Exam review Flashcards
What are the characteristics common to all land plants?
- multicellular, eukaryotic
- photosynthetic (using chlorophyll a and b, synthesize simple sugars to create more complex compounds including starch as the main storage molecule)
- have cellulosic cell walls
Which phylum contains the closest relative to land plants?
Charophyta
What surrounds a plant cell?
- Primary cell wall (sits outside of plasma membrane)
2. May also haave a secondary cell wall (found between primary wall and plasma membrane
Most abundant carbohydrate polymer on earth
Cellulose
What makes up a cell wall?
Cellulose, hemicellulose, pectin
What is the role plasmodesmata
- cytoplasmic chanel between cell walls that allows for comunication between adjacent cells
- all for rapid and regulated exchange of molecules betwen cells
Describe the structure of a chloroplast
- surrounded by two membranes
- have their own circular DNA
- contain thylakoid membranes organized into grana
- within thylakoid membranes are photosystems containing chlorophyll a and b
- fluid within the membranes is the stroma where the Calvin-Benson cycle takes place
Name the specialized chloroplasts
- chromoplasts (yellow, orange or red, contain carotenoids)
- leucoplasts (synthesize starch and oils)
(can all interconvert)
Summarize endosymbiotic theory
primitive eukaryotic cell engulfed a photosynthetic bacterium (prokaryote)
Evidence for endosymbiotic theory
chloroplasts and mitochondria
- have their own circular DNA
- are surrounded by two membranes
Describe the role of vacuoles
- stores cell metabolites and waste products
- maintains cell pressure and pH
- may contain anthocyanins
Name the main evolutionary milestones in the evolution of land plants
- developent of the cuticle (protection from UV rays, limits water loss)
- Epidermal pores allowed for gas exchange
- Development of Vasculature (lignification)
- Dominant sporophyte (first observed in seed plants)
- Flowers
State the main characteristics defining bryophytes
- non-vascular
- rely upon water for survival and reproduction (flagellated sperm)
- no true roots (instead use rhizoids)
- no leaves or stems
- dominant gametophyte
Name the bryophyta phyla
Hepaticophyta: the liverworts
Anthocerophyta: the hornworts
Bryophyta: the mosses
State the main charcteristics of the Seedless Vascular Plants (SVPs)
- first lignified plants (lignin reinforces cell walls, allows for upwards growth)
- developed megaphylls (leaves)
- developed sporophylls
- heterosporous
- endosportic development
Name the phyla of the SVPs
Psilorophyta: whisk ferns
Lycophyta: club mosses and quillworts
Equisetophyta: horsetails
Polypodiophyta: ferns
Whisk Ferns characteristics
- no true leaves or roots
- simple branching patter
- associated with mycorrhizal fungi which gametophyte cannot grow without
- homosporous
Lycophyta: Club mosses and quillworts characteristics
- heterosporous
- endosporic development
Equisetophyta: Horsetails
- contain silica deposits in their epidermal cell walls
Polypodiophyta: Ferns
- leaves with sporangia (sporophylls) and large leaves (megaphylls)
Name the phyla of gymnosperms
Pinophyta: Conifers
Ginkophyta: Ginkgos
Cycadophyta: Cycads
Gnetophyta: Gnetophytes
Characteristics of Pinophyta
- create seed cones
- have needle-like leaves (very well suited for cold, dry environments)
- use wind as the primary mechanism for seed dispersal
- some produce resin with antiseptic properties that deter insect attack
Characteristics of Ginkophyta
- only one living species remains
- male and female reproductive structures occur on separate trees
- male gametophyte produces flagellated sperm
Characteristics of cycadophyta
- cone bearing (only have one cone)
- male and female cones occur on separate plants
- male gametophyte produces flagellated sperm
Welwitschia mirabilis
- gnetophyte
- only one of its genera
- only opens stomata at night
How do gemnosperms promote outcrossing?
