BIOLOGY Volume 1 - A Guide to General Biology - 2004

7. AUTOTROPHIC NUTRITION

7.10. Mineral Nutrition in Plants and Animals

Autotrophic Nutrition involves not only the synthesis of CARBOHYDRATES from carbon dioxide and Water, but also the subsequent utilization of substances such as nitrates, sulfates, and phosphates to produce other essential Organic compounds, including Proteins and Nucleic Acids. Heterotrophic organisms, such as animals, also require certain mineral compounds to Complement their organic diet. In many cases, the same physiological processes rely on identical nutrients, making it convenient to view the entire field of mineral nutrition as a bridge between autotrophic (Ch. 7) and heterotrophic nutrition (Ch. 8).

Nutrients essential for the successful GROWTH AND REPRODUCTION of an Organism are termed essential elements. The primary essential elements for life are carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus, potassium, sodium, magnesium, calcium, and chlorine. In addition to these, all organisms require trace amounts (a few parts per million) of several other elements. These include manganese, iron, cobalt, copper, and zinc; compounds of molybdenum, vanadium, chromium, and other heavy metals, as well as boron, silicon, fluorine, and iodine, are sometimes necessary (see Table 3.1). With the exception of carbon, hydrogen, and oxygen, green plants obtain all of these substances from soil and water in the form of minerals. The mechanisms of uptake are discussed in Chapter 13.

In heterotrophic organisms (animals and Fungi), inorganic Trace Elements are sometimes grouped together with organic compounds (Vitamins) under the term micronutrients. Although both types of compounds are required only in trace amounts, they play similar and vital roles in cellular METABOLISM, frequently acting as enzyme Cofactors. Vitamins are discussed in Chapter 8. Autotrophic organisms are capable of synthesizing the vitamins they require on their own. Other essential elements are designated as Macronutrients. A deficiency in any of these elements leads to The Development of deficiency diseases.

Some Examples of the Functions of major minerals are given in Table 7.7. As this table shows, minerals are absorbed by plants in the form of individual ions, either as anions (negatively charged) or cations (positively charged). The same holds true for trace elements, although their specific ions are not listed in the table.

Animals do not acquire all their necessary elements in mineral form. For example, the majority of an animal's nitrogen intake is supplied in the form of proteins.

The proper balance of trace elements plays a crucial role in maintaining soil fertility. However, extreme cases exist where plants thrive in environments heavily contaminated with metals, such as around discarded ammunition dumps or over natural mineral deposits. While such plants may be toxic to herbivores, they can nevertheless provide some ecological benefit to humans by covering unsightly tracts of land.

Class="center">Table 7.7. Selected essential minerals and examples of their utilization by living organisms

MACRONUTRIENTS			Common deficiency diseases and symptoms associated with the elements
Element and symbol	Form absorbed by plants	General significance	in plants	in humans		Common dietary sources for humans
Nitrogen, N	Nitrate, NO₃^- Ammonium, NH₄	Synthesis of proteins, nucleic acids, and many other organic compounds, such as Coenzymes and chlorophyll	Stunted growth and severe chlorosis, particularly in older leaves	Severe Protein deficiency (kwashiorkor),		Protein, particularly lean meat, fish, and milk
Phosphorus, P	Phosphate, PO₄^3- Orthophosphate, H₂PO₄^-	Synthesis of nucleic acids, ATP, and certain proteins. Phosphate is a constituent of bones and tooth enamel, as well as membrane Phospholipids	Stunted growth, especially of roots			Abundant in milk
Potassium, K	K⁺	Primarily involved in membrane function, including Nerve Impulse Conduction, maintenance of electrical potential, operation of the (Na⁺, K⁺)-pump, and regulation of anion-cation and osmotic balance. Cofactor for Enzymes involved in Photosynthesis and Respiration (Glycolysis). A component of The Cell sap in plant vacuoles.	Yellow and brown leaf margins and premature plant death	Rare		Vegetables, such as Brussels sprouts, and meat
Sulfur, S	SO₄^2-	Synthesis of proteins (e.g., keratin) and many other organic compounds (e.g., coenzyme A)	Chlorosis, e.g., tea yellows			Protein, e.g., lean meat, fish, and milk
Sodium, Na	Na⁺	Functionally similar to potassium, although required in smaller amounts. Participates in the operation of the (Na⁺, K⁺)-pump		Muscle cramps		Common salt (sodium chloride) and bacon
Chlorine, Cl	Cl^-	Functions similar to those of Na⁺ and K⁺, such as maintaining anion-cation and osmotic balance. Involved in the chloride shift occurring during Carbon dioxide transport in the Blood. Present in gastric juice as Hydrochloric acid		Muscle cramps	Common salt and bacon
Magnesium, Mg	Mg²⁺	A constituent of chlorophyll. Present in bones and Teeth. Cofactor for many enzymes, such as ATPase.	Chlorosis		Vegetables and many other foods
Calcium, Ca	Ca²⁺	Formation of the middle lamella (calcium pectate) between Plant Cell Walls; normal Cell wall development. A constituent of bones, tooth enamel, and shells. Activates ATPase During Muscle contraction. Essential for blood clotting.	Stunted growth	Poor skeletal development, sometimes leading to Rickets	Milk, hard water

