Unit 3: Roots (A) Flashcards
Vegetative organs, such as (3), help plants make and use food, obtain water and minerals, and store resources, like food and water.
2 types
roots
stems
leaves
monocots (herbaceous)
dicots (woody)
functions of roots
- Absorption
- Anchorage
- Conduction
- Reproduction
- Food storage
- Photosynthesis
Characteristics of Roots
- Cylindrical in form
- Colorless or with drab colors
- Lack nodes and internodes
- Lack buds, leaves and flowers
- Generally branching
root systems
- diffuse or fibrous roots
- taproot or primary root system
- fleshy root system
- fascicled root system
- adventitious root
carrot
taproot
blazing star
taproot
sunflower
taproot
oat
fibrous root
poison ivy
adventitious root
________ (primary) and ________ (Diffuse) Root Systems
Both arise from radicle
taproot (primary)
fibrous (diffuse)
have several or many main roots, usually slender and about the same size and length, with numerous smaller root branches.
Diffuse or Fibrous roots
distinguished by the presence of a primary or main root which is the first root to develop during seed germination and which penetrates deep into the soil.
taproot or Primary Root System
a taproot system wherein the main root has considerably enlarged in size
Fleshy Root System
have swollen bulb-like parts in the roots.
Fascicled Root System
- roots that arise from anything other than the radicle
- can arise in the stems, or other parts of the plant
adventitious root
2 types of seedsq
dicot and monocot seed
external anatomy or Root Structure: Four Regions (Longitudinal section, L-S)
- Root cap
- Region of Cell division or Meristematic region
- Region of Elongation
- Region of Differentiation or Maturation
- Thimble-shaped mass of parenchyma cells at the tip of each root (protects the root from injury)
** the interior cells are meristematic - _____________ release a mucilaginous lubricant called mucigel. It also favors the growth of beneficial commensal bacteria.
- _____________ on the sides of the root cap cells contain starch which act as gravity sensors
ROOT CAP
dictyosomes
amyloplasts
- Region in which new cells are formed via mitosis
- Cells in this area are small, nearly cube-like, with thin cell walls and very distinct nucleus
REGION OF CELL DIVISION OR MERISTEMATIC REGION
- _____________: group of cells known as growth initiating cells
- _____________: consist of group of actively dividing cells directly beneath the root cap; these cells make up the primary meristem
- _____________: consist of cells that have begun to show differentiation
- _____________: group of cells where no cell division takes place
– function as a cellular reserve (a source of replacement to the apical initials)
REGION OF CELL DIVISION OR MERISTEMATIC REGION
- apical initials (in the apical region)
- growing point
- primary meristem
- quiescent center
- Area of cell enlargement
- The cells in this region increase in cell length (up to 10x their original length)
- Cells are mature and columnar in shape
- The cells of this region make up the embryonic tissues /generative tissues (procambium, ground meristem and the protoderm)
3 TYPES OF TISSUES
REGION OF ELONGATION
protoderm/dermatogen
ground meristem/periblem
procambium/phlerome
- Embryonic/Generative tissues:
- ____________ or _____________: produces the epidermis
- ___________ or _____________: produces the cortex and pericycle (ground tissue)
- ____________ or _____________: produces the vascular tissues and the pith
REGION OF ELONGATION
protoderm or dermatogem
ground meristem or periblem
procambium or phlerome
- Region above the elongation region where the cells differentiate into specific vascular tissues (_____ & _____)
- The youngest part of the region is called the ____________
- ____________: outgrowths and elongations of the epidermal cells
REGION OF MATURATION OR DIFFERENTIATION
- xylem & phloem
- root hair zone
- root hairs
- In this region, the embryonic tissues undergo modification and maturation:
____________: -> epidermis
- Ground meristem cortical cells (_________ & ___________)
____________: -> vascular tissues (xylem and phloem) and pith
REGION OF MATURATION OR DIFFERENTIATION
- protoderm
- cortex and pericycle
- procambium
- the region between the epidermis and the pericycle
- stores food
cortex
- region lying between the
endodermis and the conducting bundles (xylem/phloem) - The cells here continue to divide
even after maturation and form the lateral branch roots and part of the vascular cambium
pericycle
undergo modification and maturation
embryonic tissue
- the “youngest” part of the region; root hair is evident in this area
- Root hair-like extensions of the epidermal cells that adhere tightly to soil particles and increase the absorptive surface of the root.
