Plant Form and Function

Soil and Plant NutritionPlant biology, perhaps the oldest branch of science, is driven by a combination of curiosity and needcuriosity about how plants work need to apply this knowledge judiciously to feed, clothe, and house a burgeoning human population.

Plant Nutrition What does a plant

need to survive?• 9 macronutrients (required

in large quantities)• C, H, N, O, P, S, K, Ca, Mg• 8 micronutrients (required

in small quantities)• Fe, Cl, Cu, Mn, Zn, Mo, B,

Ni usually serve as cofactors of

enzymatic reactions

Soil Bacteria and Nitrogen Availability

Nitrogen-fixing bacteria convert atmospheric N2

plants absorb ammonium (NH4+), nitrate (NO3

-)

Atmosphere

N2

Soil

N2 N2

Nitrogen-fixingbacteria

Organicmaterial (humus)

NH3

(ammonia)

NH4+

(ammonium)

H+

(From soil)

NO3–

(nitrate)Nitrifyingbacteria

Denitrifyingbacteria

Root

NH4+

Soil

Atmosphere

Nitrate and nitrogenous

organiccompoundsexported in

xylem toshoot system

Ammonifyingbacteria

Mineral Deficiency• The most common deficiencies are those

of nitrogen, potassium, and phosphorus

Phosphate-deficient

Healthy

Potassium-deficient

Nitrogen-deficient

Hydroponics Remove only one

macronutrient to see effects on plant

Soil Texture and Composition

• Texture depends on size of particles

• sand-silt-clay• loams: equal amounts of

sand, silt, clay• Composition• Horizons-living organic matter

A horizon: topsoil, living organisms, humus

B horizon: less organic, less weathering than A horizon

C Horizon: “parent” material for upper layers

• Soil conservation issues fertilizers, irrigation, erosion

Soil Aeration A mixture of mineral particles, decaying

organic material, living organisms, air, and water, which together support the growth of plants

Nutritional Adaptations Symbiotic Relationships

• symbiotic nitrogen fixation Legume root nodules contain bacteroids (Rhizobium

bacteria) mutualistic relationship Crop rotation

• Mycorrhizae symbiotic associations of fungi and roots mutualistic relationship Ectomycorrhizae - mycelium forms mantle over root Endomycorrhizae - does not form mantle; hyphae extend

inward• Parasitic plants

plants that supplement their nutrition from host mistletoe, dodder plant, Indian pipe

• Carnivorous plants supplement nutrition by digesting animals

Staghorn fern, an epiphyte

EPIPHYTES

PARASITIC PLANTS

CARNIVOROUS PLANTS

Mistletoe, a photosynthetic parasite Dodder, a nonphotosynthetic parasite

Host’s phloem

Haustoria

Indian pipe, a nonphotosynthetic parasite

Venus’ flytrap Pitcher plants Sundews

Dodder

Venus flytrapPitcher plant

Phytoremediation Poplars remove nitrates Mustard removes

uranium

Phytoremediation

WetlandsPhytoremediation

Pesticide Levels (ppb) in Ground Water Before & After Phytoremediation Activities