UTA Plant Science Exam 3

urethra!

what do all seeds contain?

• seed coat

• food reserves

• embryo

seed coat

hard, outer covering

food reserves

endosperm and/or cotyledons

embryo

axis with attached cotyledons

what are the two steps in seed development?

1. embryogenesis

2. seed maturation

embryogenesis

establishes the body plan

what are the two superimposed patterns in embryogenesis?

• apical-basal pattern

• radial pattern

seed maturation

• build up of food reserves

• desiccation

• hardening of seed coat

• dormant or quiescent phases

seed development image 

study this image! 

is early embryogenesis the same in ALL angiosperms?

yes all early embryogenesis is the same in all angiosperms

formation of the embryo

begins with [apical cell] and [basal cell]

• establishes polarity

• IMPORTANT! fixes the structural axis of the body (the backbone!)

• determines arrangement of lateral appendages 

results in [Embryo proper] and [Suspensor]

what does the first mitosis division establish?

it establishes polarity 

• what is the top vs what is the bottom

what does the apical cell develop into?

it develops into the embryo proper

what does the basal cell develop into?

it develops into the suspensor

suspensor

stalk-like, anchors the embryo

micropylar 

lower end

globular stage

development of the three, concentrically arranged tissue systems 

• AKA [radial pattern]

what are the primary tissues of the globular stage?

1. protoderm

2. ground meristem

3. procambium

heart stage

• [cotyledons]: seed leaf, emerge

• all three primary meristems are present

• notch forms at the base of emerging cotyledon

  • site of future apical meristem of the shoot

• suspensor is still present!

  • metabolically active in angiosperms

  • provide nutrients and growth regulation

  • short-lived! dies before embryo matures

torpedo stage

• cotyledons elongate

• suspensor NO LONGER PRESENT

• embryo is near maturity

• apical-basal pattern discernible

study this image!

mature embryo

consists of an axis bearing one or two cotyledons

• Axis: (polar body of embryo)

  • epicotyl

  • hypocotyl

  • radicle

  • apical meristems

• cotyledons: food storage, photosynthetic and/or food absorption

  • NOT PART OF THE EMBRYO

epicotyl

region ABOVE the cotyledon attachment poin

hypocotyl

region BELOW the cotyledon attachment point

radicle (embryonic root)

at terminal end of the [hypocotyl]

how many cotyledons are present in eudicots and basal angiosperms?

two cotyledons are present

what is the primary function of the cotyledons in eudicots and basal angiosperms?

store nutrients (pinto bean)

• stored in the form of oils, starch, proteins

• when embryo mature: cotyledons are large, and endosperm reserves depleted

some function to absorb nutrients (castor bean)

• cotyledon is an absorptive structure

• endosperm present as nutrient source 

think about how peanut butter is full of lipids and protein

how many cotyledons are present in monocots?

one cotyledon is present

• primary function is to absorb nutrients

• Large reserves of endosperm remain in the seed

most of the grains we eat (rice, wheat, corn) are monocots

monocot vs eudicot 

ill come back to this

seed maturation

• massive buildup of food reserves in endosperm and cotyledons

• flow of nutrients from parent DISCONTINUES

• seed desiccates (lose 90% water)

• metabolism slows

• seed coat hardens

• enters either a [dormant] stage or [quiescent] stage

quiescent

resting state

• seeds germinate upon favorable conditions (water)

dormant

DOES NOT GERMINATE EVEN IN FAVORABLE CONDITIONS

seed-coat imposed dormancy

• impermeability of seed coat

• rigidity of seed coat

• escape prevented by growth inhibitors

• embryonic growth suppression

embryo dormancy

• hormone imbalance

• physiological immaturity

what are some ways you can bring a seed out of dormancy?

• passing through a digestive tract (birds)

• rainfall (for desert species)

• mechanical cracking (stone fruit)

• heat of fire

germination

resumption of growth of the embryo

• cell enlargement and cell division

what are the requirements of germination?

