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level: 9.3 Plant Growth

Questions and Answers List

level questions: 9.3 Plant Growth

QuestionAnswer
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