Plant nutrition by Muhammad Fahad Ansari12IEEM14


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Muhammad Fahad Ansari12IEEM14

Plant nutrition by Muhammad Fahad Ansari12IEEM14

  1. 1. Plant nutrition lecture # 6Muhammad Fahad Ansari 12IEEM14
  2. 2. PLANT NUTRITION Section A: Nutritional Requirements of Plants1. The chemical composition of plants provides clues to their nutritional requirements2. Plants require nine macronutrients and at least eight micronutrients3. The symptoms of a mineral deficiency depend on the function and mobility of the element Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  3. 3. Introduction• Every organism is an open system connected to its environment by a continuous exchange of energy and materials. – In the energy flow and chemical cycling that keep an ecosystem alive, plants and other photosynthetic autotrophs perform the key step of transforming inorganic compounds into organic ones. – At the same time, a plant needs sunlight as its energy source for photosynthesis and raw materials, such as CO2 and inorganic ions, to synthesize organic molecules. – The root and publishing as systems Copyright © 2002 Pearson Education, Inc.,shoot Benjamin Cummings extensively network
  4. 4. 1. The chemical composition of plants provides clues to their nutritional requirements• Early ideas about plant nutrition were not entirely correct and included: – Aristotle’s hypothesis that soil provided the substance for plant growth – van Helmont’s conclusion from his experiments that plants grow mainly from water – Hale’s postulate that plants are nourished mostly by air.• Plants do extract minerals from the soil. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  5. 5. • Mineral nutrients are essential chemical elements absorbed from soil in the form of inorganic ions. – For example, plants acquire nitrogen mainly in the form of nitrate ions (NO3-).• However, only a small fraction of the water entering a plant contributes to organic molecules. – Over 90% is lost by transpiration. – Most of the water retained by a plant functions as a solvent, provides most of the mass for cell elongation, and helps maintain the form of soft tissues by keeping cells turgid.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  6. 6. • By weight, the bulk of the organic material of a plant is derived not from water or soil minerals, but from the CO2 assimilated from the atmosphere.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  7. 7. • The uptake of nutrients occurs at both the roots and the leaves. – Roots, through mycorrhizae and root hairs, absorb water and minerals from the soil. – Carbon dioxide diffuses into leaves from the surrounding publishing as Benjamin Cummings Fig. 37.1Copyright © 2002 Pearson Education, Inc.,
  8. 8. • Roots are able to absorb minerals somewhat selectively, enabling the plant to accumulate essential elements that may be present in low concentrations in the soil. – However, the minerals in a plant reflect the composition of the soil in which the plant is growing. – Therefore, some of the elements in a plant are merely present, while others are essential.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  9. 9. 2. Plants require nine macronutrients and at least eight micronutrients• A particular chemical element is considered an essential nutrient if it is required for a plant to grow from a seed and complete the life cycle. – Hydroponic cultures have identified 17 elements that are essential nutrients in all plants and a few other elements that are essential to certain groups of plants. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  10. 10. • Hydroponic culture can determine which mineral elements are actually essential nutrients. – Plants are grown in solutions of various minerals dissolved in known concentrations. – If the absence of a particular mineral, such as potassium, causes a plant to become abnormal in appearance when compared to controls grown in a complete mineral medium, then that element is essential. Fig. 37.2
  11. 11. • Elements required by plants in relatively large quantities are macronutrients. – There are nine macronutrients in all, including the six major ingredients in organic compounds: carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus. – The other three are potassium, calcium, and magnesium.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  12. 12. • Elements that plants need in very small amounts are micronutrients. – The eight micronutrients are iron, chlorine, copper, zinc, manganese, molybdenum, boron, and nickel. – Most of these function as cofactors of enzymatic reactions. – For example, iron is a metallic component in cytochromes, proteins that function in the electron transfer chains of chloroplasts and mitochondria. – While the requirement for these micronutrients is so modest (only one atom of molybdenum for every 16 million hydrogen atoms in dry materials), a deficiency of a micronutrient can weaken or kill a plant.
