review for midterm 2 Flashcards
Out of the meristematic tissue, which one corresponds to primary growth and which to secondary growth?
Apical = Primary
Lateral = Secondary
What’s the purpose of the root cap?
Protects that apical meristem as root pushes through soil
What are the 3 zones of growth in roots?
1) Zone of division
2) Zone of elongation
3) Zone of differentiation
What is the closest relative to plants?
Green algae (charophytes): absorbed water, minerals, and CO2 directly from surrounding tissue
Where did early non-vascular plants live and what kind of roots did it have?
They lived in shallow water and had aerial roots
What kind of plant w/ what characteristics were favoured by natural selection?
Tall plants with flat appendages, multicellular branching roots, and efficient transport, were favoured by natural selection
What evolution made it possible for long-distance transport of water, minerals, and products of photosynthesis?
The evolution of xylem and phloem in land plants made possible the long-distance transport of water, minerals and products of photosynthesis
What are the 2 basic functions of stems?
1) serve as conduits for water and nutrients
2) support structures for leaves
What 2 characteristics affect light capture and what’s the trade-off?
Shoot length and branching pattern affect light capture; trade-off b/w growing tall and branching
What is phyllotaxy?
the arrangement of leaves on a stem, this is a species specific important trait for light capture
What is the phyllotaxy of most angiosperms?
Alternate w/ spirally arranged leaves
What’s the angle b/w leaves that likely minimizes shading on lower leaves?
137.5 degrees
What is leaf area index?
ratio of total upper leaf surface of a plant divided by surface area of land on which it grows
What does leaf area index affect?
light absorption
What are root and shoot systems specialized for?
harvesting light, water, and nutrients
What are 2 characteristics of plants?
1) autotrophs
2) performing photosynthesis
What characteristic of leaves affect light capture?
Leaf orientation
In low light conditions, what kind of leaf orientation is best?
Horizontal
In sunny conditions, what kind of leaf orientation is best?
Vertical leaves as they get less damaged by the sun and they allow for lower leaves to get light
In what soil condition do roots branch the most?
They branch higher in high nitrate soil
What are the 3 transport routes for water and solutes?
1) apoplast
2) symplast
3) transmembrane
What does the apoplast route consist of?
through cell walls and extracellular space
What does the symplast route consist of?
through the cytosol (and plasmodesmata)
What does the transmembrane route consist of?
across cell walls
What is the short distance transport of water in plants called?
Osmosis
How do plants balance water uptake and loss?
Osmosis which is the diffusion of water into and out of the cell affected by solute concentration
What happens if a flaccid plant cell was placed into a hypertonic (higher salt in the solution) solution?
Plasmolysis: occurs when the protoplast shrinks and pulls away from the cell wall
What are aquaporins and what do they do?
they’re transport proteins in cell membrane that facilitate passage of water; these affect the rate of water movement across the membrane
What rate is affected by aquaporins?
rate of water movement across the membrane
What happens with cells that have fewer aquaporins?
slower rate of osmosis
What is the casparian strip and what does it do?
strip of endodermis wall that blocks the apoplast route which is the transfer of minerals from cortex to the vascular cylinder
What is xylem sap made of?
Water and dissolved minerals
With what mechanism is xylem sap transported from roots to leaves?
Bulk flow which is driven by transpiration and doesn’t require energy from the plant since it’s solar powered
How is the movement of xylem sap against gravity maintained?
cohesion-tension hypothesis: transpiration and water cohesion pull water from roots to shoots
Is xylem sap under + or = pressure/tension?
-
What 2 things drive bulk flow upwards?
1) Adhesion: offsets gravity since water adheres to cellulose in xylem cell
2) Cohesion: 2 water molecules attach to each other
Where are products of photosynthesis transported through and how?
Products of photosynthesis are transported through phloem by translocation: Phloem sap moves through a sieve tube by bulk flow driven by positive pressure called pressure flow
What would decrease transpiration?
lower stomatal density
What are the 2 basic physical properties of soil?
1) texture
2) composition: refers to organic and inorganic components
What are soil particles classified by?
By size:
1) sand
2) silt
3) clay
What is the soil that is most fertile?
Loams: most fertile topsoils have equal amounts of sand, silt and clay
What layer of soil contains humus?
upper layers of soil contain humus
What is humus?
decaying organic material
What are the 3 benefits of soil containing humus?
1) Crumbly soil that retains H2O
2) Increases soil’s capacity to exchange cations
3) Serves as a reservoir of mineral nutrients
What does fertilizer do?
replaces mineral nutrients that have been lost from the soil (N, P, and K)
What does excess nutrients from fertilizers cause?
Algal blooms
How many nutrients are essential?
17
How many nutrients are macronutrients and what are they?
