1. Biology, 9th ed, Sylvia Mader
Chapter 26
Chapter 26
Plant Nutrition
Nutrition and Transport in Plants

2. Essential Inorganic Nutrients
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 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. Worldwide, removes about 25 billion tons of topsoil annually
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 entering roots creates a positive pressure (root pressure)
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 of Xylem 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. Essential Inorganic Nutrients
Review
Essential Inorganic Nutrients
Soil Formation
Soil Profiles
Soil Erosion
Water & Mineral Uptake
Transport Mechanisms
Water
Organic Nutrients

32. Biology, 9th ed, Sylvia Mader
Chapter 26
Ending Slide Chapter 26
Plant Nutrition
Nutrition and Transport in Plants