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265 Cards in this Set

  • Front
  • Back
Sporic life cycle
Occurs in ALL plants and but there is tremendous variation
Variation: Isomorphisic alternation of generations
the gametophyte and sporophyte are morphologically identical (sea lettuce)
the gametophyte and sporophyte are not identical
Can have dominant gametophyte (mosses) or dominant sporophyte (ferns - where gametophyte is freeliving)
Trees, shrubs, grasses, herbs are:
all dominant sporophyte - gametophyte is hidden
Zygotic Life cycles
most primitive type, some algae, protozoa and fungi
the ZYGOTE is the ONLY diploid cell
can go into resting stage or dormant stage and amke a zygospore
zygote is one cell from teh fusion of gametes - diploid undergoes meiosis (NEVER mitosis)
there is no sporophyte or sporangia
spores undergo mitosis and produce gametes or gametophytes
Gametic life cycles
NO gametophyte stage
Cells in the sporophyte undergo meiosis and produce spores (equal to gametes)
Found in protists and all mammals
haploid individual or stage of life that produces gametes in gamentangia by mitosis; do NOT undergo meisois
diploid individuals or stage of life that produces haploid spores by meiosis, in the gametic life cycle spores are equal to gametes
all spores are identical
give rise to bisexual gametophyte
production of two types of spores (gives rise to male or female gametes)
male and female gametes that are the same, flagellated and tend to be small
still flagellated, one big and one small
one flagellated and have one egg (don't fuse, sperm has to find egg)
a single set of genes
has two copies of each gene, sporophites can be diploid or polyploid
flowering plants
have grass like leaves (corn, onions)
have broader leaves
Dicots divided into two groups:
magnoliids and eudicots
Monocots and eudicots evolved from the magnoliids
two cotelydons
flower parts in fours or fives
leaves with netlike vein network
vascular cambium present
vascular bundles in stem in ring
one cotelydon
flower parts in threes
leaves with parallel primary veins
vascular cambium abesnt
vascular bundles scattered
Gamentangia in males and females
antheridia (male)
archegonia (female)
Calyx and corolla
collectively called the perianth
evolved from infolded leaves with ovules on their margins
Is a carpel the same as a pistil?
They can be (when pistil is simple) a pistil can have one or many carpels
Superior ovary
when ovary is above the other flower parts
corolla, stepals, stamens are hypogynous whe they are under the ovaries
Inferior ovary
it has fused with the receptical so it is below the other flower parts
flower parts are ABOVE the ovary
tube like structure partially fused with petals, sepals and stamens
many ovaries inside
Perfect flowers
have both stamen and carpels
Imperfect flowers
lack either stamens or carpels (pistillate flower - lackes stamens, stamenate flower - lacks pistils)
Complete flowers
have all four whorls (petals, sepals, stamens and carpels)
missing one or more of the whorls
Example: Flower missing petals is...
perfect but incomplete
Imperfect flowers can have..
stamenate and pistillate flowers on teh same plant (monoecious)
imperfect flowers with stamenate and pistilate flowers on different plants
A group of flowers
flowers are directly ont he main stem
Simple umbrel
peduncle lower and pedicles all come out from one point
have a peduncle which is hanging downwards (poplar, birch)
megaspore mother cell
produce a cell (not a spore)
layer of tissue surrounding the ovule
opening into the ovule allowing things in
arm which is holding the ovule in place
Sporangeous cells
inside there are many microspore mother cells which undergo meiosis and produce microspores (2N)
filled with tetrads of pollen grains, eventually splits open (dehisses) and releases the pollen --> doesn't release sperm but a tiny 2 cell gametophyte
After pollen grains are released
pollen grains then land on stigma --> the pollen germinates and grows a pollen tube
Pollen Grain
Male gametophyte
outer layer of pollen grain, highly sculptured, made from sporopollenin which is VERY decay resistant
How does pollen grain move to the stigma?
