Section 4: FLowering Plants Nutrition

MUN BIOL 1002

hydroponic Culture

a method in which plants are grown in mineral solutions rather than soil and can be used to determine which chemical elements are essential

Number of essential elements in plants

17 in total:

• 9 are macronutrients

• 8 are micronutrients

macronutrients

major building elements for structure (cell walls, membranes) and function (enzymes, DNA, ect.)

micronutreints

function as cofactors; nonprotein helpers in enzymatic reactions

• only needed in small amounts

Liebig’s Law of the Minimun

plant growth is limited by the resource that is in the shortest supply

antagonistic

in plants and soil microbes; microbes can be pathogens of plants

Commensalistic

in plants and soil microbes; can have 0 effect on the plant

• ie: secretions from living roots support a wide variety of microbes in the near-root environment

mutualistic

in plants and soil microbes; microbes can benefit both the plant host and itself

• ie:
  Soil microorganisms access essential elements from living or dead organisms, releasing them in an inorganic form when they respire organic matter, which benefits plant growth, as they couldn’t reach those nutrients before

Rhizobacteria

a soil bacterium whose population is enhanced in the rhizosphere

Rhizosphere

the layer of soil bound to the plant’s roots

Endophytes

non-pathogenic bacteria that live between the cells of host plant tissues

Role of Rhizobacteria

• rhizosphere contains decomposers and nitrogen fixers

• produces hormones that stimulate plant growth

• produces antibiotics that protect roots from disease

• absorb toxic metals

Nitrogen-fixing bacteria

the conversion of nitrogen from N2 to NH3

• costs energy and in some mutualistic relationships they will produce more than they need by using energy from the plant

Nodules

a swelling on the root of a legume. Composed of plant cells that contain nitrogen-fixing bacteria (Rhizobium)

bacteriods

a form of the bacterium Rhizobium contained within the vessels formed by the root nodule

crop rotation

the practice of planting non legumes one year and legumes in alternating years to restore concentration of fixed nitrogen in the soil

Mycorrhizae

mutualistic associations of fungi and roots

• fungus benefits from a supply of sugar from host

• host benefits from an increased surface area for water uptake and mineral absorption

Ectomycorrhizae

fungal mycelium forms dense sheath over surface of roots. The hyphae form a network in apoplast but does not penetrate root cell walls

Endomycorrhizae

fungal hyphae extend into root and penetrate cell wall

Arbuscules

specialized branching hyphae that are found in some mutualistic fungi and exchange nutrients with living plant cells

Epiphytes

grow on another plant and obtains water and minerals from rain

Parasitic Plants

absorb sugars and minerals from their living host plant

Carnivorous Plants

are photosynthetic but obtain nitrogen by killing and digesting animals