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  1. Nutrition and Transport in Plants

  2. Outline • Essential Inorganic Nutrients • Soil Formation • Soil Profiles • Soil Erosion • Water & Mineral Uptake • Transport Mechanisms • Water • Organic Nutrients

  3. Plant Nutrition and Soil • Essential Inorganic Nutrients • About 95% of a plant’s dry weight is carbon, hydrogen, and oxygen • Primary nutrients are carbon dioxide and water • Essential nutrients have identifiable role, and a deficiency causes a plant to die • Macronutrients • Micronutrients

  4. Overview of Plant Nutrition

  5. Nutrient Deficiencies

  6. Soil Formation • Soil formation begins with weathering of rock • Organisms also play an important role • Lichens and Mosses • Humus begins to accumulate • Under ideal conditions, a centimeter of soil may develop within 15 years

  7. Nutritional Function of Soil • Soil is a mixture of: • Soil particles • Decaying organic material • Living organisms • Air, and • Water • Roots take up oxygen from air spaces • Soil particles consist primarily of • Sand • Clay • Silt

  8. Absorbing Minerals

  9. Soil Profiles • Soil profile is a vertical section from ground surface to unaltered rock below • Parallel layers - Horizons • A (topsoil) - Litter and humus • B (subsoil) - Inorganic nutrients • C (weathered rock) • Because parent material and climate differ, soil profile varies according to particular ecosystem

  10. Simplified Soil Profile

  11. Soil Erosion • Soil erosion occurs when water or wind carry soil away to a new location • Worldwide, removes about 25 billion tons of topsoil annually • Deforestation • Desertification • Agricultural contaminants

  12. Adaptation of Roots for Mineral Uptake • Important Symbiotic Relationships • Rhizobium bacteria fix atmospheric nitrogen • Live in root nodules • Mycorrhizal association between fungi and plant roots • Ectomycorrhizas • Endomycorrhizas

  13. Water and Mineral Uptake

  14. Root Nodules

  15. Mycorrhizae

  16. Spanish Moss

  17. Transport Mechanisms in Plants • Transported in vascular tissues • Xylem transports water • Two types of conducting cells • Tracheids • Vessel Elements • Water flows passively from an area of higher water potential to an area of lower water potential

  18. Plant Transport System

  19. Conducting Cells of Xylem

  20. Transport Mechanisms in Plants • Transported in vascular tissues, cont. • Phloem transports organic materials • Conducting cells are sieve-tube members • Have companion cells to provide proteins • End walls are sieve plates • Plasmodesmata extend through sieve plates

  21. Water Transport • Water entering roots creates a positive pressure (root pressure) • Pushes xylem sap upward • May be responsible for guttation • Water forced out vein endings along edges of leaves

  22. Guttation

  23. Cohesion-Tension Model • Cohesion-tension model of xylem transport suggests a passive xylem transport • Water molecules tend to cling together • Polarity of water allows interaction with molecules of vessel walls • Water column moves passively upward due to transpiration • Column must be continuous • Waxy cuticle prevents water loss

  24. Cohesion-tension Model ofXylem Transport

  25. Opening and Closing of Stomata • Each stoma in leaf epidermis is bordered by guard cells • Increased turgor pressure in guard cells opens stoma • Caused by active transport of K+ into guard cells

  26. Opening and Closing of Stomata

  27. Organic Nutrient Transport • Role of Phloem • Phloem transports sugar • Girdling of tree below the level of leaves causes bark to swell just above the cut • Sugar accumulates in the swollen tissue

  28. Acquiring Phloem Sap

  29. Pressure-Flow of Phloem Transport • Positive pressure drives sap in sieve tubes • Sucrose is actively transported into sieve tubes • Water follows by osmosis • Increase in volume creates flow that moves water and sucrose to a sink

  30. Pressure-flow Model of Phloem Transport

  31. Review • Essential Inorganic Nutrients • Soil Formation • Soil Profiles • Soil Erosion • Water & Mineral Uptake • Transport Mechanisms • Water • Organic Nutrients

  32. Nutrition and Transport in Plants