Morphoanatomy of Root Flashcards
usually an underground part of the
plant
root
The root with its branches is known
root system
Functions of the roots
(1) anchoring the plant firmly to a substrate,
* (2) absorbing water and minerals,
* (3) producing hormones
types of root systems
tap root system
fibrous root system
develops from the embryonic root in the seed
Tap root system
The roots are adventitious and
develop from stem tissue
fibrous root system
has a main root that grows down vertically, and from which many smaller lateral roots arise
tap root system
Most ___ have a single prominent ___ that is much larger than all the rest and numerous small ___ ___ or ___ ___ coming out of it
dicot ; taproot ; lateral roots ; branch roots
has several to many roots of the same size that develop from the end of the stem, with smaller lateral roots branching off these roots
fibrous root system
form in plants in which the embryonic root is short-lived.
fibrous root system
The roots originate initially from the base of the embryonic root and
later from stem tissue.
fibrous root system
do not arise from preexisting roots but from the stem, they are called adventitious
fibrous roots
fibrous roots do not arise from
preexisting roots but from the stem, they are called
adventitious
located closer to the soil surface, and forms a dense network of roots
that also helps prevent soil erosion
fibrous root system
increase the absorptive and transport capacities of the root system
adventitious roots
often extend down into the
soil to obtain water deep underground
tap root system
relatively close to the ground surface, are adapted to obtain
rainwater from a larger area as it drains into the soil
fibrous root system
The tip of a root is covered
by a thimble-like structure
root cap
protects the delicate apical meristem as the root pushes through the abrasive soil during
primary growth
root cap
secretes a polysaccharide slime
called mucigel that lubricates the soil around the tip of the root
root cap
lubricates the soil around the tip of the root
mucigel
what are the zones of cells at successive stages of primary growth
zone of cell division
zone of elongation
zone of maturation/differentiation
is closest to the root tip; it is made up of the actively dividing cells of
the root meristem
zone of cell division
includes the root apical meristem and its derivatives
zone of cell division
New root cells are produced in this
region, including the root cap.
zone of cell division
A group of cells between the root cap meristem and the zone of cell division (meristem) of the root is called
quiescent center
The cells in this region are also
meristematic, but divide very
slowly
quiescent center
can provide new cells for both the root and the root cap meristems as needed
quiescent center
the cell division zone of roots is
usually only about
1 mm
Typically, about a millimeter behind the tip of the root
zone of elongation
pushes the tip farther into the soil
zone of elongation
keeps adding cells to the younger
end of the zone of elongation
root apical meristem
cells complete their differentiation and become distinct cell types
zone of differentiation
a region in which many of the epidermal cells extend out as narrow trichomes
root hair zone
short-lived tubular extensions of epidermal cells located just behind the growing tip
root hairs
can form only in a part of the root that is not elongating or they would be shorn off
root hairs
greatly increase the root’s surface
area
root hairs
A single layer of protective tissue covers its roots
epidermis
composed primarily of loosely arranged parenchyma
cortex in eudicot root
The outermost layer of the stele is a single layer of cells, which is just inside the endodermis
pericycle
composed of parenchyma cells that remain meristematic, gives rise to lateral roots
pericycle
the phloem and xylem are in separate alternating strands that in cross section are arranged in a circle, which consists of parenchyma cells
pith
absorb most of the water that goes
into plants
roots
thin-walled slender extensions of root epidermal cells that greatly
increase the surface area for absorption
root hairs
Plants absorb water and dissolved
minerals from the soil with the help of
root hairs
Water moves into the roots by
osmosis
The rate of water uptake is regulated by specialised water channels called
aquaporins
The inner layer of the cortex controls the amounts and kinds of water and dissolved materials that enter the xylem in the root’s center.
endodermis
Endodermal cells fit snugly against one another, and each cell has a special bandlike region, called
casparian strip
Casparian strips contain ____, a
fatty material that is waterproof.
suberin
the continuous system of cell
walls and intercellular air spaces in plant tissues.
apoplast
Water moves exclusively
through the cell wall without
crossing any membranes.
apoplastic pathway
is obstructed by the Casparian
strip
apoplastic pathway
consists of the entire network of
cell cytoplasm interconnected by
plasmodesmata
symplast
Water travels from one cell to the next via the plasmodesmata
symplastic pathway
primarily function to store starch and water underground as
reserves for perennial species
storage roots
examples of storage roots
carrots, sweet potatoes, turnips
are capable of extensive growth
through the air
prop roots
examples of prop roots
banyan tree
adventitious roots that grow from lower stem nodes.
stilt roots
provide anchorage to the tree
or plant to stand strong in the ground.
stilt roots
living attached to the branches of trees
epiphytic aerial roots
Their roots spread along the surface of the bark and often
dangle freely in the air.
epiphytic aerial roots
The snake·like roots gradually wrap around the host tree
strangling aerial roots
shallow and concentrated near the
surface
buttress roots
some roots grow upward until they are above the high-tide level
pneumatophores/breathing roots
may assist in getting oxygen to
the submerged roots
pneumatophores
thickened specialized root which is designed to shrink vertically under conditions of seasonal drought
contractile roots
arise from nodes and helps the
plant in climbing
climbing roots
arise from leaf
foliar roots / Epiphyllous roots
roots enter in the stem of host plant to absorbed nutrition from host
parasitic roots
become green and synthesize
food
assimilatory roots
The roots of most species of seed
plants (at least 80%) have a symbiotic relationship with soil fungi in which both organisms benefit.
mycorrhizae
fungal hyphae penetrate between the outermost root cortex cells but never invade the cells themselves
ectomycorrhizal relationship
fungi with slender, threadlike cells
hyphae
hyphae penetrate the root cortex as far as the endodermis
endomycorrihizal association
what type of plant does endomycorrhizal association occurs?
herbaceous plant
allow plants to draw more
nutrients and water from the soil
mycorrhizal fungi
They also increase plant tolerance to different environmental stresses.
mycorrhizal fungi
these fungi play a major role in soil
aggregation process and stimulate microbial activity
mycorrhizal fungi
In a small number of plants, especially legumes, a symbiotic relationship has evolved with nitrogen-fixing bacteria of the genus
rhizobium
The nodules on plant roots contain bacteria capable of absorbing atmospheric nitrogen and converting it to ammonia, which the
plant can use to make amino acids
rhizobium/ rhizobial bacteria
produce multiple beneficial effects on plant growth stimulation,
host defense against disease and survival under stress
rhizobia
These chemicals tell every other living thing in the root zone how the
plant is doing.
root exudates
