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155 Cards in this Set

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phloem transport is driven by
an osmotically generated pressure flow
why can't transport in phloem be explained by diffusion followed by cytoplasmic streaming
because velocity of assimilates (~50-100 cm/h) are too great for either phenomena to account for long distance transport via sieve tubes
what is the pressure flow hypothesis
erns munch 1972. assimilates are transported form source to sink along a turgor pressure gradient developed osmotically

(phloem transport)
what is a source
area of supply or exporters of assimilates. sources are photosynthesizing leaves and also storage tissues
what are sinks
all parts of plants that cannot meet their own nutritional needs. sinks are roots and storage tissue
what two factors does the source and sink relationship depend on;
physiological and developmental factors.
sink/source in younger seedlings
1. younger seedlings - source to sink is simple and direct in young seedlings: that is where cotyledons are SOURCE as they contain reserve food and the growing roots are SINK
sink/source in older seedlings
older plants - the upper most recently matur eleaves commonly exports assimilates to the shoot tip, the lower leaves export to the roots and those in between export both directions
sink/source change form begetative to reporductive growth
developing fruits are highly competitive sinks that monopolize assimilates from nearest as well as distant leaves
during reproductive growth, the ______growth declines
vegetative
what direction is phloem transport?
it is not exclusively upward or downward. the direction of phloem transport is determined by the demands of the organ
what are the steps in phloem translocation
1. phloem loading - sucrose produced in mesophyll cells is ACTIVELY LOADED to sieve tubes (higher sucrose concentration in sieve tubes).

2. increase concentration of sugars --> decrease in water potential thus water from xylem goes to the sieve tubes.

3. unloading - sugars are removed at the sink, water potential is increased, and thus water leaves sieve tube.
where does passive movement of sugars occur?
with the movement of water into the sieve tube at the source and out of it at the sink, sugars are carried passively by water along concentration gradient between source and sink.
where does active movement of sugars occur?
when the sugars are loaded into and unloaded out of the sieve tube at the source and the sink
is the rate of translocation sensitive to the energy supply
yes, b/c laoding and unloading require energy!!
so phloem loading is symplastic or aploplastic?
can be both
what is proton gradient pump?
this is a plasma membrane h+ ATPase that utilizes the energy form hydrolysis of atp to transport H+ across the membrane. this proton gradient is used by specific carries in the plasma membrane to couple movement of proton back to symplast ot the transport of sucrose
what is growth?
an irreversible increase in size by a combination of cell division and cell elongation
does cell division by itself consititute growth?
NO!
morphogenesis
the process during growth and development in which the plant assumes a particular shape/form
what determines morpholog?
plane of cell diviison and expansion
differentiation
the prcoess by which cells with identical genetic material cebome different from one another
differentiation is controlled by
1. gene expression - companion cell and sieve tube from same mother clel, but due to differential gene expression they have become distinct form on another.

2. by the position in the developing organ: if an undifferentiated cell is displaced it will differentiate appropriate to its new position

also: determination and competency
what is determination
progressive commitment to specific course of devleopment, thus reducing the capacity to resume growth

e.g. plants always grow, animals don't
competency
the ability to maintain the capacity to differentiate, divide and have progeny that differentiate into any cell type.
what is secondary growth
increase in diameter of regions that no longer elongate
secondary growth results from 2 lateral meristems, what are they?
vascular cambium, cork cambium
secondary growth in roots and shoots consist of?
1. secondary vascular tissue - xylem and phloem from vascular chambium

2. periderm composed mostly o cork tissue form cork cambium
which group of plants undergo secondary growth? annual, biennial, perennial
annuals = no

biennials = a little maybe?

perennials = alot

(they all have diff life cycles)
what is the life cycle of a plant?
seed --> vegetative plant --> flowering plant --> seed
annuals
complete life cycle in one year. many weeds, wild and graden flowers, and vegetables
biennials
complete life cycle in two years
perennials
grow over more growing seasons. all gymnosporms, some monocots and many dicots
what is vascular cambium? how is it different from procambium?
it produces 2 xylem and phloem, which procambium produces primary xylem and phloem
cork + cork cambium + phelloderm =
periderm
fasicular cambium + interfasicular cambium =
vascular cambium
where is fasicular cambium?
within bundles
where is interfasicular cambium
between bundles
what is pith and pith ray?
cortex between bundles = pith ray, cortex in middle of all bundles = pith
what are fusiform initials
they make up the axial system of the vascular tissue. they are vertically oriented, many times longer than wide.
what are ray initials
they divide to form radial system of the vascular tissue. radial system = vascular ray system. lays at a right angle to fusiform initials. they lay horizontally oriented and are slightly elongated.
what are the funciton of ray initials
pathway for movement of food from phloem to xylem and water form xylem to phloem.

