1. Plant Nutrition

2. Basic Plant Composition
Dry Weight: 96% Organic: mostly carbohydrates
– starch and cellulose
4% Inorganic: non – carbon containing nutrients
Essential Elements: necessary to grow – 17 types
- determined by hydroponic experimentation

3. Macronutrients 9 of 17 essentials – needed in large amounts
C O H N P S K Ca Mg
NUTRIENT
FUNCTION
Carbon, Hydrogen, Oxygen
Carbs, Proteins, lipids
Nitrogen
Nucleic Acids Proteins, Chlorophylls
Potassium
Cofactor, stomata control
Calcium
Cell stability and response
Magnesium
Central atom of chlorophyll
Phosphorous
ATP, Phospholipids, Nucleic Acids
Sulfur
Proteins

4. Micronutrients:
8 of 17 essentials – need in very small amounts: Cl Fe Mn B Zn Cu Ni Mo
NUTRIENT
FUNCTION
Chlorine
Hydrolysis of water
Iron
In ETC
Manganese
Hydrolysis of water, Amino Acid Synthesis
Boron
Chlorophyll synthesis
Zinc
Copper
Lignin Synthesis
Nickel
Nitrogen Metabolism
Molybdenum
Symbiosis with N2 Fixing Bacteria

5. Signs of Mineral Deficiencies
Phosphate-deficient
Healthy
Potassium-deficient
Nitrogen-deficient

6. Role of Soil in Plant Nutrition
Soil Formation:
Physical Weathering
Freeze/thaw cycles
- water seeps into small cracks in rocks
– freezes – expands – makes crack bigger
- rocks break down
Erosion
- break down by wind and water
Root Expansion
- small roots in small crevices expand by lateral growth and break the rock open

7. Chemical Weathering:
Acids dissolved in water
Acids released by organisms
Type of rock affects the quality of the soil
Ex: Limestone (shale) – calcium carbonate
– neutralization of acids
- can lead to a natural buffering effect on acid rain

8. Soil Composition:
Topsoil – rock particles, living organisms and humus (remains of partially decayed organic material – Sphagnum moss)
Soil Layers – stratification
- Top layer - top soil
O, A, B, C, and E.

9. Soil Texture
- based on the particles in the soil
- coarse – sandy – good for drainage – too much results in an inability to retain nutrients
- medium – silt
- fine – clay
- negatively charged – attract water molecules
– good for retaining water and minerals that forms a soil solution that the plant roots extract if the water and minerals are not bound to the clay particles too tightly
– anions (nitrate, phosphate, sulfate) are not bound tightly – may leach (wash away) in the presence of heavy rain
– cations (potassium, calcium, magnesium) are bound tightly to the clay and are harder to extract
– too much clay in the soil results in an inability to have sufficient oxygen for root metabolism
- loamy –mixture of sand (40%), silt (40%) and clay (20%)

10. Role of living organisms
- decomposers: fungi, bacteria, worms (annelids, nematodes) – break down organic matter – larger organism help aerate (make air spaces) the soil
- plant roots
- hold soil in place
- cation exchange – release organic acids which put H+ in the soil solution, the H+ replace the positive ions (Mg, K, Ca) bound to the clay particles making them available for root uptake

11. Cation Exchange Figure 37.6b
(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.
H2O + CO2
H2CO3
HCO3– +
Root hair K+
Cu2+
Ca2+
Mg2+ H+
Soil particle –

12. Soil Amendments: changing the soil for better plant growth
- too sandy, add silt
- too fine, add humus or sand
- lacking nutrients – add fertilizer

13. Types of Fertilizers:
Organic – dead plant materials or poo – must be further decomposed for nutrients to be absorbed by plants – retained in the soil longer
Inorganic – industrial manufactured chemicals (Ex: plant “food”)
N-P-K Ratio: percentage of nitrogen, phosphorous and potassium in fertilizer
- typically available to the plants almost immediately (may be a slow release) – enter the soil solution quickly
- easily leached by heavy rains or excessive irrigation – run-off into ground water (wells) by percolation (methemoglobinemia – blue baby syndrome) , streams or lakes (lead to algal blooms and eutrophication)
- pH adjustments – incorrect pH may prevent cation exchange
- low pH (acidic) add powdered lime stone
- high pH (base) add acidifiers (peat moss)

14. Ecological Impact of Irrigation:
- taking water from somewhere else
- desertification – salts in the water remain after the water has evaporated – the soil has a higher saline content and can become hyperosmotic preventing the plants from taking in water
Nitrogen:
- must be in ammonia or nitrate form for plants to absorb – plants mainly absorb nitrate and then convert it to ammonia in their cells
- Two basic sources
- decomposed materials release absorbable forms
- atmospheric nitrogen is converted to these forms by nitrifying bacteria in the soil or in root nodules of plants (legumes)

15. Plant Nutrition and Symbiosis:
- Root Nodules – Nitrogen Fixation
- Mycorrhizae: “fungus roots”
- plants provide sugar to fungus
- fungus increases the surface area of the roots for absorption of water and minerals
- also secrete growth factors that stimulate roots growth and antibiotics that protect against bacteria
- fungal species is usually specific to the plant
Two Types:
- Ectomycorrhizae – form a sheath of mycelium and penetrate the apoplast of the plant roots
- Endomycorrhizae – very fine fungal hyphae that extend into the plant root cell walls but don’t puncture the cell membrane – form branching structures called arbuscules that facilitate nutrient transfer

16. Strange Nutrition in Plants
Epiphytes: grow on other plants – absorb water and minerals from rain, usually through their leaves EX: orchids,
Parasites: roots function as haustoria (grow into the cells of other plants) and absorb sugars and nutrients – may or many not be photosynthetic: EX: mistletoe and Indian pipes
Carnivores – eat animals – not for energy but for minerals – usually live in environments that are nitrogen and mineral poor – roots can’t absorb the proper minerals so they are extracted from digested animals EX: Venus fly trap, Pitcher plants, Sundews
Aggressive Plants: strangler fig

17. Staghorn fern, an epiphyte Mistletoe, a photosynthetic parasite
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