- ovulate and pollen cones that develop on the same plant can be at different locations
- male and female reproductive structures can be produced on separate treens
- wind pollinations is common, aiding the dispersal of gametes
Name the dominant phases of different plant groups
Bryophytes: gametophyte
SVPs: sporophyte
Seed Plants: sporophyte
Name the dependent phase of differerent plant groups
Bryophytes: sporophyte
SVPs: Independent sporophytes and gametophytes
Seed plants: gametophyte and young sporophyte
Identify the relative sizes of the different plant groups
Bryphytes: small and similar is size
SVPs: sporophyte size varies but generally large, gametophyte is relatively small
Seed plants: large sporophytes, gametophyte greatly reduced
Why are angiosperms so successful?
- Flowers (attract polinators and have become specialized due to co-evolution)
- Fruits (help in seed dispersal and help ensure daughter plants do not compete with the parent)
- they have competitive advantage
Describe the evolutionary history of flowers
- sporophylls with microsporangia evolved into stamens and megasporangia evolved into carpels (sepals and petal are sterile modified leaves)
- Stamens and carpels become less leaf-like
- Carpels fuse to form compound pistils
- Sepals and petals evolving to become more dissimilar (less alike)
- Floral parts progressing from a spiral arrangement on the central axis to that of whorls (three or more organs attached at one node)
- The number of whorls eventually decreasing from four to three, two and one
- Radial symmetry giving way to bilateral symmetry
Name the components of the carpels
produce ovules and contain
- a stigma
- a style
- an ovary
Name the components of the stamen
- the anther
- the filament
What is unique about Angiosperm sexual reproduction?
- both male and female gametophytes are microscopic
- the femal gametophyte does not produce archgonia
- sperm are not flagellated
- embryo obtains nutrients from a tissue that is the product of fertilization and is triploid (the endosperm) because of double fertilization
Name the sequence of primary tissues that arise from the apical meristem.
- Protoderm = dermal tissue
- Ground meristem = ground tissue
- Procambium = vascular tissues
Name the three cell types that make up ground tissue.
- parenchyma
- collenchyma
- sclerenchyma
What are some characteristics of parenchyma cells?
- most abundant, least specilized plant cell
- have thin primary cell walls therefore ‘space filling’
- functions include
- photosynthesis
- storage
- structure
- wound healing
What are some characteristics of collenchyma cells?
- main function is flexible support
- have thickened primary cell walls
- elongated cells, alive at maturity
What are some characteristics of sclerenchyma cells?
- two types (fibers and sclereids)
- have secondary walls often containing lignin
- main function is rigid support (key for upwards growth)
- dead at maturity
Name the components of xylem tissue
- parenchyma cells
- fibers
- vessels (conduct water)
- tracheids (conduct water)
- ray cells
Which water conducting structure in the xylem has better conducting capacity?
Vessel elements
- largest diameter of all conducting cells
- can conduct 100X as much water and minerals as tracheids
- open at each end and can stack on top of one another
What is the draw back of vessel elements?
- flow is more prone to blockage by air bubbles and ice crystals
- water column is not as wel supported by secondary walls
- if blocked, water flow in the entire column is impacted
Name the conducting components of the phloem
- sieve-tube members
2. companion cells
What cell types make up the phloem?
- conducting cells
- parenchyma
- fiber
- ray cells
How does the phloem prevent infection from a pathogen?
Sieve-tube members prodce callose and a special p-protein that plugs the memrane lined pores (sieve plates) which prevents pathogens from spreading through the phloem to uninfected areas.
What is the role of the epidermis?
Protect the plant from 1. water loss 2. harmful irradiation 3. infiltration by harmful microbes Allow for 1. photosynthesis 2. gas exchange
what is special about the epidermal cuticle?
