Soil, Plant Nutrition & RootsChapters 29, 30,
24
Soils and Plant Nutrition• Plants require nutrients from soil• In eastern US, 200 yr to form 2 cm
topsoil (even slower in western where arid)
• What is soil? • A mixture of:
• Mineral particles (sand, silt, clay)• Decomposing organic matter (humus)• Air• Water• Living Organisms
humus
Mineral Particles• Sand 0.05-2.0 mm• Silt 0.002-0.05 mm• Clay < 0.002 mm• Clay soils
• soil water holding capacity, but all water not available for plants
• infiltration rates so runoff• Loamy soils
• even mixture of particle sizes
• best for agricultural
siltsand
clay
Many soils in southeastern Nebraska were formed in parent materials deposited by the glaciers, usually referred to as glacial drift, glacial till or glacial outwash.
Much of the parent material deposited in ancient times has been covered by windblown material. The windblown silty material is called loess. It covers most of Nebraska to varying depths, except in the Sandhills and western portions of the Panhandle.
Where does soil come from?
• Weathering of parent material (bedrock)
• Soil horizons• O horizon
• organic, few cm thick• humus – organic decay products• contained within A horizon in
some classifications• A horizon
• topsoil, 10-30cm thick• greatest physical, chemical, and
biological activity• B horizon
• subsoil, larger particles, 30-60cm
• leaching from A horizon by water percolation
• iron oxide, clay particles, little organic material
• mixed with A horizon when plowed
• C horizon• soil base• partially weathered parent
material, 90-120 cm
Soil Forming Factors• Parent material• Climate• Living organisms• Topography• Time
Extent of North American glaciation
2008 Iowa Floods
June 2008 Rainfallhttp://www.srh.noaa.gov
Cedar Rapids Iowahttp://www.treehugger.com
Soil erosion20 tons/acre
40,000lbs/acre
Some farms in Iowa have no topsoil remaining
(Mary Skopec, Iowa DNR)
Essential Elements for Plants
Macronutrients (9)• required in greater amounts• What do these macronutrients do?
C, H, O - basic organic constituents
N, K, Ca, P - oh my gosh, some very essential
organics: amino acids, nucleotides, ATP,
NADPH, cell wall, regulatory, osmoregulation
Mg, S - chlorophyll, electron transport chain,
amino acids
chlorophyll
Required for normal growth & reproductionNo other element can replaceDirect or indirect action in plant metabolism
Magnesium deficiency Iron deficiency
Chlorosis
amine group
Essential Elements (continued)
Micronutrients (8)• required in lesser quantities
Fe, Mn, Cu, Zn, B, Mo, Cl, Ni• What do these micronutrients do?
essential for enzyme function, organ and organelle function, photosynthesis
Manganese: involved in photosynthetic reaction in which oxygen is produced from waterCopper: associated with enzymes involved in redox reactionsIron: component of enzymes involved in the transfer of electronsEtc…..
