1. Soil and Plant Nutrition Ch
Soil and Plant Nutrition Ch. 37 study of necessary elements for plant growth

2. Plants…
Critical role in energy flow and chemical cycling of ecosystems
Transform light energy  chemical energy
Transform inorganic compounds  organic compounds
Dry weight
95% organic
5% minerals

3. The uptake of nutrients by a plant: a review
CO2, the source
of carbon for
Photosynthesis,
diffuses into
leaves from the
air through
stomata.
Through
stomata, leaves
expel H2O and
O2.
H2O O2
CO2
Roots take in
O2 and expel
CO2. The plant
uses O2 for cellular
respiration but is a net O2 producer.
Roots absorb
H2O and
minerals from
the soil.
Minerals

4. Table 37.1 Essential Elements in Plants

5. Nutritional Requirements
Essential nutrient
required to develop from a seed through its life cycle
Sunlight
Carbon dioxide
Water
Supplies most of H and O2 for photosynthesis; 80-85% of plant
90% lost during transpiration

7. Soil Texture Major factors in what kind of plants will grow
Texture depends upon particle size
sand mm; silt mm;
clay < 2 mm
Horizons
distinct soil layers
Topsoil
Horizon A
decomposed rock, living organisms, humus
Humus
decomposing organic matter
prevents clay from packing together
crumbly soil
reservoir of mineral nutrients
Loams
most fertile, mixture of sand, silt, clay
fine particles retain water & minerals
coarse particles provide air spaces

8. Texture and Composition of Soil
Living organisms
Worms aerate the soil
Bacteria alter soil mineral composition
Fungi, algae, protists, insects, nematodes, plant roots

9. Topsoil Composition
Surface charges of soil particles determine binding ability
Positively charged adhere…
Not likely to leach away
Potassium, calcium, magnesium
Mineral cations enter by absorption from soil solution
Cation exchange
Negatively charged ions are easily released and leached away

10. The availability of soil water and minerals
Soil particle surrounded by
film of water
Root hair
Water available to plant
Air space
H2O + CO2
H2CO3
HCO3– +
Soil particle K+
Cu2+
Ca2+
Mg2+ H+ –
(a) Soil water. A plant cannot extract all the water in the soil because some of it is tightly held by hydrophilic soil particles. Water bound less tightly to soil particles can be absorbed by the root.
(b) Cation exchange in soil. Hydrogen ions (H+) help make nutrients available by displacing positively charged minerals (cations such as Ca2+) that were bound tightly to the surface of negatively charged soil particles. Plants contribute H+ by secreting it from root hairs and also by cellular respiration, which releases CO2 into the soil solution, where it reacts with H2O to form carbonic acid (H2CO3). Dissociation of this acid adds H+ to the soil solution.

11. Soil Conservation & Sustainable Agriculture
Irrigation
causes huge drain on water resources; main source is aquifers
gradually makes soil salty (hypertonic) and infertile  salinization
Solutions 
Drip irrigation
Develop plant varieties that require less water or can tolerate more salinity
Fertilizers
Way to reverse nutrient depletion
N, P, K
mined, chemically produced, organic
soil pH important
organic
Manure, fishmeal, compost

12. Soil Conservation & Sustainable Agriculture
Adjusting soil pH
Influences mineral availability
Most prefer slightly acidic soils
Controlling Erosion
Water and wind are the main causes
Plant rows of trees, terrace hillside crops, contour pattern
No till agriculture
Special plowing technique
Phytoremediation
Nondestructive biotechnology
Harnesses the ability of some plants to extract pollutants and concentration them in portions of the plant that can be easily removed

13. Macro and Micronutrients
Soil, water, and air all contribute to plant growth
80-90% of fresh mass is water
Essential Elements
Required for a plant to complete its life cycle
Determined by hydroponic culture
Variety of inorganic, mineral ions in the soil
macronutrients (9)
micronutrients (8)
Mostly cofactors
Deficiencies depend on
role of nutrient in the plant
its mobility within the plant
K, N, P
Phosphate-deficient
Healthy
Potassium-deficient
Nitrogen-deficient

14. Genetic Modification - Improving Plant Nutrition
Resistance to Aluminum Toxicity
Introduction of the citrate synthase gene from bacteria
Flood Tolerance
Flood resistant rice (submergence gene)
Smart Plants
Signal when a mineral deficiency is imminent

15. Soil Bacteria and Plant Nutrition
Rhizobacteria
Soil bacteria with especially large populations in the rhizosphere
Soil layer that surrounds plant roots
Produce chemicals to stimulate plant growth
Produce antibiotics to prevent root diseases

16. Bacteria and the Nitrogen Cycle

17. Figure 37.10 Root nodules on legumes
(a) Pea plant root. The bumps on this pea plant root are nodules containing Rhizobium bacteria. The bacteria fix nitrogen and obtain photosynthetic products supplied by the plant.
(b) Bacteroids in a soybean root nodule. In this TEM, a cell from a root nodule of soybean is filled with bacteroids in vesicles. The cells on the left are uninfected.
5 m
Bacteroids
within
vesicle
Nodules
Roots

18. Development of a soybean root nodule

19. Nitrogen Fixing Bacteria
Root nodules
Legumes
Roots secrete chemicals to attract nearby bacteria
Bacteria emit chemicals to cause root hairs to elongate and curl to prepare for infection within the root cortex
Mutualistic relationship
Bacteria supplies nitrogen and legumes supply the carbs
Crop rotation
Legumes planted in off years to restore nitrogen in the soil
If not harvested, plowed under

20. Mycorrhizae
1 Ectomycorrhizae. The mantle of the fungal mycelium ensheathes the root. Fungal hyphae extend from the mantle into the soil, absorbing water and minerals, especially phosphate. Hyphae also extend into the extracellular spaces of the root cortex, providing extensive surface area for nutrient exchange between the fungus and its host plant.
2 Endomycorrhizae. No mantle forms around the root, but microscopic fungal hyphae extend into the root. Within the root cortex, the fungus makes extensive contact with the plant through branching of hyphae that form arbuscules, providing an enormous surface area for nutrient swapping. The hyphae penetrate the cell walls, but not the plasma membranes, of cells within the cortex.
Mantle (fungal sheath)
Epidermis
Cortex
Endodermis
Fungal hyphae between cortical cells
(colorized SEM)
100 m
Fungal hyphae
Root hair
10 m
(LM, stained specimen)
Cortical cells
Vesicle
Casparian strip
Arbuscules

21. Nutritional Adaptations
Parasitism
Photosynthetic but supplement diet from the host - mistletoe
If lose photosynthetic ability then get all nutrition from phloem sap – dodder
Indian Pipe – nonphotosynthetic parasite of mycorrhizae

22. Nutritional Adaptations
Epiphytes
live on other plants but not parasites
anchored by roots and nourish themselves from water and minerals absorption
ferns, mosses, orchids

23. Carnivorous plants: Venus fly trap (left), pitcher plant (right)

24. Nutritional Adaptations
Carnivorous plants
supplemental diets because of living in poor soil conditions
Venus fly trap, Pitcher plants, Sundew

25. Mangroves – Root, Stems, and Reproductive adaptations