ESSENTIAL ELEMENTS/NUTRIENTS - FUNCTIONS AND DEFICIENCIES

ESSENTIAL ELEMENTS/NUTRIENTS - FUNCTIONS AND DEFICIENCIES

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  ESSENTIAL ELEMENTS/NUTRIENTS: FUNCTIONSAND DEFICIENCIES Dr. K. Vanangamudi Formerly Dean (Agriculture), Dean Adhiparasakthi Agricultural College, Professor & Head, Seed Science & Technology, TNAU, Coimbatore. 1. Classification of essential nutrients 1.1. Based on the amount required by the plant  Major nutrients – required in large quantities eg. N, P, K.  Secondary nutrients – required in lesser quantities compared to major nutrients eg. Ca, Mg, S.  Micronutrients – required in trace quantities eg. Fe, Mn, Zn, Cu, B, Mo. 1.2. Classification based on the role of element in plant system (according to TRUOc, 1954)  Accessor structural elements: N, P, S  Regulator and carriers: K, Ca, Mg  Catalyst and activators: Fe, Mn, Zn, Cu, Mo, Cl, B.  Seventeen elements are considered essential to plant growth.  Carbon (C), hydrogen (H) and oxygen (O) are the most abundant elements in plants.  Carbon, H and O are not considered as mineral nutrients. 2. Essential nutrients and their principal forms for uptake Nutrient Chemical symbol Principal forms for uptake Carbon C CO2 Hydrogen H H2O Oxygen O H2O.O2 Nitrogen N NH+4 .NO-3 Phosphorus P H2PO-4 , HPO2 -4 Potassium K K+ Calcium Ca Ca2+ Magnesium Mg Mg2+ Sulphur S SO2 -4 , SO2 Iron Fe Fe2+, Fe3+ Manganese Mn Mn2+ Boron B H3BO3 Zinc Zn Zn2+ Copper Cu Cu2+ Molybdenum Mo MoO2 -4 Chlorine Cl Cl-
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  Nickel 3. Functions ofessential nutrients in plants Nutrient Function Carbon (C)  Basic molecular component of carbohydrates, proteins, lipids and nucleic acids Oxygen (O)  Occurs in all organic compounds of living organisms Hydrogen (H)  Hydrogen plays a central role in plant metabolism.  Important in ionic balance and as main reducing agent.  Plays a key role in energy relations of cells. Nitrogen (N)  Component of proteins to nucleic acids and chlorophyll.  Essential role in plant growth.  Also foods in soils. Phosphorus (P)  Central role in plants is in energy transfer during respiration ADP + Pi → ATP and protein metabolism.  Root growth and photosynthesis. Potassium (K)  Helps in osmotic and ionic regulation.  Cofactor or activator for many enzymes of carbohydrate and protein metabolism.  Resistance to cold, disease and insects. Calcium (Ca)  Involved in cell division and maintenance of membrane integrity.  Signal transduction pathway. Magnesium (Mg)  Component of chlorophyll.  Cofactor for many enzymatic reactions. Sulphur (S)  Involved in plant cell energy. Iron (Fe)  Essential component of many heme and nonheme Fe enzymes.  Involved in key metabolic function such as N fixation, photosynthesis and electron transfer.  Chlorophyll production. Zinc (Zn)  Essential component of several dehydrogenases and peptidases, including carbonic anhydrase, alcohol dehydrogenase, glutamic dehydrogenase and malic dehydrogenase.  Synthesis of protein, hormones, enzymes. Manganese (Mn)  Involved in the O2 – evolving system of photosynthesis.  Component of the enzymes arginase and phosphortransferases.  Chlorophyll production. Copper (Cu)  Constituent of enzymes like cytochrome oxidase, ascorbic acid oxidase and laccase. Boron (B)  Involved in carbohydrate metabolism and synthesis of cell wall components.  Pollen production, fertility and fruit formation. Molybdenum (Mo)  Required for the normal assimilation of N in plants.  Essential component of nitrate reductase as well as nitrogenase (N2 fixation enzymes). Chlorine (Cl)  Essential for photosynthesis and as an activator of enzymes involved in splitting water.  Involved osmoregulation of plants growing on saline soils.