- control water loss
- translucent to photosynthetically active light
- provides protection from UV light
- is flexible
- self-heals
Name the two root systems and their characteristics
- Taproot
- found in dicots and gymnosperms
- develop directly from the embryonic root
- better for surviving a prolonged drought - Fibrous
- typical of monocots
- embryonic root dies and adventitious roots arise from lower part of the stem
- shallower but better at water aquisition
Order the regions of a root from tip inwards
- Root cap
- Region of cell division
- Region of elongation
- Region of maturation
What is the role of the endodermis?
- encircles the cascular cylinder and the pericylce
- refulates the flow of substances beween the root cortex and the vascular cylinder (biofilter)
- impregnated with lignins and suberin forming casparian strip (regulates what minerals enter vasculature)
What is the role of the pericycle?
- internal to the endodermis, encircles root vascular cylinder
- give rise to lateral roots
- contributes to the vascular cambium (important for lateral growth)
What are examples of specialized roots?
- food or water storage organs
- air roots (pneumatophores) provide oxygen
- aerial roots (absorb water and nutrients from rain)
- Contractile roots (pull plant deeper in soil)
- Buttress roots (stabilize large trees)
- Parasitic roots
What are mycorrhizal associations?
- mutualistic association between roots and soil fungi
- can remain on the root surface (ectomycorrhizae) or penetrate the roots (endomycorrhizae)
- fungi aid in mineral absorption and increase the SA of the root
- fungi benefits by getting sugars and amino acids from the plant
Name the components of a stem.
- Nodes (where leaves attach to the stem)
- Internode (space between nodes)
- Axillary buds (angle between leaf petiole and the stem)
- Terminal bud (contains meristem)
Name the different vasculature arrangements in SVP stems.
- Protosteles (star shape in centre of stem)
2. Siphonostele (circular, continuous vasculature inside stem with pith inside)
Name the arrangment of vasculature in seed plants
Vascular bundles
Eustele: arranged in a ring shape for dicots and gymnosperms
Stele: vascular bundles have dispersed configuration in monocots
Name the specialized stems
- Rhizomes (horizontal stems that grow below ground)
- Runners (horizontal stems that grow above ground)
- Tubers: stems that function in storage and asexual reproduction
- Tendrils (modified stems that function in support)
What are the phyllotaxy (order patterns) of leaves
Alternate: one leaf per node
Opposite: two leaves per node
Whorled: three or more per node
Distinguish between a simple leaf and a compound leaf
simple: one blade for one axillary bud
compound: multiple blades (leaflets) for one axillary bud
How do guard cells regulate gas exchange?
When turgid stomata is open. Meaning stomata can only be open when the plant has enough water
Describe vasculature of a leaf
- Netted: dicots/ ferns
2. Parallel: monocots
Name the specialized leaves
- Drought tolerance: sunken stomata and thick cuticles
- Protective leaves: spines (thorns are modified stems and prickles are modified epidermal cells)
- Tendrils: attach plant to supporting structure
- Flotation: extra air pockets (Water Lilies)
- Bracts: Colorful foliage (Poinsettias)
- Asexual reproduction (mother of thousands)
- Insect-Trapping leaves to acquire nitrogen
Define symplasm and apoplasm
symplasm: living space of the plant in the interior of the cells (cytoplasm)
apoplasm: non-living space surrounding the protoplast, external to the plasma membrane (includes cell wall)
What is water potential?
combination of the osmotic potential (≤0) and the pressure potential (≥0)
usually water potential is ≤0
Water will move from an area of high water potential to an area of low water potential (move towards more negative)
How does water get transported from root to leaf?
Cohesion-Tension theory
- water evaporates from the stomata of leaves and stems
- causes tension, brings water molecules to replace it
- because water molecules are cohesive all the water rises from roots to leaves
How do sugars/organic molecules get transported from leaf to root?
