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Leaf structure: function always follows structure
primary function of leaves is photosynthesis
have broad/flat surface to capture sunlight
Pinnately compound: one large leaf where blade is broken down into leaflets
Palmately compound: all leaflets are attached at a certain point
How can we tell the difference?: by the presence of axillary buds; all leaflets in compound leaves are in the same plane
Cuticle: non cellular layer of wax - used to minimize water loss
Use wax to minimize water loss because it is a hydrocarbon
Hydrocarbons: composed of hydrogen and carbon - have same electronegativit and thereofre all bonds are nonpolar
But water is polar so can't pass through
Palasade mesophyll: elongated cells, where most of chloroplasts are found - where photosynthesis takes place
veins: xylem on top and phloem on bottom - way it is arranged in the stem
Also have parenchyma and sclerenchyma
Most of the time do NOT contain chloroplasts
Spongy mesophyll: also have chloroplasts - not as much (bc it is farther away from the surface)
Why is mesophyll widely spaced?: plant requires CO2 - can diffuse around these cells
Bundle sheath function: regulates water and sugar into and out of veins
Stoma: function is to allow CO2 to diffuse into the leaf
How to tell high plant from low plant?: by layers of palasade mesophyll - more layers in high plant
Mesophytes: plants which grow in intermediate moisture (lilac)
Have collenchyma instead of sclerenchyma to allow for flexibilty
Collenchyma: thicked PCW at edges of cells - provides flexible support - has pectin rather than lignin
Why do smaller leaves have lower temperatures than large leaves?: smaller leaves have larger SA to volume ratio, so can get rid of heat easier - air is also a factor: able to conduct heat away from leaves
Epidermal cells shape:: not rectangular - have interdigitated shape - which allows it to be stronger
Xerophytes: plants that grow in very dry conditions
Agave: desert plants - only out cell wall on outside to minimize water loss
Trichomes Functions: Protection - against insects
Increases reflectance
Reduces transpiration
Secrete compounds onto leaf surface
Insulation - reduces heat loss
Increased reflectance: when too much light is absorbed it will overheat
Reduces transpiration: increases boundary layer which slows water loss
Insulation: Keeping stilla ir near leaf reduces heat loss
Lamb's ear: has dense covering for defence, increased reflectance, slows transpiration
Hydrophytes have: sclereids
very large air spaces
stomata only on upper surface
Sclereids: large, star shaped, thick cell walls - defence
air spaces: for storage of oxygen (aerenchyma tissue)
Xerophytes have: thick cuticle
stomatal crypt
multiple layers of epidermis
reduced air spaces
Stomatal crypt: on lower leaf surface to reduce water loss because traps humid air inside crypt
Monocot leaves: all spongy mesophyll
stomata on top and bottom because grass leaves are at an angle and both sides are exposed to light
Bulliform cells: found next to midrib - store water - when loses water leaves fold up in grasses because they are found in dry environments and therefore will transpire less
Epidermal cells in monocots: linear arrangement of cells - dicot is randomly
cells are still integrated to increase strength
C4 plants: have no distinction between palasade and spongy mesophyll
have well developed bundle sheaths with chloroplasts
Krantz anatomy - mesophyll is aranged around bundles
Modified leaves for food storage: Onion
bulb underground for root storage
Modified leaves for water storage: leaves are rounded to increase volume and decrease SA to minimize transpiration
sometimes have large epidermal cells to store water
Lithops - stone plant
Modified leaves for defence/protection: cactus - green part is stem and prickles are leaves
Modified leaves for carnivory: venus fly trap
trichomes on surface sense movement and send impule to cells to decrease water content and fold up
other cells secrete enzymes to digest fly - get N and other minerals
Modified leaves for support: pea leaf - has tendrils (modified leaves) to coil around surrounding plant and support its weight
