Bio Ch 36

What do roots usually lack?

'supporting collenchyma cells

xylem often has

234 or more extensions called xylem arms

what are transcription factors

DNA binding proteins that regulate the synhesis of RNA from a DNA template

what is a fibrous root system

it has several to many roots of similar size developing from the end of the stem with lateral roots branching off these roots

what is the pericylce

it is just inside the endodermis

what does the pericylce make up

it is made up of a single layer of parenchyma cells that give rise to multicellular lateral roots also called branch roots

the pericycle is involved in forming the

lateral meristems that are responsible for secondary growth in woody plants

what is the path of water up until now

look at pg 765 last paragraph

the cortex is made of primarily

loosely packed parenchyma cells

taproots are characteristic of

many eudicots and gymnosperms-a few trees retain their taproots which become massive as they grow

the root hairs are a ______of the root epidermis that enables it to absorb more water from the soil

modification

prop roots are more common in

monocots than eudicots

because no monocots have secondary growth

no vascular cambium exists in monocot roots

a taproot system consists of

one main root that formed from the seedling's enlarging radicle. Many lateral roots of various sizes branch out from a taproot

water moves through aquaporins only along the

osmotic gradient from a region of higher to lower

the root increases in girth and the vascular cambium continues to move

outward

minerals enter endordermal cells by

passing through carrier proteins in their plasma membranes

phloem is located in

patches between the xylem arms

the cork cambium in the root initially arises from regions in teh

pericycle

the outermost layer of the stele is the

pericycle

the root epidermis is replaced by what

periderm

because it has an inner core of vascular tissue, the primary eudicot root lacks

pitch

in most herbaceous eudicot roots, the central core of vascular tissue lacks what

pith

The main roots of the fibrous root system don't arise from

pre existing roots but from the stem-such roots are called adventitious roots

what does the endodermis do

regulates the movement of water and minerals that enter the xylem in the roots center

What structures do roots have that shoots lack

root caps and root hairs

pathway of water to this point

root hair/epidermis--> cortex--> endodermis-->pericycle-> root xylem

from the endrodermis water and mineral ions enter the

root xylem and water is conducted to the rest of the plant

once water enters the xylem, it is transported upward through

root xylem into stem xylem and from there to the rest of the plant

after passing through the endodermal cells, water enters the

root xylem often at one the xylem arms

the vascular cambium is

sandwhiched between the xylem and phloem

before secondary growth starts in a root, the vascular cambium is

sandwiched between the primary xylem and the primary phloem

woody plants have roots with

secondary growth

the vascular cambium gives rise to what

secondary tissues in woody plants

the root epidermis does NOT

secrete a thick, waxy cuticle in the region of root hairs because this layer would impede the absorption of water form the soil

instead the phloem and xylem are in

separate alternating bundles arranged around the central pitch which consists of parenchyma cells

the roots of many tropical rainforest trees are

shallow and concentrated near the surface in a mat only a few centimeters thick

each root hair is

short but quite numerous

Fibrous roots form in plants with a

short lived embryonic root-the roots originate first from the base of the embryonic root and later from the stem tissue

Root hairs are

short lived tubular extensions of epidermal cells located just behind the growing root top

dissolved sugar (sucrose) is conducted in

sieve tube elements of phloem

xylem does NOT form the central tissue in what

some monocot roots

What is the most common form of stored energy in plants

starch

at the center of a eudicot primary root is the

stele or vascular cylinder

What is the primary function of the root cortex

storage

What does the casparian strips contain

suberin

What are the two kinds of root systems found in plants

taproot and fibrous

How do taproots obtain water

taproot systems extend down into the soil to obtain water located deep underground(TREE)

Many trees have _____roots when they are young and later develop large shallow_____ roots

taproots;lateral roots

Root hairs continually form in

the area of cell maturation closest to the root tip to replaces those that are dying off at the more mature end of the root hair zone

what distinguishes the roots of herbaceous eudicots and monocots

the arrangement of vascular tissues

the symplast is what

the continuum of living cytoplasm, which is connected from one cell to the next by cytoplasmic bridges called plasmodesmata

what is the inner layer of the cortex

the endodermis

what happens as the root increases in girth

the epidermis cortex endodermis and primary phloem are gradually torn apart

the apoplast consists of

the internconnected porous cell walls of a plant along which water and minerals dissolve mineral ions move freely

