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Roots (Other Types of Roots and Root Modifications (Prop Roots (Buttress…
Roots
Other Types of Roots and Root Modifications
Storage Roots
Carbohydrates accumulated form photosynthesis
Used to produce new shoot in Spring
Prop Roots
Transport additional nutrients and water to stem
Act as Stabilizer
Buttress roots
Brace trunk against wind drafts
Mangrove tree
Aerial Roots of Orchids
Epiphytic
Dangly freely in air
Adapted to drought conditions
Velamen
Waterproof barrier
Contractile Roots
Base of shoot level with soil or barried
Grow out then pull in
Mycorrhizae
Ectomycorhizal Relationship
Penetrate cortex
Never invade the cells themselves
Endomycorrhizal Association
Hypae penetrate cortex cells as far as endodermis
Cannot pass Casparian Strip
Root Nodules and Nitrogen Fixation
Nitrogen Fixation
Conversion of atmosphere nitrogen
Infection Thread
Bacteria
Parasoe
Haustorial Roots of Parasitic Flowering Plants
Haustoria
Parasitic roots
Burrow down and do not let go
Roots of Strangler Figs
Grow at various angles
Roots fuse to each other
Kills tree by strangulation by roots
Internal Structure of Roots
Root Cap
Cells small and meristematic
Develop:
Dense starch grains
Endoplasmic reticulum dispelled to forward of cell
Detect gravity
Constant regeneration of itself
4-5 days from cell formation to sloughing off
Root Apical Meristem
Quiescent Center
More reistant to:
Radiation
Toxic Chemicals
Act as a reserve of healthy cells
Form a new apical meristem when old is damaged
Zone of Maturation / Root Hair Zone
Root hairs grow outward
Increase of absorption:
Water
Minerals
Zone of Elongation and Zone of Maturation merge
Transfer of from epidermis to vascular tissue
Casparian strings
Control mineral types that enter xylem water stream
Pericycle
Production of lateral roots
Mature Portions of the Root
Passage Cells
Only casparian strips
Root Pressure
Water and Mineral pressure
Zone of Elongation
Protoderm
Epidermis
Provascular Tissue
Primary Xylem
Primary Phloem
Expanded cells
Permeable tissue
Origin and Development of Lateral Roots
Initiated by cell division in pericycle
Premordium
Endodermis torn or crushed
Cell division
Formed in mature regions of root
Never develop into flowers
Initiated deep within the root
External Structure of Roots
Organizations of Root Systems
Radicle
Beginning of a taproot
Embryonic root
Dies immediately after germination
Lateral Roots
Branch roots
Sprout from taproot
Monocots and Eudicots
Fibrous root system
Similar sized roots
Monocots
Cannot undergo secondary growth
Conducting capacity cannot be increased
Eudicots
Perineal
Undergo secondary growth
Increased quantity of health
Adventitious Roots
Increase:
Transport
Absorption
Do not arise from preexisting roots
Structure of Individual Roots
Absence of:
Leaves
Leaf scars
Leaf axils
Axillary buds
Root Cap
Mucigel
Zone of Elongation
Division
Expansion
Root Hair Zone
Epidermal cells extend as narrow trichomes
Root Hairs
Part of root not elongating
Increase roots surface area
Can enter any crevice
Extract water and minerals
Unicellular
No thick walls
Extremely transitory
Die and regenerate within 4-5 days after forming