Modified leaves for water collection: epiphytes -plants that grow on top of other plants (problem because not very rooted so need to get moisture from rain - form cup to collect water)
Water potential: Ability of water to do work or diffuse - always moves from high to low potential
Why does pressure develop within plant cells?: When higher solute conc. inside than outside - water moves into cell
Membranes are semi-permeable so allow water molecules in but not solute molecules - therefore pressure builds
Equilbirium: when water movement stops because potentials are the same
Turgor: pressure potential of the cells
Only in cells with rigid cell walls
Primary means of physical supprt in herbaceous plants
Wilting: occurs when turgor is lost - pressure is lost
Hydroskeleton: use water pressure within body to support their own weight
Osmosis: diffusion of water across a semipermeable membrane in response to a change in water potential
Water movemtent: from the soil through the xylem into individual cells and through the stomata onto the atmosphere - along a water potential gradient
Cohesion-adhesion-tension hypothesis: derived from the idea that water molecules are capable of forming Hbonds because they are polar
Cohesion: H-bonding within water molecules
Adhesion: H bonding between water and matrices - causes them to adhere to the sides of xylem vessles
Tension: evaporation of water in leaves pulls the coninuous water column from the leaves down the roots through teh plant
Problems: if air bubble develops within system (cavitation/embolism) the whole system falls apart
xylem constructed to avoid cavitation: cells are bigger when formed under wet conditions, but in dry conditions get very narrow because cavitation is more likely to occur - by having narrow diameter can suck up more water
Bordered pits: allow water to move from one xylem to another (around the embolism) but embolism cannot move around pits
How to measure water status of a plant: meausreing the water status of the shoot - by pressure chamber or scharticoff's technique
Pressure chamber: cuts plant stem off and puts in a pressurized chamber - increased pressure in chamber to force water in xylem up to surface - meausre potential of that movement
How do roots maximize water uptake: maximize SA - don't become broad bc have to grow through soil - have long tubular structure one cell thick (root hairs)
Water moves by three routes:: apoplastic - least resistant
symplastic
Transcellular
Apoplastic: movement through the nonliving portion of pant body (cells walls and intracellular matrix)
Symplastic: movement through interconnected cytoplasm of cells in the plant body; plasmodesmata
Transcellular: movement from cell to cell passing through vacuoles of each
Apoplastic route ends: at the endodermis
When reaches the endodermis: there are waxes (suberin) and has to travl symplastic route - advantage is to control what goes in and out of cell
Mineral nutrients are absorbed: at any point - energy requiring process - bc have a higher conc. in roots than in soil and therefore are moving against a conc. gradient
As amount of light decreases: rate of mineral uptake decreases - runs out of energy
When have a higher solute concentration inside root than outside root: leads to osmotic uptake of water and the buildup of pressure in the root under conditions of low transpiration - pressure developes inside central vacuole colum -only at night
Root pressure: only occurs at areas of low transpiration and does not account for movement of water in xylem under normal conditions
Guttation: process that relieves excess pressure in the xylem at night - water comes out of pore in epithelium called hydathode
Conditions when water moves from plant into soil: at night because stomata are closed - roots are in two different parts of soil(large tree)
Hydraulic lift: when some roots are in ground water and some in dry soil - water leaves tree at higher ground into dry soil
Evidence of assimilate transport: when tree is girdled can transport water from roots to shoots - but can't transport sugars because phloem has been removed
Characteristics of phloem transport:: can occur in two directions (depending on where in the plant you are)
