Soil and Plant Nutrition - Fundametnals of Biology - Lecture Notes, Study notes for Biology. Avinashilingam University
sashti21 January 2013

Soil and Plant Nutrition - Fundametnals of Biology - Lecture Notes, Study notes for Biology. Avinashilingam University

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These are the lecture notes of Fundametnals of Biology. Key important points are: Soil and Plant Nutrition, Macronutrients and Micronutrients, Symptoms of Mineral Deficiency, Genetic Modification, Resistance to Aluminum...
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Microsoft PowerPoint - 37_Lecture_Presentation.ppt


1 Chapter 37 Soil and Plant Nutrition


3 Concept 37.2: Plants require essential elements to complete their life cycle • Plants derive most of their organic mass from the CO2 of air, but they also depend on

soil nutrients such as water and minerals

4 Macronutrients and Micronutrients • More than 50 chemical elements have been identified among the inorganic substances

in plants, but not all of these are essential to plants • A chemical element is considered an essential element if it is required for a plant to

complete its life cycle • Researchers use hydroponic culture to determine which chemical elements are





• Nine of the essential elements are called macronutrients because plants require them in relatively large amounts

• The macronutrients are carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium


• The remaining eight are called micronutrients because plants need them in very small amounts

• The micronutrients are chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum

9 Symptoms of Mineral Deficiency • Symptoms of mineral deficiency depend on the nutrient’s function and mobility within

the plant • Deficiency of a mobile nutrient usually affects older organs more than young ones • Deficiency of a less mobile nutrient usually affects younger organs more than older

ones • The most common deficiencies are those of nitrogen, potassium, and phosphorus


11 Improving Plant Nutrition by Genetic Modification: Some Examples • Genetic engineering can improve plant nutrition and fertilizer usage

12 Resistance to Aluminum Toxicity • Aluminum in acidic soils damages roots and greatly reduces crop yields • The introduction of bacterial genes into plant genomes can cause plants to secrete

acids that bind to and tie up aluminum

Chapter 37 - Soil and Plant Nutrition


13 Flood Tolerance • Waterlogged soils deprive roots of oxygen and cause buildup of ethanol and toxins • The gene Submergence 1A-1 is responsible for submergence tolerance in flood-

resistant rice

14 Smart Plants • “Smart” plants inform the grower of a nutrient deficiency before damage has occurred • A blue tinge indicates when these plants need phosphate-containing fertilizer


16 Concept 37.3: Plant nutrition often involves relationships with other organisms • Plants and soil microbes have a mutualistic relationship

– Dead plants provide energy needed by soil-dwelling microorganisms – Secretions from living roots support a wide variety of microbes in the near-root


17 Soil Bacteria and Plant Nutrition • The layer of soil bound to the plant’s roots is the rhizosphere • The rhizosphere has high microbial activity because of sugars, amino acids, and

organic acids secreted by roots

18 Rhizobacteria • Free-living rhizobacteria thrive in the rhizosphere, and some can enter roots • Rhizobacteria can play several roles

– Produce hormones that stimulate plant growth – Produce antibiotics that protect roots from disease – Absorb toxic metals or make nutrients more available to roots


• Inoculation of seeds with rhizobacteria can increase crop yields

20 Bacteria in the Nitrogen Cycle • Nitrogen can be an important limiting nutrient for plant growth • The nitrogen cycle transforms nitrogen and nitrogen-containing compounds • Most soil nitrogen comes from actions of soil bacteria



• Plants absorb nitrogen as either NO3– or NH4+ • Bacteria break down organic compounds or use N2 to produce NH3, which is converted

to NH4+ • Nitrification is carried out by bacteria that convert NH3 into NO3–

23 Nitrogen-Fixing Bacteria: A Closer Look • N2 is abundant in the atmosphere, but unavailable to plants • Nitrogen fixation is the conversion of nitrogen from N2 to NH3 • Symbiotic relationships with nitrogen-fixing bacteria provide some plant species with a

Chapter 37 - Soil and Plant Nutrition


built-in source of fixed nitrogen • Key symbioses occur between nitrogen-fixing bacteria and plants, including those in

the legume family (peas, beans, and other similar plants)


• Along a legume’s roots are swellings called nodules, composed of plant cells “infected” by nitrogen-fixing Rhizobium bacteria

• Inside the root nodule, Rhizobium bacteria assume a form called bacteroids, which are contained within vesicles formed by the root cell

• The bacteria of a root nodule obtain sugar from the plant and supply the plant with fixed nitrogen



• Each legume species is associated with a particular strain of Rhizobium • The development of a nitrogen-fixing root nodule depends on chemical dialogue

between Rhizobium bacteria and root cells of their specific plant hosts


28 Nitrogen Fixation and Agriculture Crop rotation takes advantage of the agricultural benefits of symbiotic nitrogen fixation • A non-legume such as maize is planted one year, and the next year a legume is

planted to restore the concentration of fixed nitrogen in the soil


• Instead of being harvested, the legume crop is often plowed under to decompose as “green manure” and reduce the need for manufactured fertilizer

• Non-legumes such as alder trees, certain tropical grasses, and rice benefit either directly or indirectly from nitrogen-fixing bacteria

30 Fungi and Plant Nutrition Mycorrhizae are mutualistic associations of fungi and roots • The fungus benefits from a steady supply of sugar from the host plant • The host plant benefits because the fungus increases the surface area for water

uptake and mineral absorption • Mycorrizal relationships are common and might have helped plants to first colonize


31 The Two Main Types of Mycorrhizae • In ectomycorrhizae, the mycelium of the fungus forms a dense sheath over the

surface of the root • These hyphae form a network in the apoplast, but do not penetrate the root cells



• In arbuscular mycorrhizae, microscopic fungal hyphae extend into the root • These mycorrhizae penetrate the cell wall but not the plasma membrane to form

branched arbuscules within root cells

Chapter 37 - Soil and Plant Nutrition



35 Agricultural and Ecological Importance of Mycorrhizae • Farmers and foresters often inoculate seeds with fungal spores to promote formation of

mycorrhizae • Some invasive exotic plants disrupt interactions between native plants and their

mycorrhizal fungi

36 Epiphytes, Parasitic Plants, and Carnivorous Plants • Some plants have nutritional adaptations that use other organisms in nonmutualistic

ways • An epiphyte grows on another plant and obtains water and minerals from rain



• Parasitic plants absorb sugars and minerals from their living host plant





• Carnivorous plants are photosynthetic but obtain nitrogen by killing and digesting mostly insects




Chapter 37 - Soil and Plant Nutrition

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got a great help in learning about macronutrients
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