bees, winds, mammals
Once pollen tube lands on stigma..
pollen tube grows up the style - tube nucleus leads the way and sperm follow - pass through the micropyle - sperm enters
Self incompatable
dont want to be fertilized by pollen of the same plant
Double fertilization
1) One sperm fuses wtih egg which produces a 2n zygote and grows into embryo
2) other sperm fuses with the 2 polar nuclei and produces a 3n endosperm nucleus
3N nucleus
undergoes division and produces multiple 3n nuclei and later forms the cell wall
cell tissue that is nutritive tissue for the developing embryo
Endosperm in monocots
endosperm present in the mature seed, it is storage for the germinative seed (corn), stores starch and protiens
Endosperm in dicots
endosperm usually gets used up during the seed maturation
Antipodals and synergids
serve no purpose
Differences in monocot and dicot seed development
coleoptile covers the SAM in monocot
scutellum in monocot transfers food from endosperm to embryo
tissue surrounding gametophyte - develops into teh seed
develops into the embryo
develops into endosperm in monocots
make up the embryonic axis
Ovule and ovary wall
ovule - develops into a seed (1 ovule = 1 seed)
ovary wall - develops into pericarp
1 ovary is equal to
one fruit
True Fruits
develop from ovary wall and consist of pericarp
False Fruits
develop from at least partly from non-ovarian tissue (accessory fruits) (strawberry)
Main tissue deveolops from hypanthium or receptical tissue
has dry, indehiscent fruit
Aggregate Accessory
swollen fleshy receptacle with many dry fruits on surface
Simple Accessory
a single ovary enclosed in receptacle tissue
have a papery endocarp by core (apple and pear)
Simple Fruits
Fruit develops from one or more ovaries in one flower
Aggregate Fruits
from many carpels in one flower but carpels are NOT fused (raspberry)
Multiple fruits
formed from carpels of several associated flowers (pineapple)
Fleshy simple fruits
pericarp is fleshy at maturity, tissues can be sugary, starchy or fatty
endocarp hard and stoney, ovary superior, single seed (cherry)
Entire pericarp is fleshy (tomato)
a type of berry with a leathery outer rind containing oils (orange)
a type of berry with a thick outer rind with no oils (pumpkin)
Dry simple fruits
pericarp composed of dead cells
fruit wall dry and not opening at maturity
pericarp hard and stony, cup at base, acorn
grains, single seed fully fused to pericarp, pericarp soft and thin
single seed only attached to pericarp at base (sunflower), pericarp soft and thin
fruit splits open at maturity (legume)
one carpel, splits open at both sides (beans)
What happens to the seeds? Case 1
seeds can germinate while still on the mother plant (not common) (called viviparity)
Case 2
Seeds can dry down and dehydrate and are shed in a dry stat (called orthodox seeds)
Orthodox Seeds
start out 90% water and 10% dry matter, during maturation udergo dehydration and become 5-20% water and 80-95% dry matter, after they dry are shed tot he mother plant and can be quiescent or dormant
Case 3
Recalcitrant seeds - cannot be dried down or they lose their viability, must germinate sooner or they die (nuts)
Germination of Orthodox Seeds
Moist developing seeds --> dehydrate --> dry seeds --> quiescent or dormant
normal, dehydrated seed, when given water, oxygen and temperates will germinate (garden vegetable)
dried down orthodox seeds, need certain special requirements to be fulfilled before they can germinate
Exogenous dormancy
dormancy imposed by factors OUTSIDe the embryo
Endogynous dormancy
dormancy due to internal factors in the embryo itself
Physical factors (exogynous)
seed coat is impermeable to gases and water therefore cannot germinate because water can't reach embryo (can break down dormancy with scarification)
Chemical factors (exogynous)
dormancy imposed by inhibitors present in the seed coat or present in the wall, break dormancy by washing away chemicals
Morphological (endogynous)
the embryo itself is still not fully developed even though seed is shed off mother plant
Physiological (endogynous)
some physiological block within the embryo itself that prevents germination (photodormancy - requires exposure to red light)
most common in small seds because large seeds have more stored reserves than small - seeds MUST have sufficient reserves to germinate, grow and reach surface before they run out - small seeds germinate near surface after exposure
How do plants detect red light?
