Lecture 11 Outline (Ch. 37)

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Lecture 11 Outline (Ch. 37)

• I. Mineral Acquisition
• II. Soil Conservation
• III. Essential Nutrients
• Relationships with other organisms
• Lecture Concepts

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Overview A Nutritional Network

• Every organism
• Continually exchanges energy and materials with
  its environment
• The branching root and shoot system provides high
  SAV to collect resources
• Plants resources are diffuse (scattered, at low
  concentration)

What are these diffuse resources?
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Light
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Mineral Acquisition

• Can a plant grow there?
• Climate
• Soil Quality
• Texture type of soil particles
• Composition organic and inorganic components

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Mineral Acquisition

• After heavy rainfall, water drains away from the
  larger spaces in soil
• But smaller spaces retain water because of its
  attraction to surfaces of clay and
  other particles
• The film of loosely bound water
• available to plants

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Mineral Acquisition

• Acids derived from roots contribute to a plants
  uptake of minerals
• When H displaces mineral cations from clay
  particles

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Soil Conservation and Sustainable Agriculture

• In contrast to natural ecosystems agriculture
  depletes
• mineral content of the soil
• taxes water reserves
• encourages erosion
• The goal of soil conservation strategies
  minimize this damage
• Fertilizers whats the problem?
• Commercially produced fertilizers Minerals are
  either mined or prepared industrially
• Irrigation Why? Why not?
• Can change the chemical makeup of soil
• Erosion Why? Why should we care?
• Topsoil from thousands of acres of farmland is
• lost to water and wind erosion each year in the
  U.S.

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Soil Conservation and Sustainable Agriculture

• Agricultural researchers
• Are developing ways to maintain crop yields while
  reducing fertilizer and water use.
• Certain precautions
• Can prevent the loss of topsoil

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Essential Nutrients and Deficiencies

• Plants require certain chemical 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

Essential elements Required for a plant to
complete its life cycle
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Essential elements in plants

• Nine of the essential elements are called
  macronutrients
• Because plants require them in relatively large
  amounts
• The remaining eight essential elements are known
  as micronutrients
• Because plants need them in very small amounts

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Nitrogen, Soil Bacteria and Nitrogen Availability

• Plants compete fiercely for key nutrients like
  Nitrogen
• Nitrogen is needed for Proteins, nucleic acids,
  chlorophyll, etc.
• Nitrogen-fixing soil bacteria convert atmospheric
  N2
• To nitrogenous minerals that plants can absorb

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Symptoms of Mineral Deficiency

• The symptoms of mineral deficiency depend on
• nutrients function
• nutrients mobility within the plant

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

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Relationship with other organisms

• Root nodulation
• Mycorrhizae
• Parasitic plants
• Carnivorous plants

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Symbiotic Nitrogen Fixation

• Symbiotic relationships between certain
  nitrogen-fixing bacteria and certain plants.
• Mainly legume family (e.g. peas, beans)

Why is this a symbiosis?
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• Nodules Swellings of plant cells infected by
  Rhizobium bacteria

Bacteroids within vesicle
5 ?m

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

(b) Bacteroids in a soybean root nodule. In this
TEM, a cell froma root nodule of soybean is
filledwith bacteroids in vesicles. The cells on
the left are uninfected.
Figure 37.10b
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• Each legume is associated with a particular
  strain of Rhizobium
• Nodule development depends on a
• chemical dialogue between Rhizobium bacteria and
  root cells of their specific plant hosts

Figure 37.11
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Mycorrhizae and Plant Nutrition

• Mycorrhizae
• Symbiotic relationship between a root and fungus
• Most but not all plants.
• The fungus gets supply of sugars from the plant
• The fungus gives Increases the surface area for
  water and mineral absorption
• Agriculturally, farmers and foresters
• Often inoculate seeds with spores of mycorrhizal
  to promote mycorrhizal relationships.

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Two Common Types of Mycorrhizae

• In ectomycorrhizae
• The mycelium of the fungus forms a dense sheath
  over the surface of the root

Figure 37.12a
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Two Common Types of Mycorrhizae

• In endomycorrhizae
• Fungal hyphae extend into the root and form
  arbuscules

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Epiphytes, Parasitic and Carnivorous Plants
Figure 37.14
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Self-Check
Macronutrients (not a complete list) Sources Any special methods for obtaining.
Carbon
Oxygen
Hydrogen
Nitrogen
Phosphorus
Magnesium
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Lecture 11 concepts

• Name the resources that plants need and must
  acquire.
• Explain how plants uptake minerals via their
  roots.
• What are the concerns for soil conservation?
• Define macronutrient and micronutrient. List
  the macronutrients.
• Describe how plants obtain carbon.
• Explain how plants acquire nitrogen (more than
  one way).
• Define symbiosis. Discuss the symbioses with
  bacteria and fungi.
• Describe epiphytes, parasitic, and carnivorous
  plants.
• Make a list of new vocabulary with definitions.