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(Plants (week 11)) - Coggle Diagram
Plants (week 11)
Plant-Animal Interactions
Types of Interactions
mutualistic (+/+)
ants and
Acacia
(ants serve as bodyguards, clear out nearby plants)
edible seeds eaten (and defecated) by animals
pollination (plants get pollinated, animals get nectar)
commensal (+/0)
animals
bird nesting, shelter
plants
seed hitch-hiking on animals (esp. fur ones)
antagonistic (+/-)
animals
direct consumption of plant for food
plants
carnivorous plants, bee orchid (trick bees by visual/chemical mimicry (female pheromone) into mating with flower
Relationship to pollinator
pollination
pollen (male gamete) is transferred to female reproductive organ of plant -> fertilisation
gymnosperms rely on abiotic dispersal e.g. wind (affected by chance and high % of loss)
angiosperms rely on animals to transfer pollen from anther of 1 flower to stimga of other flower
animal pollinators
65% of flowering plants use insects e.g. bees, flies, moths, butterflies
bees
attracted to bright colours (yellow, blue)
80% of commercial crops pollinated by bees
see UV radiation -> many flowers have UV markings/nectar guides
honey
foraging bee stores nectar in special stomach
returns to hives and passes by mouth to indoor bee
stored into specialised storage cells (honeycomb)
moisture content decreased by wind fanning/evaporation
once thickened, honey capped with beeswax
pollen mixed in to make bee bread, fed to larvae
CCD (colony collapse disorder)
since mid-200s
neonicotinoid insecticides
chemical stress, reduce reproduction and life span
parasites more likely to affect stressed individuals
colonies with inexperienced young males less likely to thrive
flies
flowers-reddish, fleshy, odour like rotten meat
flies lay eggs which day after they hatch due to no food
limited benefit for flies (flies may harvest chemical scents, which are used for male pheromone reproduction)
moths and butterflies
detect odours
flowers-sweet fragrance and colourful (white, yellow)
other pollinators are birds, mammals
birds
low sense of smell
flowers- large, bright red/yellow, little odour
flowers product highly sugary nectar (to meet energy requirements of birds)
mammals
bats, non-flying mammals
flowers- light-coloured, aromatic to attract nocturnal pollinators
reward is
nectar
specialised sugar-rich liquid produced in nectarines (specialised glands)
floral nectarines
produced in flowers to reward pollinators
extrafloral nectarines
produced elsewhere (e.g.base of leaves) to reward bodyguards (e.g. ants, wasps)
Co-evolution
natural selection favours deviation in floral structure that increase likelihood of pollination by pollinator
large diversity in insects is linked to large diversity in floral morphology and physiology of angiosperms
e.g. Madagascar orchid and hawk moth
Plant Defences
Threats
herbivorous animals
parasitic fungi
bacteria
viruses
Types of Defences
Chemical
plants produce toxic chemicals/poisons
nicotine (toxic to insects)
Digoxin (used for heart med)
toxic alkaaloids (morphine, strychnine, coniine (hemlcok))
phytoecdysteroids
chemicals that mimic moulting hormones
interfere with insect moulting
clover disease
chemicals in clover mimic phytoestrogen
potent animal female hormone
causes infertility in sheep
volatile alarm chemicals
released when injured
alert nearby plants of danger
attract carnivorous insects (bodyguards)
attract insectivorous birds
attract ants
to serve as standing army against herbivores
by providing food
Biological
biological warfare
silencing RNA
silence RNA of pathogens using small interfering RNA molecules
target genes for growth/development and survival
holds potential for crop protection
Immune System
2 types
Effector-triggered immunity
some bacteria have effectors (chemicals) to suppress PAMP response
hypersensitive response
kills plant tissue at site of infection
systematic acquired resistance (call to arms)
infection site produces
alarm chemical
(salicylic acid from methyl salicylate), which induces plant wide expression of
defense genes
PAMP-triggered immunity
"pathogen associated molecular pattern"
based on detection of non-plant molecules
plant detects alien molecule -> produce broad-spectrum antimicrobial chemicals with fungicidal/bactericidal properties
Behavioural responses
wild tobacco
mimicry
appear to have eggs (dissuading egg laying insects)
mimic carnivorous insect
appear partially eaten
look uninviting
response to herbivory
releases nicotine (neurotoxicant) when fed upon
some caterpillars immune
plant releases volatile chemical messenger attracting insect mercenaries that eat caterpillars
evil lollipop
sugar attracts caterpillars, which causes them to smell, attracting predators
to many caterpillars still
change flowering time
bloom during the day instead of at night
Physical
first line of defense
macroscopic level
waxy cuticle
epidermis
periderm
large spines or thorns
large herbivores
fine hair spine ("trichomes")
herbivorous insects
some trichomes produce toxic chemicals cocktails (e.g. azadirachtin, pyrethrum)
barriers can be breached (damage from grazing herbivores)
microbes can also gain entry at open stomata
microscopic level
tough cells (plant cell wall, sclerenchyma cells)
difficult to eat
silica used to create "plant stones" ("plytoliths")
really difficult to eat (reduces growth rate of herbivorous insects, abrades teeth)
Plant Behaviour
Behaviour (definition)
Examples
Plants
Detection of
photoreceptors (detect light)
mechanical stimulation (wind, herbivory, physical environment e.g. support structures)
physical environment (gravity, temperature, soil water salt, CO2)
gravity
shoots grow upwards, roots grow downwards even int eh absence of light because plants can detect gravity
statoliths
1 more item...
