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Translocation of Photosynthate (Photoassimilate)

Translocation of Photosynthate (Photoassimilate). No Known Pumping Organ Two Separate Conducting Tissues: Xylem Phloem. Translocation of Photosynthate. Two Separate Conducting Tissues: Xylem tracheids vessel elements Phloem - photosynthate (photoassimilate)

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Translocation of Photosynthate (Photoassimilate)

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  1. Translocation of Photosynthate (Photoassimilate) No Known Pumping Organ Two Separate Conducting Tissues: Xylem Phloem

  2. Translocation of Photosynthate Two Separate Conducting Tissues: Xylem tracheids vessel elements Phloem - photosynthate (photoassimilate) sieve tube elements companion cells (nucleus)

  3. Dicot

  4. Stem X-Section -Herbaceous Dicot

  5. Phloem Tissue Parenchyma fibers

  6. Phloem Cytoplasmic connections P-Proteins (slime) Callus Plugs (carbohydrate)

  7. Seive Plate - Callose Plugs

  8. Phloem Sap - Sugars • * Sucrose C12H22O11 • Glucose - some Lilies, Liliaceae • Mannitol & Sorbitol (sugar alcohols) - Rosaceae • Raffinose, Stachyose, Verbascose -Cucubitaceae

  9. Chemical Interconversions • PCR Cycle – 1st hexose phosphate = fructose-6-phosphate phosphoglucomutase • F-6-P  G-6-P ------------------------------ G-1-P • G-1-P starting pt. for synthesis of sucrose, starch, cellulose

  10. Chemical Interconversions • G-1-P starting pt. for synthesis of sucrose, starch, cellulose • UTP + G-1-P  UDPG (uridine diglucophosphate) + P P • UDPG + F-6-P  G-F-6-P (sucrose-6-phosphate) • G-F-6-P  G-F (sucrose) + P

  11. Carbon AllocationStarch (storage) Sugars (translocation) Sugarbeets and Sugarcane - store sucrose

  12. Chemical Interconversion • Starch Synthesis: • glucose polymer – amylose 1-4 linkages Alpha • amylopectin 1-4 and 1-6 Beta linkages • Build Up • ATP + G-1-P  ADPG (adenosine diphosphoglucose) + P • ADGP + glucose  G-G… + ADP

  13. Chemical Interconversion • Starch Synthesis: • Break Down • G-G-G… + P  G-P

  14. Chemical Interconversions • Cellulose • Most abundant carbohydrate on earth (cell walls) • Formed like starch (glucose donor is a different nucleotide sugar- GDPG) • Beta linkages between all glucose units • Seldom broken down in nature • Microrganisms - cellulase

  15. Phloem Sap - Non-Sugars • Phytohormones - • Amino Acids (Glutamic and Aspartic Acids) & Other Organic Acids • Minerals - Anions (Phosphate, Sulfate, Chloride, etc.) & Cations (Potassium) • ?

  16. Aphids Use Stylus to Extract Phloem Sap

  17. Carbon Distribution • Source --> Sink

  18. Sinks Under Varying CO2 Levels

  19. Munch Pressure-Flow HypothesisE. Munch 1930A Mechanism for Moving Phloem Sap from Source to Sink within the Plant • 1. Sugars (solute) accumulate in leaves and other photosynthetic organs. SOURCE • 2. Sugars are pumped into phloem of photosynthetic organ by active transport. LOADING

  20. Munch Pressure-Flow HypothesisE. Munch 1930A Mechanism for Moving Phloem Sap from Source to Sink within the Plant • 1. Sugars (solute) accumulate in leaves and other photosynthetic organs. SOURCE • 2. Sugars are pumped into phloem of photosynthetic organ by active transport. LOADING

  21. Phloem Loading

  22. Munch Pressure-Flow HypothesisE. Munch 1930A Mechanism for Moving Phloem Sap from Source to Sink within the Plant • 1. Sugars (solute) accumulate in leaves and other photosynthetic organs. SOURCE • 2. Sugars are pumped into phloem of photosynthetic organ by active transport. LOADING • 3. Loading of phloem causes phloem sap to take on water by osmosis. HYDROSTATIC PRESSURE