  13. 13. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  14. 14. 3. The symptoms of a mineraldeficiency depend on the function and mobility of the element• The symptoms of a mineral deficiency depend partly on the function of that nutrient in the plant. – For example, a magnesium deficiency, an ingredient of chlorophyll, causes yellowing of the leaves, or chlorosis. Fig. 37.3 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  15. 15. • The relationship between a mineral deficiency and its symptoms can be less direct. – For example, chlorosis can also be caused by iron deficiency because iron is a required cofactor in chlorophyll synthesis.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  16. 16. • Mineral deficiency symptoms depend also on the mobility of the nutrient within the plant. – If a nutrient moves about freely from one part of a plant to another, then symptoms of the deficiency will appear first in older organs. • Young, growing tissues have more “drawing power” than old tissues for nutrients in short supply. • For example, a shortage of magnesium will lead to chlorosis first in older leaves. – If a nutrient is relatively immobile, then a deficiency will affect young parts of the plant first. • Older tissue may have adequate supplies which they retain during periods of shortage.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  17. 17. • The symptoms of a mineral deficiency are often distinctive enough for a plant physiologist or farmer to diagnose its cause. – This can be confirmed by analyzing the mineral content of the plant and the soil. – Deficiencies of nitrogen, potassium, and phosphorus are the most common problems. – Shortages of micronutrients are less common and tend to be geographically localized because of differences in soil composition. • The amount of micronutrient needed to correct a deficiency is usually quite small, but an overdose can be toxic to plants.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  18. 18. • One way to ensure optimal mineral nutrition is to grow plants hydroponically on nutrient solutions that can be precisely regulated. – This technique is practiced commercially, but the requirements for labor and equipment make it relatively expensive compared with growing crops in soil. Fig. 37.4Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  19. 19. • Mineral deficiencies are not limited to terrestrial ecosystems, nor are they unique to plants among photosynthetic organisms. – For example, populations of planktonic algae in the southern oceans are restrained by deficiencies of iron in seawater. • In a limited trial in the relatively unproductive seas between Tasmania and Antarctica, researchers demonstrated that dispersing small amounts of iron produced large algal blooms that pulled carbon dioxide out of the air. • Seeding the oceans with iron may help slow the increase in carbon dioxide levels in the atmosphere, but it may also cause unanticipated environmental effects.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  20. 20. 1.Plant Nutrients  Macronutrients  Micronutrients
  21. 21. 1. Essential Nutrietns of Plants Chemical Atomic Ionic forms Approximate dry Element symbol weight Absorbed by plants ____ concentration_____Mccronutrients Nitrogen N 14.01 NO3-, NH4+ 4.0 % Phosphorus P 30.98 PO43-, HPO42-, H2PO4- 0.5 % Potassium K 39.10 K+ 4.0 % Magnesium Mg 24.32 Mg2+ 0.5 % Sulfur S 32.07 SO42- 0.5 % Calcium Ca 40.08 Ca2+ 1.0 %Micronutrients Iron Fe 55.85 Fe2+, Fe3+ 200 ppm Manganese Mn 54.94 Mn2+ 200 ppm Zinc Zn 65.38 Zn2+ 30 ppm Copper Cu 63.54 Cu2+ 10 ppm Boron B 10.82 BO32-, B4O72- 60 ppm Molybdenum Mo 95.95 MoO42- 2 ppm Chlorine Cl 35.46 Cl- 3000 ppmEssential But Not Applied Carbon C 12.01 CO2 40 % Hydrogen H 1.01 H2O 6% Oxygen O 16.00 O2, H2O 40 % ________________________________________________________________ Plant tissues also contain other elements (Na, Se, Co, Si, Rb, Sr, F, I) which are notneeded for the normal growth and development.
