1. Plant Nutrition (ch37)
For a typical plant water and minerals come from the soil, while carbon dioxide comes from the air
Branching roots and shoots of a vascular plant ensure procuring these raw materials for photosynthesis

2. Plants derive most of their organic mass from the CO2 of air
they also depend on soil nutrients such as water and minerals
CO2, source
of C; through
stomata.
stomata, expels
H2O and O2.
H2O O2
CO2
H2O and
minerals
Minerals

3. SOIL – must be rich in minerals and sufficient H2O
37.2: Soil quality is a major determinant of plant distribution and growth, along with climate
Soil Texture
Is the soil’s general structure
Composition
Refers to the soil’s organic and inorganic chemical components

4. Many types of soil: Clay, silt, sandy, salty
Loam is a type of soil with equal parts of sand, silt, and clay
topsoil : a mixture of particles of rock and organic material

5. water drains rapidly from the larger spaces of soil
Loam is a type of soil with equal amounts of sand, silt, and clay
topsoil is a mixture of these sized particles of rock and organic material
water drains rapidly from the larger spaces of soil
But clings to surfaces of clay and
org. particles

6. Soil pH determines availability of minerals to plants
Acids derived from roots contribute to a plant’s uptake of minerals
The H+ produced releases
mineral cations from soil
particles (esp clay)
H2O + CO2
H2CO3
HCO3– +
Root hair K+
Cu2+
Ca2+
Mg2+ H+
Soil particle –

7. Human Agriculture: Erosion, Irrigation, etc
Topsoil from thousands of acres of farmland is lost to erosion each year in the United States
Irrigation, & changes the chemical makeup of soil can make it saline
lost to salinization, in millions of acres:

8. Soil Bacteria and Nitrogen Availability
Nitrogen-fixing bacteria convert atmospheric N2
To nitrogenous minerals that plants can absorb as a nitrogen source for organic synthesis
Nitrogenase is the enzyme used to catalyze the nitrogen fixation reaction
Figure 37.9
Atmosphere N2
Soil
Nitrogen-fixing bacteria
Organic material (humus)
NH3 (ammonia)
NH4+ (ammonium)
H+ (From soil)
NO3– (nitrate)
Nitrifying bacteria
Denitrifying bacteria
Root
NH4+
Nitrate and nitrogenous organic compounds exported in xylem to shoot system
Ammonifying bacteria

9. Symbiosis feeds the plants that feeds us
Legumes possess root nodules containing nitrogen-fixing Rhizobium bacteria
Nodules
Roots

10. Symbiotic Nitrogen Fixation and Agriculture
nitrogen fixation is the Underlying reason for crop rotation
Corn and soybeans may be rotated to improve the soil for the sake of the corn

11. Mycorrhizae and Plant Nutrition
Are modified roots consisting of mutualistic associations of fungi and roots
The fungus
Benefits from a steady supply of sugar donated by the host plant through photosynthesis
In return, the fungus
Increases the surface area for uptake of water and minerals

12. The Two Main Types of Mycorrhizae
In ectomycorrhizae
The mycelium of the fungus forms a dense sheath over the root
Mantle (fungal sheath)
(colorized SEM)
100 m
(a)

13. In endomycorrhizae
Microscopic fungal hyphae extend into the cells of the root
Epidermis
Cortex
Fungal hyphae
Root hair
10 m
(LM, stained specimen)
Casparian strip
(b)

14. Agricultural Importance of Mycorrhizae
Farmers and foresters
Often inoculate seeds with spores of mycorrhizal fungi to promote the formation of optimal root systems

15. Epiphytes, Parasitic Plants, and Carnivorous Plants
Some plants
Have nutritional adaptations that use other organisms in non-mutualistic ways
Epiphytes are plants that nourish themselves but grow on other plants
Parasitic plants absorb nutrients from host plants
Carnivorous plants procure additional minerals and nitrogen by digesting insects