Sources: area of high assimilate concentration (leaves)
Sins: areas of low assimilate concentration (roots, meristems)
Roots: sinks because they are respiring constantly - are reproductive organs - are growing rapidly
Assimalate trasport: very rapid - 50-100 cm/hour
Pressure flow hypothesis: Sources and sinks are always in phloem
- water moves from low to high solute concentration
Passive process - but we know it requires energy
Phloem Loading and unloading: energy requiring process
Photosynthesis: 6CO2 +6H20 --> 6C6H12O2 + 6O2
Light that plants can use in photosynthetic process: visible light - 400-700 nm
leafs reflect GREEN light
PAR: photosynthetically active radiation - measured in micromoles - measures the number of particles of protons
Pigments: chlorophyll a and b and various carotenoids (carotenes and xanothytes)
Chlorophyll a: red light and blue light
porphyrin ring containing N and Mg and hydrophobic tain
chlorophyll b: blue light and red light
has CHO bond in place of CH3
Carotenoids: violet and green and yellow light
cleaved in center to give to VA molecules (beta carotene)
VA is converted to retinol
Xanthophyll: have OH group on rings
responsible for colour of corn kernals
Where does light dependent reactions take place?: mesophyll cells of leaves - not in epidermal cells
Thylakoid: all are interconnected to each otehr
all pigments are found in thylakoid membrane - light dependent takes place within the thylakoid membrane - light independent within the stroma
Photosystems: collections of pigments - usually 200-300 molecules
pigments are found in antennae
have two parts - antennae and rxn center
rxn center: only has two chlorophyl molecules
Purpose of pigments in antennae: to absorb light over a broad wavelengths and convert all t o one type of light - rxn center only absorbs either 680 or 700
Energy of a photon is called: a quantum
Flourece: when photons fall back down to lower energy level and reemit light - not 100% efficent
Longest and shortest wavelength: blue light has shortest wavelength - red light has longest
NADP: nicotinamide adenine diphosphate
can accept electrons
Difference between photophosphorillation and respiration: in ppl use light energy, non cyclic, electrons used over and over
respiration use O2
ATP and NADPH: products of light dependent rxns - then go on to other photosynthetic processes
Problem with Z-scheme: produces same ATP as NADPH, but subsequent reactionsneed more ATP than NADPH - therefore cyclic comes in
Cyclic: does not get electrons from water - PSII is not involved
not as efficient
Cyclic takes place: in the mesophyll within the thylakoid membrane - NOT within the stroma
starch is stored within the chloroplasts
Chemiosmosis: the synthesis of ATP using an electrical and chemical gradient - occurs in both resp. adn photo - in thylakoid membrane
Light independent reactions: calvin cycle
converts energy to sugars using energy produced in light dependent reactions
Rubisco: also functions as an oxygenase (can load O2 to RuBP as well as carbon)
Oxygen is: a competitive inhibitor of photosynthetic process - under low CO2 conditions this is a problem
Conditions that enchance oxygenase activity and photorespiration process: high light
high temperatures
water stress
Rubisco cannot: distinguish between O2 and CO2, so sometimes adds an O2 molecule to RuBP to get 1 PGA and 1 phosphglycalate
Photorespiration: takes O2 to get CO2 - occurs in light only, does not give ATP
Converts phosphoglycalate to PGA
C4: evolved in hot dry conditions
plants do not use Rubisco but PEP carboxylase - never functions as an oxygenase
C4 pathway gives off...: CO2 wich then goes to the cabon cycle
In order for the C4 pathway to work: there has to be spatial separation between initial and final fixation of CO2 - so occurs in the bundle sheath and mesophyll
How do C4 plants avoid photorespiration?: mesophyll chloroplasts fix CO2 which the goes to bundle sheath chloroplasts - have a high CO2 concentration so Rubisco will never function as an oxygenase
Mesophyll vs. Bundle sheath: granum are extremely well developed in mesophyll - less well developed in bundle sheath but more stroma
CAM pathway: identical to C4 pathway
oxaloacetates and malates accumulate
