Plant biology Flashcards
What is the precursor to all plastids called?
A protoplastitd
What are plasmodesmata?
Thin cytoplasmic strands that connect adjacent cells, similar to gap junctions
Where are apical meristems found?
At the tips of roots and shoots
Where do primary tissues of plants derive from?
Where do secondary tissues of plants derive from?
Apical meristems
Other types of meristems
What are parenchyma?
Unspecialised cells that form most of the ground/packing tissue, perform most metabolic functions
What are collenchyma?
Cells with thickened corners which are used for structure/support in young plants, have protoplasmic content (are living)
What are sclernchyma?
What are the two types?
Have a supportive or protective function, have thickens secondary cell walls, cells are usually dead and cannot elongate
Sclerids boxier and irregular in shape, thick lignified secondary walls, impart hardness to nuts
Fibers grouped in strands, hemp, rope
Describe the functions of these primary tissues:
- ground tissue
- dermal tissue
- vascular tissue
For packing, storage and support, mostly parenchyma
For protection and gaseous exchange
Water conducting and/or sugar conducting
What is the role of the xylem?
What is the role of the pholem?
Water conducting, primarily from roots to shoots/leaves
Sugar conducting, primarily from shoots/leaves to roots
Where are tracheary elements found?
Whee are sieve elements found?
In the xylem
In the phloem
What are some of the roles of vacuoles?
Storage (amino acids, sugars, toxins)
Space filler
Pigment deposition
Digestion of macromolecules
Name the three most basal angiosperms.
Water lillies (e.g. nymphaea)
Star anise (e.g. Illicium floridanum)
Amborella trichopoda
What is field capacity?
What is permanent wilting percentage?
The % of water a soil can hold against gravity
% water remaining when irreversible wilting happens to a plant in a soil
Sandy soils have a lower capacity to hold onto water, true or false?
True
What is the best form of nitrogen for plants to take up?
Nitrate ion NO3-
What is the usable form of phosphorous?
What is the source of this?
Phosphate (PO4)
The earths crust
What type of mycorrhiza penetrates the cell wall?
What type grows between cell walls?
Arbuscular mycorrhiza
Ecto-mycorrhiza
What are epiphytes?
What do they gain?
What adaption do they have?
Plants that grow upon plants but are not parasitic
Height
Require high humidity (no water for roots), May trap water in tanks, may collect plant debris and utilise minerals from decaying material
Name some parasitic plants and describe them.
Dodder, has no chlorophyll, steals products of photosynthesis
Mistletoe, is photosynthetic steals nutrients from vascular tissue of host
Indian pipe, utilises host’s mycorrhiza
What structures are found in the light absorbing pigments of photosynthetic organisms (e.g. chlorophyll A)?
Porphyrin ring - Mg at centre, excitable electrons
Hydrophobic tail - anchors to hydrophobic proteins in thylakoid membrane of chloroplast
Eukaryotes may have essential acessory pigments that increase breadth of usable wavelengths
Photon energy is proportionally related to wavelength, true or false?
False it’s inversely related
What do C4 plants do?
What do CAM plants do?
Store CO2 in malate in mesophyll cells, CO2 released from malate, and recycled back to mesophyll cells
Open stomata at night, collect CO2, store CO2 in organic acids, stomata close during day
In Gause’s experiment when grown together which species (P. Aurelia or P. caudatum went extinct?
P. Caudatum
Give some examples of the ways animals and plants compete.
Black Walnut - releases other chemicals into the soil to prevent other plants from growing
Desert ant - throws rocks down the hole of the honeypot ant so it can’t leave to get at resources
Honeypot ant - can fill up abdomen with resources
Briefly describe Connell’s study on barnacles.
Chthamalus and Balanus have stratified distribution on rocks. C found higher up than B. When B removed C covered region formerly occupied by B. So C’s realised niche is much smaller than its fundamental niche
What is Batesian mimicry?
What is Müllerian mimicry?
Where a palatable or harmless species mimics an unpalatable or harmful one
Two or more unpalatable species (e.g. Cuckoo bee and Yellow jacket) resemble each other
What is a keystone predator?
What happens if a keystone predator is removed?
One carnivorous species at the top of the food chain crucial to maintaining balance of a community
Reindeer of St Mathew Island, carnivores removed
What are the three types of symbiosis?
Parasitism
Mutualism
Commensalism
What is commensalism?