Pressure-flow hypothesis
- transpoted via the phloem
- moves from source to sink
- sugar enters sieve tube members from source by active transport
- water potential of sieve tube members decreases so water enters by osmosis
- turgor pressure increases, moves water and sugars down the sieve tubes to sinks where pressure is low
- sugar actively transported out of seve tbes at sinks, water potential decreases, water moves out, water diffueses into xylem, pressure lowers at sinks again
Describe the light reaction of photosynthesis (non-cyclic photophosphorylation)
- takes place within thylakoid membranes of the chloroplasts
- starts in PSII with P680 reaction centre (chlorophyll a)
- PSI has P700 reaction centre
- photon hits PSII, electrons are excited and reach electron acceptor molecule: pheophytin
- water is split at OEC, electrons are replaces in PSII and ATP is generated
- electrons move down ETC (plastoquinone, cytochrome and plastocyanin), generates ATP, hit PSI
- light excites electrons in PSI, reaches Fe-S acceptor molecule, electrons from PSII replace them
- electrons are transfered to ferredoxin and flavoprotein to reduce NADP to NADPH
What is the difference between cyclic and non-cyclic photophosphorylation
Cyclic produces: no NADPH, no O2 (no splitting of water)
Describe the progression of the calvin cycle
- RuBP (5-carbon) combines with CO2 (catalyzed by rubsico) to form two 3-carbon molecules, 3PGA
- 3PGA turns into GA3P while producing ATP and turning NADPH to NADP
- some GA3P synthesizes sucrose, starch and other molecules, the rest remain in the cycle and regenerate the amount of RuBP
What is photorespiration?
When rubisco catalyzes the oxygen-fixing reaction instead of the carbon fixing one
Describe the C4 pathway
- CO2 is fixed to PEP by PEP carboxylase
- first molecule is oxaloacetate
- oxaloacetate is converted to malic acid, aspartate or other acids and through this process NADPH becomes NADP
- acid is used to make NADPH again and becomes pyruvic acid by releasing CO2 which can be used in calvin cycle
- pyruvic acid converted to PEP by using 1 ATP, cycle starts over
Describe CAM plants
- use temporal separation between initial carbon dioxide fixation and the calvin cycle
- run the C4 pathway at night and malic acid accumulates in the vacuole
- during the day malic acid in vacuoles is used to supply CO2 to the calvin cycle
Name the 5 “classic hormones”
- Auxin
- Cytokinins
- Gibberellins
- Abscisic acid
- Ethylene
What are the main functions of auxin (IAA)
- define the plant shoot-root xis which is established during embryogenesis
- stimulate cell expansion growth
- play an important role in diffrentiation of the vascular tissue during normal development and following wounding
- stimlate lateral root meristem formation
- promote fruit development
Describe transport of auxin in the plant
Transported by diffusion (within sieve tubes in roots)
polar transport (basipetal, ‘towards the plant base’)
- mediated by proteins (auxin influx carriers=located at the cell apex, auxin eflux carriers = found at the base of the cell)
- in vascular parenchym in leaves and stems
Describe the characteristics of Cytokinins
- found a a growth promoting factor in coconut milk
- chemically similar to adenine
- synthesized in actively dividing tissues (seeds, fruits, leaves, roots)
- promotes growth through cell division
- cytokinin effectus usually dependent on the presence of auxin
What happens when [auxin]=[cytokinin]
induced callus (like stem cell) formation from a stem explant
What happens when [auxin]
induced shoot formation
What happens when [auxin]=0
Induced branching (shoot multiplication) because auxin inhibits lateral growth
What happens when [auxin]>[cytokinin]
induced root formation
Describe the role of gibberellins (GA)
- synthesized in apical meristems, young leaves and embryos
- travel through xylem and phloem
- present in highest concentration in immature seeds
- regulate seed dormancy and promote germination
- promote floral transition, shoot elongation and fruit development
Describe the role of abscisic acid (ABA)
- growth inhibitory substance
- regulates seed dormancy and many stress response pathways
- plays key role in opening/closing of stomata under water stress (signal produced and sent from roots to leaves when under water stress to close stomata)
Which 2 hormones work antagonistically?
