Plant Bio Quiz 1 Flashcards
Plants, like most animals, are what?
multicellular eukaryotes
Fungi & animals are what?
sister groups
Are fungi and plants close in lineage?
No
What is the common ancestor of land plants?
green algae
What is the evolutionary order of plants?
(1) land plants - (2) vascular plants - (3) seed plants - (4) flowering plants
What is the size of the largest flower?
1m
What is the age of the longest living plant?
5000 years
How big is the largest organism?
> 100m
Plants produce what?
oxygen, sugars (chemically stored energy), and useful chemicals
Joseph Priestly 1770s experiment/discovery?
animals need oxygen to live. An animal kept in a sealed container would eventually pass out; “injured” air
He also recognized that plants have the ability to “restore” the air.
Plants convert what into sugars through the process of photosynthesis?
CO2
Why do plants produce an assortment of chemicals?
protection/defense
Why study plants?
- help conserve endangered plants & environments
- learn more about the natural world
- better harness the abilities of plants to provide us with food, medicines, and energy
Robert Hooke (1965) first discovered cells in what?
plants
What did Robert Hooke call plant cells?
cork cells
Plants first purified what?
viruses
What was discovered in plants (related to viruses)?
Transposable elements
Mendel’s studies of peas revealed what?
laws of inheritance
What is the major objective of plant science?
increase food production
Globally, how many people per year are chronically hungry?
1 billion
How can plant scientists contribute to the alleviation of hunger?
By developing plants that
- are drought or stress tolerant
- require less fertilizer or water
- are resistant to pathogens
- are more nutritious
Plants provide us with more than food. What are some examples of other provisions?
- plants are sources of novel therapeutic drugs
- plants provide better fibers for paper or fabric
- plants are sources of biorenewable products
- plants provide renewable energy sources
What is Willow’s (Salix) medical contribution?
bark as a source of aspirin
What is foxglove’s (Digitalis purpurea) medical contribution?
source of digitalis (treatment for cardiac problems)
What is Pacific yew’s (Taxus brevifolia) medical contribution?
source of taxol (treatment of cancer)
What is coffee (Coffea arabica) and tea’s (Camellia sinensis) medical contribution?
sources of caffeine (stimulant)
Wood is primarily composed of what?
plant cell walls
What is everywhere?
plant wood and fibers
Plants can be a source of what?
biofuels; sugars, starches & cellulose can be fermented into ethanol
Plants can be a source of biodiesel. How is biodiesel produced?
from rape, algae and soybeans
Plants can be sources of what? Think plastics.
biorenewable and biodegradable resources
One more time, why study plants?
studying plants increases our knowledge about life in general and helps us to work with them to keep us fed, healthy, sheltered, clothed, and happy
What are the Plant cell structures shared with most eukaryotes (8)?
- lipid bilayer plasma (cell) membrane
- Cytoplasm (cytosol)
- Membrane bound nucleus
- Rough ER & ribosomes
- Smooth ER
- Mitochondria
- Golgi apparatus (dictyosomes)
- Microbodies (peroxisomes & glyoxysomes)
Ultra thin fluid bilayer comprising:
- hydrophobic tails
- Hydrophilic heads
- extrinsic proteins
- intrinsic proteins
Lipid bilayer cell membrane
All of the contents of the cell including all organelles and nucleus
cytoplasm
the liquid component of the cytoplasm: a rich broth of macromolecules and smaller organic molecules, including glucose and other sugars, amino acids and nucleic acids, fatty acids, and a diversity of ions
Cytosol
Houses the chromosomes and machinery for replication and transcription and includes a nucleolus
Enveloped by a double membrane, the outer of which is continuous with the membranes of the ER
Nucleus
A region within which ribosomal RNA is concentrated and site where ribosomes are initially constructed before export to cytoplasm
nucleolus
has ribosomes on it’s surface; translation of mRNAs/ protein synthesis occurs at the ribosomes and polypeptides are concentrated and trafficked here
rough ER
lacks ribosomes and is the location of lipid synthesis and membrane assembly; as new membrane is assembled, vesicles are pinched off and transported to target sites, where membrane fusion occurs
Smooth ER
membrane rich organelle where ATP is produced and oxygen consumed
mitochondria
Glycolysis occurs where and produces what?
cytoplasm; 2 pyruvate
What is imported into the mitochondrion?
pyruvate
The citric acid cycles oxidizes pyruvate into what?
