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Chapter 8 Roots - Coggle Diagram
Chapter 8 Roots
Other Types of Roots and Root Modification
Storage Roots - provide longterm carb storage
carbs accumulate during summer and used in winter
Prop Roots - roots that extend out of trees and enter the ground
act as roots and supports
buttress roots - prop roots that are tall and plate like
Aerial Roots of Orchids - spread across surface of tree bark or hang freely
Mycorrhizae
80% of plant roots have symbiotic relationship with soil fungi
ectomycorrhizal association - most woody forest plants. Fungal hyphae penetrate outermost root cortext but never enter cells.
endomycorrhizal association - most herbaceous plants. hyphae enter roots as far as endodermis. Form abuscule in cell which fills with phosphorous.
Contractile roots - contract and pull base of shoot into the soil
Root Nodules and Nitrogen Fixation
nitrogen is a limiting factor for growth
Nitrogen Fixation - conversion of atmospheric nitrogen into usable compounds
some plants have symbiotic relationship with nitrogen fixing bacteria
Infection thread - tube-like invagination rhizobium uses to enter cell
Haustorial Roots of Parasitic Flowering Plants
Haustoria are roots of parasitic plants
penetrate the host body
other plant is substrate
Roots of Strangler Figs
grow perched on host trees brances
birds eat figs and deposit seeds on other branches
Internal Structure of Roots
Root Cap
meristematic near meristem
many changes
Root Apical Meristem
quiescent center - area where cells are mitotically inactive
Zone of Elongation
behind apical meristem
cells expand greatly
Zone of Maturation / Root Hair Zone
several processes occur
root hairs grow
Casparian strips control types of minerals that enter xylem
External Structure of Roots
Organization of Root Systems
branches give large surface area
these branch roots called lateral roots aswell
Radicle - embryonic root which taproot grows from
most monocots and some eudicots have a mass of similarly sized roots called a fibrous root system
caused by radicle dying during or after germination
adventitious roots are those initiated in stem tissue later in life
Structure of Individual Roots
growth at root tip
apical meristems
protected by root caps
just behind is zone of elongation
here cells undergo division and expansion
behind this is root hair zone
here epidermal cells extend out as trichromes
mucigel lubricates growth through soil
fairly simple
Concepts
roots have 3 main functions
absorb water and minerals
produce hormones
anchor plant to substrate
taproots - site of carb storage
Origin and Development of Lateral Roots
initiated by cell division in pericycle