• water

• oxygen

• temperature

role of water in germination

• resumes metabolic activity 

• activates enzymes

• new enzymes created to synthesize and digest food stores

• enlarges the seed

role of oxygen in gerrmination

• respiration 

• is anaerobic for a period

• becomes aerobic when seed coat breaks open

• waterlogged soil can prevent germination

  • no air! can’t breathe!

role of temperature in germination

most have a wide range of Temp.

• Min: 0° - 5°C

• Max: 45° - 48°C

• Optimum 25° - 30°C

think of how temperature affects enzyme and chemical processes!

from embryo to adult plant

primary root (taproot, radicle)

• first structure to emerge

• produces [lateral roots]

• [Eudicots]

  • maintain taproot/lateral root morphology

• [Monocots]

  • primary root is short-lived, replaced by stem-borne roots

what is a primary root also called?

the radicle

eudicot roots

maintain taproot/lateral root morphology

monocot roots

primary root short-lived, replaced by stem-borne roots

what are the two kinds of germination that eudicots have

• epigeous germination

• hypogeous germination

epigeous germination

• cotyledons carried Above Ground to provide nutrients 

• [Hypocotyl] elongates, forms a hook

• shoot tip protected by being pulled from soil

hypogeous germination

• cotyledons remain Underground, provide nutrition

• [Epicotyl] elongates and forms hook

• shoot tip protected by being pulled from soil

most monocots have these characteristics

• elongation of a single, tubular cotyledon

• forms a hooked cotyledon

• seed coat and endosperm carried Upward with cotyledon to absorb nutrients

[monocots]: Corn (Zea mays)

• cotyledon is called a [scutellum]

• highly differentiated embryo

• [coleorhiza]: protective covering for radicle, emerges first

• [coleoptile]: protective covering for plumule, elongates to soil surface

• [plumule]: young shoot, emerges

eudicot garden bean diagram

cotyledons are food!

monocot onion diagram

large endosperm reserves!

maize diagram [monocot]

cotyledon is called a scutellum! in corn!

what are the three processes of development?

1. growth

2. differentiation

3. morphogenesis

growth

• irreversible increase in size

• cell division and cell enlargement

differentiation

• Cells with identical genetic constituents become different from each other and from meristematic cells

• fate is determined by final position in organ

morphogenesis

• the Plant assumes a particular shape or form

  • depends on the planes in which cells divide and how tissues expand

differentiation diagram

how many phases of growth are there in plants

there are up to two phases of growth 

• NOT ALL PLANTS WILL HAVE BOTH!

primary growth

• form primary meristems and extension of the plant body

• present in ALL plants (must have primary!)

• responsible for elongation of the plant

• occurs as a result of cell division in the apical and primary meristems

• parts of the plant derived from primary growth form the primary plant body

secondary growth 

• NOT present in all plants

• responsible for growth in diameter

• occurs as a result of cell division in the secondary meristems

• forms the secondary plant body

apical meristems

• tips (apex) of roots and shoots

• responsible for producing new cells and growth

  • elongation/extension of the plant body

  • formation of primary meristems

primary meristems

• protoderm

• ground meristem

• procambium

secondary (lateral) meristems

• vascular cambium

• cork cambium

meristems

cells divide in a way so that one cell remains in the meristem as an “initial” and the other becomes part of the body as a “derivative”

initial

a cell that remains in the meristem and never differentiates

derivatives 

can divide several times before differentiating 

what are primary meristems derived from and where are they found

derived from apical meristem

• found in the “sub-apical” region

protoderm

• future epidermis

• formed by divisions parallel to the surface in outermost cells of embryo

procambium

future vascular tissues

• xylem

• phloem

ground meristem

future ground tissue

what is the ground tissue system comprised of

• parenchyma

• collenchyma

• sclerenchyma

parenchyma tissue (simple)

composed of parenchyma cells

• living at maturity 

• found throughout the plant in many shapes and form

  • mesophyll, pith, cortex of stems, interspersed in xylem and phloem

  • typically only possess primary wall

parenchyma tissue functions

• often metabolically active

• photosynthesis

• storage

• secretion

• regeneration 

cortex

• in eudicots, the mass of ground tissue between the epidermis/periderm and the vascular cylinder