CO2 and energized electrons
electrons are passed along an electron transport chain producing ATP and reducing O2 to H2O
oxidative phosphorylation
An extension of the ER whereby proteins are packaged, modified and transported intracellularly to destination
Golgi apparatus
refers to an individual stack with the Golgi apparatus
dictyosome
small spherical vesicles scattered throughout the cytoplasm and the sites of specialized reactions utilizing O2 and H2O2
microbodies
associated with chloroplasts and mitochondria; they detoxify toxic byproducts of metabolism
Peroxisomes
convert stored fats into sugars and are important during seed germination (plants only)
glyoxysomes
Animal cell vs Plant cell: Central vacuole
Animal cell: absent
Plant cell: present
Animal cell vs Plant cell: Chloroplast
Animal cell: absent
Plant cell: present
Animal cell vs Plant cell: Cell wall
Animal cell: absent
Plant cell: present
Animal cell vs Plant cell: Endoreduplication
Animal cell: rare
Plant cell: common
Animal cell vs Plant cell: Cytokinesis
Animal cell: cleavage furrow
Plant cell: Cell plate
Animal cell vs Plant cell: cell signaling
Animal cell: Gap junctions
Plant cell: plasmodesmata
- often constitutes 80% or more of intracellular space of plant cell
- pushes the cytoplasm & organelles into a thin layer around the perimeter of cell
- contains water & solutes
- maintains turgor pressure within cell & thus supports the plant
Central Vacuole
What happens when the central vacuole loses water?
the plant can no longer support itself
- Site of pigments that absorb light energy; energy is then used to fix CO2 to make sugars
- much larger than mitochondria
- contains complex internal membranes which are important to light capture & electron transfer
- storage organelles for starches
- endosymbiotic origin (prokaryotic cyanobacteria)
chloroplasts
- complex multi-layered structure produced to exterior of cell membrane
- fixes plant cells inplace creating a kind of endo-skeleton for a plant
- can be primary or secondary
Cell wall
- present for every plant cell
- comprises complex fibers (consisting of cellulose & hemicellulose) embedded within pectin
- strong but flexible; allows growth & expansion of cells
primary cell wall
- layer present between two adjacent plant cells
- comprises pectins, jelly like polysaccharids
- glues adjacent cells together
Middle Lamella
- found to the interior of primary cell wall; thicker & stronger
- produced only after the growth & expansion of primary wall has stopped
- comprises a complex mix of cellulose, hemicellulose, and lignin
- produced by a diversity of specialized cell types, including: water conducting cells (xylem) & support sclerenchyma cells (fibers & sclerids)
- major component of wood & plant fibers
- can have a very complex multi-layered structure
- can greatly reduce the volume of cell contained within cell membrane
secondary cell walls
Plant and animal cells are similar in that both have:
a) same fundamental chromosomal structure
b) same cell cycle (G1, S, G2, mitosis/cytokinesis)
c) same steps in cell division; mitosis (PPMAT)
- instead of cell entering into G1/G0 after mitosis as a mature cell, the cell enters into S (synthesis) and replicates its DNA without mitosis & cytokinesis
- this may occur multiple times to greatly increase the size of the nucleus in the particular cell
- important in hair cells, glandular cells, nectar producing cells; have extremely rapid and intense metabolism
endoreduplication
Daughter cell separation
cytokinesis
Cytokinesis in plants: following telophase of mitosis a what forms?
phragmoplast
a group of short microtubule fibers that form as the metaphase plate
phragoplast
Cytokinesis in plants: What fibers trap dictyosome vesicles that contain materials for building new cell wall
phragomoplast’s microtubule fibers
Cytokinesis in plants: What coalesces to form a large plate vesicle within which cell wall and middle lamella are assembled?
dictyosome vesicles
Cytokinesis in plants: what comprises the cell plate?
phragmoplast, vesicle & cell wall
Cytokinesis in plants: What expands laterally, extending toward the parental cell wall?
cell plate
Cytokinesis in plants: What is the final step?
