Soil pH influences availability of soil nutrients

Download Soil pH influences availability of soil nutrients

Post on 03-Jan-2016

213 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • Soil pH influences availability of soil nutrients.

  • Fine roots and root hairs mine the soil for nutrients. Mycorrhizal hyphae do this even better.

    4. Roots and mineral nutrient acquisition

  • RootsProvide large surface area for nutrient uptake- Root hairs

  • Why are fine structures like hyphae and root hairsparticularly effective at nutrient absorption?For a given volume (or mass) of roots, what size rootpresents the most surface area?

  • Surface area of a cylinderSA = circumference x lengthSA = x diam x lengthSA = x 2r x length

    Volume = area x lengthVol = x r2 x length

    SA/Vol = ( x 2r x length)/( x r2 x length)

    SA/Vol = 2/rAs the radius decreases, the surface area per volume increases.

  • Minirhizotron photos of yellow birch roots in the Hubbard Brook Experimental Forest (New Hampshire) in April (left) and June (right). 0.3 mm in diameter.

  • Fig. 5.7Depletion zones - regions of lowernutrient concentration -developaround roots

  • A depletion zone of low concentration forms near the rootwhen the rate of nutrient uptake exceeds the rate of diffusion

  • Mycorrhizaefungus - rootSymbiosis with fungiNutrient Uptake and Mycorrhiza

  • Roots and Mycorrhiza an old symbiosisMutual benefit Carbohydrates for the fungus P, Zn, Cu, water, N for plant

    Different types

    1. Vesicular-arbuscular mycorrhiza VA-mycorrhiza2. EctomycorrhizaOther typesericoidorchid endomycorrhiza

  • 1. Vesicular arbuscular mycorrhiza (AM)

    Glomales (130 species infects 300.000 plant species)

    Found on roots of herbaceous angiosperms, most trees, mosses, ferns

    not present on Cruciferae, Chenopodiaceae, Proteaceae

    small biomass compared to roots

  • Vesicular Arbuscular Mycorrhiza

    Inside root Intercellular mycelium Intracellular arbuscule tree-like haustorium Vesicle with reserves

    Outside root Spores (multinucleate) Hyphaethick runnersfilamentous hyphae

    Form extensive network of hyphaeeven connecting different plants

  • AMArbuscule of Glomus mosseae branching provides large surface area

  • Outside of root network of hyphae and spores

  • 2. Ectomycorrhiza (EM)

    Ascomycetes and Basiodiomycetes form large fruiting bodies

    5000 species interact with 2000 plant species

    Interaction with trees: angiosperms and all Pinaceae

  • Ectomycorrhiza

    Inside root Intercellular hyphae

    Does not enter cells

    Outside root Thick layer of hyphae around root Fungal sheath Lateral roots become stunted

    HyphaeMass about equal to root mass

    Forms extensive network of hyphaeeven connecting different plants

  • Ectomycorrhizal root tip

  • Mantle HyphaeHartig Net

  • Why mycorrhiza? Roots and root hairs cannot enter the smallest pores

  • Why mycorrhiza?Root hairSmallest hyphae Roots and root hairs cannot enter the smallest pores

    Hyphae is 1/10th diameter of root hair

    Increased surface area

    Surface area/volume of a cylinder: SA/vol 2/radius

  • Why mycorrhiza? Roots and root hairs cannot enter the smallest pores

    Hyphae is 1/10th of root hair

    Increased surface area

    Extension beyond depletion zone

  • Why mycorrhiza? Roots and root hairs cannot enter the smallest pores

    Hyphae is 1/10th of root hair

    Increased surface area

    Extension beyond depletion zone

    Breakdown of organic matterC C NH2 --> C C + NH3

  • Summary on mycorrhizae

    Symbiosis with mycorrhiza allows greater soil exploration, and increases uptake of nutrients (P, Zn, Cu, N, water)

    Great SA per mass for hyphae vs. roots

    Mycorrhiza gets carbon from plant

    Two main groups of mycorrhiza Ectomycorrhiza and VA-mycorrhiza

  • For usmore on nitrogen nutrition

    Why is N so important for plant growth?

    What percentage of the mass of plant tissues is N?

    What kinds of compounds is N found in?

    Why is there a strong relationship between the Nconcentration of leaves and photosynthesis?

  • Nitrogen - the most limiting soil nutrient

    Evidence - factorial fertilization experiments (N, P, K, etc.)show largest growth response to N.

    Required in greatest amount of all soil nutrients

    2. A component of proteins (enzymes, structural proteins,chlorophyll, nucleic acids)

    3. The primary photosynthetic enzyme, Rubisco, accountsfor a 25 to 50% of leaf N.Photosynthetic capacity is strongly correlated with leaf N concentration.

    4. Availability in most soils is low

    5. Plants spend a lot of energy on N acquisition - growingroots, supporting symbionts, uptake into roots, biochemical assimilation into amino acids, etc.

  • The inorganic forms of nitrogen in soils.

    NH4+, ammonium ion. A cation that is bound to clays.NO3-, nitrate ion. An anion that is not bound to clays.

    Nutrient mobility in soils refers to the rate of diffusion,which is influenced by nutrient ion interactions with soil particles.

    Would you expect NH4+ or NO3- to diffuse more rapidly?

    Would you expect a more pronounced depletion zone for NH4+ or NO3-?

  • The Nitrogen Cycle

  • SoilOrganic N

    NH4+

    Plant N

    NO3-

    NH4+ uptake

    Mineralization

    NH4+ immobilization

    Nitrification

    NO3-uptake

    NO3- immobilization

    NO, N2O

    N2

    Leaching

    Denitrification

    N Fixation

    Atmospheric N2

  • 1. Emissions to atmosphereDead organismsand tissuesPathways of N loss from ecosystems2.

  • SoilOrganic N

    NH4+

    Plant N

    NO3-

    NH4+ uptake

    Mineralization

    NH4+ immobilization

    Nitrification

    NO3-uptake

    NO3- immobilization

    NO, N2O

    N2

    Leaching

    Denitrification

    N Fixation

    Atmospheric N2

    PP05040.jpgPP05070.jpg

Recommended

View more >