| what are undifferentiated cells in the meristem used for? | indeterminate growth |
| what do mitosis and cell division do? | proved cells with extension of stem and leave development in the shoot apex |
| What do plant hormones control? | growth in the shoot apex |
| What do auxin efflux pumps do? | set up conc gradients of auxin in plant tissue |
| what does auxin do? | influences the cell growth rates by changing the pattern of gene expression |
| What are meristems? (3) | tissues made up of undifferentiated cells = indeterminate growth
similar to totipotent stem cells
they have specific regions of growth and development |
| What is meristem tissue used for? (2) | regrow structures
form new plants (vegetative propagation) |
| What are the 2 types of meristems? | apical: shoot and root tips (primary growth) = plant lengthening
EG: leaves, flowers
lateral: cambium (Secondary growth) = plant widening
EG: bark |
| what processes lead to apical growth? | cell enlargement and repeated cell division (mitosis and cytokinesis) |
| How does growth take place in the lateral meristem? | in nodes = forms inactive axillary bud
can form new shoots |
| What is auxin? | a plant hormone that controls the stem growth and formation of new nodes
promotes growth in the shoot apex with cell elongation + division |
| What is apical dominance? (2) | auxin production prevents growth of lateral buds = plant uses its energy to grow up towards the light
as distance bw the terminal bud + axillary bud increase = inhibition of axillary bud by auxin reduces |
| How can we prevent apical dominance? (2) | pruning = remove apical bud
removing terminal bud allows the lateral buds to develop = bushier plants |
| What do auxin efflux pumps do? (3) | set up concentration gradients = changes distribution of auxin#
controls direction of plant growth = determines which regions have high auxin levels
changes position bec of fluidity |
| How does the mechanism of auxin differ in the roots and shoots? | shoots: stimulates cell elongation = high conc of auxin = promotes growth = larger cells
roots: inhibits cell elongation = high conc of auxin = limits growth - smaller cells |
| How can the difference between how auxin influences shoots and roots be explained? | auxin changes the pattern of gene expression = diff gene pathways are activated in each tissue |
| How does auxin promote plant growth in shoots? | + flexibility of cell wall = cell elongation
1) activates proton pump in membrane
2) H+ ions are secreted into cell wall
3) -PH = cellulose fibers loosen = breaks bonds
4)upregulates expression of expansins = + elasticity of cell wall
5) influx of water in vacuole = cell + in size |
| What is tropisms? | growth or turning movement of a plant in response to directional external stimulus |
| What are the two main types of tropism? | phototropism: growth movement in response to unidirectional light
geotropism: growth movement in response to gravity |
| How is phototropism controlled by the distribution of auxin? (3) | light receptors (phototropins) trigger redistribution of auxin to the dark side of the plant
dark side elongates and shoots grow towards light
lower side of shoot elongates and grows away from ground |
| How is geotropism controlled by the distribution of auxin? (3) | auxin build up on the lower side of the plant bec of gravity
high auxin concs inhibit cell elongation = dark side become shorter and roots grow away from light
roots turn downwards |
| What is micropropagation? | used to produce large number of clones from a stock plant
plants reproduce asexually from meristems |
| What are the two types of propagation? | vegetative propagation: plant cutting is used to reproduce asexually in native environment
micropropagation: plant tissues are cultures in a lab to reproduce asexually |
| What are the steps for micropropagation? (5) | 1) plant tissue from shoot apex is sterilised
2) tissue sample (explant) grown in sterile nutrient agar
3) explant is treated with growth hormones (Auxin) = shoot and root development
4) growing shoots = continuouslt divided and separated to form new samples
5) once root + shoot are developed = transferred to soil |
| What are the 3 main uses of micropropagation? | rapid bulking
virus-free strains
rare species |
| How can micropropagation be used for rapid bulking? | conserves fidelity of the characteristic
reliable than selective breeding bec plants are genetically identical
can make large quantities of plants via genetic mods |
| How can micropropagation be used for virus free strains? | plant viruses can ruin crops = famine
spreads through infected plants via vascular tissue
meristems dont contain V tissue
propagating non infected meristems = rapid production of virus free plants |
| How can micropropagation be used for rare species? | increases no of species that are difficult to breed sexually
EG: Orchids
increases no of plants that are in demand |