fusion
- the membranes of the plate vesicle fuse with the parental margins to yield a new cell membrane
- the new cell wall components inside the vesicle fuses with parental wall to complete wall formation
Why is cell to cell communication different in plants vs animals?
because of their cell wall & middle lamella
- channels of communication via small molecules
- tightly regulated
- animal cell-to-cell communication
gap junctions
- directs communication between living plant cells
- small channels through the cell wall layers that connect adjacent cells
plasmodesmata
what passes through the plasmodesmata to create a contiguous system?
plasma membrane, cytoplasm & sections of the ER
- creates the “symplast”
Plasmodesmata are especially important in forming connections between what?
phloem cells
cells that specialize to transport sugars and solutes through the plant body
phloem cells
Aggregations of plasmodesmata form what?
- Sieve areas
- Sieve plates
Patches of plasmodesmata
Sieve areas
large sections of plasmodesmata spanning the entire cross-section of a phloem cell
Sieve plates
- refers to characteristics of plants that are herbaceous (non-woody)
- growth occurs from apical meristems
primary growth
herbaceous plants
- annual plants
- short lived perennial plants
All growth of herbaceous plants occurs from apical meristems located:
- at the tips of shoots
- tips of roots
(intensely dividing regions)
Herbaceous plants lack what?
wood & bark
characteristic of plants that have woody tissue
secondary growth
Stems, leaves & roots all share a basic, simple organization. All plant cells in these structures belong to just three classes based on the nature of their cell wall. What are these classes?
- Parenchyma
- Collenchyma
- Sclerenchyma
- cells have only thin primary walls
- most common cell type of plants
- metabolically active & serving diverse functions
- remains alive at maturity (has cytoplasm & nucleus)
parenchyma
a mass of parenchyma cells
parenchyma tissue
Par- =
beside
- enchyma =
filled in/poured in
Specialized parenchyma types include:
- chlorenchyma
- glandular cells
- transfer cells
- phloem
- include green-photosynthetic parenchyma cells of leaves
- the thin walls allow light & carbon dioxide to pass through the chloroplast
- packed with chloroplast
Chlorenchyma cells (chlor = color)
the chloroplast rich cells of a leaf & the specialized pigmented cells (petals & fruits) of plants are both what?
chlorenchyma cells
specialized parenchyma that secrete substances such as nectar, fragrances, mucilage, resins, oils
Glandular cells
- mediate short-distance transport of materials in high volumes
- have a large, extensive plasma membrane with numerous molecular pumps
- function e.g: influx of sugars into fruits or excretion of salts in high-salt adapted plants
transfer cells
parenchyma tissue that conducts nutrients over long distances
phloem
Metabolically, parenchyma cells are what?
inexpensive to build
- little glucose expended in constructing primary cell walls
- leaves = energetically cheap (almost entirely parenchyma)
Secondary cell walls require what?
logs of glucose to make cellulose and hemicellulose (polymers of glucose)
- have a primary cell wall that is thin in some areas and thickened in others
- allows flexibility & support
- no secondary wall
- lumen is relatively large (because no secondary wall)
Collenchyma (Coll- = glue)
Where are collenchyma cells found?
- beneath the stem and leaf epidermis
- supporting vascular bundles
- has a primary wall & thick secondary wall that is usually heavily lignified
- elastic but strong
- once mature, the cell dies, leaving just the still functional cell walls
Sclerenchyma
What are the two types of sclerenchyma?
1) mechanical
2) conductive
- a class of complex organic polymer
- particularly important in the formation of cell walls, especially in wood and bark
- lends rigidity and flexibility & does not rot easily
- made by cross-linking phenolic precursors
lignin
Mechanical (nonconducting) sclernechyma types
1) fibers
2) Sclereids
- long and tough
- important structural component of stems
- may form bundles in tough leaves
- mechanical (nonconducting) sclernechyma
Fibers
- short, isodiametric (cuboidal), inflexible & brittle
- Mechanical (nonconducting) sclerenchyma
Sclereids
Conducting Sclerenchyma
Xylem
- transport water
- dead at maturity & have thick walls that provide support while also conducting water
Xylem
Cells of the vascular system
phloem & Xylem
Types of Xylem
Tracheids & Vessel elements
Outline: Primary plant body
shoots (stem & leaves), Roots, Meristems
Outline: Plant tissues
(1) Epidermis
- trichomes
- stoma
(2) Cortex
(3) Vascular tissue: vascular bundles
- Xylem: Tracheids & Vessel elements
- Phloem
consists of stems and leaves
shoot system
anchors the plant and provides water and nutrients for the shoot system
root system
Primary growth occurs where?
