Roots Flashcards
What are the functions of roots?
● Anchor plants into soil
● Absorb water and minerals
● Store food or water
● Other specialized functions
When a seed germinates, the _____ grows out and develops into the first root
Radicle
Dicots have taproot systems with one or more _______
Primary root
They arise from primary roots
Secondary roots
They develop from non-root tissues (e.g., stems or leaves)
Adventitious roots
It develops from adventitious roots
Fibrous root system
The four regions/zones of root structure:
○ Root cap
○ Region of cell division
○ Region of elongation
○ Region of maturation
● Parenchyma cells covering the tip of each root
● Protects tissues from damage as root grows
Root Cap
● Secretes mucilage that acts as lubricant
○ Secreted by dictyosomes of outer cells
○ Allows growth of beneficial bacteria
Root Cap
It lives for <1 week. Functions in perception of gravity
Root Cap
When root cap is removed, roots grow in random directions. True or false?
True
They pool on downward side of cells
Amyloplast
● Apical meristem in center of root tip
● Produces the root cap
● Most of the cell division near root cap
○ Divide every 12-36 hrs
● Rhythmic division, usually noon or midnight
Region of Cell Division
It produces epidermis
Protoderm
It produces parenchyma of cortex
Ground meristem
It produces primary xylem and phloem
Procambium
● Cells elongate by merging of vacuoles
○ Occupy 90% of cell volume
● Only root cap and apical meristem push thru soil
● Rest of the root remain stationary
● Girth may increase if cambium is present
Region of Elongation
Cells differentiate and forms root hairs
Region of Maturation
○ Absorb water and minerals
○ Tubular extensions of specialized epidermal cells
Root hairs
● Parenchyma cells between epidermis and inner tissues
● Mostly store food
Cortex
It is the inner boundary. Can be seen in between the pericycle and cortex.
Endodermis
It is one cell layer thick. Cell walls embedded with lignin and suberin
Endodermis
Substances form bands called?
Casparian strips
● Found on radial and transverse cell walls
● Prevent water from passing through cell walls
● Forces water and solutes through cell membranes or plasmodesmata of endodermis
Casparian Strips
Contains vascular tissues and the pericycle
Vascular Cylinder
The parenchyma cells that produces lateral roots and part of vascular cambium.
Pericycle
● Consists of core and arms
○ Made of tracheids or vessels
● Surrounds pith parenchyma cells in monocots
Primary xylem
● Conducts food
● Forms patches between xylem arms
Primary phloem
● Creates secondary xylem and phloem
● Develops from parts of the pericycle and other parenchyma cells between the xylem arms and phloem patches
Vascular Cambium
● Develops from pericycle outside of vascular cambium
● Forms the cork tissue
Cork Cambium
● Growth that stops after an organ is fully expanded or after a plant has reached a certain size
Determinate Growth
● New tissues are added indefinitely, season after season
Indeterminate Growth
Adventitious buds on roots develop into aerial stems called
Suckers
Suckers can be grown individually and separate from original plant. This an example of what type of specialized root?
Propagative Roots
In plants with roots growing in water. Spongy roots that extend above the water’s surface. Enhance gas exchange between atmosphere and subsurface roots. This an example of what type of specialized root?
Pneumatophores
● Velamen roots of orchids prevent water loss
● Corn prop roots support the plants in a high wind
● Photosynthetic roots manufacture food
● Adventitious roots aid in climbing
These are examples of what type of specialized root?
Aerial roots
● Pull plants deeper into soil
● Found usually in bulbous plants
These are examples of what type of specialized root?
Contractile Roots
They are a specialized root that stabilize large trees.
Buttress Roots
● Haustoria are rootlike projections that penetrate host tissue.
● Plants without chlorophyll parasitize through haustoria.
These are examples of what type of specialized root?
Parasitic Roots