A relationship where one organism benefits and one is neither benefitted or harmed
Where are roots derived from?
What is a taproot?
What is the general function of roots?
Primary root apical meristem
One main vertical root which usually develops from the primary root and helps prevent the plant from toppling
Anchorage, water absorption
Where are stems derived from?
What are shoots?
What is the function of stems?
Primary shoot apical meristems
Stem + leaves
Structural, supportive, transport of water and minerals
What are the three layers of tissue found in plants? What do they do?
Dermal tissue (outer layer), outer protection, made of epidermis in non-woody plants (a layer of tightly packed cells). In woody plants the periderm replaces the epidermis
Ground tissue tissues that are neither dermal or vascular, ground tissue internal to the vascular tissue is pith, external ground tissue is the cortex, includes cells specialised for storage, photosynthesis, support
Vascular tissue, facilitates transport, provides mechanical support, two types xylem and pholem
Describe how a dicot root looks.
Describe how a monocot root looks.
Outer epidermis, then cortex. Endodermis forms a circle in the centre, vascular cylinder contains xylem and phloem, xylem forms a cross, phloem is spaces in between the cross
Epidermis on outside, the cortex, vascular cylinder, xylem forms dots, phloem spaces in between, pith in centre
Describe primary growth.
Describe secondary growth.
Lengthens roots and stems (increases length)
Widens roots and stems (increases width)
Describe herbaceous dicot and monocot stems.
In dicot vascular bundle arranged in ring around the ground tissue
In monocot vascular bundles are scattered throughout the ground tissue
What are the two main cell types of the xylem? Describe them.
Tracheids and vessel elements
Tracheids, slindle shaped and have pits that allow water to move through
Vessel elements have partially perforated end walls.
Both are no longer living, only cell wall left
What happens to guard cells when a plant has plenty of water?
What happens to them when a plant is trying to conserve water
Guard cells swell, causing the stoma to open due to inner thickened wall of guard cells being pulled apparat
Guard cells shrink and stomata closes
What are the two cell types of the phloem? Describe them.
Sieve tube elements and companion cells
Sieve tube elements, tubular cells with sieve plate at end, living cells
Companion cells, non conducting cells that provide mechanical support for sieve tubes, connected by intercellular connections
Nucleus of companion cell proves the metabolic support for the living sieve tubes
Where is primary xylem/phloem derived from?
The procambium of apical meristems
The vascular cambium
Vessel elements can be found in gymnosperms, true or false?
False they are only found in angiosperms
What is the meristem that causes primary growth?
What are the meristems that causes secondary growth?
Apical meristem
Lateral meristems: the vascular cambium and cork cambium
What does the vascular cambium do?
What does the cork cambium do?
Adds layers of vascular tissue (secondary xylem and phloem)
Replaces the epidermis with the tougher thicker periderm
As cork cells mature they produce a waxy hydrophobic material called what in their walls before dying?
Suberin
What allows living cells in the interior tissues of woody organisms to absorb oxygen and respire?
Lenticels, small raised areas that dot the periderm in which there is more space between cork cells enabling living cells to exchange gases with the outside air. Lenticels appear as horizontal slits
In the transport of water and minerals from root hairs to the xylem, what is the apoplast pathway? What is the symplast pathway?
Apoplast pathway - uptake of soil solution by the hydrophilic walls of root hairs
Symplast - through the cells
What is guttation? What causes it?
The secretion of droplets of water from the pores of plants, when there is high soil moisture, water will enter plant roots (the water potential of the roots is lower than the soil). Water accumulates in the plant creating slight root pressure. The root pressure forces some water out through leaves
What is adhesion? Give an example of where adhesion occurs.
What is cohesion? Give an example of a molecules with a high cohesive force.
The attractive force between water molecules and other polar substances,
Between water and cellulose molecules in the xylem cell wall
Cohesion is the attractive force between molecules of the same substance
Water has an unusually high cohesive force due to hydrogen bonds
Describe how transport works in the phloem.
Sap flows from source to sink, the build up of pressure at the source and the reduction of pressure at the sink causes sap to flow from source to sink
Loading of sugar into the sieve tube at the source reduces the water potential in the sieve tube causing the tube to take up water by osmosis
This uptake of water generates a positive pressure that forces the sap to flow along the tube
The pressure is relieved by the unloading of sugar and the consequent loss of water at the sink
List some of the adaptions of leaves:
Climbing/support - tendrils
Storage - e.g. Onion
Storage of water - crassulaceae
Protection - cactae
Reproduction - ponsetta (attract pollinators), mother of thousands (kalanchoe daigremontiana)
Feeding - Venus fly trap, pitcher plants, sundew
What are the traits of angiosperms?
