1. ROOTS ► Absorb water and nutrients ► Anchor plant in soil ► Store carbohydrates/starch

2. Types: ► Taproot system ► Fibrous root system

3. Root Adaptations ► Need to adapt to soil env. ► Root cap  Protects  Covers apical meristem  Involved in gravitropism ► Root hairs  Numerous  Increase surface area

4. Structure of roots ► Epidermis  No cuticle in area of root hairs ► Cortex  Loose parenchyma cells, some sclerenchyma  Main function is storage  Large intercelluar spaces ► aeration and water uptake

5. Structure of roots cont. ► Endodermis  Inner layer of cortex  Snug fit  Casparian strip ► Stele  Vascular cylinder in center  Outermost layer is pericycle ► Parenchyma cells give rise to lateral roots

6. Movement of Water into the Root ► Root hairs  Difference in water potential ► 2 pathways water can take:  Symplast  Apoplast

7. Movement of water cont. ► Most water moves along cell walls, does not enter the cell  Cellulose absorbs water like sponge  Apoplastic route  Water and mineral ion diffuse across cortex ► When endodermis reached, waterproof Casparian strip prevents further movement along cell walls

8. ► http://plantandsoil.unl.edu/croptechnology2005/pa ges/animationOut.cgi?anim_name=water_movem ent_roots.swf http://plantandsoil.unl.edu/croptechnology2005/pa ges/animationOut.cgi?anim_name=water_movem ent_roots.swf http://plantandsoil.unl.edu/croptechnology2005/pa ges/animationOut.cgi?anim_name=water_movem ent_roots.swf

9. Movement of Water cont. ► Endodermis regulates movement of minerals from soil into vascular tissue and throughout the plant ► Water enters by osmosis ► Dissolved minerals are actively transported against concentration gradient ► Once though endodermal cells, water/minerals enter xylem

10. MUTUALISTIC RELATIONSHIPS ► Mycorrhizae  Soil fungi  Hyphae increase surface area  Fungi provide essential nutrients ► Root nodules  Roots of legumes  Nitrogen-fixing bacteria  Atmospheric nitrogen converted to ammonia ammonia

11. Soil Environment ► 4 main components:  Inorganic mineral particles  Organic matter  Water  Air ► 3 sizes of inorganic particles:  Sand  Silt  Clay

12. Soil Environment ► Clay particles  Negative charge  Attract positive cations ► Roots pump out H + ► Cation exhange occurs at clay ► Positive minerals can be absorbed by roots ► Negative anions tend to wash out of soil

13. Soil Properties affect Plants ► Pore Space  Equals roughly 50%  Allows air and water to diffuse ► Acidity  Determines solubility of nutrients  May lead to leaching of minerals ► Erosion = lost fertility