root hair zone
Internal Anatomy of the Root
3 main parts
EPIDERMIS
CORTEX
STELE
- one-cell thick that covers the root except the root cap
- absorbs water and dissolved material from the soil
epidermis
- formed by the ground meristem
- occupies the largest cross-section area of the root
3 LAYERS
CORTEX
hypodermis
parenchyma cells
endodermis
- the outermost layer with suberin
- fxn: slows down the outward flow of water and nutrients
hypodermis
make up most of the cortex; often contain starch and are separated by large intercellular spaces
parenchyma cells
- innermost layer (cells are packed tightly)
- lined with the _____________ (function as water dam to prevent the outward passage of water)
endodermis
Casparian strip
central part of the root containing the tissues derived from the
procambium
3 TYPES
STELE
pericycle
vascular tissue
parenchymatous pith
outermost layer which is one to several layers of parenchyma cells that give rise to branch roots
pericycle
xylem and phloem
vascular tissues
innermost region of monocot roots (for food storage and support)
parenchymatous pith
Root Anatomy: Dicot Root Cross Section
epidermis
cortex
endodermis
pericycle
vascular cambium
phloem
xylem
root hairs, mineral and water intake
epidermis
storage, defense
cortex
selective mineral uptake
endodermis
in radial walls
casparian strips
lateral root formation (periderm)
pericycle
makes 2° tissues
vascular cambium
CH2O delivery from leaves
phloem
conduct water and mineral upwards
xylem
- made up of lignin and suberin and arranged similarly to a rubber band around a rectangular box
Casparian Strip
Physiology of Root Absorption (2)
- water (through osmosis)
- minerals (by active transport)
- absorption occurs only when the water concentration in the root cells is _______ than that of their environment
WATER
lower
- water from the soil goes inward through the ___________, passing the semi-permeable plasma membrane of the root cells
- it passes through the ___________ until it reaches the __________
- it is interrupted by the _____________ of the endodermis (it makes sure that water first is absorbed by the cells before they enter the stele, because some water particles may also pass through the intercellular spaces)
WATER
epidermis
cortical cells, endodermis
Casparian strip
- water then crosses the __________________ and enters into the ___________ of the endodermal cells
** up to this point, this phenomenon will then permit the cells to regulate the movement of materials from the cortex to the stele and determine what materials will enter the xylem
- water then enters the xylem and moves upward into the stem
WATER
plasma membrane
cytoplasm
- absorbed to maintain the _____________ of root cells for the roots to keep on absorbing water from the soil and for continuous water movement
- nutrients will serve as the solutes
MINERALS (by active transport)
hypertonicity
The path of water into roots (2)
____________: a set of interconnected porous CELL WALLS which function for conduction of water
____________: involves an interconnected CYTOPLASM for the conduction of water and minerals
apoplastic pathway
symplastic pathway
- have their xylem centrally located usually in an X formation
- no pith is present
dicot root
- have pith tissue that is centrally located
- xylem cells arranged in a wing
monocot root
factors controlling the growth and distribution of roots
- temperature
- organisms in soil
- light
- gravity
- genetic differences
- stage of plant dev’t
- soil properties
- soil texture
- moisture and air
- nutrients - other factors
- roots that perform functions other than the usual functions of roots
- have modifications that adapt them for performing specific functions other than absorption of water and minerals.