at the terminal buds & the axillary buds
A bud is a what?
embryonic shoot
a region of cells that divide to produce new growth and tissues
meristem
A bud is an embryonic shoot:
- protected by scale or bracts (modified leaves)
- including a meristem
What contains a shoot apical meristem?
terminal bud
Why is the terminal bud the only bud that grows?
The terminal bud secretes a hormone that blocks axial bud growth
Axillary buds are what because of the terminal bud?
dormant
For most plants, most axillary buds are not needed as long as what?
the apical meristem is healthy
If the apical meristem is killed, what happens?
axillary buds become active & replace it by growing a new shoot
- hormone is no longer inhibiting axillary bud growth
- outermost surface of a herbaceous stem
- single layer of parenchyma cells
- all interchange of material between a plant and its environment occurs by means of this
- functions in protection of the stem & preventing water loss
epidermis
Outer epidermal walls are coated with waxy, waterproof what?
cutin
Cutin builds up to form what layer?
the cuticle
What does the cuticle do?
prevents desiccation but also prevents gas exchange; no CO2 can get in, no O2 can get out
gas exchange is allowed by what?
stomates
stoma occur where?
on leaf surfaces & stems
Stoma include:
1) 2 guard cells
2) the stomatal pore
the hole between the guard cells through which gases can pass into the stem interior
the stomatal pore
Guard cells open and close the pore based on what?
tugor pressure within the cells
High turgor pressure does what to the stoma?
Opens it by causing the guard cells to bend
Low turgor pressure does what to the stoma?
Closes it; guard cells are not forced open
Guard cells have _ around the pore, but _ to the exterior
thick walls; thin walls
When water enters, cells swell, and distort creating what?
the pore opening; permits entry of CO2 and exit of O2
Loss of water does what?
relaxes the guard cells & pore closes
Some epidermal cells elongate outward and become what?
trichomes (hairs)
Trichomes have diverse shapes and serve many roles:
- deter herbivory
- minimize water loss
- protect from over exposure to sunlight
- can act as secretory glands
- part of the stem is interior to the epidermis
- composed of photosynthetic parenchyma and sometimes collenchyma (for support)
Cortex
responsible for the conduction of material throughout the plant
vascular tissues
two types of vascular tissues occur in plants:
1) Xylem: conducts water & minerals
2) Phloem: distributes sugars & minerals
Xylem and phloem occur together in primary plant stem in what?
vascular bundles
Xylem is what at maturity?
dead & hollow
Phloem is what at maturity?
alive
What are the types of xylem cells (tracheids & vessel elements) collectively called?
tracheary elements
Tracheids and vessel elements are both what?
types of conductive sclerenchyma with secondary cell walls deposited on interior of the primary wall
Types of secondary cell wall thickenings
- annular thickenings (rings)
- helical thickening (spirals)
- Scalariform thickening (ladder-like)
- Reticulate thickening (network-like)
Degree of strength of cells is correlated with what?
amount of secondary cell wall
Water is free to pass through any regions that lack what?
secondary cell wall
The most derived and strongest tracheary elements have what?
circular bordered pits
- cells have extensive secondary walls
- small passage ways to the primary wall through secondary wall
- bordered by extra wall material to increase strength
circular bordered pits
- long and narrow with pointed ends
- an ancestral type of xylem
- All plants with vascular tissue have tracheids
- water moves between tracheids through lined-up pit (pit pairs)
- water thus passes through 1 wall from cell to cell
Tracheids
- short and broad with non-tapered ends
- only flowering plants have these
- form a vertical, continuous tube
- provide a way to move water very efficiently, with little resistance
Vessel elements
refer to the open ends of the cells that results from loss of the primary cell walls
perforations
stack of vessel elements forms what?
vessel
plug that acts as an emergency valve
torus
Water is normally free to flow from one tracheid to the next having to pass only through what?
primary cell wall/ middle lamella layers
- yields a continuous, unbroken flow of water
What happens if there is a breach and air enters cell 2?