storage sites for starch, proteins and lipids.
how is secondary xylem and phloem produced
through periclinal devisions of fusiform and ray initials. that is, cells from these divisions are formed parallel to the surface of roots and stems.
when secondary xylem is formed, cambium is displaced outward thus increasing circumfrence. thus new cells are added to the cambium by ________ division of initials
anticlinal
the periderm(part of bark) is made up of
phellem, cork cambium, phelloderm
the functions of the periderm are
inhibits water evaporation

protects against insect and pathogen invasion
what is bark
protective covering over wood of tree. everything between vascular cambium and outside of woody stem.(phloem + periderm + cortex) composition varies depending on age of tree
young tree composition of bark
secondary phloem, few cortex cells, 1 or 2 increments of periderm
old tree composition of bark
layers of secondary phloem and several layers of periderm
what are annual rings
rings in which tell you how many years old the tree is. they are rings of cells of secondary xylem.

irregular growth of rings in tripical rain forests
earlywood/spring wood
cells in inner part of annual ring, cells larger in diameter, formed during first growth spurt of new season
latewood/summerwood
cells smaller in diameter, formed later in growing season.
heartwood
darker wood in center

cells blocked with resins and other materials

no longer funcitons in transport

vessel members may be blocked

DEAD
sapwood
ligher wood near periphery

secondary xylem

has funcitonal xylem cells

where actual transport of water and dissolved minerals takes place

LIVING
what factors determine the width of annual rings
light, temperature, length of growing season, water availability: rainfall, available soil water
what are the two types of factors controlling plant growth and development
endogenous factors

exogenous factors
endogenous factors
hormones: chemical messenger from one cell to another. plant hormone= phytohormone.
auxin
phytohormone

(to increase)

functions:
apical dominance

tropic responses

differentiaion of vascular tissue

promotion of cambial activity

induction of adventitious roots on cuttings

inhibition of fruit and leaf abcission

promotion of fruit development
chemical name of auxin
indoleacetic acid (IAA)
site of auxin biosynthesis
prinarily in leaf primordia

young leaves

developing seeds
polar transport of auxin
always towards base

from shoot tips and leaves downwards in stem, via vascular parenchyma cells

from root tips towards base of root
non polar transport of auxin
auxin reach root tip in the sieve tubes non polarly at much fast rate than the polar movement
you can use auxin to grow _____
fruit
cytokins
phytohormone

founded in cocoanut milk

functions:

cell division

promotion of shoot formation in tissue culture

delay of senescence

promotion of cambial activity

release of lateral buds from apical mersitem
transport of cytokinins is accomplished by ____ from roots to shoots thus, cytokinins are primarily produced in ________
xylem

root tips
the most common cytokinin in plants is
zeatin
ethylene
phytohormonoe

c2h4

gas synthesized from methionine. founded in gas lamp

produced in most tissues as a response to stress, senescene and ripening

functions:

fruit ripening

senescene

leaf and fruit abscission
ethylene is moved by ______ because its a gas
diffusion
abscisic acid (ABA)
phytohormono

founded in buds of ash and potatoes

functions:

stomatal closure

induction of photosynthate transport form leaves to developing seeds

induction of protein synthesis in seeds

maintenance of dormancy in seeds
site of synthesis of ABA
in mature leaves and roots, wspecially in response to water stress

potentially in seeds
transport of ABA
exported from leaves in phloem from roots in xylem
gibberellins (gibberellic acid GA)
phytohormonoe
founded in rice disease

functions:

associated w/ dwarfism and hyperelongation of shoots... can affect fruit development (grapes e.g.)

effective in breaking dormancy and seed germination

stimulates flowering in long day plants
biosynthesis of GAs
in young tissues of the shoot and devloping seed

uncertain if it is produced in roots
transport of GA
probably in phloem and xylem
the mechanism of action of hormones: 3 things
1. hormones control gene expression

