Please enable JavaScript.
Coggle requires JavaScript to display documents.
Unit 9 plant - Coggle Diagram
Unit 9 plant
9.1 xylem transport
transpiraton: the loss of water vapor from a plant
light energy converts water in the leaves into vapour
evaporates from the leaves via stomata
new water is absorbed from the soil by the roots
creates a difference in pressure between the leaves(low) and roots(high)
water flow via the xylem among the pressure gradient to replace the water loss
Transpiration stream: the flow of water from root to leaf
Xylem structure:
tube composed of dead cells that are hollow
allow free water movement
numberous pores
water transferred between cells
walls have thickened cellose + reinforce by ligin spiral
transport under tension
Root uptake (ex Na, K, Po4)
root cell contain protein pumps
expel H+ ions into the soil
H+ ions displace positively charged mineral ions
These displaced mineral diffuse into the root along a gradient
Water uptake
water will follow the mineral ions into the root = osmosis
regulated by specialised water channel
water can move through Cytoplasm (symplastic) or Cell wall (apoplastic)
root uptake
absorbed by root epidermis
diffuse across cortex
pumoed into xylem
Capillary action
Cohesion: water molecules stick tgt by H bonding
Adhesion: water molecules adhere to the xylem wall
Water conservation
Xerophytes(desert plants)
reduced leaves
lowers evaporative surface ares
thick waxy cuticles
reduced water loss from leaves
stomata in pits with hairs
traps vapor
CAM physiology
only opens stomata at night
Halophytes(salt water plants)
cellular sequestration
salt is stored within the vacuoles
tissue partioning
concerntrate salts in particular leaf then drop off
salf excretion
salf is actively removal from the plant
root level exclusion
roots avoid salt uptake
evaporation
water lost from leaves by converting to vapour and diffuse from the stomata
light eneregy absorbed by leaves converted to heat
evaporate water via stomata
vapour diffuses creastes a negative pressure gradient
negative concern grad creates as a tension force
draw water from the xylem (transpiration pull)
water is pulled from the cylem
due to the adhesive attraction
9.2 Pholem transport
Active translocation: plants transport organic molecules from source to sink
Source: photosynthetic tissues (leaves)
Sink: storage organs (fruits, seeds, roots)
pholem structure: consists of two main types of cells
Sieve element:
form sieve tube
connected by sieve plates = porous to enable flow
no nuclei = maximise space for translocation of materials
thick rigid cell walls = withstand the hydrolastic pressure
Companion cells:
metabolic support for sieve - facilitates the loading and unloading of aterials
posses infolding plasms membrane = increases SA: Vol ration
-many mitochondria = fuel the active transport
parenchyma cells:
fill spaces + support
phlorm loading:
organic compouns produced at the source loaded into the pholem sieve tubes by companion cell
materials pumped across cell wall by membrane proteins =active transport
H+ transported out pholem cells by protein pump
concerntrated H+ builds up outside of the cell and create a proton gradient
H+ diffuse back into phloem cell with sucrose
Mass flow
Mass flow (source)
active transport solute loads into the phloem by companion cells making the solute hypertonic
water drawn from xylem (osmosis)
build of water in the pholem causes hydrotastic pressure to increase
increase of pressure causes pholem sap moves to lower pressure
transports colutes away from the source
Mass flow (sink)
loaded solute cause sap solution become hypotonic
water is drwn out the phloem and back into the cylem
=to ensure the hydrolastic pressure always lower than source
=alawys move from the source towards the sink
Xylem versus Phloem
xylem
composed of perforated inner layer of dead cells that are fused into a continuous tube
the cell walls have thickened cellulose are reinforced with lignin (spiral)
Phloem:
composed of living cells connected by porous plates at their transverse ends(sieve elements)
are supported by companion cells that are connected via plasmidesmasta to mediate material change
Translocation rate:
measured using ahpid stylets
aphids are insects that feed on the sap in phloem via protruding mouthpiece called a stylet
if the stylet is cutted the sap will continut to flow from the plant and can be collected and measured
-plants exposed to radioactive carbon dioside will produce radioactivey labelled sugars within the phloem
the rate of translocaiton can be identified bt the time taken for radioisotopes to be detected along the phloem
9.4 plant reproduction
flowering plants: flowers are the reproductive organs of certain types of plant
pollination: transfer of pollen(male) to an ova(female)
pollianation
transfer of pollen grains from anther(male) to stigma(female)
many plants posses both male + female structures=self-pollinate
fertilisation
male gamete nuclei + female gamete nuclei=zygote
male gamte stored in pollen grain
female gamete stored in ovule
seed dispersal
fertilisation of gametes form seed and move away from the parental plant = reduces competition
seed dispersal mechanisms: 1. wind 2. water 3. fruites 4. animals
