External and Internal Structure of Roots Flashcards
key adaptation for plants on land to allow access
nutrients and water stored in soil
plant roots
FUNCTIONS OF ROOTS
§ Anchorage of the plant body in the soil
§ Absorption of water and minerals from the soil
§ Storage of foods
§ Conduction of food and water from the soil and from storage reserves
into the shoot
TYPES OF ROOT SYSTEM
FIBROUS ROOT & TAPROOT
§ Consist of a dense mass of slender, adventitious
roots that arise from the stem
§ The roots grow downward and outward from the
stem, branching repeatedly to form a mass of
fine roots.
Ex: grass and other monocots including lilies and
palm plants
FIBROUS ROOTS
§ Features a single, dominant primary root
which grows straight down into the soil; much
smaller, fibrous secondary roots run outward
§ The large primary root can reach deep into the
soil for water and store food, adaptations
which help them to survive drought and
seasonal variations in temperature and
sunlight.
Ex: carrots, radish
TAPROOT
after a bean germinated, what emerges from it that looks like a hook?
radicle
It becomes the primary root (usually the most important root in
some plants)
radicle
Other roots branch out from the primary root; called _________ ____
secondary roots
found at the root tip, where new cells develop, covered by root cap
apical meristem
protects the apical meristem from damage as it passes through coarse soil particles
root cap
- An ideal system to study plant tissue formation
- Directing root growth in soil environment
- Adjusting soil environment by secretion and cell dispersal
root cap
The surface of the root is protected by skin cells called the?
hint: Where water and minerals enter the root by osmosis and diffusion
Can grow long, hair like projections called root hairs (they greatly
increase the surface area of the root to allow more water intake)
epidermis
root cap is composed of a _____________________________ covering the tip of each root
thimble-shaped mass of parenchyma cells
function of root cap
Function: protects the root apical meristem
(RAM); protects the root from mechanical injury
ROOT CAP
Dictyosomes or Golgi bodies release a
_________________________ lasts less
than a week, then these die
mucilaginous lubricant (mucigel) cells
Possibly important in perception of gravity (i.e
geotropism or gravitropism)
ROOT CAP
ROOT CAP
also called statoliths – dense
containing starch plastids, appear to accumulate at
the bottom of cells
Amyloplasts
REGION OF CELL
DIVISION
Composed of apical meristem (cells divide
once or twice per day)
REGION OF CELL DIVISION
The transitional meristems arise from the
tips of roots and shoots. These include:
§ Protoderm: forms the epidermis
§ Ground meristem: forms the ground
tissue
§ Pro cambium: forms the primary
phloem and xylem
Cells become several times their original
length and also somewhat wider; the tiny
vacuoles merge and grow until one or two
large vacuoles, occupying up to 90% or
more of the volume of each cell have been
formed
REGION OF ELONGATION
§ Root hairs develop as protuberances from
epidermal cells
§ Increase the surface area for the
absorption of water
§ Cuticle exists on root but not on root hairs
REGION OF MATURATION
REGION OF MATURATION
this is where the root stores the
food produced by the leaves; it is made
out of parenchyma tissue
CORTEX
REGION OF MATURATION
the inner boundary of the
cortex; one cell layer thick; controls the
movement of water and minerals into
the xylem and phloem
ENDODERMIS
REGION OF MATURATION
a layer found inside the
endodermis which may produce lateral
roots; also produces vascular cambium
in dicots
PERICYCLE
REGION OF MATURATION
forms the central
cylinder of the root; it is made out of two
secondary transport tissues
Vascular cylinder/stele
REGION OF MATURATION
carries the water taken in by the
root hairs and epidermis up the plant to
the stems and leaves
Xylem
REGION OF MATURATION
carries the food produced by the
leaves down to the roots to be stored in
the cortex
Phloem
SPECIALIZED ROOTS
§ FOOD STORAGE ROOTS
§ WATER STORAGE ROOTS
§ PROPAGATIVE ROOTS
§ PNEUMATOPHORES
§ AERIAL ROOTS
§ BUTRESS ROOTS
§ CONTRACTILE ROOTS
§ PARASITIC ROOTS
In certain plants, the roots or part
of the root system is enlarged in
order to store large quantities of
starch and other carbohydrates.
carrots, beets and turnips have
storage organs that are actually a
combination of root and stem.
FOOD STORAGE ROOTS
Plants that grow in particularly
arid regions are known for
growing structures used to retain
water. Some plants in pumpkin
family produce huge water
storing roots. The plant will then
use the stored water in times or
seasons of low precipitation.
Some cultures will harvest the
water storing root and use them
drinking water.
WATER STORAGE ROOTS
§ The root word of this one means to produce more of
oneself. Its structures are a
way for a plant to produce more of itself.
§ Adventitious buds are buds that appear in
unusual places. Many plants will produce
these buds along the roots that grow near
the surface of the ground. suckers, or aerial
stems with rootlets, will develop from these
adventitious buds. The new plant can be
separated from the original plant and can
grow independently.
PROPAGATIVE ROOTS
§ Breathing roots to help plants that grow in very wet areas like
swamps get enough oxygen. These roots basically act like snorkel
tubes for plants, rising up above the surface of the water so that the
plant can get oxygen.
§ Ex. mangrove trees
PNEUMATOPHORES
§ There are many different kinds of these roots
produced by a wide variety of plants.
§ Orchids produce vela men roots, corn plants
have prop roots, ivies have adventitious roots
and vanilla orchids even have photosynthetic
roots that can manufacture food.
§ Banyan trees have aerial roots that grow down
from the tree branches until they touch the soil.
§ These are roots that are not covered by soil
hence out in the air.
§ They can facilitate climbing and various types of
support.
AERIAL ROOTS
§ These are large roots on all sides of a
shallowy rooted tree.
§ Typically, they are found in nutrient-poor
rainforest soils and do not penetrate to deeper
layers.
§ Almost all types of mangroves have these types
of roots.
§ They prevent the tree from falling over while
also gathering more nutrients.
BUTRESS ROOTS
§ These roots continually pull the plants
deeper into the ground as the stem elongates
so that it remain subterranean or at an
appropriate level in the ground.
§ These are usually broad, fleshy,
vertical, tapering, wrinkled looking and very
distinct of the after cylindrical fine absorbent
roots and are capable of incredible effort
CONTRACTILE ROOTS
§ These roots are found in non-green parasitic
plants.
§ These plants cannot make their own food and
obtain food from the host.
§ These plants have no chlorophyll necessary for
photosynthesis.
§ Dependent on chlorophyll-bearing plants for
their required food materials, adventitious roots
from the nodes of these plants penetrate into
the host tissue (via peg like projections called
haustoria) and enter into its conducting tissue
(water-conducting and food-conducting) to
acquire their nutrition.
PARASITIC ROOTS
§ Forms a mutualistic association with plant roots
§ Fungus can absorb and concentrate phosphorous much better
than it can be absorbed by the root hairs
§ Particularly susceptible to acid rain
MYCORRHIZAE
- A swelling on the root of a leguminous plant, such as pea or clover,
that contains bacteria of the genus Rhizobium, capable of nitrogen
fixation
§ Root knots
§ swellings that may be seen in the roots of tomatoes and many
other plants that develop in response to the invasion of tissue by
small, parasitic roundworms (nematodes).
ROOT NODULES