1) Photosynthesis - using light as a source of energy (chlorophyll and carotenoids)
2) photomorphogenesis - using light as a source of information (phytochrome)
involved in seeds needing light, exists in two photoreversible forms (Pr and Pfr)
Pr and Pfr
Pr - inactive - present in the dark
Pfr - active form, causes germination
imbibe seeds in moist, usually cool conditions for weeks to months mimmiciing spring time or fall time
apomatic seeds
- production of an embryo without fertilization (dandylions)
- no union of sperm and egg, clone of mother
development of the fruit without seeds (seedless grapes)
first piece of stem above the roots but below the cotelydons
shoot apical meristem - where new cells are produced, most important part of the shoot
Hypocotyl hook
to protect the SAM
as the hook emerges above ground into surroundings PR is converted to PFR and this is the signal for the hypocotyl hook to straighten anad for the cotelydons to green up
Etiolated Seedlings
pale, yellowish due to carotenoid
seedlings grown in no light - an etiolated seedling devotes most of its time and energy to extension growth
Epigeous germination
cotelydons come above ground
1) cotelydons can come above ground and become leaflike (watermelons)
2) cotelydons can come above ground but they are purley storage organs so wither away and die
Hypogeous germination
the cotelydons stay where they are but shoot grows up to form EPICOTYL hook
Fruit in monocots
caryopsis - seed coat is fused to the fruit coat
De-etiolation in monocots
coleoptile stops growing and leaves grow green and emerge - comes from SAM
coleoptile then splits open and withers away
Purpose of coleoptile
provides a safe passageway for the leaf to push it's way up through the g ground
Shoot and Root
shoot - everything above the root shoot interface
root - everything below
SAM - produces new nodes and internodes
RAM - at the end of every root there is a RAM
the stem between nodes
Axillary buds
buds in the axils of a lead at nodes
they are resting or dormant SAMs waiting for the right signal to grow
repeating unit of shoot (internode, node, axillary buds, leaves)
just another shoot growing from a node, same as main stem
Primary plant body
built on repeating units called a phytomere
Plant body of monocots
built on the same plan as dicots except typically hvae very short stem with short internodes
How do plants grow?
1) cell division at meristems to increase cell number
2)cell expansion to increase cell size
groups of specialized cells that are more or less capable of continuous cell division
Primary Meristems
give primary plant body (basic stem, root and leaves)
Shoot Apical Meristem
Transitional meristems, protoderm, ground meristem, procambium
Root Apical Meristem
transitional meristems
Lateral meristems
give secondary growth, increase girth of stems and roots
Intercalanary meristems
meristem stuck between two nodes
Basal meristems
only found at the base of monocot leaves
Marginal meristems
just know it exhists
Initials and derivitives
initials - cells that divide
derivitives - cells that are produced
a process by which cells with the same genes become different from one another in terms of form and function
differentiation produces different cells and tissues
groups of cells that form a structural or functional unit
Simple tissues
made up of only one type of cell (parenchyma)
Complex tissues
made up of MORE than one type of cell (dermal tissues)
Vascular Tissues (type of complex)
invovled in long distance transport
Two types of vascular tissues:
Xylem- carries water and minerals from the root to the shoots
Phloem - carries water and sugars and some hormones from sources to sinks
sources of sugars either freshly made in leaves or stored
reguions that are using/need sugars (either growing regions or where they are stored)
cotelydons are sinks during development and sources durin germination
Ground Tissue
everything between the vascular and dermal tissues
Basal meristem
leads to the growth of monocot leaves - makes new cells which undergoes cell expansion
Basal meristems located at the base of each leaf in monocot plants