temporal separation between initial and final fixation
all occurs within one cell
CAM plants: live int he desert
diurnal acidity levels
all store water within their leaves
NO Krantz anatomy
Night vs. day: C4 takes place at night
Calvin cycle takes place during the day
Temporal separationa advantage?: Stomata are open at night to so the transpiration rate at night is lower than during the day - thereofre there is decreased water loss
Difference between C4 and CAM: phosphenol pyruvate in CAM comes from stored strach instead of reactions as in C4
Algae: largely aquatic, photosynthetic organisms
most are microscopic/single celled
Algae belongs to two separate kingdoms: prokaryotae and protista
Kingdom Protista: includes: animal like, fungus like, and plant like species
Groups of photosynthetic protists:: euglenophyta
rhodophyta
dinophyta
bacillariophyta
chrysophyta
phaeophyta
chlorophyta
Euglenophyta: 900 species
mostly heterotrophs
chlorophylls a, b, and carotenoids
2 unequal flagella
no cell wall but have pellicle
Carb reserve: paramylon
Origin of Eukaryotic cells: Endosymbiotic
photosynthetic or aerobic prokaryotes englufed by phagocytosis and persists as endosymbionts
outer membrane and inner membrane: outer - food vacuole
inner - plasma membrane of prokaryotes
Chloroplsts of euglenophyta: have three membranes
Rhodophyta (red algae): 4000-6000 species
chla, phycobillins, carotenoids
no flagella
mostly marine
Cell wall: cellulose embedded in a matrix of mucilaginous algin, plasmadesmata in some
Life cycle: gemetic life cycle
spends most of its time in the gametophyte generation
Dinophyta (dinoflagellates): 2000-4000 species
cha, c, and carotenoids, some heterotrophic
one transverse and one longitudinal flagella
cellulose plates beneath cell membrane
produce deadly toxins
Three known stages in life cycle: biflagellated cell
amoeboid stage
amoeboid cyst
Bacillariophyta: 100,000 species
heterotrophic and autotrophic w/ cha,c and carotenoids
cell wall composed of silica
no flagella
unicellular or colonial
Carb storage: chrysolaminarin
Centric and pennate diatioms: centric - radially symmetical
pennate - bilaterally
Frustrules: cell walls of diatoms
composed of silicon oxide
consists of two overlapping halfs
contain many pores and channels in ornate paterns
Diamotaceous earth: earth compose of shells of these diatoms
Asexul reproduction: diminishing reproduction
when divides in two halfs pulls apart - can only reconstruct bottom part - one will be the same size as parent and one will be smaller - when becomes so small can no longer make a viable cell then undergoes meiosis and goes to sexual reproductoin
Phaeophyta (brown algae): 1500 species
cha,c and focoxanthin
two flagella in reproductive cells
truly multicellular
three parts of body: holdfast
stipe
blade
Oogonia: where meiosis takes place to produce the egg
antheridia: where meiosis takes place to produce the sperm
Isogamy: gametes are the same, both move
call + and - mating strands
Anisogamy: one large motile and one small motile
Oogamy: one small motile and one large immotile
Heteromorphic: haploid and diploid generation are different
Chlorophyta (Green algae): gave rise to otehr species of higher plants bc have same chlorophylls (a,b) and same cell walls and store starch the same way
Cell walls: cellulose, glycoproteins, noncellulose polysaccharides
Three major classes of green algae: Chlorophyceae
Ulvophyceae
Charophyceae
Chlorophyceae: motile and non motile
colonial and unicellular
largest class
Zygospore: resting state of zygote with thick cell wall
isogamous life cycle
+- mating strains: do not equal gametes
but form gametes
Plasmogamy: the joining of the cytoplasm of two cells
Class Ulvophyceae: mostly marine
siphonous - no cell walls connecting adjacent cells
composed of flat sheets of cells
meiosis occurs in: the sporangia to produce spores
Charophyceae: most similar to land plants
unicellular, filimentous, parencymal, and colonial generations
Desmids: unicellular forms, freshwater
constricted cells - have a rigid shape like diatoms
Spirogira: circular, coiled chloroplast
has +- mating strains, makes a zygospore
Chrysophyta (Golden brown algae): 1000 species
cha,c and carotenoids