2. hormones regulate cell expansion and cell division

3. hormones function via alteration of signal transduction pathway
exogenous factors
light

gravity

biological clock

temperature

mechanical stimuli

water

nutrients
waht happens when a plant is grown in the dark?
it grows taller trying to reach the light
how is light absorbed by plants?
by plant photoreceptors
what is a photoreceptor?
a pigment (chromophore) contianing protein.

a chromophore is the light absorbing portion of a molecule
plant photoreceptor types
phytochrome - abosorbs light in far red 660-750

phototropins - blue region, kinase, 450

cryptochromes - blue region, not a kinase 450
what is etiolation
causing a plant to grow white by eliminating light
phytochromes Pr
regular red light. inactive when perceiving red light.

when activated for 30 secs converts to Pfr
phytochromes Pfr
far red light. active form. absoarbs far red light.

bio activity

breaks down back into Pr
so if the last light seen is Pr will plant germinate?

what if last light seen is Pfr
yes because will convert into active Pfr and remain there.

no becuase will convert into Pr (inactive form)
how do plants avoid shade
they grow taller and compete with their neighbors for more light

they respond to far red light for elongation (fr exposed plants will be taller??)
what is tropism
growth response of plants towards or away form an external stimuli

towards = positive tropism

away from = negative "
what is phototropism?

phototropism is controlled by
caused by elongation of the cells under shaded side of the tip by plant hormone auxin

auxins and light
role of light in phototropism
light decreases the auxin sensitivity on the lighted side

light destroy auxin

light drives auxin to the shaded side of the growing tip
what is gravitropism
redistribution of auxin from the upper to the lower side
how do plants perceive gravity
by sedimentation of amyloplasts (starch containing plastids)
the coordination of both _____ factors and _____ factors control __________
endogenous and exogenous

plants growth and development
what are the 5 division(phlya) of fungi
chytridiomycota

zygomycota

glomeromycota

ascomycota

basidiomycota
what is mycology
the study of fungi
fungi are more closely related to which? plants or animals?
animals
6 characteristics of fungi
1. composed of hyphae (mass of hyphae = a mycelium)

2. hyphae of most species are separated by septa

3. hyphae lacking septa are coenocytic

4. cells walls of fungi contain chitin

5. fungie are hetertrophic and obtain their food by absortption (enzymes)

6. fungi have zygotic life cycle that includes separate steps of plasmogamy and karyogamy
zygomycota
1100 named species

economically important as food storage

eproduce sexually with meiospores called zygospores and asexually with sporangiospores

e.g.=rhizopus - common break and fruit mold
ascomycota
32000 species

many familiar and economically important species:

human diseases - athletes foot, pnuemocystis

plant diseases - powder mildew, dutch elm disease

parasites - cordyceps (mind control of ants)

medicines - penecillin, cyclosporin

food delicacies - truffles, morel mushrooms

botrytis - "the noble root"

yeast - bread, beer, wine, importnat reserach organism

other info:

form meiotic spores called ascospores, which are enclosed in a special sac-like structure called an ascus

have only been observed undergoing asexual reproduction. Because the products of meiosis are retained within the sac-like ascus, several ascomyctes have been used for elucidating principles of genetics and heredity
basidiomycota
26000 species

produce meiospores called basidiospores on club-like stalks called basidia. Most common mushrooms belong to this group, as well as rust (fungus) and smut fungi, which are major pathogens of grains.

Amanita (poisonous) mushrooms - the death cap,

puffballs

many edible mushrooms too

psliocybe muschrooms
what is fungal symbioses
the living together of two dissimilar fungi??
types of fungal symbioses
1. mycorrhizae - endomycorrhizae(glomeromycota), ectomycorrhizae (some asco, and basidio)

2. lichens - mutualistic symbiotic relationship between a fungal partner (usually asco and green alga or cyanobacteria)
what are oomycota
previously grouped w/ fungi, but now it is clear they are unrelated. water moldes, slime molds.
waht is taxonomy?
identifying, naming, and classifying species
what is phylogeny
evolutionary relationships among organisms
cladistics
a set of quantitative methods and concepts for exploring the evolutionary relationships between taxa

(phylogeny trees?)
chytridiomycota
1000 species

possess flagellated swimming cells

disease caused by one chytrid species is implicated in mass amphibian die-offs
glomeromycota
157 species

use to be goruped w/ zygomycota

form symbiotic associations w/ 80% of wild plants

sexual reproduction is unknown.

