PLANT NUTRITION. Development of Agriculture critical to civilization Top three major human foods are grass seeds/fruit (grains) Wheat: Near East 9,000 years ago 684.4 million Metric Tons 2008/09 global wheat production is projected. Watch a Kansas Wheat Field Grow!.
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Development of Agriculture critical to civilization
Top three major human foods are grass seeds/fruit (grains)
Wheat: Near East 9,000 years ago
684.4 million Metric Tons 2008/09 global wheat production is projected
Watch a Kansas Wheat Field Grow!
441.0 million Metric Tons 2008/09 global rice production is projected
Watch a Japanese Rice Field Grow!
772 million metric tons 2008/09 global corn production
is projected (U.S. ethanol is consuming
roughly 13% of the corn produced in the world).
Visit the Iowa Corn Cam!
Continually exchanges energy and materials with its environment
For a typical plant
Water and minerals come from the soil, while carbon dioxide comes from the air
Ensure extensive networking with both reservoirs of inorganic nutrients
Plants derive most of their organic mass from the CO2 of air
But they also depend on soil nutrients such as water and minerals
CO2, the source
of carbon for
leaves from the
expel H2O and
Roots take in
O2 and expel
CO2. The plant
uses O2 for cellular
respiration but is a net O2 producer.
To determine which chemicals elements are essential
APPLICATION In hydroponic culture, plants are grown in mineral solutions without soil. One use of hydroponic culture is to identify essential elements in plants.
TECHNIQUE Plant roots are bathed in aerated solutions of known mineral composition. Aerating the water provides the roots with oxygen for cellular respiration. A particular mineral, such as potassium, can be omitted to test whether it is essential.
containing all minerals
RESULTS If the omitted mineral is essential, mineral deficiency symptoms occur, such as stunted growth and discolored leaves. Deficiencies of different elements may have different symptoms, which can aid in diagnosing mineral deficiencies in soil.
(Not always) (Clean)
CuMn CoZn MoB(y)!
With some apologies to Edward Hopper (American 1882-1967) Nighthawks, 1942 Oil on canvas; 33 1/8 x 60 in. (84.1 x 152.4 cm)
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
Key to role elements play in plants for next two slide
Cofactors, osmotic relationships
H = Hydrogen = Major structural component of organic molecules
O = Oxygen = Major structural component of organic molecules; Final electron acceptor in Oxidative Phosphorylation
P = Phosphorus = Important structural component of nucleic acids, phospholipids, coenzymes
K = Potassium = Important cofactor of some enzymes, stomatal opening, membrane potentials, osmotic balance
N = Nitrogen = Important structural component of nucleic acids, proteins, chlorophyll, some phytohormones
S = Sulfer = Important structural component of some amino acids, forms disulfide bridges that are important to enzyme activity
Fe = Iron = Site of catalytic reaction in many redox enzymes, essential for chlorophyll formation
Mg = Magnesium = Involved in stabilization of ribosomes, cofactor for many enzymes, structural component of chlorophyll
Cl = Chlorine = Involved in photolysis of water in photosynthesis
Cu = Copper = site of catalytic reaction for some enzymes
Mn = Manganese = Respiratory enzyme cofactor, involved in photolysis of water, required for auxin synthesis
Co = Cobalt = Structural component of vitamin B12, necessary for nitrogen fixation
Zn = Zinc = Involved in auxin synthesis, enzyme cofactor
Mo = Molybdemun = Involved in reduction of nitrates
B = Boron = Involved in translocation and absorption of sugar, interacts with Ca flux
Cofactors, osmotic relationships
Depend partly on the nutrient’s function
Depend on the mobility of a nutrient within the plantSymptoms of Mineral Deficiency
Are those of nitrogen, potassium, and phosphorus
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
Is the soil’s general structure
Refers to the soil’s organic and inorganic chemical components
Along with organic material (humus) in various stages of decomposition
The eventual result of this activity is topsoil
A mixture of particles of rock and organic materialTexture and Composition of Soils
Are often visible in vertical profile where there is a road cut or deep hole
The A horizon is the topsoil, a mixture of
broken-down rock of various textures, living
organisms, and decaying organic matter.
The B horizon contains much less organic
matter than the A horizon and is less
The C horizon, composed mainly of partially
broken-down rock, serves as the “parent”
material for the upper layers of soil.
Soils in the Miamian series, for example, are well drained. They typically have a very dark grayish brown to brown silt loam or loam topsoil layer ("A horizon") 5 to 10 inches thick. They commonly have a brown or yellowish brown subsoil layer ("B horizon"), 8 to 35 inches thick, with a higher clay content than the A horizon. Below the subsoil, soils in the Miamian series have a brown to light olive brown substratum ("C horizon") that is slightly or moderately alkaline and has a lower clay content than the B horizon.
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
Soil particle surrounded by
film of water
Water available to plant
(a) Soil water. A plant cannot extract all the water in the soil because some of it is tightly held by hydrophilic soil particles. Water bound less tightly to soil particles can be absorbed by the root.
