Plant Nutrition Chapter 35 - 2017 PDF

Chapter 35 Plant Nutrition p. 805-823 © 2017 Cengage Learning. All Rights  Lecture 9 PLANT NUTRITION: pp. 805-809; 815-817 At the end of this chapter, you should be able to:  Differentiate essential from beneficial elements  Distinguish between macro- and micronutrie...

Chapter 35 Plant Nutrition p. 805-823 © 2017 Cengage Learning. All Rights  Lecture 9 PLANT NUTRITION: pp. 805-809; 815-817 At the end of this chapter, you should be able to:  Differentiate essential from beneficial elements  Distinguish between macro- and micronutrients  Describe in which forms are macro- and micronutrients absorbed  Explain the metabolic functions and typical deficiency symptoms of macronutrients  Discuss the reactions associated with every stage of the nitrogen cycle © 2017 Cengage Learning. All Rights Why It Matters… In contrast to animals, plants can synthesize all substances required for their growth through photosynthesis However, they need optimum nutrient (inorganic and organic forms) and water supply; roots-from the soil) The carbon for organic compounds comes from the CO2 in air, and with enough available water, plant roots gain access to needed hydrogen, oxygen and other nutrients p. 805 © 2017 Cengage Learning. All Rights 35.1 Plant Nutritional Requirements Some minerals are needed in small quantities (Micro-elements) while others in large quantities(Macro-elements) Method for studying if an element essential or not= Hydroponics By growing plants in hydroponic culture (hydro = water; ponos = work), a German - Julius von Sachs in 1860 deduced six essential plant nutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) More essential plant nutrients (17) were identified later p.805-807 -study © 2017 Cengage Learning. All Rights Essential Nutrients An essential element: 1. is necessary for normal growth and reproduction, 2. cannot be replaced by a different element, 3. and has one or more roles in plant metabolism NB: With 17 essential elements, plants can synthesize all the compounds they need 9 elements = macronutrients -required in relatively large amounts 8 elements = micronutrients - required in trace amounts p. 807 © 2017 Cengage Learning. All Rights Macronutrients Macronutrients: C,H,O – N,P,K, Mg, Ca, S Available in the forms of ions dissolved in water C, H, O make up 96% of a plant’s dry mass N = essential to proteins and nucleic acids P = nucleic acids, ATP, and phospholipids K = enzyme activation & stomatal movement Mg = chlorophyll, enzyme activation Ca = cell wall p. 807; Table 35.1 © 2017 Cengage Learning. All Rights Essential Plant Nutrients NB !! C H O N P K Ca S Mg p. 807 © 2017 Cengage Learning. All Rights Micronutrients Micronutrients: copper (Cu), chlorine (Cl), nickel (Ni), iron (Fe), boron (B), manganese (Mn), zinc (Zn), and molybdenum (Mo) Some species of plants may require additional micronutrients: (Read) Many C4 plants require sodium (Na) A few plant species require selenium (Se) Horsetails and some grasses (such as wheat) require silicon (Si) They are called Beneficial elements p. 808 © 2017 Cengage Learning. All Rights Essential Plant Nutrients (cont’d.) © 2017 Cengage Learning. All Rights Nutrient Deficiencies The nutrient content of soils - an important factor determining if plants will grow well Plants differ in the quantity of each nutrient they require – an adequate amount for one plant may be harmful to another Plants deficient in one or more essential elements develop characteristic symptoms, like stunted growth, abnormal leaf color (yellow = chlorosis), dead spots (necrosis), or abnormal stems p. 808 © 2017 Cengage Learning. All Rights Nutrient Deficiencies NB !!! p. 807 © 2017 Cengage Learning. All Rights Nutrient Deficiencies (cont'd.) Nitrogen, essential for synthesis of amino acids, chlorophylls, and other compounds vital to plant metabolism – deficiency causes chlorosis in older leaves first Iron, a component of cytochromes – deficiency causes chlorosis, a yellowing that results from lack of chlorophyll in younger leaves first Magnesium is a component of chlorophyll – deficiency causes pale color (chlorosis) and stunted growth p. 808-809 © 2017 Cengage Learning. All Rights Fertilizers Soils are more likely to be deficient in nitrogen (N), phosphorus (P), and potassium (K) Farmers add nutrients in the form of fertilizers to suit plant requirements Commercial fertilizers use a numerical