  23. Munch Pressure-Flow HypothesisE. Munch 1930A Mechanism for Moving Phloem Sap from Source to Sink within the Plant • 1. Sugars (solutes) accumulate in leaves and other photosynthetic organs. SOURCE • 2. Sugars are pumped into phloem of photosynthetic organ by active transport. LOADING • 3. Loading of phloem causes phloem sap to take on water by osmosis. HYDROSTATIC PRESSURE • 4. The Phloem sap is pushed through the seive tube column to a SINK area of low solute concentration. (root, bud, grain, bulb, etc.) Sap is pulled out by active transport or stored as starch. UNLOADING • 5. Sap continues to flow toward the sink as long as sugars (solutes) do not accumulate in the phloem.

  24. Phloem Unloading

  25. Munch Pressure Flow Hypothesis is supported by the evidence. • Known rates of movement 100cm/hr., squash 290 cm/hr. • Living cells are necessary (active transport)

  26. Direction of Phloem Sap Movement(Radioactive Feeding Techniques)Distribution of Photosynthate • Sap moves in both directions (up & down) - in separate phloem ducts.

  27. Direction of Phloem Sap Movement(Radioactive Feeding Techniques)Distribution of Photosynthate • Sap moves in both directions (up & down) - in separate phloem ducts. • Very little tangential movement on maturre stem. • Growth is decreased on defoliated side. • Feed radioactive CO2 to one side - very little radioactive photosynthate shows up on other side.

  28. Direction of Phloem Sap Movement(Radioactive Feeding Techniques)Distribution of Photosynthate • Sap moves in both directions (up & down) - in separate phloem ducts. • Very little tangential movement on maturre stem. • Growth is decreased on defoliated side. • Feed radioactive CO2 to one side - very little radioactive photosynthate shows up on other side. • More tangential movement among young leaves.

  29. Between Phloem and Xylem • Some exchange - mostly to remove mineral from senescent leaves (source to sink).

  30. Factors Affecting the Translocation of Sap • Temperature • Increased temperature – increased loading & unloading optimum 20 - 30 degrees C • Chilling Sensitive Plants (most) • Chilling Tolerant Plants (beets) • Can acclimate translocation of photosynthate to increasingly cold conditions

  31. Factors Affecting the Translocation of Sap • Light • In the dark root translocation of photosynthate is favored over stem translocation. • At least one study shows that the translocation of sap in the stem was increased by BLUE and RED light.

  32. Factors Affecting the Translocation of Sap • Hormones • Both cell division (cytokinins) and cell elongation (auxins) creates sinks – absorbs sap. • Bud break • Increased G A, decreased ABA

  33. Development of Tissues of Transport and Translocation

  34. Development of Tissues of Transport and Translocation

  35. Development of Tissues of Transport and Translocation

  36. Development of Tissues of Transport and Translocation

  37. Consequences of Ambient Conditions on Tree Growth Rings

  38. Dormant Woody Stem

  39. Cellular Respiration • Oxidation of Organic Molecules - production of ATP • Intermediates (carbon skeletons) produced • Aerobic: • C6H12O6 --> Pyruvate (C6) + O2 --> CO2 + H2O + ATPs • Anaerobic: • C6H12O6 --> Pyruvate (C6) --> Ethanol (C2)+ CO2 • + ATPs

  40. Cellular Respiration - 3 Stages • 1. Glycolysis - Ebden Myerhoff Parnas Pathway • (in the cytosol; no O2 required) • Glucose - ATP • C6H12O6 --------------> Glucose-6-Phosphate --> • -----------------------> Fructose-6-Phosphate (C6) ----> • - ATP • ------------------------> Fructose-1,6-Diphosphate (C6) --> • Dihydroxyacetone <--> Phosphoglyceraldehyde (C3) • Phosphate (C3) ----->

  41. Glycolysis - EMPP (Anaerobic) 2 ATPs Used 4 ATPs Gained + 2 NADH2s Pyruvic Acid (C3) intermediates

  42. Fate of Pyruvate

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