When H+ displaces mineral cations from clay particles
H2O + CO2
(b) Cation exchange in soil. Hydrogen ions (H+) help make nutrients available by displacing positively charged minerals (cations such as Ca2+) that were bound tightly to the surface of negatively charged soil particles. Plants contribute H+ by secreting it from root hairsand also by cellular respiration, which releases CO2 into the soil solution, where it reacts with H2O to form carbonic acid (H2CO3). Dissociation of this acid adds H+ to the soil solution.
All fertilizer labels have three bold numbers. The first number is the amount of nitrogen (N), the second number is the amount of phosphate (P2O5) and the third number is the amount of potash (K2O). These three numbers represent the primary nutrients (nitrogen(N) - phosphorus(P) - potassium(K)).
This label, known as the fertilizer grade, is a national standard.
A bag of 10-10-10 fertilizer contains 10 percent nitrogen, 10 percent phosphate and 10 percent potash.
A Homeowner's Guide to Fertilizer
International Fertilizer Industry Association
Recent estimates indicate 70% of all Nitrogen within Nitrogen Cycle on Earth is currently contributed by human activity!
Death in the Gulf
Hypoxia means an absence of oxygen reaching living tissues. In coastal waters, it is characterized by low levels of dissolved oxygen, so that not enough oxygen is available to support fish and other aquatic species.
Nutrients, such as nitrogen and phosphorous, are essential for healthy marine and freshwater environments.
However, an over overabundance of nutrients can trigger excessive algal growth (or eutrophication) which results in reduced sunlight, loss of aquatic habitat, and a decrease in oxygen dissolved in the water.
Excess nutrients may come from a wide range of sources:
Runoff from developed land
Sewage and industrial discharges also contribute nutrients.
Plants require nitrogen as a component of
Proteins, nucleic acids, chlorophyll, and other important organic molecules
To nitrogenous minerals that plants can absorb as a nitrogen source for organic synthesis
Nitrate and nitrogenousorganiccompoundsexported inxylem toshoot system
H+ (From soil)
RootSoil Bacteria and Nitrogen Availability
Two types of relationships plants have with other organisms are mutualistic
Symbiotic nitrogen fixation
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)The Role of Bacteria in Symbiotic Nitrogen Fixation
Composed of plant cells that have been “infected” by nitrogen-fixing Rhizobium bacteria
(a) Pea plant root. The bumps onthis pea plant root are nodules containing Rhizobium bacteria.The bacteria fix nitrogen and obtain photosynthetic productssupplied by the plant.
Obtain sugar from the plant and supply the plant with fixed nitrogen
Is associated with a particular strain of Rhizobium
Dividing cellsin root cortex
2 The bacteria penetrate the cortex within the Infection thread. Cells of the cortex and pericycle begin dividing, and vesicles containing the bacteria bud into cortical cells from the branching infection thread. This process results in the formation of bacteroids.
Roots emit chemical signals that attract Rhizobium bacteria. The bacteria then emit signals that stimulate root hairs to elongate and to form an infection thread by an invagination of the plasma membrane.
Dividing cells in pericycle
3Growth continues in the affected regions of the cortex and pericycle, and these two masses of dividing cells fuse, forming the nodule.
The nodule develops vascular tissue that supplies nutrients to the nodule and carries nitrogenous compounds into the vascular cylinder for distribution throughout the plant.
Underlie 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 soilSymbiotic Nitrogen Fixation and Agriculture
Are modified roots consisting of mutualistic associations of fungi and roots
Benefits from a steady supply of sugar donated by the host plant
In return, the fungus
Increases the surface area of water uptake and mineral absorption and supplies water and minerals to the host plantMycorrhizae and Plant Nutrition
The mycelium of the fungus forms a dense sheath over the surface of the root
aEctomycorrhizae. The mantle of the fungal mycelium ensheathes the root. Fungal hyphae extend from the mantle into the soil, absorbing water and minerals, especially phosphate. Hyphae also extend into the extracellular spaces of the root cortex, providing extensive surface area for nutrient exchange between the fungus and its host plant.
(colorized SEM)The Two Main Types of Mycorrhizae
Microscopic fungal hyphae extend into the root
2Endomycorrhizae. No mantle forms around the root, but microscopic fungal hyphae extend into the root. Within the root cortex, the fungus makes extensive contact with the plant through branching of hyphae that form arbuscules, providing an enormous surface area for nutrient swapping. The hyphae penetrate the cell walls, but not the plasma membranes, of cells within the cortex.
(LM, stained specimen)
Staghorn fern, an epiphyte
Mistletoe, a photosynthetic parasite
Indian pipe, a nonphotosynthetic parasite
Dodder, a nonphotosynthetic parasite
Pitcher plantsEpiphytes, Parasitic Plants, and Carnivorous Plants
Have nutritional adaptations that use other organisms in nonmutualistic ways