shorthand (etc., 15-30-15) to indicate the percentages of nitrogen (N), phosphorus (P), and potassium (K) p. 809 © 2017 Cengage Learning. All Rights Plants Depend on Bacteria for Nitrogen Lack of nitrogen is the single most common limit to plant growth – there usually is not enough nitrogen available in usable ionic forms Plants can’t extract gaseous nitrogen (N2) from air because they lack the enzyme necessary to break the N2 molecule (N=N) apart However, plants can absorb nitrogen from the soil in the form of nitrate (NO3–) or ammonium (NH4+), which are produced by bacteria as part of the nitrogen cycle p. 815-817 - NB !!! © 2017 Cengage Learning. All Rights Nitrogen Cycle – Nitrogen fixation Nitrogen fixation (N2 - atmospheric molecule) Nitrogen-fixing bacteria in soil add hydrogen to N2, producing two molecules of NH3 (ammonia) and one H2 (requires ATP, catalyzed by nitrogenase) H2O and NH3 react, forming NH4+ (ammonium) and OH– NH4+ - uptake by plant roots p. 815 - 817 - NB !!! © 2017 Cengage Learning. All Rights Nitrogen cycle - Ammonification and Nitrification Ammonification - produces ammonium (NH4+) when ammonifying soil bacteria break down decaying organic matter NH4+ - uptake by plant roots Nitrification - NH4+ also oxidized to nitrate (NO3–) by nitrifying soil bacteria NO3– - uptake by plant roots Because of ongoing nitrification, nitrate (NO3-) is more abundant than ammonium (NH4+) in most soils p. 815 - 817 - NB !!! © 2017 Cengage Learning. All Rights Nitrogen cycle - Nitrogen Assimilation Nitrogen assimilation In root cells, absorbed NO3– is converted by a multistep process back to NH4+ NH4+ used to synthesize nitrogen-rich organic molecules - amino acids (building blocks of proteins) Amino acids then transported throughout the plant In some plants, nitrogen-rich precursors transported to leaves, where different organic molecules are synthesized p. 816 NB !!! © 2017 Cengage Learning. All Rights Nitrogen cycle - Denitrification Denitrification Some soil bacteria carry out denitrification Conversion of nitrites (NO2-) or nitrates (NO3-) into nitrous oxide (N2O) and then into molecular nitrogen (N2) - escapes to the atmosphere Because denitrification removes nitrates from the soil, it reduces the amount of nitrogen available to plant roots Denitrification completes the nitrogen cycle p. 816 - NB !!! © 2017 Cengage Learning. All Rights How Plants Access Nitrogen – Nitrogen cycle N2 = 79% Atmospheri c Nitrogen (N2) Atmospheri c Nitrogen Decaying (N2) Organic matter Nitrogen-fixing bacteria convert Denitrifying N2 to ammonia (NH3), which Ammonifying bacteria dissolves to form bacteria ammonium (NH4+ ). NO3– converted to NH4+, which is moved via Nitrifying xylem to the shoot bacteria system. Ammonium Nitrate (NH4+ ) (NO3– ) © 2017 Cengage Learning. All Rights Nitrogen cycle - Ammonification and Nitrification Ammonification and Nitrification What do you see / realise ??? - action of soil bacteria - decaying organic matter Humus - and concept of compost making !!!!!! Basis of “Organic farming” !!!! © 2017 Cengage Learning. All Rights What is your viewpoint? © 2017 Cengage Learning. All Rights  Lecture 10 PLANT NUTRITION (Soil): pp. 809-812 At the end of this section, you should be able to:  Describe soil structure and composition  Describe the underlying concept of compost making  Discuss adsorption of inorganic nutrients to the soil  Discuss uptake of inorganic nutrients from the soil © 2017 Cengage Learning. All Rights 35.2 Soil – Self study Soil anchors plant roots and is the main source of water and inorganic nutrients Soils develop due to the weathering: Physical - break rock and inorganic particles Chemical – acid rain Biological – decay of organic matter Physical and chemical properties of soils have a major impact on the ability of plants to grow, survive, and reproduce p. 809; Self study © 2017 Cengage Learning. All Rights  Soil: composition https://www.youtube.com/watch?v=HmEyymGXOfI &list=PPSV https://youtu.be/HmEyymGXOfI?si=YnN_Go2okrus yVLp © 2017 Cengage Learning. All Rights Properties of a Soil Soil is a complex mixture of mineral particles, chemical compounds, ions, decomposing organic matter, air, water, and assorted living organisms Soil particles: - sand (2.0–0.02 mm) - silt (0.02–0.002 mm) - clay (less than 0.002 mm) Amounts of sand, silt & clay determine soil type: Clay soils (>30% clay) - sticky, with few air spaces Sandy soils (