9 — plant biology Flashcards
describe the transport of carbon compounds such as sucrose and amino acids in phloem (7)
- translocation in phloem sieve tubes
- flow of sap through pores in end walls
- sugar/ amino acids are transported dissolved in water
- loaded into phloem through companion cells by active transport
- proteins pumped out and sucrose then enters by cotransport
- high solute concentration created in phloem
- water enters by osmosis
- hydrostatic pressure in sieve tube increases
- unloading from sieve tubes in sink
- water leaves by osmosis, lower the hydrostatic pressure
- sap movement in phloem from higher to lower pressure
- movement from source to sink
describe how carbohydrates are transported from plant leaves (7)
- translocation by mass flow
- in phloem sieve tubes
- lack of organelles in phloem allow flow of sap
- carbohydrates transported as sucrose
- sucrose loaded into phloem by active transport
- loading of sugars by companion cells
- high solute concentration generated at the source
- water enters by osmosis due to the high solute concentration
- hydrostatic pressure increased
- pressure gradient causes flow from source to sink
- leaves are a source because carbohydrates are made there
- transport to sink where carbohydrates are stored/ used
describe how plants transport organic compounds from where they are made to where they are stored (4)
- translocation
- sugars produced in leaves
- loaded by active transport
- transported in phloem
- high concentrations of solutes at the source cause uptake of water
- water provides hydrostatic pressure for transport
- used at sink
- lowers pressure at sink
outline how the properties of water make it an ideal transport medium in plants (4)
- polarity of water
- hydrogen bonds between water molecules
- cohesion between water molecules
- cohesion allows transpiration pull
- adhesion to cellulose generates pull in xylem
- solvent for many substances
- liquid at most temperatures experienced by plants
distinguish between the xylem and phloem of plants (4)
xylem
- transport water
- from roots to leaves
- dead
- continuous
- flows due to low pressure
- thicker wall
- lignified walls
- wider lumen
phloem
- transport of organic compounds
- from source to sink
- membranes present
- sieve plates
- flow due to high pressure
- thinner walls
- does not provide support
- narrower lumen
describe how the hormone auxin controls phototropism in plant shoots (5)
- grows towards brightest light
- auxin moved from lighter to shadier side
- moved by auxin efflux pumps
- auxin promotes cell elongation
- more growth in shady side of stem
- binds to auxin receptors in target cells
draw a half view of an animal pollinated flower (4)
- sepals as the outermost part of flower
- petals as largest part of flower
- stamen drawn with recognisable anther and filament
- carpel drawn with recognisable stigma, style and ovary
- nectary at base of the ovary
- ovule inside the ovary
outline the growth of plant shoot apex (4)
- growth in shoots is indeterminate
- produces stems and leaves
- growth controlled by hormones
- extra cells produced by mitosis
- trophism
- auxin moved away from sunny side to shady side
explain calvin’s experiment and what was discovered about photosynthesis through his work (8)
- calvin cycle is light independent
- carbon fixation
- algae placed in thin glass container
- given plenty it light and bicarbonate
- at start of experiment algae supplied radioactive carbon
- samples taken at intervals
- C-compounds separated by chromatography
- radioactive compounds identified by autoradiography
- showed that RuBP was phosphorylated
- after five seconds more glycerate 3 phosphate labelled than any other compound
- shows glycerate 3 phosphate as the rust stable product
- next compound to be detected containing radioactive carbon was triose phosphate
- showed that a wide range of carbon compounds was quickly made in sequence
- showed that a cycle of reactions was used to regenerate RuBP
describe the roles of the shoot apex in the growth of plants (5)
- shoot apex has undifferentiated cells
- mitosis in shoot apex
- cell division in shoot apex
- cell elongation in shoot apex
- stem growth due to cell division and elongation
- produced auxin
- auxin stimulates growth
- growth towards light
- differentiation of cells produced by the shoot apex
outline the process used to load organic compounds into phloem sieve tubes (3)
- active transport
- sucrose moves by symplastic routes
- loaded at source into compassion cells of sieve tubes
- movement of sucrose through plasmodesmata
- high concentration of solutes in phloem leads to water movement by osmosis
outline how plants make use of the different wavelengths of light (4)
- light used in photosynthesis
- chlorophyll absorbs red and blue light
- chlorophyll reflects green light
- absorption spectrum of chlorophyll has peaks in the red and blue
- action spectrum showing peaks in the blue and red
- accessory photosynthetic pigments absorb different wavelengths
- violent is the shortest wavelength and red the longest
- red light and far red absorbed to measure length of light/ dark periods
explain the process of water uptake by plants (8)
- roots absorb water
- water is absorbed by osmosis
- solute concentration inside the root is higher than in the soil
- due to active transport of ions into the root
- transport of water in xylem vessels
- flow of water from roots to leaves
- water movement in xylem due to transpiration pull
- cohesion between water molecules allows water to be pulled up the xylem
- transpiration in leaves generates tension
- evaporation of water from cell walls
- adhesion of water to leaf cell walls creates tension
- lignin in xylem prevent collapse
- passive process
outline three processes required for successful reproduction of angiospermophyta (3)
- meiosis — production of male and female gametes
- pollination — transfer of pollen from anther to stigma
- fertilisation — joining of gametes
- seed dispersal — spread of seeds to new locations
outline the effects of putting plant tissue in a hypertonic solution (4)
- hypertonic solution has more solutes
- water moves out of the cells by osmosis
- water moves from lower solute concentration to higher solute concentration
- pressure inside cell drops
- volume of cytoplasm drops -> plasmolysed