Cross pollination: transferring pollen grains from one plant to the ovule of a diff plant
pollinators=animals
mutualistic relationship with flowring plant
flowering plant=sexual reproduction
animal- source of butrition
plants secrete nectar to attract
eg birds bats insects
flower structure: develop from the shoot apex
change in gene expression trigger enlargement of the shoot meristem
tissue differentiates=form flower structures eg sepals, petalsm stamen, pistil
stamen: male part of the flower
anther: pollen(male gamete) producing organ
filament: slender stalk supporing the anther + makes anther accessible to polliators
pistil: female part of the flower
ovule: contains female reproductive cells + develop into a seed after fertilisation
stlye: elevates stigma to catch pollen
stigma: sticky + receptive tip of the pistil + catching pollen
support structures
petals: attract pollinators
sepal: protects the flower in the bud
peduncle: stalk of the flower
photoperiodism: response of a plant to the length of day or night
phystochromes: leaf pigments used by plant to detec periods of light+ srakness
Active far red form (Pfr) absorcs far red light to become Pr
inactive ref form(Pr) absorbs red light to become Pfr
Sunlight contains more red light:
the active far red form is predominant during the day
reverts to mainly the inactive red form at night
Short day plants: Pfr inhibits flowering in short day plants + flowering induced when night length is long
ex violet / crysanthemums
long day plants: Pfr activates flowering in long day plants + lowering incuduced when night length is short
carnation / iris
seed structure
cotyledon: contains the food stores for the seed + forms the embruonci leaves
epicotyle: the embryonic shoot
micropyle: allows for the passage of water
radicle: the embryonic root
testa: protects the embryonic plants
germination: process by which a seed emerges frpm a period of dormancy and sprouts
oxygen=aerobic respiration
water: metabolically activates the seed
temperature: require certain temp to sprout (for enzyme)
pH" suitable soil pH in order to sprout (for enzyme)
9.3 Plant growth
sections called nodes (inactive axillary bud)
Meristems:
undifferentiated cells in plants that are capable of indeterminate growth
have specific regions of growth
Lateral meristems:
occurs at the cambium =secondary growth(widening)
ex bark
Apical meristems:
occurs in shoot + root tips =primary growth (length )
ex. leaves + flower
Auxin
a group of plant hormones
control in the shoot apex by stimulating or ihibiting cell division
auxin efflux pumps can set up concerntration gradients of aucin in plant tussues to allow for differentiated growth rates - released by the shoot apical meristem =coordinates both apical and directional growth
influences cell growth rates by changing the pattern of gene expression within the plant tissue
apical growth:
auxillary buds have the potential to form new shoots
auxin promotes growth in apec but inhibit growth in lateral buds(=aka apical dominance)
=ensure plant will grow up
Root:
auxin inhibits cell growth
lower cell layer is shorter =turn down from light
Stems
auxin stimulates cell growth
lower cell layer is longer
turns up to the light
Tropisms: movement of a plant response to a directional external stimulus
phototropism=response to light
light receptor trigger the redistributioin of auzin to tehe dark side of the plant
geotropism=responce to gravitational forces
controlled by the distribution of auxin
auxin accumulate on the lower side of plant
Micropropagation: plant tissues are reproduce in laboratory asexually
used fofr the rapid buling up of new plant variaties(gene modification)
the production of virus free stains of existing varieties
the propagation of rare plant species
specifc plant tissue is selected and sterilised
tissus sample is grown in an agar gel
plant trated with hormone (ausin) to stimulate shoot + root developement
growing shoots can be devided and seperated to form new samples
Plant structure
Roots: highly branches with a high SA: Vol ration
water and mineral uptake
root tissue
fibrous root systems: contain many branching roots
thin+spread out
Tap root systems: deeply penetrating central root
with many connected lateral branched
Root epidermis: have many small extensions aka root hairs
Stems: transfer essential materials in vascular bundles
transpiration of water
translocation of nutrients
vascular bundles: pholem+xylem
Roots
Monocots: vascular bundle are radially arranged within a big stele
Dicots: arranged within a small stele
Stems
Monocots: scattered haphazardly
Dicots: form a ring around
Leaves: contain chloroplasts and stomal pores
photosynthesis
gas exchange
(sugars)
leaf tissue
Palisade mesophyll: upper layer of tightly packed cells that are rich in choloroplasts
light absoroption
Spongy mesophyll: lower layer of cells intersperesed by space and located near the stomata
gas exchange
Stomata
pores on the underside of the leaf
facilitate gas exchange
guard cells control the opening by becoming increasingly flaccid
When a plant wilt
dehydrated mysiphyll cells release hormone abscidic acid
abscidic acid trigger potassium from guard cells = decrease water presuure = become flaccid (loss tugor)=stomata pores close
Factors affect stomata
humidity
temperature
light intensity
wind