What increases absorption

the lack of a cuticle and the presence of root hairs

what is carrier mediated transport

the minerals ions are pumped against their concentration gradients-requires energy in the form of ATP

what orients the root to grow downward

the root cap

What happens as the root grows?

the root pushes it way through the soil, cells of the root cap are sloughed off by the frictional resistance of the soil particles and replaced by new cells formed by the root apical meristem. The root cap cells secrete lubricating polysaccharides that reduce friction as the root passes through the soil. The root cap also appears to be involved in orienting the root so that it grows downward. when root cap removed, the root apical meristem grows a new one

What make up the entire plant body

the symplast and apoplast

The water and dissolved minerals that enter the root cortex from the epidermis move in solution along two pathways:

the sypmplast and apoplast

what is the stele called

the vascular cylinder

How do the water and dissolved mineral ions move?

the water and mineral ions can diffuse across the cortex without ever crossing a plasma membrane to enter a living cell

How do fibrous root systems obtain water

they are located relatively close to the surface-are adapted to obtain rain water from a larger area as it drains into the soil

What is the shape of the enderdermal cells

they fit snygly against one another and each has a special bandlike region called a casparian strip on it's radial (side) and transverse (upper and lower) walls

What do root hairs do

they greatly increase the absorptive capacity of roots by increasing their surface area in contact with moist soil(microvilli). Soil particles are coated with microscopically thin layer of water in which minerals are dissolved. The root hairs establish an intimate contact with soil particles which allows efficient absorption of water and minerals

what do buttress roots do

they hold the trees upright and aid in the extensive distribution of the shallow roots

at the onset of secondary growth, the vascular cambium extends out

to the pericycle which develops into vascular cambium opposite the xylem arms

water and dissolve minerals are conducted in

tracheids and vessel elements

the development of root hairs is under the control of two regulatory genes that code for

transcription factors

in swampy or tidal environments where the soil is flooded or waterlogged, some roots grow

upward until they are above the tide level

what is the centermost tissue of the stele

xylem

the root mat does what

catches and absorbs almost all minerals released from leaves by decomposition

lateral roots originate when

cells in a portion of the pericycle start dividing, as it grows, the lateral root pushes through several layers of root tissue before entering the soil

one of the major componenets of cells walls is

cellulose

what is periderm

composed of cork cells and cork parenchyma

what composes the bulk of a herbaceous eudicot

cork

as the vascular cambium divides to produce secondary tissue, it eventually forms a

cylinder of vascular cambium that continues to divide producing secondary xylem (wood) tot he inside and secondary phloem(inner bark) to the outside

what is a radicle

embryonic root

in a herbaceous eudicot, a single layer of protective tissue called the what covers its rotos

epidermis

the layers of monocots starting from the outside are

epidermis cortex endodermis and pericycle

pith is what

ground tissue found in the centers of many stems and roots

what are aquaporins

integral membrane proteins that facilitate the rapid transport of water across the membrane

The oxygen that root cells need for aerobic respiration diffuses from air spaces in the soil into the

intracellular spaces of the cortex and from there into the cells of the root

what is the stele or vascular cylinder

a central cylinder of vascular tissues

as a result, the pericycle links the separate sections of vascular cambium so that the vascular cambium becomes

a continuous loop of cells in cross section

what is suberin

a fatty material that is waterproof

How do we know this

a microscopic examination of the parenchyma cells that form the cortex often reveals numerous amyloplasts which store starch

each lateral root has all the structures of

a normal root that it came from

What do the large intracellular spaces provide?

a pathway for water uptake and allow for aeration of the root

what is a root cap

a protective thimblelike layer many cells thick that covers the delicate apical meristem

each root tip is covered by

a root cap

the xylem in monocot roots doesnt form

a solid cylinder in the center

cellulose does what

absorb water like a sponge

prop roots are

adventitious roots that develop from branches r a vertical stem and grow downward into the soil to help support the plant in an upright position

these plants have primary growth at

apical meristems and secondary growth at lateral meristems

water enters by osmosis both directly across the lipid bilayer of the endodermal plasma membrane and through

aquaporins

Why do roots lack that?

because the soil supports the root although roots as they age may develop some sclerenchyma cells

Trace the path of water

beginning with root hairs, most of the water enters the root moves along the cell walls rather than enter the cells

swollen bases or braces called

buttress roots