asexual reproduction = miltospores
what are monera?
today the kingdom is called prokaryotes.. however it used to be called monera.
what are the four kingdoms?
protista, monera, eukaryota, bacteria
basics of prokaryotes
structurally simplest and physically smallest and most abundant organisms

evolutionaryily the oldest organisms and most successful form of life

capable of living in enviornment that supports no other form of life
waht are the two domains?
prokaryotes and eukaryotes
why are prokaryotes so successful
1. metabolic diversity

2. rapid division

3. adaptability
how are prokaryotes metabolically diverse
1. autotroph (both photosynthetic and chemosynthetic)

2. heterotrophs requir organic compounds as a carbon source. majority are saprophytic. important decomposers in the enviornment.
why are prokaryotes important
autotrophic bacteria are major contributers to carbon balance

nitrogen fixation

producers of 90% co2

biological decomposers

source of ABs

commercial use for production of aa's and enzymes

food industry

potent disease causing agents
characterstics of prokaryotic cells
lack of organized nucleus bounded by nuclear envelope

circular dna in a region of cells called nucleoid

they may contain extra dna called plasmids that replicated independent from cells

cytoplasm contians 10,000 riobosomes

smaller size ribosomes

lack of cytoskeleton

lacks membrane bounded organelles

plasma membrane is formed form lipid bilayer

plasma membrane of aerobic bacteria has the electron transport chain that is in the mitochondria of eukaryotes

the site of photosynthesis in purple and green photosnthetic bacteria are in plasma membrane

usually rigid or flexible cell wall
bacteria can be divided into two groups based on their ability to retain the dye crystal violet in their cell wall.
gram positive - retains dye - PURPLE 90 percent peptidioglycans and is thick

gram negative - do no retain dye PINK- has outer membrane and thinner layer of peptiodioglycans then an inner membrane
major forms of prokaryotes
rod, spiral, spherical
reproduction through gene exchange
conjugation, transformation, transduction
formation of _____ increases the ability of prokaryotes to survive
endospores
phylogenetic analysis
based on sequences of rRNAs there are 17 major bacterial lineages

selected groups:
cyanobacteria
purple and green bacteria
mycoplasmas
cyanobacteria
phylum of bacteria that obtain their energy through photosyntheis (aka blue algae)

phycocyanin gives them their nme

they have chlorophyll a and carotenoids

unicellular

filamentous: linear or branched

colonies
purple and green bacteria
grow in light, but under anaerobic conditions because oxygen suppress the synthesis of their pigment, bacteriochlorophyll

contian accessory pigments: yellow and red carotenoids


two types

1. sulfur bacterium

2. nonsulfor bacterium
mycoplasmas
bacteria w/o cell wall

smallest organism incapable of independent growth

assume various shapes

they are plant pathogens

chlorosis (yellowing the foliage) movies w/in sieve tubes transmitted form plant to plant by vectors such as aphids. lethal yellowing
4 distinct groups of archae
halophiles

methanogens

extreme thermophiles

thermoplasma
halophiles
salt loving

high salt limits 02 necessary for respiration

they use bacteriorhodopsin, a protein in plasma membrae to conver light energy to atp
methanogens
methane producing

only organism that produce ch4 from h2 and co2

strictly anaerobic

use nh4+ as a nitrogen base

most gas resserves are produced by activities of methanogens

found in the digestive trck of ruminants where they digest cellulose
extreme thermophiles
heat loving

enzyles are stable at 80 to 110 deg c

most species metabolize sulfur and are strict anaerobes

h2s rising to surface

highly acidic
thermo plasma
archaea w/o cell walls

single genus and single species

no cell wall, spherical and small

occurs in acidic, self heaitng coal
what are viruses
submicroscopic parasites found in animals, plants, fungi and bacteria

it is genome + coat
nucelic acids
protected by protien coat that also helps virus attach to host

outside the cell is called virion and is metabolically inert
viruses usually host specific responsible for many infectious diseases such as
chicken pox, measles, mumps, influenza, polio, aids, herpes, hepatits, ebola virs, west nile virus
waht do plant diseases do to the plant
reduce grwoth

yellow the leaves

mosaic and ring spots
3 types of plant firuses have dan as genetic material
geminiviruses

badnaviruses

caulmoviruses
how do viruses invade plants
by vectors such as aphids, leafhoppers, whitefliet etc etc

transmission thorugh polle tube of an infected pollen into an ovule

once inside the cell, virion shed it's coat and it's rna or dna multiplies using the host cell machinery
genome of viruses is either composed of...
dna and rna... single strand or doublestranded
what are hte stages of the life cycle of a virus
infection

replication inside the host

spread to new host aided by vector organisms
movement of viruses within the plant
short distance movement (cell to cell) through plasmodesmata

long distance movement trough sieve tubes of phloem tissue
what is endosymbiosis
symbiosis in which one symbiont lives within the body of the other.