Marginal meristems
around the outside of dicot leaves - makes new cells which expans
What causes different leaf shapes
varying activity of marginal meristems
monocots do not have marginal meristems (because they are long and have a basal meristem and grows UPWARD vs. dicot leaves which grow WIDTH wise)
Vascular cambiums
occurs only in platns have secondary growth, not in monocots
Part of lateral or secondary meristems
Produces Phloem to the outside and xylem to the inside
Cork Cambium
only in dicots with secondary growth, produces cork cells to the outside (bark) and secondary cortex to the inside
Tunica-corpus model
(model of how SAM works)
have anticlinal and periclinal division
tunica - produces cell surface/epidermis
corpus - produces vascular tissues and ground tissues
when SAM is damaged mother cell produces new cells
Central mother cell zone
cells which rarely divide and are held in reserve
Periclinal division
division parelell to tissue surface -corpus
increases volume
Anticlinal division
increases SA
cells divide perpendicular to the surface
corpus and tunica
Plants can be chimeras
plants that have cells with different genes
occurs because plant growth is MERISTEMATIC
How do plants have cells with different genes?
if there is a mutation, all cells that derive from that cell are going to have a different gene - may show up in leaves, bud etc. depending on where in the SAM mutation occured
Examples of Mutations
Blackberry: wild blackberries are VERY thorny but cultivated are thornless but revert in exceeding years
How do blackberries revert?
thornless have a mutation in the tunica (which produces epidermal cells that make thorns), mutation is not in the corpus
If tunica is damaged the corpus produces new tunica that does not have the mutation
Mutations in the corpus
if have a mutation int eh corpus may never see it unless the tunica is damaged
What is the advantage of rarely dividing mother cells?
unlikely to develop a mutation
do NOT arise from axillary buds,arise adventitiously (occuring in an abnormal way or area - never grow into healthy normal plant)
Where do flowers and inflorescences come from?
SAM and axillary buds can be converted into floral meristems by signals (like daylength)
Floral meristems
produces flowers and inflorescences
tells plants when to flower, measure of daylength
Cell expansion
cells expand in two ways
1) tip growth
2) diffuse growth
Tip growth
occurs in root hairs, pollen tubes
new material is added into the ends
How do root hairs grow?
grow as extensions of dermal tissues
grow by adding new material to the tip
Diffuse growth
99.9% of plants
cell wall expands similar to a balloon
For diffuse growth to occur:
requires turgor (pressure within the cell)
need cellular microfibrules to slide past each other to allow the cell wall to expand
need low pH in cell wall to allow cellulose to slide past each other
Where is diffuse growth occuring?
anywhere plant organs are increasing in size (just behind the SAM, internode, behind RAM)
Middle lamella
material that holds adjacent cells together
made of pectins
complex polysaccharide made from many sugars linked together
Galacturonic acid
main sugar in pectins
has a carboxyl group that makes in negatively charged
Divalent cations
(have two charges) (Mg++)
go in and make pectins stick together and form a gel
if remove divalent cations middle lamella will fall apart
Middle lamella and fruit ripening
includes action of pectinases (enzymes which digest pectins)
Primary Cell Wall
consists of cellulose microfibrils imbedded in a matrix of pectins, hemicellulose and glycoproteins
Properties of Pectins
very strong but flexible, but needs turgor to assume it's shape
turgor comes from the cytoplasm
has lots of spacing - very permeable to ions, water and small molecules
polysaccharide made from thousands fo glucose molecules linked by B1-4 bonds which animals cannot break
Cellulose microfibril
take 60-80 cellulose molecules held together with H bonds
very strong, cannot be stretched, layed down in patterns
How is the PCW synthesized?
