Plant responses Flashcards
how can plants respond to changes in their environment
- produce chemicals and hormones
how can plants respond to changes to herbivory
- alkaloids
- tannins
- alarm pheromones
- fold upw
what are alkaloids
- chemicals with bitter tastes, noxious smells
- deter or kill herbivores
what are tannins
- taste bitter
- bind to proteins in the gut making the plant hard to digest
what are alarm pheromones
- cause nearby plants to detect chemicals and can make chemical defences
how can some plants fold up
- mimosa pudicana
- knock off small insects
- scare off animals
what is the abiotic response
- carrots can produce antifreeze proteins at low temperatures
- proteins bind to ice crystals and lower the temperature that water freezes at
- prevents more ice crystals forming
what is a tropism
response of a plant to a directional stimulus
what is phototropism
- growth of a plant in response to light
- shoots = positively phototrophic
- roots = negatively phototrophic
what is geotropism
- growth of a plant in response to gravity
- shoots = negatively geotropic
- roots = positively geotropic
what is hydrotropism
- plant growth in response to water
what is thigmotropism
- plant growth in response to contact with an object
what is thermotropism
- plant growth in response to temperature
what are growth hormones
- produced in growing regions of the plant and move to where they are needed in the plant
- gibberellins = stimulate seed germination, stem elongation, side shoot formation
- auxins = shoot growth, cell elongation
- high concentrations of auxin inhibits root growth
what is indoleacetic acid
- type of auxin
- stimulates cell elongation
- moved around the plant to control tropisms
- moves by active transport and diffusion over short distances and phloem for long distances
- uneven distribution of IAA means uneven growth
how does indoleacetic acid control tropisms
Phototropism
- IAA moves to shaded parts of shoots and roots = uneven growth
Geotropism
- IAA moves to the underside of shoots and roots = uneven growth
how are auxins involved in apical dominance
- auxins stimulate the growth of apical bud
- auxins inhibit growth from lateral buds
- apical dominance = apical bud is dominant over lateral buds
- prevents side shoots from growing
- can grow tall faster as it has more energy
- remove apical buds no auxin is produced and side shoots grow
- replace tip with a source of auxin and side shoot development is inhibited
- auxin becomes less concentrated the further away from the apical bud
what are gibberellins
- produced in young leaves and seeds
- stimulate seed germination, stem elongation, side shoot formation, flowering
how do gibberellins stimulate seed germination
- triggers breakdown of starch into glucose in the seed
- plant embryo in the seed can use the glucose to respire and release energy to grow
- inhibited by abscisic acid
how do auxins inhibit leaf loss
- auxins are produced by young leaves
- as leaf gets older less auxin is produced
- more leaf loss
how does ethene stimulate leaf loss
- ethene produced by ageing leaves
- older leaf = more ethene produced
- abscission layer develops at the bottom of the leaf stalk
- layer separates leaf from the plant
- ethene stimulates cells in layer to expand breaking the cell wall and leaves fall
how are hormones involved in stomatal closure
- abscisic acid triggers stomatal closure
- ABA binds to receptors on guard cell membranes
- ion channels open
- calcium ions enter cytosol from vacuole
- other ion channels open
- potassium ions leave the guard cells
- water potential of cell is raised
- water leaves the guard cells
- guard cells become flaccid and close
how does the fruit industry use plant hormones
- ethene stimulates enzymes that break down cell walls
- break down chlorophyll and convert starch into sugars
- fruit is soft and ripe
how are auxins commercially used by farmers
- used in herbicides
- auxins make weeds produce long stems instead of leaves
- weeds grow fast