  22. 22. 2. Macronutrients a. Nitrogen (N) 1) Soil Nitrogen Cycle
  23. 23. A. Nitrogen (N) 1) Soil Nitrogen Cycle a) Nitrogen Fixation -Transformation of atmospheric N to nitrogen forms available to plants - Mediated by N-fixing bacteria: Rhizobium (symbiotic) found in legumes (bean, soybean) Azotobacter (non-symbiotic bacteria) b) Soil Nitrification - Decomposition of organic matter into ammonium and nitrate - Mediated by ammonifying and nitrifying bacteria Ammonifying bacteria Nitrifying bacteria (Actinomycetes) (Nitrosomonas) (Nitrobacter) Plant residue → NH4+ → NO2 → NO3- (Protein, aa, etc) Ammonium Nitrite Nitrate
  24. 24. 2) N Functions in Plants - Component of proteins, enzymes, amino acids, nucleic acids, chlorophyll - C/N ratio (Carbohydrate: Nitrogen ratio) High C/N ratio → Plants become more reproductive Low C/N ratio → Plants become more vegetative - Transamination NO3- → NH2 → Glutamic acid → Other amino acids (a.a.) → Protein Enzymes - Essential for fast growth, green color3) Deficiency and Toxicity Symptoms Deficiency: - Reduced growth - Yellowing of old leaves Toxicity (excess): - Shoot elongation - Dark leaves, succulence4) Fertilizers - Ammonium nitrate (NH4NO3) Calcium nitrate [Ca(NO3)2] Potassium nitrate (KNO3) Urea [CO(NH2)2] - Most plants prefer 50:50 NH4+ : NO3- NH4+-form of N → lowers soil pH NO3--form of N → raises soil pH - Organic fertilizers (manure, plant residue) – slow acting
  25. 25. Nitrogen (N) Deficiency Symptoms Yellowing of mature lower leaves- nitrogen is highly mobile in plants
  26. 26. B. Phosphorus (P) 1) Soil Relations - Mineral apatite [Ca5F(PO4)3] - Relatively stable in soil - Has a low mobility (top dressing not effective) 2) Plant Functions - Component of nucleic acid (DNA, RNA), phospholipids, coenzymes, high-energy phosphate bonds (ADP, ATP) - Seeds are high in P 3) Deficiency and Toxicity - P is mobile in plant tissues (Deficiency occurs in older leaves) - Deficiency: dark, purplish color on older leaves - Excess P: causes deficiency symptoms of Zn, Cu, Fe, Mn 4) Fertilizers - Superphosphates (may contain F) Single superphosphate (8.6% P): CaH4(PO4)2 Triple superphosphate (20% P): CaH4(PO4)2 - Ammonium phosphate: (NH4)2PO4, NH4HPO4 - Bone meal - Available forms: PO43-, HPO42-, H2PO4- P absorption influenced by pH
  27. 27. Influence of pH on different forms of phosphorus (P)
  28. 28. C. Potassium (K) 1) Soil Relations - Present in large amounts in mineral soil - Low in organic soils 2) Plant Functions - Activator of many enzymes - Regulation of water movement across membranes and through stomata (Guard cell functions) 3) Deficiency and Toxicity - Deficiency: Leaf margin necrosis and browning Older leaves are more affected - Toxicity: Leaf tip and marginal necrosis 4) Fertilizers - Potassium chloride (KCl)- murate of potash - Potassium sulfate (K2SO4) - Potassium nitrate (KNO3)
  29. 29. Leaf Margin Necrosis in Poinsettia Potassium (K) Deficiency
  30. 30. Macronutrients N, P, K Deficiencies Leaf LettuceControl
  31. 31. Macronutrient Deficiencies Beans
  32. 32. D. Calcium (Ca) 1) Soil Relations - Present in large quantities in earth’s surface (~1% in US top soils) - Influences availability of other ions from soil 2) Plant Functions - Component of cell wall - Involved in cell membrane function - Largely present as calcium pectate in meddle lamela Calcium pectate is immobile in plant tissues 3) Deficiency and Toxicity - Deficiency symptoms in young leaves and new shoots (Ca is immobile) Stunted growth, leaf distortion, necrotic spots, shoot tip death Blossom-end rot in tomato - No Ca toxicity symptoms have been observed 4) Fertilizers - Agricultural meal (finely ground CaCO3·MgCO3) - Lime (CaCO3), Gypsum (CaSO4) - Superphosphate - Bone meal-organic P source
  33. 33. Blossom End Rot of Tomato Calcium DeficiencyRight-Hydroponic tomatoes grown in the greenhouse, Left-Blossom endrot of tomato fruits induced by calcium (Ca++) deficiency
  34. 34. Influence of Calcium on Root Induction on Rose Cuttings
