Week 7 Full

TA: Zara Tabi ([email protected]) BICD 120: Dr. Crawford AIM: ztabi06 OH: By email Appt. Week 7 Plant Nutrition -Nutrients essential for life  Found dissolved in the soil solution and taken up by the roots •The Macronutrients: S(SO42-), P(PO43-), •The Micronutrients: B, Cu, Mo, Mn, etc. + N(NO3 , NH4 ), K, Mg, Ca, Fe  “SPaNK My CaFe!” Root Structure

Matching: (1) Root Meristem- Site of cell division (2) Root Cap- Protects root meristem from damage (3) Epidermis- Outermost layer of a root - Reponsible for H2O absorbtion (4) Root Hairs- Projections from epidermal cells - Increased surface area for H2O

(5) Cortex- Middle layer of root - Can consist of one or many layers depending on the plant (6) Endodermis- Surrounds vascular tissue (7) Casparian Strip- Layer of endodermis impermeable by Ions and H2O (8) Stele- Region of vascular tissue (xylem, phloem)

Nutrient Uptake - Ions can travel 2 ways through a root: 1) Symplasm- System of cytoplasm connected via plasmodesmata 2) Apoplasm- System of cell walls - Cannot reach the stele of a root through apoplasmic transport • Casparian strip of the endodermis acts as a block - Ions eventually need to cross a plasma membrane to enter the symplasm • Active transport  Needs ATP! - Uses ATPase & Co-transporter • Can bypass the Casparian strip by plasmodesmata

Transpiration: How H2O & Salts travel from roots to shoots - H2O evaporation from the stomata “pulls” water up shoot  Pulling/Tension Force - H-Bonding between water molecules allows H2O column to stay in tact  Cohesion -Controlled by the opening & closing of stomates! • When open, allows CO2 in (for Photosynthesis) and H2O out -Open: Light, -Close: Dark, High Temp, High CO2, Low O2 Low H2O (ABA) Photosynthate Transport: Occurs through the phloem and can be multidirectional; Primarily Succrose Source: Where photosynthate is Sink: Where photosynthate is needed produced or stored • Mature Leaves • Leaves (in • Young Leaves • Roots (in Summer) • Storage Organs Summer) • Fruits  Leaves (in • Roots (in • Cotyldons • Flowers Spring) Spring) • Seeds - Osmotic Pressure Flow Theory- Use of osmotic pressure, based on sucrose [ ], to transport Nitrogen Fixation: The conversion of N2 into a usable form (NH4)  Symbiotic Relationship - Key Enzyme: Nitrogenase  Provided by the Bacteria (Rhizobium) • Energy Intensive process  Energy and Proper environment Needs ATP • Needs Fe & Mo  Sensitive to supplied by plant! O2

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The Steps: 1) Plants release compounds to attract bacteria - Nod genes in bacteria are activated to synthesize nitrogenase

2) Bacteria attach to roots, causing root hair to curl.

3) Bacteria enter the plant via an infection thread - Bacteria is protected from plant defense systems

4) New plant meristem formation - Site of future nodule

5) Bacteria terminally differentiate to bacteroids - Can NO LONGER DIVIDE

6) Nodule formation is complete

Plant Pathology and Defense - Plant Epidemics—Result in a large amount of crop lost • Ex. Great Potato Blight (Phytoptera), SD Citrus Quarantine (Psylid) • Chance of epidemic is greater with monoculturing  use of one variety over a large area - Plant Stresses: Can be Abiotic or Biotic  understand the difference between the two and know examples! - Methods of biotic attack: • Herbivory—eating of plant tissue  Performed by insects and animals • Cell Infection—gain acess to cytoplasm  Microbes (bacteria, fungi, etc.) -Plants vs. Predators Plant Defense—How do they protect themselves?

Microbe Attack—How do they get past these defenses?

1) Physical Defense- Protect entry into cytoplasm • Ex. Bark, Wax cuticle, cell wall

1) Oppurtunistic- Infect at wound sites already present (due to herbivory, pruning, etc.)

2) Chemical Defense • Proteins: Lectins (fungi, bacteria) or protease inhibitors (insects, animals) • Organics: Secondary metabolites - Phenolics, Tanins, Alkaloids - Phytoalexins- similar to antibiotics • Most toxins are PATHOGEN SPECIFIC - If a general toxin, can be stored safely in vacuole, cell wall, or specialized structures until needed

2) Brute Force- The breaking down of protective layers with enzymes or toxins • Enzymes are HOST SPECIFIC: Hydrolases - Break down cell wall • Toxins: Small organics, phytohormones (auxin, cytokinin, gibberellin) 3) Specialized mechanisms: can differ between different microbes • Ex. Entrance through natural openings (stomates)

- Specific Case: Herbivory Defense in Potato • When attacked, protease inhibitors (PI’s) are released, disrupting digestion in the herbivore’s stomach - Simple wounding induces this effect • Leaf-to-leaf communication is possible  Signal molecule systemin (protein) - Transported through the phloem • Plant-to-Plant communication also possible  Signal molecule methyl jasmonate (volatile) - Only wounded plants can produce signal