no flagella or 2 apical flagella (1 tinsel and 1 whiplash)
no cell wall or silica scales
Green algae and plants similarities: photosynthetic pigments (cha, c and carotenoids)
store carbs as starch
cellulose is major component of cell walls
cell division is similar - formation of cell plate
chloroplasts have thylakoid membranes staked into grana
Plants evolved in terrestrial environments: characteristics are adaptatiosn
angiospermsa are best adapted plants to dry environments
Problems terrestrial plants face: obtaining enough water -roots
transporting water from soil to above ground parts and photosynthate to below ground parts - vasc. system
prevent excessive water loss - cuticle and stomata
support plant body - sclerenchyma
exchange gases - stomata
Reproduction in terrestrial plants: don't have flagellated cells so have wind or inset pollination
Four types of terrestrial plants: mosses and other bryophytes
fern and fern allies
gymnosperms
angiosperms
Bryophytes: need to be moist because have flagellated sperm cell
lack well developed vasc. tissue so can't get very large
have rhizoids for water and nutrient absorbtion
multicellular sex organs with a layer of sterile cells to protect from dessication
gametophyte dominant - sporophyte parasitic
Thallus: means it has a two dimensional strcution - thalloid liverwort
antheridiophores: stemlike structures produced on top of liverwort where sperm is produced
Pores (stomata): when bryophytes have a cuticle they have pores - which are multiple layers of guard cells but have same function as stomata
Anthocerophyta (Hornworts): have thallus and long horn like structure growing up
Horns: are sporophyte, parasytic on gametophyte generation
Bryophyta (mosses): two growth forms found: cushiony and feathery forms
Germination of mosses: why related to green algae: when spores first germinate form a structure that resembes a green algae (protonema) - then forms a bud which becomes a gametophyte
Gametophyte stage: is dominant
sporophyte is parasitic on gametophyte stage
Primitive conducting tissue: epidermis, cortex and conducting strand - has hydroids in middle and leptoids outside (start of evolution of xylem and phloem)
Sporophyte generation: foot
capsule
calyptera
foot: produced inside archegonium and absorbs nutrients
Capsule: has sporangium
Calyptera: falls off and spores are released
Guard cells: only have one guard cell with two different nuclei and a single stomata inside
Seedless vasc. plants: fern and fern allies
Characteristics: protective sterile jackets around reproductive organs
multicellular embryos in archegonium
cuticle on above ground parts xylem and phloem
dominant sporophyte
all have true stems
Dominated Earth: during the Silurian period
grew woody in carboniferous period
Microphylls: generally smaller
grows as an outgrowth of the stem that was vascularized but only have a SINGLE vasc. strand
Megaphylls: leaf developed from an entire branch - arranged in 2-D space perpendicular to light to maximize light interception
has well developed vascular system
Homosporous: only one type of spore produced - gives rise to sporophyte generation
Heterosporous: have separate male and female spores which gives rise to antheridia and archegonia
Psilophyta: only two living genera - Psilotum and Tmesipteris
resemble earliest land plants in terms of structure - lack true roots and leaves and have dichotomous branching
reduction evolution
Psilotum: subterranean generation - because wants to find a moist place
saprophytic
not parasitic
Lycophyta: Lycopodiacea
selaginellacea
isoetacea
Gametophyte generation: only has rhizoids
no vasc. tissue
sperm are flagellated
Sporophylls: major advantage over psilotum, they are leaves which bear sporangia on surface - gives rise to seeds
Stroboli: groups of sporophylls clustered together in a club
Selaginella: can grow in very dry environments
Isoetes: called the quill plant because of quill-like microphylls
have a cuticle but lack a stomata - they are CAM plants - take CO2 through roots and transport it as inorganic acid
Spenophyta: arose during Devonian period
only 1 genus - Equisetum
Equisetum: unchanged since carboniferous
found in moist, damp places
hollow jointed stems with whorled microphylls