  35. 35. E. Sulfur (S) 1) Soil Relations - Present in mineral pyrite (FeS2, fool’s gold), sulfides (S-mineral complex), sulfates (involving SO4-2) - Mostly contained in organic matter - Acid rain provides sulfur 2) Plant Functions - Component of amino acids (methionine, cysteine) - Constituent of coenzymes and vitamins - Responsible for pungency and flavbor (onion, garlic, mustard) 3) Deficiency and Toxicity - Deficiency: light green or yellowing on new growth (S is immobile) - Toxicity: not commonly seen 4) Fertilizers - Gypsum (CaSO4) - Magnesium sulfate (MgSO4) - Ammonium sulfate [(NH4)2SO4] - Elemental sulfur (S)
  36. 36. F. Magnesium (Mg) 1) Soil Relations - Present in soil as an exchangeable cation (Mg2+) - Similar to Ca2+ as a cation 2) Plant Functions - Core component of chlorophyll molecule - Catalyst for certain enzyme activity 3) Deficiency and Toxicity - Deficiency: Interveinal chlorosis on mature leaves (Mg is highly mobile) - Excess: Causes deficiency symptoms of Ca, K 4) Fertilizers - Dolomite (mixture of CaCO3·MgCO3) - Epsom salt (MgSO4) - Magnesium nitrate [Mg(NO3)2] - Magnesium sulfate (MgSO4)
  37. 37. Magnesium (Mg) Deficiency on PoinsettiaInterveinal Chlorosis on Mature Leaves
  38. 38. Micronutrients• Micronutrient elements – Iron (Fe) – Manganese (Mn) – Boron (B) – Zinc (Zn) – Molybdenum (Mo) – Copper (Cu) – Chlorine (Cl)• Usually supplied by irrigation water and soil• Deficiency and toxicity occur at pH extremes
  39. 39. Influence of pH on Nutrient Availability
  40. 40. 3. Micronutrients A. Iron (Fe) - Component of cytochromes (needed for photosynthesis) - Essential for N fixation (nitrate reductase) and respiration - Deficiency Symptom: Interveinal chlorosis on new growth Fe is immobile Iron chlorosis develops when soil pH is high Remedy for iron chlorosis: 1) Use iron chelates FeEDTA (Fe 330) – Stable at pH < 7.0 FeEDDHA (Fe 138) – Stable even when pH > 7.0 2) Lower soil pH Iron is in more useful form (Fe2+)
  41. 41. Iron (Fe) Deficiency Symptoms1 23 4 A B 1-Piggyback Plant, 2- Petunia, 3-Silver Maple, 4-Rose (A-normal, B-Fe-deficient)
  42. 42. Iron Chelates
  43. 43. Iron (Fe) Absorption by Plants
  44. 44. B. Manganese (Mn) - Required for chlorophyll synthesis, O2 evolution during photoshynthesis - Activates some enzyme systems - Deficiency: Mottled chlorsis between main veins of new leaves (Mn is immobile), similar to Fe chlorosis - Toxicity: Chlorosis on new growth with small, numerous dark spots Deficiency occurs at high pH Toxicity occurs at low pH - Fertilizers: Manganese sulfate (MnSO4) Mn EDTA (chelate) for high pH soilsC. Boron (B) - Involved in carbohydrate metabolism - Essential for flowering, pollen germination, N metabolism - Deficiency: New growth distorted and malformed, flowering and fruitset depressed, roots tubers distorted - Toxicity: Twig die back, fruit splitting, leaf edge burns - Fertilizers: Borax (Na2B4O710H2O), calcium borate (NaB4O7 4H2O)D. Zinc (Zn) - Involved in protein synthesis, IAA synthesis - Deficiency: (occurs in calcarious soil and high pH) Growth suppression, reduced internode lengths, rosetting, interveinal chlorosis on young leaves (Zn is immobile in tissues) - Toxicity: (occurs at low pH) Growth reduction, leaf chlorosis
  45. 45. Micronutrient Toxicity on Seed Geranium BCuFeMnMoZn Cont 0.25 0.5 1 2 3 4 5 6 Concentration (mM)
  46. 46. E. Molybdenum (Mo) - Required for nitrate reductase activity, vitamin synthesis Nitrate reductase NO3 - ————————————— NH2 Mo Root-nodule bacteria also requires Mo - Deficiency: Pale green, cupped young leaves (Mo is immobile) Strap leafe in broad leaf plants Occurs at low pH - Toxicity: Chlorosis with orange color pigmentation - Fertilizer: Sodium molybdateF. Copper (Cu) - Essential component of several enzymes of chlorophyll synthesis, carbohydrate metabolism - Deficiency: Rosette or ‘witch’s broom’ - Toxicity: Chlorosis - Fertilizers: Copper sulfate (CuSO4)G. Chlorine (Cl) - Involved for photosynthetic oxygen revolution - Deficiency: Normally not existing (Only experimentally induced) - Toxicity: Leaf margin chlorosis, necrosis on all leaves - Fertilizer: Never applied (Cl- is ubiquitous!)
  47. 47. Molybdenum Deficiency on Poinsettia