2. Soil, Roots and Water Balance of the Plant

3. Soil Profile – aka Soil Layers

5. Soil 101 1. Humus = organics layer on top 2. Topsoil = mix of humus, sand, clay and minerals 3. Subsoil = mix of rocks, inorganic soil with little air or water for plant roots 4. Bedrock = solid rock

6. Soil Nutrients 1. Nitrogen 1. Nitrogen – critical for leaf, stem development 2. Phosphorus 2. Phosphorus – critical for flowering 3. Potassium 3. Potassium – proteins and carbohydrates 4. - Roots (stunted if not enough) 4. Calcium 4. Calcium – metabolism, growth, cell wall 5. Magnesium 5. Magnesium – essential for chlorophyll 6. Trace 6. Trace Elements: Elements: S, Fe, Zn, Mb, B, Cu, Mn, Cl

8. Modified Roots and Root Associations Prop roots develop from branches (or a vertical stem) to offer support to the plant

9. Mycorrhizae = fungus root; Root Nodules may form from a symbiotic association with soil bacteria

10. A root graft is a natural union between the roots of two trees, same or different species

11. The 4 main functions of roots: 1)Anchorage, 2) absorption, 3) Conduction 4) storage Two main types of root systems are: 1) Taproot (DICOTS) 2) Fibrous root systems (MONOCOTS)

12. Nutrient transport in plants 1. Roots absorb water and minerals from the soil 2. Below ground gaseous exchange - roots 3. Xylem - water and minerals 4. Transpiration = water loss through leaves (evaporation) via stomata 5. Photosynthesis – cells need a lot of water to do this 6. Phloem - Sugar transport to non-photosynthetic tissues

13. Xylem and Water movement Two types of xylem cells Tracheids Tracheids - gymnosperms Vessels Vessels and tracheids - angiosperms Water is moved through xylem by 1. Root pressure 1. Root pressure – water is pushed by absorption of more water by roots 2. Transpiration tension 2. Transpiration tension - pulled by evaporation from leaves 3. Cohesionsticky 3. Cohesion – water molecules are “sticky” or attracted to each other, which help pull water up the plant

14. Primary tissues of a young Dicot Root Ex. Beans or Buttercups

15. Cross-section through a Monocot root Eg. Corn

16. Roots have a root cap and root hairs ; they do not usually have nodes, internodes, leaves, or buds

17. Endodermis- the innermost layer of the cortex; regulates movement of minerals into root xylem (which will eventually be transported up the plant); cells of the endodermis contain the Casparian strip, which blocks movement of water ; this prevents loss of water out of roots back to the soil Waterproof layer between the veins and outside. Cuts off water loss!

18. Primary roots possess an epidermis, ground tissues (cortex and pith in certain plants), and vascular tissues Epidermis- protects the root; root hairs aid in water/nutrient absorption (isn’t permeable) Cortex - consists of parenchyma cells which store starch

19. Pericycle - gives rise to lateral roots and lateral meristem Xylem conducts water and dissolved minerals UPWARDS Phloem conducts dissolved sugars up and down the plant

21. Leaf surfaces are dotted with millions of stomata such as this one. This stomate is lined by two guard cells that control its aperture. Because control requires movement, and movement requires energy, these cells contain numerous mitochondria and chloroplasts (the little green photosynthetic factories that look a bit like brussel sprouts in this shot). Thus they are the only cells in the epidermis that are green. Guard Cells