9 macronutrients:
1) Oxygen
2) Nitrogen
3) Calcium
4) Phosphorous
5) Carbon
6) Sulfur
7) Potassium
8) Magnesium
9) Hydrogen
How many nutrients are micronutrients and what are they?
8 micronutrients
1) Iron
2) Manganese
3) Mo
4) Boron
5) Chlorine
6) Copper
7) Nickel
8) zinc
What is the rhizosphere?
Soil near root environment containing microbes that rely on sugars, amino acids, and organic acids secreted from living roots
What are endophytes and where do they live?
nonpathogenic bacteria that live b/w the cells of host plant tissue
What are the 2 forms of Nitrogen that plants can absorb?
1) NO3-
2) NH4+
What are the 2 functions of mycorrhizae?
1) increase surface area of plants for water uptake and mineral absorption
2) secrete growth factors that stimulate root growth and branching
How do mycorrhizae benefit from plants?
constant supply of sugar from host plant
What are 3 non-mutualistic plants?
1) Epiphytes: live on plants and obtain water and minerals
2) Parasitic: absorbs sugar and nutrients and can kill host plant
3) Carnivorous: can photosynthesize, but obtain nitrogen by killing insects
What are plant lifecycles characterized by?
Alternation of multicellular generations; sporophyte (2n) and gametophyte (n)
What generation of the plant can we see and lives longer?
Sporophyte
What are the 3 F’s of angiosperm lifecylce?
1) Double fertilization
2) Flowers
3) Fruits
What are flowers to an angiosperm?
They are reproductive shoots of angiosperm
What part of the stem do flowers attach to?
receptacle
What are the 4 organs of flowers?
1) Carpels
2) Stamens
3) Petals
4) Sepals
Which organ is the female reproductive organ?
Carpel: ovary, style, and stigma
Which organ is the male reproductive organ?
Stamens: filaments and anthers
What is pollination?
Transfer of pollen from an anther to the stigma; after landing on a receptive stigma, a pollen grain produces a pollen tube that grows down into the ovary and discharges 2 sperm cells near embryo sac
What are the 3 mechanisms of pollination?
1) wind
2) water
3) animals
What % of plants are pollinated by insects?
65%
What is coevolution?
Joint evolution of interacting species in response to selection imposed by each other, common b/w animals and flowers. Shapes and sizes of flowers often correspond to the pollen-transporting parts of their animal pollinators
What are the 4 steps in the angiosperms lifecycle?
1) Gametophyte development
2) Pollination
3) Double fertilization
4) Seed development
What is the male gametophyte?
Pollen develops from 4 microspores and each microspore undergoes mitosis to produce 2 cells: generative cell and tube cell. Generative cells will form 2 sperm
What is the female gametophyte?
Female gametophyte (embryo) develops in the ovule. 1 cell in megasporangium undergoes meiosis, producing 4 megaspores, but only 1 survives. The Megaspore then divides without cytokinesis producing one large cell w/ 8 nuclei then it’s partitioned into a multicellular female gametophyte, the embryo sac
How many integumentary surround megasporangium within ovule?
2 integumentary surround megasporangium
In seed development what develops into what?
ovule develops into a seed, ovary develops into a fruit
What happens in embryo development of seed development?
In embryo development of seed development; zygote splits the fertilized egg into a basal cell and a terminal cell. Basal = suspensor, and Terminal = gives rise to most of the embryo
What does the basal cell give rise to?
gives rise to multicellular suspensor that anchors embryo to the ovule
What does the terminal cell give rise to?
gives rise to most of the embryo
Why is seed dormancy important?
It increases the chances that seed germination will occur at a place and time most advantageous for seedling
How is seed dormancy broken?
seed dormancy is broken by environmental cues such as temp and lighting changes
What does seed germination depend on?
Imbibition: water uptake by the seed due to lower water potential in dry seed
What are the 2 main methods of asexual reproduction?
1) Fragmentation: separation of a parent plant into parts that develop into whole plants
2) Apomixis: seed production without fertilization (from diploid cell)
What is the advantage of sexual reproduction?
generates genetic variation that makes evolutionary adaptation possible
What is the disadvantage of sexual reproduction?
Only a fraction of the seed survives
What are the 4 mechanisms of preventing selfing?
1) Dioecious: staminate and carpellate flowers on separate plants
2) Self incompatibility: reject its own pollen
3) Reject pollen that has an S-gene arching allele in the stigma cells
4) Recognition of self blocks pollen tube growth
What results in high genetic diversity?
Outcrossing/outbreeding
What is outcrossing/outbreeding?
The process of transferring gametes from one individual to another that is genetically different
What process do megasporocytes and microsporocytes both undergo?
Meiosis
What is phototropism?