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  Nickel (Ni) Involvesin N metabolism and nitrogen fixation 4. Deficiency symptoms of nutrients 4.1. Nitrogen (N)  Promotes rapid vegetative growth  Gives plants healthy green colour  Deficiency:  Stimulated growth, pale yellowish colour.  Burning tips and margins of leaves starting at the bottom of the plant. 4.2. Phosphorus (P)  Stimulates early growth and root formation.  Hastens maturity.  Promotes seed production.  Makes plants hardy.  Deficiency:  Small root growth, spindly stalk, delayed maturity.  Purplish discoloration of leaves.  Dying of tips of older leaves, poor fruit and seed development. 4.3. Potassium (K)  Improves plant ability to resist disease and cold.  Aids in the production of carbohydrates.  Deficiency:  Slow growth.  Margin on leaves develop a scorched effect on the older leaves.  Weak stalk, shriveled seed and fruits. 4.4. Calcium  Absorbed by plants as Ca2+ and concentration in plant ranges from 0.2 to 1.0%.  Deficiency:  Young leaves of terminal buds dieback at the tip and margins.  Root may become short, stubby and brown.  Causes acidity of soil.  Cell may become rigid and brittle.  Young leaves of cereals remain folded
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  4.5. Magnesium  Absorbedas Mg2+ and concentration in plant varies between 0.1 and 0.6%.  Deficiency:  Interveinal chlorosis.  Stiff brittle, twisted, wrinkled and distortion of leaves.  Cotton – lower leaves develop a reddish purple finally nicrotic (Redding of leaves).  In brassica, chlorosis with interveinal mottling uniformly distributed in older leaves and other vascular tissues remain green called Puckering. 4.6. Sulphur  Absorbed by plant roots as SO4 2- ions.  Concentration in plants ranges between 0.1 and 0.4%.  Deficiency:  Stunted growth, pale green to yellow colour.  Immobile in plants and plants symptoms start first at younger leaves.  Poor seed set in rapeseed.  Tea –tea yellows. 4.7. Iron  Absorbed by plants roots as Fe2+ , Fe3+ .  Concentration in plant tissue is 50-250 ppm.  Deficiency:  Occurs in younger leaves since Fe is immobile element.  Occurs in calcareous or alkaline soils and poorly drained water logged soils.  Younger leaves develop interveinal chlorosis.  Entire leaf turns yellow colour. 4.8. Manganese  Mn concentration in plant ranges from 20 to 500 ppm.  Deficiency:  Immobile in plant and deficiency starts in the younger leaves.  Interveinal chlorosis occurs.  Oats - gray specks / streaks  Peas - marsh spot  Sugarbeet - speckled yellow
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   Sugarcane -pahala blight 4.9. Zinc  Normal concentration in plant is 25 to 150 ppm.  Deficiency:  Light yellow or white areas between the veins of older leaves.  Death of tissue, discoloured.  Malformation of fruits.  Cotton : White bud (or) little leaf  Citrus : Mottle leaf  Potato : Fern leaf  Fruit trees : Rosette (Upnormal growth)  Paddy : Khaira 4.10. Copper  Absorbed Cu2+ .  Normal concentration in plants is 5-20 ppm.  Deficiency:  Chlorosis, withering and distortion of terminal buds.  Guava - cracking of fruits and terminal bud dieback. 4.11. Boron  Since it is immobile, deficiency occurs in terminal bud growth.  Poor pollen production and fertility.  Restricted flowering, fruit development and fruit set.  Sterility and mal formation of reproductive organs.  Discolouration, cracking or rotting of fruit, tubers or roots.  In apple, Internal cracking.  Break down of internal tissue in root crops gives rise to darkened areas - brown heart / black heart.  Cotton - weeping disease. 4.12. Molybdenum  Absorbed as molybdate (MoO4).  Plant contains <1 ppm Mo.  Deficiency:
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   Inhibits flowerformation.  Whiptail in cauliflower. 4.13. Chlorine  Absorbed by plants as Cl- through roots and aerial parts.  Normal concentration in plant is 0.2-2.0%.  Deficiency:  Partial wilting and loss of turgidity.  Necrosis, leaf bronzing and reduction in growth. 4.14. Nickel  Content in plant is 0.1 - 1.0 ppm.  Legumes: whole leaf chlorosis along with necrotic leaf tips in cowpea.