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Translocation of Photosynthate

Translocation of Photosynthate. Two Separate Conducting Tissues: Xylem tracheids vessel elements Phloem - photosynthate (photoassimilate) sieve tube elements companion cells (nucleus). Dicot. Stem X-Section -Herbaceous Dicot. Phloem Tissue. Parenchyma fibers. Phloem.

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Translocation of Photosynthate

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

  2. Dicot

  3. Stem X-Section -Herbaceous Dicot

  4. Phloem Tissue Parenchyma fibers

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

  6. Sieve Plate - Callose Plugs

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

  8. 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

  9. 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

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

  11. 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

  12. 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

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

  14. Aphids Use Stylus to Extract Phloem Sap

  15. Carbon Distribution • Source --> Sink

  16. 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

  17. 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

  18. Phloem Loading

  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 • 3. Loading of phloem causes phloem sap to take on water by osmosis. HYDROSTATIC PRESSURE

  20. 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 pushes 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.

  21. Phloem Unloading

  22. 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)

  23. 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.

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

  25. 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

  26. 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.

  27. 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

  28. Development of Tissues of Transport and Translocation

  29. Development of Tissues of Transport and Translocation

  30. Development of Tissues of Transport and Translocation

  31. Development of Tissues of Transport and Translocation

  32. Consequences of Ambient Conditions on Tree Growth Rings

  33. Dormant Woody Stem

  34. If Aerobic: • 1. Pyruvate (C3) is further broken down in the KREBS CITRIC ACID CYCLE (in mitochondrion) • 2. NADH2s are used to build ATPs in the ELECTRON TRANSPORT CHAIN (ETC)

  35. Krebs Citric Acid Cycle

  36. Energy Budget • Glycolysis: 2 ATPs net gain from 1 glucose Anaerobic • Krebs Cycle & ETC: 36 ATPs net gain from 1 glucose • Aerobic: 38 ATPs

  37. Cyanide Resistant RespirationMany plants have been discovered to have a branch point in the ETC. • After Coenzyme Q • - Only 1 ATP produced • - H2O2 produced • + More heat produced • + in plant tissues. • + Fruit ripening • + Rids excess NADH2. • Krebs Cycle continues • to produce intermediates.

  38. Oxidative Pentose Phosphate Pathway NADPH2 for PCR Cycle and Biosyntheses Biosynthesis of Nucleic Acids, RuBP Up to 20% of Glucose may use OPPP rather than Glycolysis.

  39. Lipid Catabolism - Glycolate Cycle

  40. Role of Respiration in Biosynthesis

  41. Rate of Respiration Aerobic Respiration in Green Plants C6H12O6 + O2 --> CO2 + H2O Respiratory Quotient RQ = CO2 production: O2 consumption Carbohydrates = 1.0, Organic Acids (highly oxidized) = 1.66, Lipids and Proteins (highly reduced) = .77

  42. Respiratory Rate and Age

  43. Photosynthesis and Respiration

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