2 types
modified roots
fleshy/storage roots
adventitious roots
- prop/brace roots
- aerial roots
- beets, turnips, radish, carrots, cassava, dandelion
BTRCCD
fleshy/storage roots
- corn, balete, pandan
CBP - cherry, pear, apple, climbing ivy
CHPACL
prop/brace roots
aerial roots
- mangroves
- water hyacinth
pneumatophores
aquatic roots
- orchids
- onion, garlic, lily, ginseng, gladiolus
- kapok tree, fig tree
photosynthetic roots
contractile roots
buttress roots
wala example
- propagative roots
- Parasitic roots/Haustorial roots
- Symbiotic roots
- mycorrhizae or “fungus roots”
- legumes (e.g., pea, beans, peanuts) and bacterium form root nodules
modified roots
- roots are modified for storage of food (starch or sucrose) or water, such as carrots and beets
- the cortex of these roots is enlarged and fleshy with abundant parenchyma cells
FLESHY OR STORAGE ROOTS
beets, turnips, radish, carrot, cassava
roots that form adventitious buds that develop into aboveground shoots, termed suckers, which form new plants, as in lilies, garlic, cherry and many others
Propagative Roots with Adventitious Buds/Stems
- roots that has strong anchorage like corn
- supportive aerial roots that grow into the soil
BRACE OR PROP ROOTS
pandan, balete, corn
- roots entirely above the ground and can be classified as climbing, photosynthetic, velamen and floating
- for support and propagation
AERIAL ROOTS
cherry, pear, apple, climbing ivy
- knee-shaped roots with aerenchyma cells, function to aerate roots to get air from the environment (for gas exchange)
- Plants with roots growing in water have spongy roots that grow above the water surface.
- This facilitates gaseous exchange between the atmosphere & the subsurface roots.
PNEUMATOPHORES
Mangroves (swampy areas)
have hairy/feathery lateral roots for buoyancy
AQUATIC ROOTS
water hyacinth
green in color, contains chloroplast, thus it functions for the manufacture of food
PHOTOSYNTHETIC ROOTS
orchids
- they pull bulbs or corms of monocots
- such as hyacinth and lily, and some taproots, such as dandelion, deeper in the soil through expanding radially and contracting longitudinally they have a wrinkled surface
- pull down deeper into the soil until a stable temperature is reached.
- commonly found in corm and bulb- forming plants.
CONTRACTILE ROOTS
onion, garlic, lily, ginseng, gladiolus
- plank-like roots in very big trees for support
- usually occur in plants that are shallow-rooted
- The roots function for stability and support.
BUTTRESS ROOTS
kapok tree, fig tree
- roots of parasitic plants that can absorb water and nutrients from another plant,
- such as in mistletoe and dodder
- have peg-like projections called haustoria (sing. haustorium) that
penetrate the outer tissues and establish connection to the xylem and phloem of the host plant.
Some parasitic plants and plant with no chlorophyll are able to _______________ from another plant in this way
HAUTORIAL/PARASITIC ROOTS
- roots with localized swellings due to the infestation of the root with ___________, a nitrogen-fixing bacteria
- the bacteria receives __________ and other substances from the host, while the plant receives ____________ from the bacteria
ROOTS WITH NODULES: symbiotic roots
Rhizobium
carbohydrates, nitrogen-containing ions
EXAMPLE: legumes (beans)
_____________ between a plant and bacterium which allows for the fixation of atmospheric nitrogen that the plant can utilize.
mutualism
___________ or “___________” consist of a symbiotic relationship between a plant and a fungus.
- the 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.
- The plant in return provides food for the fungus in the form of sugar and amino acids
Mycorrhizae, fungus roots
pine, oak, orchids
Economic Importance of Roots
◦food
◦ornaments
◦industry
◦drugs/medicines
Roots with Medicinal Value
pandan (Valerian)
tanglad (Ipecac)
tsaang gubat (Reserpine)
ginseng (Rhubarb/Rheum)
a characteristic feature of dicotyledons gymnosperms (flowerless plants that produce cones and seeds)
Secondary growth