Gibberellins and abscisic acid
Describe the role of Ethylene
- produced by fruits, flowers, seeds and leaves
- major role is fruit ripening (degradation of chlorophyll, softening of fleash, synthesis of sugars)
- large commercial applications
- produced in response to touch and physical stress (bruising)
Define ‘etoliated’
Seedling grown in the absence of light
- elongatated internodes, yellow tissue, small leaves
What hormone regulates photo and gravitropism and how
Auxin
Light
- concentration are higher on the dark side causeing cell expansion growth increases on the dark side, bends stem towards light
Gravity
- concentrations are higher on the lower side, growth is inhibited on this side which bends root down
How do plants sense light
Phototropins
- upon absorbing blue light, phototropins auto-phosphorylate and initiate a signal transduction cascade
How do phototropins regulate chloroplast migration in response to low and high light intensities?
High light: chloroplasts show an avoidance response
Low light: chloroplasts show an accumulation response and distribute uniformly to maximize light capture
What are phytochromes
- proteinaceous pigments found in all higher plants
- respond to red and far-red light
- exposure of Pr to red light converts it to far-red form (Pfr) and vice versa
Effects of phytochromes
- greening of leaves
- synthesis of key photosynthetic proteins
- seed germination
- flowering time
- photomorphogenesis
What is the role of bulliform cells
- water conservation
- cause leaves to roll up or fold when they lose turgor
Name the types of systemic aquired resistance
- Hypersensitive response (HR)
2. Systemic acquired resistance (SAR)
What is hypersenstitive response
- limits the spread of infection by causing localized cell death
- stimulates the production and/or release of antimicrobial compounds
- causes lesions in the site of infection
What is systemic acquired resistance
- dying cells release salicylic acid and nitric oxide, initiates whole plant response
- produces comopunds that attenuate (slow) pathogen growth
- reults in elevated levels of resistance at the whole organism level
What is the role of plant volatiles
- released in response to berbivore and ozone damage
- act as signals that can be perceived by other plants and organisms
- synthesized by the epidermis, can freely cross membranes
- ex. floral scent to attract pollinators
What are tritrophic interactions?
- plants can attract natural predators of attacking herbivores by using volitiles
List the factors that limit the utility of plant breeding
- biological barriers to sexual hybridization
- introduction of undesirable traits
- cost
What are biological barriers?
Sexual hybridization cannot occur across different taxonomic families
How does Agrobacterium tumefaciens transform plant cells
- bacterial DNA is transferred into the plant cell
- bacterial DNA ntegrates into the plant chromosome
- once integrated, DNA becomes stably inherited
- bacterial DNA replicates whenever the plant cell replicates
what is intercallary meristematic tissues?
Meristematic tissue found at nodes and adds to the length of the plant
order these from least to most specialized:
quiescent center, ground meristem, parenchyma, guard cells
ground meristem
parechyma
quiescent center
guard cells
Which of these are not dead at maturity:
traheids, vessel elements, cork cells, sieve-tube members
sieve-tube members
Lenticels in bark share functions with…
Stomata
In which type of environment will water move into the cell?
Hypotonic
Water will move to where…
water potential is most negative
Where does the dark reaction take place?
Stroma
Chloroplasts are thought to have evolved when early eukaryotes established endosymbiotic relationships with…
Photosynthetic prokaryotes
In flowers, the two innermost whorls of organs are…
stamens and carpels
Leading to the evolution of carpels, which had to of occured first
heterospory and endosporic development
What is a tissue
group of cells that have a similar structure or common function
What hormone promotes leaf abscission and fruit ripening
ethylene
What hormone promotes apical dominance
auxin
What light do phytochromes detect?
red region of the spectrum
What is florigen?
a protein that plays a role in floral induction