Flowers
Double fertilisation
Fruits
Define:
- hypogenous
- perigynous
- epigenous
Below gynaecium, ovary superior, above other parts, sepals, petals stamens attached below ovary e.g. buttercup
Superior ovary, petals sepals and stamens attached below ovary but fused to form cup-shaped hypathium, typical in roses e.g. wild rose
Inferior ovary, below other parts, sepals, petals and stamen attached above ovary e.g. honeysuckle
What is the microsporangium in the anther?
The pollen sac
What are the four types of pollination?
Wind - 20%, scent/less colourless, lots of pollen produced, reduced/absent petals, examples, catkins, hazel
Insects - 65%, bees most common, nectar, showy petals, scent, colour, UV markers for bees dandelion, carrion flower for flies
Birds - showy petals, often fused to form bent floral tube to fit curved beak of bird, bright colour, nectar, scentless e.g. Columbine flower
Mammals - bats, scent, lots of pollen (bats lap nectar with tongue), light colour, nocturnal pollinators e.g. organ pipe cactus and bats
How many megaspores are produced in the ovary?
How many survive?
4
1
In plants the diploid zygote unevenly divides into what?
A larger basal cell divides to produce suspensor (hold embryo in place and provide nutrients)
A smaller apical cell divides to produce embryo
What does anticlinal division do?
What does peri-clinal division do?
Expands the cell layer
Puts another cell layer on top
What is epigenous germination?
What is hypogeous germination?
Cotyledons emerge above soil
Cotelydons remain below soil
What activates expansins in cell growth?
What do expansins do?
Auxins activate proton pumps which cause acidification of the cell wall.
Break cross links between cellulose microfibrils loosening the cell wall fabric
What is the triple response?
Response to mechanical pressure, ethylene produced, slows stem elongationp, stem curves to avoid obstacle
Name and describe the actions of the plant hormones other than auxins.
Cytokinins - synthesised in root, stimulate growth and development, work with auxins to regulate morphogensis
Gibberellins - discovered in fungi, produced in young roots and leaves, cause stem elongation, loosen cell wall allowing expansin in, together with auxins promote fruit development (seedless grapes), causes germination
Ethylene - Stress hormone, fruit ripening, produced in response to auxins, triple response, senescence (dying of whole plant), abscission leaf fall change in balance between auxin and ethylene, fruit ripening burst of ethylene cause breakdown
Abscisic acid - slows growth, drought resistance stomata close, seed dormancy
Brassinosteroids - similar to auxins, cell division, seed germination pollen tube formation
Strigolactones - produced in roots, response to low phosphate, seed germination, attract micorrhizal fungi
Provide details of two plant responses to light.
Germination, red light, photo homes, Pfr is active form, ratio of Pfr to Pr increases in sunlight trigger germination, production of amylase developmental genes
Shade avoidance, chlorophyll absorbs red light so more far red reaches forest floor, in shade Pr predominant, causes growth in height
In light Pfr dominant causes branching, mediated by regulation of gene expression
Give an two causes of chlorosis (yellowing of the leaves).
Magnesium deficiency - Mg needed as a component for chlorophyll
Iron deficiency - iron ions required as a cofactor in an enzymatic step of chlorophyll synthesis
Describe the three distinct layers of soil.
A horizon (topsoil) - most active part, zone of physical chemical and biological activity, living organisms, decaying matter (bacteria, protisits, fungi, invertebrates, decomposers)
B horizon (subsoil) - region of deposition, materials leech down, less organic material and weathering than A
C horizon (soil base) - made of partially broken down, rock, where true soil forms from
What are loams?
Soil ideal for growing with equal amounts of sand silt and clay
What are the usable forms of nitrogen for plants?
Ammonium ions (NH4+) and nitrate ions (NO3-)
Describe the development of a root nodule.