7.10.1. Mineral Deficiency

It is not always easy, or even possible, to isolate the effects of individual elements. For example, chlorosis (yellowing of leaves) in plants can be caused by either a magnesium or an iron deficiency, although these elements perform distinct functions in chlorophyll synthesis (Tables 7.7 and 7.8). A deficiency disease in sheep and cattle characterized by diarrhea is linked to a shortage of copper, which in turn results from high molybdenum levels in the pasture. Different organisms may respond differently to a shortage of the same element: manganese deficiency, for example, leads to gray speck and 'marsh spot' in peas, and causes similar disorders in oats.

Table 7.8. Selected essential trace elements and examples of their utilization by living organisms

MICRONUTRIENTS (all are cations, except for boron, fluorine, and iodine)			Common diseases or symptoms associated with element deficiency
Element and its symbol	Compounds containing it	Functions	plants			humans	Common dietary sources for humans
Manganese, Mn	Phosphatases (Phosphate group transfer)	Bone development ("growth factor")	Leaf spotting, e.g., gray speck of oats			Impaired bone development	Vegetables and A wide variety of foods
	Decarboxylases Dehydrogenases	Fatty acid oxidation, respiration, photosynthesis
Iron, Fe	Heme group in Hemoglobin and Myoglobin Cytochromes	Oxygen transport Electron transport, e.g., in respiration and photosynthesis				Anemia	Liver, meat, certain vegetables such as spinach
	Catalase and peroxidases	Breakdown of H₂O₂
	Intermediates in chlorophyll synthesis	Chlorophyll synthesis	Severe chlorosis, particularly in young leaves
Cobalt, Co	Vitamin B₁₂	Erythrocyte development				Pernicious anemia	Liver, meat (as a source of vitamin B₁₂)
Copper, Cu	Cytochrome oxidase	Terminal electron acceptor in the Respiratory Chain; catalyzes the reduction of oxygen to water	Dieback of shoots				A wide variety of foods
	Plastocyanin	Electron carrier in photosynthesis
	Tyrosinase	Melanin formation				Albinism
Zinc, Zn	Alcohol dehydrogenase	Plant Anaerobic respiration (Alcoholic Fermentation)		Little-leaf or rosette in citrus
	Carbonic anhydrase	Carbon dioxide transport in vertebrate blood		Leaf malformations, e.g., sickle leaf in cacao			A wide variety of foods
	Carboxypeptidase	Hydrolysis of peptide bonds during Protein Digestion
Molybdenum, Mo	Nitrate reductase	Reduction of nitrates to nitrites during Amino acid synthesis in plants		Slight growth retardation; 'whiptail' in legumes			A wide variety of foods
	Nitrogenase	Nitrogen Fixation in prokaryotes
Boron, B		Required exclusively by plants. Normal meristematic Cell Division. Nutrient mobilization?		Abnormal growth and death of SHOOT tips; 'Heart rot' in beets; 'stem crack' in celery	Not required
Fluorine, F	Present in animals as calcium fluoride	A component of tooth enamel and bones			Rapid tooth decay		Milk, drinking water in certain areas
Iodine, I	Thyroxine (apparently not required by plants)	Hormonal Regulation of basal metabolic rate			Goiter; cretinism in children		Seafood, iodized salt

The close interplay and diverse effects of mineral elements stem from their profound impact on cellular metabolism. Nevertheless, through various experimental approaches (such as altering mineral uptake conditions in laboratory settings), it can be demonstrated that certain specific symptoms are tied to the deficiency of particular elements. Such knowledge is vital in both medicine and agriculture, as deficiency diseases are widespread among humans, crops, and livestock alike.

Plant experiments, which have now become classics, were conducted in the late 19th and early 20th centuries primarily by German botanists using water and sand cultures. In these experiments, plants were grown in specially prepared nutrient solutions of known composition. Many economically important plant deficiency diseases have been cataloged with the aid of color photography, facilitating rapid Diagnosis.

Last update: 06/08/2026

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