Plant Nutrition

1
Chapter 37

• Plant Nutrition

2
Nutrient Reservoirs

• Every organism continually exchanges energy and
  materials with its environment
• For plantswater and minerals come from the soil,
  while carbon dioxide comes from the air
• The branching root system and shoot system of a
  vascular plant ensure extensive networking with
  both reservoirs of inorganic nutrients

3
Macronutrients and Micronutrients

• Plants derive most of their organic mass from the
  CO2 of air but they also depend on soil nutrients
  
• More than 50 chemical elements have been
  identified among the inorganic substances in
  plants, but not all of these are essential
• A chemical element is considered essential if it
  is required for a plant to complete a life cycle

4
How would you identify an essential nutrient?

• Hydroponic culture can be used to determine which
  chemicals elements are essential

5
Macronutrients and Micronutrients

• Nine of the essential elements are called
  macronutrients because plants require them in
  relatively large amounts
• C, O, H, N, K, Ca, Mg, P, S
• The remaining eight essential elements are known
  as micronutrients because plants need them in
  very small amounts
• Cl, Fe, Zn, Mn, Boron, Cu, N, Molybdenum

6
Mineral Deficiency

• The symptoms of mineral deficiency
• Depend partly on the nutrients function
• Depend on the mobility of a nutrient within the
  plant
• Deficiency of a mobile nutrient
• Usually affects older organs more than young ones
  (young tissue can more efficiently draw minerals
  to it)
• Deficiency of a less mobile nutrient
• Usually affects younger organs more than older
  ones (older tissue has a store of minerals to
  fall back on when the mineral is in short supply)

7
Mineral Deficiency

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

Reddish-purple margins esp. on young leaves
Firingdrying along tips and margins of older
leaves
Yellowing that starts at the tip and moves along
the center of older leaves
8
Soil Characteristics

• Soil quality is a major determinant of plant
  distribution and growth
• Along with climate
• The major factors determining whether particular
  plants can grow well in a certain location are
  the texture and composition of the soil
• Textureis the soils general structure (sandy,
  clay, etc)
• Compositionrefers to the soils organic and
  inorganic chemical components
• Various sizes of particles derived from the
  breakdown of rock are found in soil along with
  organic material (humus) in various stages of
  decomposition
• Topsoil is the mixture of particles of rock and
  organic material

9
Soil Horizons

• The topsoil and other distinct soil layers, or
  horizons are often visible in vertical profile
  where there is a road cut or deep hole

10
Availability of Soil Water

• After a rainfall, water drains away from the
  larger spaces of soil but smaller spaces retain
  water because of its attraction to surfaces of
  clay and other particles.
• The film of loosely bound water is usually
  available to plants

11
Fertilizers

• Commercially produced fertilizers contain
  minerals that are either mined or prepared by
  industrial processes
• Organic fertilizers are composed of manure,
  fishmeal, or compost

12
Irrigation

• Is a huge drain on water resources when used for
  farming in arid regions
• Can change the chemical makeup of soil
• Salinization (salt buildup)

sprinkler
drip
Ditchtrench
13
Erosion

• Topsoil from thousands of acres of farmland
• Is lost to water and wind erosion each year in
  the United States

The U.S. Soil Conservation Service reports that
more than 4 million acres of cropland are being
lost to erosion in this country every year.
That's an area greater than the size of
Connecticut. Our annual topsoil loss amounts to 7
billion tons. That is 60,000 pounds for each
member of the population.
Erosion on conventionally tilled field
14
Prevention of topsoil loss

• Strip cropping practice of growing field crops
  in narrow strips either at right angles to the
  direction of the prevailing wind, or following
  the natural contours of the terrain to prevent
  wind and water erosion of the soil
• Contour tillage (slows water runoff and erosion)

15
Prevention of topsoil loss

• Conservation tillage (Min-till)

• Terraces

A minimum tillage system may involve quicker and
fewer passes at a shallower depth

• Cover Crops

Cover crop in an orchard
Cover crop in vegetable garden
16
Soil Reclamation

• Some areas are unfit for agriculture
• Because of contamination of soil or groundwater
  with toxic pollutants
• Phytoremediation is a biological, nondestructive
  technology that seeks to reclaim contaminated
  areas by using the ability of some plants to
  remove soil pollutants

17
Nitrogen

• Nitrogen is often the mineral that has the
  greatest effect on plant growth
• Plants require nitrogen as a component of
  proteins, nucleic acids, chlorophyll, and a host
  of other important organic molecules

18
Soil Bacteria and Nitrogen Availability

• Nitrogen-fixing bacteria convert atmospheric N2
  to nitrogenous minerals that plants can absorb as
  a nitrogen source for organic synthesis

19
The Role of Bacteria in Symbiotic Nitrogen
Fixation

• Symbiotic relationships with nitrogen-fixing
  bacteria provide some plant species with a
  built-in source of fixed nitrogen
• From an agricultural standpoint the most
  important and efficient symbioses between plants
  and nitrogen-fixing bacteria occur in the legume
  family (peas, beans, and other similar plants)

20
Root Nodules

• Along a legumes roots are swellings called
  nodules composed of plant cells that have been
  infected by nitrogen-fixing Rhizobium bacteria
• The bacteria of a nodule obtain sugar from the
  plant and supply the plant with fixed nitrogen
• Each legume is associated with a particular
  strain of Rhizobium

21
Symbiotic Nitrogen Fixation and Agriculture

• The agriculture benefits of symbiotic nitrogen
  fixation are the basis for crop rotation
• In this practice a non-legume such as maize is
  planted one year, and the following year a legume
  is planted to restore the concentration of
  nitrogen in the soil
• Agricultural importance Farmers and foresters
  often inoculate seeds with spores of mycorrhizal
  fungi to promote the formation of mycorrhizae

22
Ectomycorrhizae

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

23
Endomycorrhizae

• In endomycorrhizae the microscopic fungal hyphae
  extend into the root

24
Epiphytes, Parasitic Plants, and Carnivorous
Plants
Epiphytes use a host for support but do not
extract nutrients from the host

• Some plants have nutritional adaptations that use
  other organisms in nonmutualistic ways

25
Improving the Protein Yield of Crops

• Plant breeding research has resulted in new
  varieties of maize, wheat, and rice that are
  enriched in protein
• Such research addresses the most widespread form
  of human malnutrition protein deficiency
• Many of the projects creating GMOs (genetically
  modified organisms) are aimed at protein
  enrichment of crops.

High lysine corn