cellulose synthase complex makes entire microfibril at one time - adds glucose to end of 60-80 glucose molecule and celllulose microfibril grows
*as the microfibril grows the cellulose synthase moves back*
What governs the orientation of the cellulose microfibril synthesis?
on underside of plasma lipid bilayer there are microtubules of the cytoskeleton which act like a railway directing movement of rosettes
5 proteins subunits in cellulose synthase complex
What controls direction that cell grows?
orientation of cellulose microfibrils - the orientation of the newer innermost layer of cellulose microfibrils
Synthesis of Pectins and Hemicelluloses
made in teh golgi - move by vescicles to PM - fuse with PM and release contents into PCW
Acid Induced Growth
at pH of 4-5 cellulose H bonds holding it to hemicellulose are loose and cellulose can slide past each other
When will cellulose slide past?
when there is sufficient internal turgor pressure
Where does the low pH in PCW come from?
proton pumps in plasma membrane pump out H ions get a hydrogen ion gradient and low pH outside cell allowing cellulose to slide past each other
What activates proton pumps?
hormones like auxins which will cause cell expansion
direct cytoplasmic connections from one cell to the other
PM of one cell linked to PM of another
What does plasmadesmata go through?
Goes through plasma membrane, cell wall, middle lamella
Why plasmodesmata?
Small substances can pass directly (without passing through PM) from one cell to another
they are basically communication junctions
extension of the ER tubules from one cell to another
small molecules can more through the plasma desmata
Gate mechanism
made of proteins that control waht goes trhough (only amino acids, smaller proteins, sugars, viruses, NOT cellular organelles)
Secondary Cell walls
much thicker that PCW
usually in 2-3 layers
complex polyphenolic which is rigid and impermeable and stains red with phloroglucenol
Differences between PCW and SCW?
PCW= flexible, strong, very permeable
SCW= regid, strong, immpermeable
small areas with no SCW to allow for exchanges of gases, sugars, etc
do NOT go through PCW
Where do we find plasmadesmata
concentrated in oval areas of thinner pcw called primary pit feilds
Where do pits occur?
occur in primary pit feilds
where there is lots of plasmadesmata cells do not put secondary cell walls
Three main types of cells in plant
oldest and most primitive
has thin flexible pcw, never has scw, alive at functional maturity
Photosynthetic parenchyma
filled with chloroplasts
Spongy parenchyma
tend to have no chloroplasts, lots of amyloplasts
has PCW that is thickened at the corners
alive at maturity
has thicker PCW that contains extra pectins (which form a gel and become glisteny white)
Plastic deformation:
living cells that can assume and maintain form in a growing leaf or stem
provide strengthening to living cells that can undergo changes later
Plastic deformation vs. elastic deformation
plastic - tends to stay in pulled shapes
elastic - goes back when pulled
Where are collenchyma founds?
young stems
young growign tissue
around edge
- main function of these are structural support
any cell with a thick, lignified SCW
never found in primitve plants
Main Functions:
1) support
2) protection
3) some involved in xylem transport
Two major categories
Mechanical sclerenchyma
conducting sclerenchyma
support and protection
1) sclereids - not elongated
2) fibre cells - like sclereids but elongated
move water and nutrients from roots to shoots in xylem
1) trachids
2) vessel elements
SCW has...
not pectins!
usualy dead at maturity
cells under programmed cell death
have mechanical scelerenchyma and conducting sclerenchyma
main function is support, structure, protection
sclerids, fibre cells
transport water and nutrients in XYLEOM
tracheids and vessel elements
found in layers such as pericarp on nuts
also isolated in leaves and fruit tissue
Fibre cells
similar to sclereids except are elongated, can be up to several inches long
found in vascular bundles
found in angiospers and lower vascular plants
elongated, usually pitted on side wall and end walls
Vessel elements
hollow cylenders with perforated end walls
H2O moves freely from cell to cell
gymnoserperms have NO vessels
Three main tissue systems
ground, dermal and vascular
exterior surface of root and shoot
1 layer thick often
not invovled in secondary growth
Types of cells
Ordinary epidermal cells - parenchyma
Guard cells - part of stomatal aparatus ( when they swell they make a pore)
Trichomes - hair cells
Trichome purpose
protection - some can inject toxins
absorbtion of nutrients
increases boundary area at leaves
shoot system of plant is coverered with
a cuticle - to reduce water loss
polymer that is incredible water proof, thick in xerophytes
waterproof and impermeable to gasses, resistant to enzymes and decay, reflect light
What leads to tissue systems?