Souring rush
Underground rhizomes with adventicious roots
Scouring rush: collects silica from soil and deposits it in leaves - leaves have sandpaper like texture
Sporangiosphores: stem that is specialized for reproduction
elators: coiled around spores, are hygroscopic meaning they absorb moisture from air - as gain or loose moisture either coil or uncoil regulating the release of spores
Pterophyta (Ferns): Arose in devonian and became important in carboniferous
11,000 living species
well developed vasc. - true roots, leaves, and stems
mostly homosporous
Leaves (Fronds): megaphylls
Sporangia: developed on the undersurface of leaves and are grouped into sori
Ostrich ferns: only ferns that can be eaten
fiddle heads
Indusium: covers the sori - sporangia are found underneath
Annulus: outer wall of sporangia - as sporangia matures annulus dries out and eventually cracks open with force to disperse spores
Seed plants share certain traits:: all are heterosporous
megasporangium protected by integuments
gametophyte generation no longer free living - parasitic on sporophyte
dont need water for reproduction
all have megaphylls
Evolution of seed plants: did not become important until permian and triasic period - surface of earth was covered by shallow seas in carboniferous
climate cooled and water levels fell at this time
What are seeds: multicellular sporophyte embryo
food reserve for germination and establishment
outerprotective covering
Ovules include: megasporangium - where magagametopyte is produced by meiosis
integuments
Ginko biloba: has separate male and female generations
Pine life cycle: sporophyte (2n) produces male and female cones on different parts of the plant
females produce seeds that disperse and are heavier - males produce pollen which is lighter bc doesn't require much height
Why separate places?: To ensure cross polination and dispersal takes place
Male cone: groups that have sporangia on surface
Female cone scales: ovuliferous scales
cone contains stem and leaf material
After meiosis in males:: microspore divides by meiosis to produce 4 haploid cells - pollen grain (male gametophyte gen)
4 cells of male gametophye: tube cell - ensures growth of pollen tube
2 prothalial cells - degenerate
1 generative cell - divides to produce sperm
air bladders: pollen grain has two air bladders to increase SA to allow it to be carried by wind
After meiosis in females: 4 megaspores produced - 3 die and only one functional one - gives rise to the female gametophyte generation
Micropyle: exudes moisture that binds pollen grain
once pollen grain has landed produces tube = once grown generative cell divides
megaspore: undergoes MITOTIC divisions to produce many cells - some archegonia which have eggs
Once eggs have developed...: the spermitogenous cell divides MITOTICALLY to produce sperm which fuzes with the egg
After fertilization: fertilized egg divides MITOTICALLY to produce embryo
Seed strucutre: has female gametophyte tissue (n) - food storage
embryo - 2n
integuments - forms seed coat (2n)
Embryophytes: have multicellular reproductive structures (sporangia and gemetangia) that are surrounded by a layer of residual sterile tissue
All bryophytes are: oogamous
Moss gametophyte: grows from an apical meristem that consists of a single apical cell
Phyllids: leaf-like structure of mosses
one cell thick - no vasc tissue
- only have cuticle on upper surface
Hydroids resemble: traechids - but with no lignin of SCW
when have no hydroids water moves along the outer surface of the plant
Leptoids resemble: sieve cells - sugar transport
Sphagnum: absorbs 20x its weight in water
Prothallus: formed by the germination of spores
heart shaped gametophyte in pteropyhyta
Gymnosperm wood: soft wood with traechids
Where is the ovule produced: develop on exposed surfaces of a modified leaves or braches
Seed differences in gymnosperms: not surrounded by a fruit wall
does not have endosperm - gets food from female gametophyte
Staminate cones: male cone
small and short lived
scales are modified leaves - microsporophylls that have two sporangia on each scale
Seed cone: ovulate cone
has ovuliferous scales - has two megasporangium

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