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
AtmosphereNitrate and nitrogenous
organiccompoundsexported inxylem to
shoot 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