Roots Framework of relatively large, woody, long-lived roots Supporting a mass of small, short-lived non-woody absorbing roots

The Power of Roots

What Do Roots Do? Anchor the tree (whole root system) Store sugars (larger roots) Generation of vegetative shoots (e.g., aspen) Production of some growth hormones Prevent soil erosion Absorption of water & minerals from soil (fine roots) Regulate water loss(?)

Root Buttresses The buttress provides support on the thin, old and highly weathered tropical soils. Decomposition is very rapid in the tropics, so having roots near the surface where the action takes place is crucial for effectively competing for the available nutrients.

We used to think that the primary reason for knees was respiration, but now it’s assumed their more for support.

Three types of roots Fibrous root Adventitious root Tap root Forms from the radicle Early stability in seedlings Survival (dry and fire-prone sites) Common in pines and species with large seeds with much food reserve (oaks, hickories, chestnuts, walnuts) Fibrous root Most common type of root Typically slender Branches and re-branches Adventitious root Form from shoot tissues. Often arise after injury to roots OR from main stem, branch, etc. Examples are those formed on stem/leaf cuttings & stilt roots

Tap Roots Tap root is one large central root. B:intermediate water C: reaching to water table D: low water growing lots of roots to meet its needs

Three types of roots Fibrous root Adventitious root Tap root Forms from the radicle. Early stability in seedlings Survival (dry and fire-prone sites) Common in pines and species with large seeds with much food reserve (oaks, hickories, chestnuts, walnuts) Fibrous root Most common type of root Typically slender Branches and re-branches Adventitious root Form from shoot tissues. Often arise after injury to roots OR from main stem, branch, etc. Examples are those formed on stem/leaf cuttings & stilt roots

Fibrous Roots The exposed fibrous roots are not typical.

Three types of roots Fibrous root Adventitious root Tap root Forms from the radicle. Early stability in seedlings Survival (dry and fire-prone sites) Common in pines and species with large seeds with much food reserve (oaks, hickories, chestnuts, walnuts) Fibrous root Most common type of root Typically slender Branches and re-branches Adventitious root Form from shoot tissues. Often arise after injury to roots OR from main stem, branch, etc. Examples are those formed on stem/leaf cuttings & stilt roots

Adventitious Roots Mangrove roots are primarily for oxygen uptake.

Root Form Form and structure of the root system is primarily genetically controlled Nevertheless, site conditions markedly influence the form and pattern of root development This goes back to the discussion on genotype (genetic heritage) and phenotype (environmental influence on genotype).

Root System Architecture Heart system- many horizontal and vertical roots Plate or sinker system- large lateral roots and some smaller vertical roots Taproot system- one major central root and smaller horizontal and vertical roots

Roots: Horizontal Distribution Depends upon stand density & competition Often 2-5 times the crown extension!

Roots: Vertical Distribution

Root Morphology { Cortex Vascular Cambium Endodermis Phloem Xylem Cortex = several layers of relatively large, thin-walled living cells with intercellular air spaced forming interconnected air channels seem to be essential for internal aeration. Suberin is a principal component of the outer cell walls of all underground organs and is associated with the cork cells of the periderm, the tissue that forms the outer bark of stems and roots during secondary growth of woody plants.

Root Morphology http://koning.ecsu.ctstateu.edu/plants_human/roots/rootlec3.html

Root Forms Suberized (permanent roots) Outer tissue is dead bark HOLD THE TREE UP!!! Unsuberized (< 1 mm diameter, white) Live 1-3 months Only 1-5% of root biomass, BUT 90% of root surface area DO THE WORK!!! Coarse roots are suberized – hold the tree up and store nutrients. Unsuberized live 1-3 months – then either die or suberization occurs absorb nutrients and water 100 times faster