Plant Growth Medium for fern gametophytes (C-fern)
• MacronutrientsNH4NO3, KH2PO4, MgSO4, CaCl2
• MicronutrientsMnSO4, CuSO4, ZnSO4, H3BO3,
(NH4)6Mo7O24, FeSO4
Nickel
Roots
• Roots are 50-80% of plant biomass in prairie
• Plants “forage” for dilute nutrients in environment
Epidermis: • one cell thick, usually no
cuticle; absorbs water
Cortex:• just interior to epidermis,
waxy protective layer• parenchyma tissue: most of
cortex, often contains starch• endodermis: tightly packed
cells with casparian strip
Stele: • tissue inside cortex• pericycle: interior to
endodermis - a meristem for branch roots
• vascular bundle: xylem as a cross with phloem in armpits
Monocot Root
Dicot Root
Dicot - young stele
Dicot - mid-aged stele
Dicot - old stele
Endodermis change through aging
Casparian Strip
Casparian Strip
• integral band-like portion of primary wall and middle lamella in endodermal cells
• lignin and suberin “valve”• regulates water because
water • must move symplastically
through the endodermal cells’s cytoplasm
• through plasmodesmata between cells
• rather than apoplastically• through intercellular spaces
• water alone moves transcellularly – across cytoplasm membranes
Root hairs
due to molecular structure
O
H H
-
++
a polar molecule - excellent solvent
adhesion
hydrogen bonding
between water molecules
between water and other molecules
cohesion
O
HH
-
++
OH
H
-
++
OH
H
-
++
tensile strength
capillarity - from cohesion and adhesion
Unique Properties of Water
Leaf Anatomy
H2O
• 85-95% of plants is water
• 95% of H20 taken up by plant transpired back into atmosphere
Transpiration and Productivity
• Leaves adapted for photosynthesis• abundant stomata• large number vein endings
• Tradeoff • CO2 in - photosynthesis
• H2O out - transpiration
• H2O limits biomass production in most areas
• Evapotranspiration• transpiration & soil
evaporation• problematic in arid areas
cohesion and adhesion cause water to rise in plants
as water evaporates from the leaf surface,
a column of water
is pulled upward from the soil water
Cohesion-tension theory
vessel elementstracheid
Size comparison of xylem elements
Note distribution of pits in walls of all xylem elements (tracheids and vessels)
pits
perforation plate (end walls)
Problems with water movement
• air bubbles• cavitation
• water column rupture
• embolism• filling with air or
water vapor• solution
• move water around embolism
Is there a limit to water column?
• How tall are the tallest trees?
• What are the tallest trees?
Tallest Tree• Coast Redwood
• Sequoia sempervirens
• Redwood National Park California
• Height = 116m (379.1 feet) named Hyperion; Steve Sillett, Humboldt State U.
• Estimated Age = 2,000+ yrs
• Sillett article
• Nat Geo short video
• Full length redwood video
Save the Redwoods League
Giant Redwood -Sequoiadendron giganteum
• Top: lithograph showing a party of 32 people dancing on the stump of the Discovery Tree, North Calaveras Grove
• Bottom: 30-foot section of the General Noble Tree, which was displayed at the Columbian Exposition in Chicago in 1893 and later at the Mall in Washington, DC; it was subsequently taken to the US government's Arlington Experiment Farm, where it was "misplaced"
http://en.wikipedia.org/wiki/Image:Giant_sequoia_exhibitionism.jpg
A good review:
• Outline the process of water movement from soil - into the atmosphere
• Include: • structural pathway• physical process
Kingdom Fungi – characteristics
1. body composed of hyphae• filaments, single cell wide• tightly packed together
forming the mycelium• high surface-to-volume
ratio
hyphae
mycelium
2. cell wall made of chitin• polysaccharide• more resistant to
microbial degradation than cellulose
Kingdom Fungi – characteristics
3. lifestyle - heterotrophic• saprophytic
• from dead organisms• parasitic
• from living organisms• mutualistic symbionts
Kingdom Fungi – characteristics
4. sexual and asexual spore producers• asexual with sporangia or
conidiogenous cells (which produce conidia)• very common in air
Alternaria conidia
Cladosporium
Rhizopus - bread mold
Leptosphaeriaceae
Kingdom Fungi – characteristics
Kingdom Fungi – characteristics4. sexual and asexual
spore producers• sexual
• zygospores• ascospores• basidiospores
• classification based in part upon sexual reproduction
Zygomycota
Ascomycota
Basidiomycota
Mycorrhizal associations
• Fungi which infect plant roots
• Mutualism benefits both organisms• increased water and inorganic
nutrient uptake for plant, especially phosphorus
• increased carbohydrate reserve for fungi
• Ectomycorrhizae and endomycorrhizae
• Increase plant yields:• wheat 200%; corn 100%;
onions 3000%
• Found in 80% of plants studied
• Significance to pioneer plants?
Spiranthes cernula Nodding Lady’-tresses
Roots have obligate mycorrhizal associations required for establishment of seedlings
Cypripedium acaulePink Ladyslipper
Long known as having a mychorrhizal association, recent studies indicate a coevolution of Cypripedium and specific fungi