Plant orientation to light
What is Darwin’s experiment about phototropism?
experiment by darwin suggests that there’s a hormone at the tip that travels down; coleoptile tip senses light
What is gravitropism?
response to gravity
+ or - gravitropism in roots and shoots?
+ in roots
- in shoots
What organelle/structure is responsible for detecting gravity?
Statoliths
What is thigmomorphogenesis?
changes in form that result from mechanical disturbance; rubbing plant fiercely results in short plant
What is thigmotropism?
growth in response to touch; vines and climbing plants
What is an example of thigmomorphogenesis?
Mimosa poudica: folds its leaflets and collapses in response to touch.
Rapid leaf movement in response to mechanical stimulation are due to what?
Rapid leaf movement in response to mechanical stimulation are due to transmission of electrical impulses called action potentials
What are 2 defenses against herbivory?
1) Physical: thorns and trichomes
2) Chemical defenses such as distasteful or toxic compounds
What is an example of an amino acid that acts as a chemical defense?
canavanine
What’s the plants first line of defense?
Epidermis and periderm but pathogens can still get in through wounds and natural openings like stomata
What’s the next line of defense?
PAMP triggered immunity: plants recognize PAMPs which triggers signaling pathway
Signaling pathway due to PAMP recognition leads to what 2 things?
1) Production of antimicrobial chemical
2) Toughening of the cell wall
How have pathogens evolved to work around PAMP-triggered immunity?
Pathogens can deliver effectors to suppress PAMP-triggered immunity; these are pathogen encoded proteins. A 2nd level of plant immune defense evolved in response to these pathogens (R-genes)
What are hormones and what do they do?
chemical signals that modify or control one or more specific physiological processes; also called plant growth regulators produced in very low concentrations
What are the 5 important plant hormones?
1) Auxin
2) Cytokinins
3) Gibberellins
4) abscisic acid
5) Ethylene
What is auxin known for and where is it found
It’s produced in shoot tips and promotes elongation of coleoptiles
What’s the major form of auxin found in plants?
Indole-3-acetic acid (IAA)
What is the acid growth hypothesis?
Auxin stimulates proton pumps in plasma membrane; pump lowers pH of the cell wall activating expansins, enzymes that loosen the wall’s fabric, then cells elongate
What are 2 functions of cytokinins?
1) Stimulates cell division; produced in actively growing tissues such as roots, embryos and fruits. Can control cell division and differentiation w/ auxin
2) Slows aging
What are the 3 processes that cytokinins use to slow the aging process?
1) inhibiting protein breakdown
2) stimulating RNA and protein synthesis
3) mobilizing nutrients from surrounding tissue
What are the 3 functions of gibberellins?
1) Stem elongation; growth of leaves and stems
2) fruit growth; w/ auxin as well
3) Germination; after water imbibition, release of gibberellins trigger germination
What disease is cause by fungus with gibberellins?
Foolish seedling disease; resulted in long thin plants
What are the 2 functions of abscisic acid?
1) Seed dormancy; some seeds dormancy is broken when ABA is removed by heavy rain, light, or prolonged cold
2) Drought tolerance; ABA accumulation causes stomata to close stomata rapidly to retain H2O
When is ethylene produced?
In response to stress and ripening
What response does ethylene induce to allow for growing shoots to avoid obstacles?
Triple response
What does triple response do (3)?
1) Slowing stem growth
2) Horizontal growth
3) Thickening
What is senescence and what is it associated with?
programmed death of cells and organs, burst of ethylene is associated with apoptosis
What controls leaf abscission?
change in balance of auxin and ethylene controls leaf abscission
How does fruit ripening work with which hormone?
Ethylene triggers ripening process in fruits and ripening triggers release of more ethylene
What kind of loop is ripening of fruits?
Positive feedback loop
What is crop domestication?
process of artificially selecting plants to increase suitability to human requirements: taste, yield, storage, and cultivation practices
What are the 4 effects of domestication syndrome?
1) Loss of dispersal
2) Increase in size
3) loss of seed dormancy
4) loss of chemical or mechanical protection against herbivores
What has been used by breeders to introduce new genes?
Hybridization
Plant breeding with mutations works how?
mutations (random) were took advantage of (beneficial mutations) and selected for beneficial mutations (desirable traits)
What does plant biotechnology generally refer to and what does it specifically refer to?
1) generally refers to innovations in the use of plants to make useful
2) specifically refers to use of GM organisms in agriculture and industry
What are transgenic organisms?
Organisms such that have even engineered to express a gene from another species; GM plants may increase the quality and quantity of food worldwide
What are 3 modifications made to plants that made them transgenic organisms?
1) Produce toxins (Bt toxin) to defend them against insect pests
2) Tolerate herbicides
3) Resist specific disease
What is Golden Rice?
increase amounts of vitamin A
What modifications were made to cassava?
Increased levels of Fe and beta-carotene
