Micronutrient
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Micronutrients are essential elements needed for life in small quantities. They include minerals and Vitamins.
Microminerals or trace elements include at least iron, cobalt, chromium, copper, iodine, manganese, selenium, zinc, and molybdenum. They are dietary minerals needed by the human body in very small quantities (generally less than 100mg/day) as opposed to macrominerals which are required in larger quantities. Note that the use of the term "mineral" here is distinct from the usage in the geological sciences.
Vitamins are organic chemicals that a given living organism requires in trace quantities for good health, but which the organism cannot synthesize, and therefore must obtain from its diet.
Micronutrient Malnutrition
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More than two billion people (i.e. one in three persons worldwide) suffer from micronutrient deficiency. The most common deficiencies can have devastating consequences:
- Vitamin A deficiency: Nearly 3 million preschool children in developing countries are blind because of vitamin A deficit.
- Iron-deficiency Anemia results in one out of four maternal deaths in the developing world. The cost of fortifying flour with iron is 20 cents (US) per person per year (World Bank estimate).
- Iodine deficiency is the world's leading cause of mental retardation -- more than 2 billion children suffer from lowered IQ and retardation due to Iodine deficiency. The costs of providing iodized salt are estimated at 10 cents per person per year.
Vitamin E and Zinc deficiency are also serious causes for concern.
Micronutrient malnutrition is practically unknown in developed countries owing to inexpensive interventions such as food fortification, supplementation, and dietary diversification,
South Asia and Sub-Saharan Africa are among the areas with the most affected people.
Micronutrients for plants
There are about eight nutrients essential to plant growth and health that are only needed in very small quantities. These are manganese, boron, copper, iron, chlorine, cobalt, molybdenum, and zinc. Some consider sulfur a micronutrient, but it is listed here as a macronutrient. Though these are present in only small quantities, they are all necessary.
Boron is believed to be involved in carbohydrate transport in plants; it also assists in metabolic regulation. Boron deficiency will often result in bud dieback.
Chlorine is necessary for osmosis and ionic balance; it also plays a role in photosynthesis.
Cobalt is essential to plant health. Cobalt is thought to be an important catalyst in nitrogen fixation. It may need to be added to some soils before seeding legumes.
Copper is a component of some enzymes and of vitamin A. Symptoms of copper deficiency include browning of leaf tips and chlorosis.
Iron is essential for chlorophyll synthesis, which is why an iron deficiency results in chlorosis.
Manganese activates some important enzymes involved in chlorophyll formation. Manganese deficient plants will develop chlorosis between the veins of its leaves. The availability of manganese is partially dependent on soil pH.
Molybdenum is essential to plant health. Molybdenum is used by plants to reduce nitrates into usable forms. Some plants use it for nitrogen fixation, thus it may need to be added to some soils before seeding legumes.
Zinc participates in chlorophyll formation, and also activates many enzymes. Symptoms of zinc deficiency include chlorosis and stunted growth.