ROOTS Flashcards
The Major Types of Root Systems
Fibrous root systems
tap root system
is one in which the primary root remains the largest and a number of smaller secondary roots are formed from it.
tap root system
are composed of large numbers of roots nearly equal in size
Fibrous root systems
roots that develop from plant parts other than the radicle of seeds, develop from stems or leaves and are almost similar in sizes and growth patterns.
adventitious roots
root system of a plant begins its development from the ______of the embryo in the seed.
radicle
grows out of the seed after the seed has absorbed water. This is the primary root of the new plant.
radicle
tip of the root is covered by a mass of loose cells called the
root cap
towards the shoot is the _______ area of the root
meristematic area
Epidermal outgrowths just above meristematic area are
root hairs
The growing region of the root is
root apical meristem
root tip consists of
root cap, the region of the apical meristem, the region of elongation and the region of maturation
extreme tip is the __________, a zone of somewhat loosely arranged corky cells.
root cap
behind the root cap. Its cells are more densely packed and arranged in orderly rows parallel to the long axis of the root. Many of these cells are almost square in outline. This is the region you examined during the exercise on mitosis.
region of the apical meristem
root apical meristem will develop into primary tissues which are partly differentiated cells. These tissues are:
protoderm
procambium
ground meristem
which will become the epidermis
protoderm
which will become the vascular or conducting tissues
procambium
which will become the cortex and pith
ground meristem
is just behind the apical meristem. The cells have enlarged chiefly in length.
region of elongation
Most of the elongation is due to
internal pressures built up by an increase of water within the large vacuoles that occupy most of the cell.
contains enlarged cells that have now developed certain structural features and you can begin to see some differences among them
region of maturation
region of maturation are organized into three tissue systems which are based on topography
vascular tissue system
dermal tissue system
fundamental or ground tissue system
region of maturation tissue systems which is based on topography
usually appears as the darker central portion. Here you may be able to see some xylem (water conducting cells) that look like vertical rows of loose spirals (because of the spiral thickenings of the walls). You may also see the phloem (food conducting cells) although at this layer, the sieve tubes (which comprise the phloem) may not yet be distinguishable;
vascular tissue system
water conducting cells
look like vertical rows of loose spirals (because of the spiral thickenings of the walls).
xylem
food conducting cells
phloem
region of maturation tissue systems which is based on topography
arise the epidermis, the layer of cells at the surface and from which root hairs arise. Sometimes in the process of making the slide, the root hairs are destroyed; and
dermal tissue system
called cortex is the zone between the epidermis and the vascular cylinder
fundamental or ground tissue system
outermost layer of cells
The inner core
inner core of root
stele
The wide zone between the epidermis and the stele
cortex
this tissues in the root is usually uncutinized and permeable to water. They also develop into root hairs especially in the region of maturation.
epidermis
are thin-walled and often contain starch grains
Cells of the cortex
what are the cells that are loosely arranged in this region of the cortex. Water and dissolved solutes easily move between cortical cells in the intercellular spaces.
parenchyma tissue of the cortex
innermost layer of the cortex
endodermis
radial walls of the endodermal cells become impregnated with a “diffusion proof” waxy substance called
suberin
layer of suberin forms the stripn called
Casparian strip
The outermost layer of the stele is in contact with the endodermis and is called the
consists of thin-walled cells that are usually only one cell wide.
pericycle
The pericycle gives rise to the
lateral roots
tissues that occupy the center of the root. conduct water and minerals and food in the plant and are found throughout the plant body.
vascular tissues
vascular tissues are of two types
xylem and phloem
The innermost tissue which forms the star-shaped core of thick-walled empty cells is
consists of vessels (and tracheids in some plants) which are the main conducting cells and are sclerenchymatous in nature
xylem
is a cylinder extending the length of the root
a mass of cells in the center of the root. In young dicot roots, the vascular tissue is comprised of 3, 4, or 5 ridges or “arms” reaching the pericycle.
xylem
functions as a conductor of water and dissolved mineral nutrients. The vessels are joined end to end to form the xylem water tubes.
Xylem
form semicircular clusters of cells between the ridges or “arms” of the xylem.
phloem
form semicircular clusters of cells between the ridges or “arms” of the xylem.
are thin-walled, living cells and function in the translocation of organic compounds (food) manufactured by the leaves.
parenchymatous in nature
sieve tube elements and companion cells
In monocot roots, the centermost portion is occupied by parenchyma cells and the tissue is called the
pith