1) Air enters the pit from cell 2
2) This pushes the torus toward the pit opening of Cell 1
- this plugs the pit in Cell 1 and thus protects the cell from catastrophic failure because air would break the water column
Tracheids are what? This is why trees need a lot of them in their wood
inefficient
Soft woods are composed of what?
primarily of rows of tracheids and tend to lack other fiber support cells
What dominates colder ecosystems?
conifers
In cold climates, extreme cold causes freezing of the water in xylem that can cause what?
intrusion of air bubbles
What protects the overall vascular system from total collapse?
pit safety valve
Hardwoods are all what?
angiosperms: maple, oak, ash, etc…
Why do hardwoods have less xylem than soft woods?
their vessels are very efficient at transporting water
Hardwoods have more efficient vessels and less xylem, which has provided the opportunity for what to develop?
fiber cells
have thick secondary walls and provide very strong support to hard woods
fiber cells
what does ‘Hard’ in hardwood mean?
heavier
Hardwood vessels are what?
open and very efficient at conducting water
What outcompetes conifers in most habitats? Why?
Angiosperms (incl. trees); the reproductive and vascular systems of angiosperms is very successful
Why can conifers outcompete angiosperms in colder temperatures?
the efficient wood of angiosperms is vulnerable to collapse in cold temperatures
Where are conifers typically found?
boreal regions
sugar/sap conducting cells of vascular plants
Phloem
Phloem has two types of conducting cells:
1) sieve cells
2) Sieve tube members
ancestral cell type
Sieve cells
Sieve tube members
Derived cell type
Sieve element refers to what?
sieve cells and/or sieve tube members
What develops from parenchyma cells and remains alive at maturity?
phloem (Sieve cells & Sieve tube members)
Plasmodesmata enlarge to become what?
sieve pores
Sieve pores aggregate where?
sieve areas
A sieve cell is similar in shape to what?
a tracheid
- elongated & tapered
What phloem type is found in nonflowering vascular plants?
ancestral phloem (Sieve cells)
similar to the vessel elements of the xylem
sieve tube members
form on each end-wall and align vertically to form a sieve tube
sieve plates
All what have sieve tubes?
angiosperms
- non-angiosperms do not
What degenerates in sieve elements?
nuclei
- at maturity, they associate with neighboring (nucleated) cells that regulate their function
Sieve cells associate with nucleated what?
albuminous cells
- small cells
- occur in clusters along the sides of the sieve cells
- regulate loading and unloading of sugars into the sieve cells
albuminous cells
Sieve tube members associate with nucleated what?
companion cells
- regulate loading and unloading of sugars into the sieve tube cells
- larger than albuminous cells, but smaller than its partner
- prominent nucleus and dense cytoplasm filled with ribosomes
companion cells
In the primary plant body, what occurs together in vascular bundles interior to the cortex?
xylem and phloem
Xylem and phloem are what? Means running parallel to each other in the plant stem
‘Collateral’
Most flowering plants have what arrangement of vascular bundles?
eudicots
vascular bundles arranged in one ring between the cortex and surrounding the pith in the stem center
- primary growth
Eudicots
Vascular bundles are distributed as a complex network throughout the inner part of the stem
- primary growth
monocots
Other cell types are found in vascular bundles: associated with tracheary elements of xylem are:
- xylem parenchyma
- xylem fibers
Other cell types are found in vascular bundles: associated with phloem are:
- storage parenchyma
- phloem fibers
Cell types in angiosperms: Xylem vs Phloem
Xylem: tracheids, vessel elements
Phloem: Sieve cells, companion cells
Contents: Xylem vs Phloem
Xylem: Water & dissolved minerals (Mg, Fe, Ca)
Phloem: sugars (sucrose), amino acids, small organic acids, plant hormones & defense compounds
Direction of Conduction: Xylem vs Phloem
Xylem: From roots in soil to shoots. Most water is lost through open stoma in leaves
Phloem: Source to sink (need basis). From leaves to flowers, fruits, stems, roots, etc…
From storage in roots & stems to growing shoots
