1. Getting to the Root of the Matter: The hidden world underfoot

2. Functions of Roots 1. Anchoring the plant
2. Absorbing water & nutrients
3. Storage of food & nutrients
4. Vegetative propagation

3. Anchoring the Plant Trees rarely have tap root Some exceptions:
Dryland trees (mesquite)
Savanna trees (oaks)
Herbaceous plants often do:
Annuals: Fast growth of radicle
Perennials: Energy storage, winter dormancy

4. Absorbing Water & Nutrients
Mantle
(fungus)
Cortex
Stele
All action is at root tips!
Mycorrhizae
Myco = Fungus
Rhiza = Root

5. Absorbing Water & Nutrients
Stele
Behind the root tips, just pipes
Xylem – Water, nutrients up
Phloem – Photosyntates down
“Casparian strips”
Hydrophobic barrier allows water into root xylem,
but not out

6. Storage of Food & Nutrients
Bulbs: Have basal plate, inflated “scales”
- Onion, Garlic, Lily, Tulip, Daffodil
Corms: Modified plant stem, solid
- Crocus, Gladiolus, Banana, Taro
Rhizomes: Tuberous stem with growth nodes
- Potato, Sweet potato, Ginger, Turmeric, Dahlia
Taproots: Just an inflated root
- Carrot, Radish, Beet, Turnip, Parsnip, Dandelion

7. Vegetative Propagation
“Pando” aspen, Utah
One organism, 106 acres
~80,000 years old
Estimated 6600 tons
Banyan – 8 acres in India
Silver maple – PNW invasive

8. Other Cool Root Tricks Nitrogen fixation Air is 78% nitrogen (N2)
Rhizobium nodules on pea roots
Frankia nodules on alder roots
Air is 78% nitrogen (N2)
Unavailable to plants!
Legumes, alders
Bacteria in root nodules convert it to usable form

9. Other Cool Root Tricks Allelopathy
Manzanita (arbutin)
Walnut (juglone)
Knapweed (catechin)
Roots of some plants exude chemicals that discourage growth of competitors

10. Other Cool Root Tricks Hydraulic lift
Excess water from deeper soil is stored in surface roots by day, leaks out at night
This is an important source of water for shallow rooted plants in dry ecosystems

11. Air exchange in brackish water
Other Cool Root Tricks
Mangroves
Roots exclude salt,
let water in
Pneumatophores
“Snorkles for trees”
Air exchange in brackish water

12. Epiphytes (“air plants”)
Other Cool Root Tricks
Epiphytes (“air plants”)
Vanilla orchid
Staghorn fern
Spanish moss
Epi = “Outside”
Phyte = “Plant”
Orchids, bromeliads,
tropical ferns
Get moisture from rain
Nutrients from leaching
Not parasitic!

13. Other Cool Root Tricks Nutrient sharing
Photosynthates shared through common mycorrhizal network
“Wood wide web”
Enables seedlings to survive and grow in full shade

14. Other Cool Root Tricks Creating organic soil
Half of fixed carbon goes below ground to roots
Roots “turn over”, grow, senesce, decay
Decayed roots add carbon to deeper soil layers
Carbon supports microbes, retains water, etc.

15. Questions?