dermal - protoderm
ground - ground meristem
vascular - procambium
Ground tissue
cortex, pith
parenchyma, collenchyma, mechanical sclerenchyma
never have vessel elements and trachids!
Purpose of ground tissue
some photosynthesis, storage, support
Vascular tissues
xyleom and phloem
Xylem in Angiosperms (monocots and dicots)
vessel elements, tracheids, fiber cells, parenchyma (only one living)
Xyleom in gymnosperms (conifers)
tracheindss and NO vessels
no fibers
Sieve elemetns (living cells)
Fiber cells
Companion cells or albuminous cells
Main difference between phloem and xyloem
in xyleom the conducting cells are dead and have thick lignified cell walls (woody)
in phloem conduction cells are living and have thin walled parenchyma (not woody)
a term used to descrie the vascular tissue in roots and stems but not leaves
Vascular cambium
has two areas (interfasicular and fasicular)
group of cells that has become meristematic and produce secondary xylem (to inside) and phloem (to outside)
Cork cambium
produces cork cells to the outside and secondary cotex tot he inside
Cork cells
regular in shape - no secondary cell wall
primary cell wall has SUBERIN
cells are dead
very impermeable lipid making the cork layer
Does wood have living tissue?
yes - secondary pholoem and parenchyma
irregular, nonsuberized cells in areas that allow oxygen to enter, groups of cells
Layers of periderm
cork cells, cork cambium, and secondary cortex
secondary phloem
secondary cortex
cork cambium
When a tree has been girdled...
removes bark - secondary xylem is still present but the secondary phloem is gone or damaged - so there is no sugar transport and roots eventually die
New cork cambia:
established by the tree in response to cork splitting - in the secondary cortex or phloem
Ways to make new cork cambia
1) make in ring - birch
2) uneven initiation (scale bark)
Wood is equal to
secondary xyloem
Two systems in wood
vertical system (axial system)
horizontal system (ray system)
Gymnosperm wood
soft wood
a) vertical system - tracheids mostly
b) horizontal - parenchyma and horizontal tracheids
Angiosperm wood
hard wood
a) vertical - vessel elements, tracheids, fibre cells, parenchyma
b) ray - entirely parenchyma for storage
groups of cells that are emminating form center
Uniserate vs. multiserate
uni - 1 cell layer thick
multi - many cell layers thick
What determines hardness
how thick secondary cell wall is and how lignified it is
Angiosperm woods are "hard wood"
because they have fibre cells
Vascular cambium
makes the secondary xyloem and phloem
it is a single layer of cells with two times of initials
Fusiform initials
long, periclinal divisions, produces the vertical growth
Ray initials
produce the ray cells - periclinal division
Growth rings
in the spring there is lots of water therefore the cells in secondary xyloem are large.
In summer less water so cells in secondary xyloem are smaller.
In winter there is no growth
Porous vs. nonporous wood
Porous - refers to the presence of vessels
Non porous - soft wood, no vessels
Types of porous woods
ring porous - all vessels layed down in one ring in spring wood
Diffuse porous - vessel elements occur anywhere
outside center, younger, still functional, has living cells
at center, darker, nonfunctional
All cells are dead
How does heart wood arise
freezing and thawing causes cavitation - breaking the water columns causing air bubbles which become blockages and block xyleom transport