(eukaryotes)
what is an endosymiont
an organism that lives within another, dissimilar organism
serial endosymbiosis
process by which eukaryotic cells originated via a series of events
what are the protista
the rest of the eukarya besides animals, plants, and fungi
evidence in support of serial endosymbiosis
1. double membrane around organelles. the mt inner membrane rsembles prokaryotic membranes, not eukarytoic membranes

2. mitochondira and hcolorplasts have their own ribosomes and the size matches that of bacterial ribosomes, not eukaryotes

3. dna. circular chomrosome, like bacteria. dna sequences are more closely related to bacteria than eukarya

4. divisoin by binary fission like bacteria
protista
an assemblage of mostly unrelated groups

all aquatic, freshwater and amrine

do not need to have much support

do not need water conductin tissue

no cuticle, stomata, or roots

water currents/waves cause more damage than air

planktonic (floaters) vs. benthic (attached) life styles
the three benthic zones
bathyal zone, sub-littoral zone, intertidal zone
living in the inter-tidal zone
negative- lots of wave action in the intertide zone, drying out, high temperatures, high salt concentrations
---strategies for this: flexible rubbery body, thick walls, water holding wall materials, slime

positivies- high light intensity, high sconcentrations of minterals
living in the sub-littoral zone
positives - less wave action, no drying out, heat or salt damage

negatives - less light, less minerals

strategies: long stipes (stalks) to get into zone w/ more light. phycoerethrins that absorb light in blue wavelengths
planktonic life
these organisms go w/ the flow (wave action) but ther eis danger of drifting too far out to sea

need to get mineral nutrients from run off form land

any that drift out die and fall to bottom

need to reproduce rapidly to make up for the organisms that die - have small bodies, single cells or small colonies

mostly in two groups - basillariohphyta and dinophyta
features of algal cells
unicellular, filamentous, siphonaceous, colonial sheetlike, or complex thallus

cell wall

chloroplast envelops and pigmentation

flagella number, placement and type
-insertion at tip or along side
-tinsel or whiplash types

storage reserves

life cycle- gametic or zygotic (sporic seen in land plants)
3 life cycle types
gametic life cycle

zygotic life cycle

sporic life cycle
gametic life cycle
(metazoons, some algae) entire life spent in diploid state, meiosis at time of gamete production
zygotic life cycle
(some algae) entire life spent in haploid state, zygote is the only diploid cell, undergoes meiosis to make body
sporic life cycle
(land plants) have both diploid and haploid multicellular bodies. dipploid body is called sporophyte, haploid body is the gametophyte. the two generations alternate during the life of the plant.
isogamy
male and female same size both swimmers
anisogamy
female larger, both swimmers
oogamy
female larger, only male is a swimmer
dinophyta
dinoflagellates

related to paramecium (protozoan)

fresh water and marine

their nuclear membranes do not disintegrate during cell division

their chromosomes are always condensed and have no histones

have two flagella, on ein groove around cell and another vertical, they spin as the flagella beat

they have cullulose plates in vesicles inside the outer cell membrane

they cause red tides and toxic blooms in water. gymnodinium breve is the case. large bodies of water can turn reddish brown. toxins cause neurologic damage.

have chl a, c and carotenoids, chloroplasts have 4 membranes

they can occur as symbionts in coral reefs

they can form resting cysts under low nutrient conditions

haploid cells-make haploid siwmming gametes that fuse to make diploid zygote. after a resting period the zygote undergoes meiosis.
diatoms
unicellular or colonial

important component of the phytoplankton - primary source of food for aquatic animals

first appeared 250 million years ago

silica in the cell walls cell walls made of two overlapping parts called frustules

pennate and centric

duaughter cells start with on half of the parent cell walls - this makes one set of cells smaller and smaller.

when cell size below threshold sexual reproductoin occurs - gametes produced by meiosis; zygote is diploid, gians the maximum size for the species by laying down new wall.

male gametes have on tinsel flagellum

diatomaceous earth has many uses - insulation, polish etc.