ROOTS Flashcards
5 Main Functions of Roots
Anchorage
Absorption
Conduction
Storage
Communication
Types of root systems
TAPROOT SYSTEM
FIBROUS ROOT SYSTEM
A root system consisting of one prominent main root with smaller lateral roots branching from it
TAPROOT SYSTEM
A root system consisting of several adventitious roots of approximately equal size that arise from the base of the stem
FIBROUS ROOT SYSTEM
In monocots when seeds germinate radicle grows to form the primary root but this root is short lived and soon perishes. Seminal roots arise from coleorhiza to help absorption of water.
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Region of Elongation or Differentiation
contains the
Protoderm
Ground Meristem
Procambium
Region of Maturation or Specialization
contains the
Epidermis
Cortex
Pith
Xylem
Phloem
a unicellular extension of the root epidermis.
Increase the surface area in contact with the soil
root hairs
Each root tip contains a protective loose layers of cells
Covers delicate root apical meristem
Detects gravity so root grows downward (positively gravitropic)
Secretes mucilagenous substance that moistens ground and facilitates root penetration and nutrient absorption
root cap
protects the root’s apical meristem.
root cap
To reach the vascular tissues, water and dissolved minerals must pass through the plasma membranes of _______
endodermal cells
A layer of cells just inside the endodermis of the root
Gives rise to lateral roots
PERICYCLE
Lateral Roots Arise from the Pericycle of the ________
Stele
Monocot roots often have a pith in the center of the root
In herbaceous eudicot roots, xylem and phloem form a solid mass in center of root
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Monocot roots lack ____, they Do not have secondary growth
vascular cambium
Outer protective covering of roots
Epidermis
tissues in roots that consists of parenchyma cells and Usually stores starch
Ground tissues:
Ground tissues in roots consists of
Cortex
Pith (in certain roots)
complex tissues for conduction of substances
Vascular tissues
Vascular tissues in the root
Xylem Phloem
Vascular tissues in the root that conducts water and dissolved minerals
Xylem
Vascular tissues in the root that conducts dissolved sugar
phloem
Innermost layer of the cortex of the root that prevents water and dissolved materials from entering the xylem by passing between cells
ENDODERMIS
A band of waterproof material around the radial and transverse cells of the endodermis
Ensures that water and minerals enter the xylem only by passing through the endodermal cells
CASPARIAN STRIP
In a primary eudicot root, water moves from soil into center of root:
Water Movement
Water Movement in plants
Root hair → epidermis → cortex (symplast or apoplast pathway) → endodermis → pericycle
→ xylem of root
Water is transported upward through
root xylem into stem xylem and rest of plant
A continuum consisting of the cytoplasm of many plant cells, connected from one cell to the next by plasmodesmata
osmosis
slower due to resistance
used for water to travel beyond the cortex
SYMPLAST
A continuum consisting of the interconnected, porous plant cell walls, along which water moves freely
passive diffusion
faster due to less resistance
used by the secondary growth
APOPLAST
route used so water could pass through the casparian strip
SYMPLAST
An extension of an epidermal cell of a root that increases absorptive capacity of the root
Short-lived
Increase surface area of root in contact with moist soil, increasing root’s absorptive capacity
Root Hairs
Modified Roots
Food storage
Propagative roots
Pneumatophores
Aerial Roots
Photosynthetic roots of some orchids
Contractile roots some herbaceous dicots and monocots
Buttress roots
Parasitic roots
Symbiotic roots
Swollen bases or braces that hold trees upright
Aid in extensive distribution of shallow roots
Found in some tropical rainforest trees
Buttress Roots
A specialized aerial root produced by certain trees living in swampy habitats
May facilitate gas exchange between the atmosphere and submerged roots
PNEUMATOPHORE
Exposed roots maximize the uptake of oxygen.
Low tide:
Submerged roots perform anaerobic respiration.
High tide:
An adventitious root that arises from the stem and provides additional support for the plant.
prop root
aerial roots that provide support to the tree. adventitious root
Prop roots
the roots that arise from the base of the plant and perform the function of supporting the plant. adventitious root
Stilt roots
root that arises from any point other than the radicle (embryonic root) or the root axis of a plant.
form from any nonroot tissue and are produced both during normal development
Adventitious root
An adventitious root that arises from the stem and provides additional support for the plant
Prop Roots
specialized root, often found on bulbs or corms, that contracts and pulls the plant to a desirable depth in the soil
Contractile Roots
often have contractile roots that lose much of their length as root cells shorten and broaden.
Plants that produce corms or bulbs
True bulbs, with the exception of some Oxalis, are exclusively found in the monocots whereas Tubers and Corms tend to be Eudicots
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are green, aerial, adventitious roots also called assimilatory roots which prepare food materials by photosynthesis
Aerial roots that perform photosynthesis. (maximizes photosynthesis by exposing the roots)
Photosynthetic Roots
2 types of symbiotic roots
MYCORRHIZA
NODULE
A small swelling on the root of a leguminous plant in which beneficial nitrogen-fixing bacteria (Rhizobium) live
Mutualism between a plant and bacterium.
NODULE
A mutually beneficial association between a fungus and a root that helps the plant absorb essential minerals from the soil
“fungus roots” where a symbiotic relationship forms between a plant and a fungus.
MYCORRHIZA
explain how nodules work
Bacteria: Fix atmospheric nitrogen to a form that the plant can utilize.
Plant: Provides food and shelter to bacteria.
explain how mycorrhiza works
Fungus: Provides protection against some types of pathogens and increase the surface area for the absorption of essential nutrients (e.g. phosphorous) from the soil.
Plant: Provides food for the fungus in the form of sugar and amino acids.
With fungus for phosporus absorption
Mycorrhiza
plant roots that form clusters of closely spaced short lateral rootlets. They may form a two- to five-centimetre-thick mat just beneath the leaf litter.
acquisition of P and other mineral nutrients. Although increase in root surface area may be a contributing factor, in many species these roots excrete large amounts of organic acids and phenolics.
Cluster roots
penetrates host plant and connecting them to vascular tissues
Parasitic roots
roots that store lareg quanitites of starch and carbohydrates
Storage Roots
Economic Importance of roots
Rootcrops as sources of starch
Some roots are used as flavorings
Medicine
