactly yellowing of younger leaves, and that. Life in diverse, interacting (Essential elements, page 2) .