- Roots emit chemical signals that attract Rhizobium bacteria, the bacteria emit signals that stimulate the root hairs to elongate forming an infection thread
- The infection thread containing the bacteria penetrates the root cortex, cells of the cortex divide and bacteria form bacteriods in the cells
- Cortex and pericycle fuse to become nodule
- Nodule develops vascular tissue that transports nutrients and nitrogenous compounds from nodule
- Nodule may grow bigger than root, layer of sclernchyma forms which reduces oxygen absorption and maintains anaerobic environment
Describe ectomycorrhizae.
Describe arbuscularmycorrhizae.
The mantle of the fungal mycelium ensheathes the root, hyphae extend into intracellular spaces
Fungal hyphae extend into the root, provide large SA for nutrient swapping, hyphae penetrate cell wall
Describe ways farmers can increase productivity.
Correct irrigation - drip irrigation, less water waste, less salty soil
Fertilisation - agriculture disrupts balance, food eaten and excreted far away, soil becomes depleted, fertilisers enriched in N-P-K, risk leeching
Windbreaks and ground cover, stop dust bowls, no till agriculture
Contamination, metals, bad pesticides, solution GM, less pesticides
What wavelength is visible light between?
380 - 750nm
What is a plants first line of immune defence?
What happens when this is activated?
PAMP-triggered immunity (pathogen associated molecular patterns)
PAMP recognition leads to a chain of signalling events that lead ultimately to the local production of broad spectrum antimicrobials
What is a plants second line of defence?
The hypersensitive response - local cell and tissue death that occurs at and near the infection site, part of effector triggered immunity
Describe some chemical defences of plants.
Pathogenesis-related proteins (PR proteins), synthesis of secondary metabolite, anti fungal, antibacterial, protein synthesis inhibitors, generate ROS, alter intracellular signalling
Peptides - ricin, endosperm of castor beans, cleaves A from 28S ribosomal rRNA
Give some examples of secondary plant metabolites.
Caffeine - alkaloid, leaves of tea, beans of coffee, antagonist of brain adenosine receptors, targets enzymes involved in signal transduction, paralyses insect herbivores, enhances honey bee reward memory, coffee inhibit germination, stimulant
Nicotine - tobacco, kills insect herbivores, agonist of post synaptic nicotine receptors in the brain, triggers release of various chemical messengers, stimulant, relaxant, addictive, insecticide and honey bees
Quinine - synthesised from tryptophan, malaria, affects DNA replication, prevents haem detox, antipyretic plant use unknown
Digitoxin and digitonin - found in foxgloves, cardiac glycoside, heart medicine, inhibits Na/K ATPase, leads to Ca increase stronger heart contraction, overstimulation toxic
What is systemin? What does it do?
Involved in inducible plant defense, 18aa peptide, release at wound, travels through apoplast and pholem, causes linolenic acid release from PM, converted to jasmonic acid which activates an ubiquitin ligase, degradation of transcription repressor»_space; activation of defence genes
What is the principle of competitive exclusion?
That two species cannot exist in the same ecological niche
What is a niche?
Odum -“if the habitat is the ‘address’ then the niche is the ‘profession’”
Sum of a species biotic and abiotic resources in its environment
How are the Cairo spiny mouse and Golden spiny mouse able to live side by side?
Live in the same area but don’t come into contact. CSM is nocturnal, whereas the GSM is diurnal, lab research has shown GSM is naturally nocturnal so it overrides its biological clock in the presence of CSM
What is character displacement?
How do Darwin’s finches show character displacement?
Differences among similar species whose distributions overlap geographically that are accentuated where species co-occur but minimised where the distributions do not overlap. Indirect evidence of past competition
Small and medium ground finches. When found together the SGF has a shallower smaller beak and the MGF a deeper larger beak.
When on separate islands they have similar beak morphologies.
Beak sizes favour eating different sized seeds
What adaption do cabbage butterflies have against mustard oils?
What adaption do monarch butterflies have against milkweed?
Evolved the ability to detoxify mustard oils, no competition, exploited niche
Caterpillars feed on milkweed, sequester cardiac glycosides in fat bodies, gives butterfly foul taste, protection
Give examples of animals that employ Batseian mimicry.
Give examples of animals that employ Müllerian mimicry.
Hawkmoth larva and green parrot snake
King snake (mimic) and coral snake
Hoverfly (mimic) and honeybee
Viceroy butterfly (mimic) and monarch butterfly
Cuckoo been and yellow jacket wasp
Poison frog species
Give examples of different types of parasite.