• composed mostly of parenchyma, some collenchyma 

pith

• the mass of ground tissue encircled by the vascular cylinder in eudicots

• usually made of parenchyma

chlorenchyma cells

specialized photosynthetic parenchyma cells

• thin walls allow light and CO₂ to pass through to chloroplast

• other types of pigmented cells are also parenchyma

  • petals and fruits

  • thin walls of parenchyma cells also allow pigments to be seen

  • any part of a plant that is colored, is likely parenchyma 

glandular cells

• contain elevated amounts of endoplasmic reticulum

• transport large amounts of sugar and minerals

• located throughout plant

• secretes:

  • nectar

  • fragrances

  • mucilage

  • resins

  • oils

what do glandular cells secrete?

nectar, fragrances, mucilage, resins, oils

transfer cells

mediate short-distance transport of material

• have many knobs/ridges on inner surface of cell wall

• creates extensive plasma membrane with numerous molecular pumps

• found in cotyledons, leaves reproductive structures, and glandular structures

collenchyma tissue

• composed of collenchyma cells

• living at maturity

• unevenly thickened, NONLIGNIFIED primary wall

• usually found in periphery

• support young, growing organs

collenchyma tissue cont. celery example

• commonly occur in strands or cylinders

• usually elongated

• commonly found under epidermis in leaves/perioles & around eudicot leaf veins

sclerenchyma tissue

composed of sclerenchyma cells

• dead at maturity

• thick lignified secondary wall

• strength and support plant parts not elongating

• two types of cells

  • sclereids

  • fibers

fibers

long and flexible

• found where strength and flexibility are important such as wood

• vascular tissue

sclereids 

short, “cuboidal”, inflexible, brittle

• forms hard impenetrable surfaces such as shells of nuts and fruit pits 

  • stone fruit pits!

if you can easily chew it (fruit)

parenchyma soft

if it is annoying to chew (celery strands)

collenchyma annoying

if you cannot chew it (cherry pits, seed coat on popcorn kernel)

sclerenchyma break yo tooth

dermal tissue system

• composed of epidermis and periderm tissues

• outermost layers of the plant

• great diversity in form and function

through what tissue does interchange of material between plant and the environment occur?

through dermal tissues

true or false: dermal tissue functions in preventing water loss

true

what specialized cells does the dermal tissue system have?

• trichomes

• guard cells

what material is dermal tissue covered in?

it is covered in cuticle

[dermal tissue system]: epidermis tissue (complex)

• cells of the aerial parts of the plant are coated with waterproof cuticle

• consists of wax and cutin exuded over surface in either smooth sheets, or rods and filaments extending upwards

• minimizes water loss!

what does the cuticle prevent the plant from doing?

• prevents dessication

• prevents gas exchange

what is each stoma composed of?

• guard cells

• stomatal pore

guard cells

responsible for opening/closing stomata

• cells swell by water absorption

• as guard cells swell, pore between them opens

• to close they lose water

trichomes

epidermal cells that elongate outward into hairs

• deter herbivory

• minimize water loss

• protect from over exposure to sunlight

absorptive roles

• root hairs

• epiphytic plants

mullen leaf

mushroom shaped trichomes are [glandular], while the branched trichomes are what gives the leaf a furry texture

periderm (complex)

replaces epidermis in secondary growth

comprised of:

• cork

• cork cambium

• phelloderm

• lenticels

cork

non-living and high suberized cell (corky)

cork cambium

secondary/lateral meristem