chemical receptors (nutrients, scents e.g. dodder vine can detect tomato smell)
respond with growth
moves in response to environmental information
stem and leaves towards the sun
foraging roots towards nutrients in the ground
root elongation slows down and root hairs spread out in areas of high nutrients
slow, so we generally don't see it but slow down
Animals
respond with movements
reactions are faster
the way that an organism responds to an external stimulus
Plant Hormones
regulate virtually all aspects of growth and development
plant hormones can have different effects in different tissues and the development stage of the plant
multiple hormones often interact to control growth and development
Signal transduction
reception
transduction
Response
Examples
Auxin
chemical messenger produced mainly by shoot, involved in
cell elongation (increases cell size)
stem elongation
enhances apical dominance
formation of lateral and adventitious roots
regulates development of fruit
phototropism (response to light)
gravitropism (response to gravity)
synthetic auxins
useful in vegetative propagation of plants by cutting (stimulates formation of adventitious roots)
monocots can rapidly degrade auxins but eudicots cannot (application of synthetic auxins (e.g. herbicide 2, 4D) kills eudicots by hormonal overdose)
Cytokinins
chemical messenger produced mainly in roots
cell division (thus works in concert with auxin for elongation)
antagonises the apical dominance action of auxin
Giberellins
involved in stem elongation
with auxin, involved in fruit development
use synthetic gibberellin sprays to make fruit bigger
when combined with water, triggers seed germination
Ethylene (gas)
tip of growing seedling meets obstacle, ethylene is produced "triple response" (enables the shoot avoid obstacle)
slows stem elongation
thickens/strengthens stem
curvature (causes the stem to grow horizontally)
responsible for
lead abscission (loss of leaves from deciduous trees)
fruit ripening (initiates enzymatic breakdown of cell wall and conversion of acids and starches to sugars to make the fruit sweet attract animals
commonly used in commercial fruit production
senescence (programmed cell death)
All living organisms must be able to
organise biological molecules on higher level
access and use energy
grow
reproduce
respond to environment
Response to Light
light
important factor for photosynthesis
triggers key events in plant development/photomorphogenesis
allows plants to measure the passage of days/seasons
plants use changing of day length (
photoperiod
) over a year to adapt to different seasons
e.g. to avoid producing leaves in winter (for deciduous trees)
photoperiod is critical for determining when
flowering
occurs
ensure flowers are produced when the right pollinators are present
long-day plants
spinach, lettuce, irises
flower only when photoperiod is more than 14h i.e. spring/summer
short-day plants
chrysanthenums, soybeans
flower only when the photoperiod is less than a specific number of hours i.e. in autumn/winter
measure is highly accurate
controlled by length of darkness rather than day length
plants detect
presence/absence of light
direction
intensity
wavelength (particularly red and blue)
blue light receptors
blue light initiates range of responses
phototropism
(growth towards light)
light-induced
opening of stomata
light-induced slowing of elongation of juvenile shoot (
hypocotyl
) after is breaks ground
red light receptors
red light measures light quality and competition
far red
(740nm
NOT absorbed
by overhanging leaves) to
red
(660nm
absorbed
by overhanging leaves)
phytochrome change shape depending on the presence of red, far red or no light
responses to red light
seed germination
seeds have limited food reserves, many seeds germinate only if light environment and other conditions are optimal e.g. death of a shading tree
shade avoidance
stimulates branching, inhibits vertical growth
setting of
internal clock
biological clocks
4 more items...
flowering
environmental stresses
biotic
living e.g. herbivores
abiotic
non-living e.g. water, temperature
water stress
drought
water needed for photosynthesis
water deficit
stomata closes
1 more item...
other responses include
grass roll into tubelike shape to reduce exposure to dry air
shed leaves
consequences of response
reduced photosythesis
enables plant to survive
flooding
flooded soils have no air space
less O2 available for cell resp.
adapted specialised aerial roots (e.g. mangroves)
some produce ethylene in response to flooding, which kills some cells in the root cortex, creating an air tube (=snorkel)
salt stresses
2 salt impacts
excess soil sodium decreases water potential of the soil, thus causing a deficit in net movement of water to the plant
sodium is toxic to plants at high concentrations
some plants can produce organic compounds to counteract these negative effects (to a certain extent)
temperature stresses
heat
heat denatures proteins
transpiration cools down plants (via evaporative cooling)
plants close stomata in dry conditions to stop cooling -> synthesize heat-shock proteins which acts as scaffolds around proteins to help maintain their shape
cold
plants in cold climates also secrete extra sugar to protects against frost
decreases membrane fluidity, alternating transport across the cell membrane -> plants increase proportion of
unsaturated fat
in membrane when exposed to low temps (which helps maintain fluidity)
mechanical stimulation
plants respond to touch
plants that are touched grow more slowly
vines coil rapidly around support, to climb upwards towards a forest canopy
most plant responses are mediated by
hormones
(chemical messengers of the endocrine system), but a few are similar to an action potential in the nervous system e.g. rapid leaf folding in response to touch in
Mimosa pudica
Plant Intelligence
define intelligence
"sensory perception, information processing, learning, memory, choice, optimisation of resource sequestration with minimal outlay, self-recognition, and foresight by predictive modellling"
"a capacity for problem solving in recurrent and novel situations"
plants may not have a brain, but they exhibit behaviour, and even intelligence
plants communicate actively with other lifeforms
other plants
competition
push and shove towards sun
release toxins and conduct chemical warfare underground
compete for sunlight and nutrients
collaborate
reduce root growth when near siblings to reduce competition
in forests, trees connected underground by huge mycorrhizal network
trees can share carbon with fungi and each other
recognise relatives (via chemical signatures)
animals (e.g. plants attacked by herbivorous insects release "help" chemicals that attract carnivorous insects)