Ectoparasite - lives on host e.g. plant parasites and ticks, leeches, lampreys, parasitoids (lay eggs on host)
Endoparasite - Platyhelminthes (tapeworms), nematodes (t. Spiralis and w. Bancrofti causes elphantitis), fungi, malaria
Give some examples of mutualism.
Pollinators and plants
Aphids and ant farming
Acacias and ants (breaks down ants enzyme that allows ants to break down sucrose, really mutualism?)
Lichens (fungi and Cyanobacteria)
Plants and mycorrhiza (arbuscular and ecto)
Legumes and rhizobium
Leaf cutter ants and fungi (take leaves home to their fungi, ant larvae eat fungus, fungus lives nowhere else, larvae depend on fungus)
Mutualistic gut microbes
Give examples of commensalism.
Epiphytes e.g. staghorn ferns, bromeliads, orchids
Egrets and buffalo (can be all three though)
What is the Lincoln-Peterson index?
Population size = (animals marked and released X total samples size on second day)/ recaptured
How can you tell dispersion type from sample variance?
S2/X 1 is clumped
Give examples of different kinds of root.
Prop roots - e.g. the arial adventitious roots of maize
Storage roots - e.g. common beet
Pnematophores - air roots, e.g. mangroves, obtain oxygen which thick waterlogged mud lacks
Strangling arial roots
Give examples of different kinds of stem.
Rhizomes - horizontal shoots that grow just below the surface e.g. iris
Stolons - e.g. strawberry plant, horizontal shoots that grow along the surface, enable plant to reproduce asexually as plantlets form at nodes along each runner
Tubers - the enlarged ends of rhizomes or stolons, for storage e.g. potatoes
What types of sieve elements are found in gymnosperms?
What types are found in angiosperms?
Sieve cells - long narrow cells
Sieve-tube elements
How many petals do monocots usually have?
How many petals do dicots usually have?
Multiples of three
Multiples of four or five
In flower inflorescences what is a:
- cyme
- umbel
Influorescent in which the topmost or outermost flower opens first
Flowers that radiate from a point
Describe the four classes of fruit.
Simple fruit e.g. pea, develops from single carpel
Aggregate fruit e.g. raspberry, develops from many separate carpels,
Multiple fruit e.g. pineapple develops from many carpels of the many flowers that form an inflourescent
Accessory fruit e.g. apples, develops largely from tissues other than the ovary
Describe the discoveries that led to the understanding of photosynthesis.
Aristotle - plants eat soil!
Helmot - no they don’t they ‘eat’ water
Priestly - mean to mice, living mint restores air
Inglehouse - restoration requires green leaves and sunlight
Blackman - two stages to photosynthesis
Niel - in plants water not CO2 split
Robin Hill - isolated chloroplasts can generate oxygen
Kamen - used 18O to prove water is split and is the electron doner
Melvin Calvin - Calvin cycle
Overview the Calvin cycle.
RuBP is converted to a 6C compound then 3-phosphoglycerate (rubisco)
ATP phosphorylates 3PG and NADPH reduces it reducing the carboxyl group to an aldehyde. Makes glyceraldehyde-3-phosphate
6 G3P made, one makes glucose 5 reform
5X3 > 3X5
3+3 = 6, 6+3=9 unstable > 4+5
4+3=7, 7+3=10 unstable > 5+5
5C sugars converted to Ru5P then 3ATP used to regenerate RuBP
In the Calvin cycle what happens when there is not enough CO2?
Rubisco is an oxygenase so can react with oxygen
RuBP is split into a toxic 2C compound, passed to the peroxisomes and mitochondria to detox, releases CO2
Photorespiration uses ATP but makes not sugar and is wasteful
Thought to be an evolutionary relic, no oxygen in early environment
What are the three meristems present in the early plant embryo?
The protoderma - produces the epidermis
The procambium - will form vascular tissue
Ground meristem - forms ground tissue (parenchyma)
At what point in plant embryo development to shoot and root apical meristems form?
Torpedo stage
What makes up the carpel?
What makes up the stamen?
Stigma, style and ovary
Anther and filament
What is epigeous germination?
What is hypogeous germination?
Cotelydons emerge above ground, a hook forms in the hypocotyl which straightens in response to light
Cotelydons remain below ground, coeloptile pushes through the soil and forms a tunnel the shoot tip grows through
What is the first thing to emerge from a germinating seed?
Radicle (embryonic root)
What is bark?
Cork layer plus secondary phloem
