9 plants (bioninja summary) Flashcards
the structure of a plant is related to…
its FUNCTIONS
eg Roots are highly branched, with a high SA:Vol ratio
(necessary for water and mineral uptake)
Leaf Tissue 2
- Palisade mesophyll – upper layer of tightly packed
cells that are rich in chloroplasts (⇧ light absorption) - Spongy mesophyll – lower layer of cells interspersed
by space and located near the stomata (⇧ gas exchange)
Root systems adaptation
extensive branching in order to maximise the available surface area for material uptake
Fibrous (adventitious) root systems
many branching roots that are thin and very spread out
- Tap root systems
deeply penetrating central root (for stability)
with many connected lateral branches
root hairs
small extentions on root epidermis (to further increase available surface area)
organisation of vascular bundles differ according to..
plant section (root vs stem) and plant type (monocot vs dicot)
vascular bundle distribution in roots
Vascular bundles are radially arranged within a big stele in monocots, but are centrally arranged within a small stele in dicots
vascular bundle distribution in stems
Vascular bundles are scattered haphazardly in monocots, but form a ring around a circular cambium in dicots
dicot root vs monocot root
dicot: ‘x’ in the middle (phloem), scattered xylem,
monocot: ring in the center, xylems outwards
dicot stem vs monocot stem
di: single ring lining inner wall
mono: scattered around, most around inner wall
what is transpiration + 3 basic steps
Transpiration is the loss of water vapor from a plant
* Active uptake of ions by roots promotes water uptake
* Water moves up the stem of a plant by mass flow
* Water is evaporated from leaves (via stomatal pores)
transpiration stream
flow of water from root to leaf
how and what do roots uptake 4
- Soil contains anionic clay particles to which minerals attach
- Roots pump H+ ions into the soil to displace the minerals
- Displaced minerals diffuse into root (indirect active transport)
- Water follows mineral ions into the root via osmosis
how does mass flow work
water moves up stem in xylem vessels
- Pressure is high in root (water in) and low in leaf (water out)
- The pressure differential results in the mass flow of water
what forces are part of capillary action?
- Cohesion (water molecules stick together by H-bonding)
- Adhesion (water molecules adhere to the xylem wall)
transpiration is a consequence of?
gas exchange in the leaf
how do guard cells manage transpiration rate
turgid – open (K+ ions pumped in, water moves in)
flaccid – closed (water moves out)
drawing of xylem structure
l spiral ll rings l l – l (sieve plates)
xylem has little gaps + little protrusions in the cell walls (pits)
water conservation adaptations Xerophytes (desert plants)
- Reduced leaves (lowers evaporative SA)
- Thick, waxy cuticles (reduces water loss from leaves)
- Stomata in pits with hairs (traps vapor = ⇩ evaporation)
- CAM physiology (only opens stomata at night)
water conservation adaptations Halophytes (salt water plants)
- Cellular sequestration (salt is stored within the vacuoles)
- Tissue partitioning (abscission of leaves containing salt)
- Salt excretion (salt is actively removal from the plant)
- Root level exclusion (roots avoid salt uptake)
modelling of water transport in xyelm 3 ways
- Capillary tubing (water moves along tubing via surface tension)
- Filter paper (absorbs water due to adhesive properties)
- Porous pots (semi-permeable containers can model osmosis)
transpiration measurement
potometers
* measure movement of air bubble
* More movement= incr transpiration rate
xylem vs phloem strcutre
Process
Transpiration // Translocation
Materials
Water, minerals // Organic nutrients
Transport
Unidirectional // Bidirectional
Composition
Vessel element and tracheid //
Sieve element and companion cell
Structure
Dead cells form a hollow tube //
Living cells form a tube with plates
Location
Inner or central region of bundle
// Outer region of vascular bundle
measurement of translocation rate
aphids feed on sap in phloem
radioactive co2 = radioactively labelled sugars
time taken for radioisotopes to be detected = rate of t
what are meristems
Meristems are undifferentiated cells in plants that are capable of indeterminate growth (analogous w totipotent stem cells)
- They have specific regions of growth or development and allow for regrowth and vegetative propagation
2 types of meristem tissue
Apical and Lateral
apical meristem
Occurs in shoots and roots and is responsible for primary growth (i.e. lengthening) and leaf development
lateral meristem
Occurs at the cambium and is responsible for secondary growth (i.e. widening) and the production of bark
what are auxins
plant hormones control growth in auxins (stimulate/inhibit cell div)
how are differentiated growth rates generated in plant tissue
Auxin efflux pumps can set up concentration gradients of auxin in plant tissues
where does auxin come from and what does it coordinate
released by the shoot apical meristem
coordinates both apical growth and directional growth (tropism)
how does auxin influence cell growth rates
by changing the pattern of gene expression within the plant tissue
apical dominance
Auxins promote growth in apex but inhibit growth in buds
how are axillary buds formed
growth occurs in sections (nodes), remaining meristem tissue forms inactive axillary buds – potential to form new shoots
what is a tropism
the turning of an organism in response to a
directional external stimulus (e.g. light = phototropism)
how do plant tropisms happen
the differential elongation of
plant cells (plant turns away from side with cell elongation)
role of auxin in tropisms in shoots and roots
- In plant shoots, auxin promotes cell elongation
- In plant roots, auxin inhibits cell elongation
what is micropropogation
technique used to produce large numbers of
identical plants (i.e. clones) from a selected stock plant
uses of micropropogation 3
- rapid bulking up of new plant varieties
- production of virus-free strains of existing varieties
- propagation of rare plant species
3 stages of sexual repro in flwoering plants
- Pollination – transfer of pollen from the anther to the stigma (usually between different plants)
- Fertilisation – fusion of the male gamete nuclei (in pollen) with the female gamete nuclei (in ovule)
- Seed Dispersal – fertilised ovule (seed) moves away from the parent plant to reduce the competition for growth
components of pistil
female
stigma
style
ovule
components of stamen
male
anther
filament
seed strcutre 5
little leaf = epicotyl
little stem/bulb = radicle
seed indent = microphyle
main body = cotyledon
opposide side of indent = testa
what is germination
the process by which a seed emerges from a
period of dormancy and sprouts (forming a new plant)
what is needed for germination 3
- Oxygen (to produce ATP via aerobic respiration)
- Water (to metabolically activate the cells)
- Suitable temperature and pH (for enzyme activity)
what is photoperiodism
The response of a plant to the length of day or night
controls flowering
2 forms of the phytochrome
- sunlight – Pr –> Pfr (fast)
- night – Pfr –> Pr (slow)
flowering requires…
a set length of uninterrupted darkness
long day plants
- Pfr activates flowering
- Flowering induced when night length is SHORT (⇧ Pfr)
short day plants
- Pfr inhibits flowering
- Flowering INDUCED when night length is long (⇩ Pfr)
