Topic 9: Plant Biology Flashcards
Explain the processes by which minerals are absorbed from the soil into the roots. [8]
- plants absorb mineral ions
- e.g. nitrate / phosphate / potassium
- absorbed by facilitated diffusion
- movement of ions from high to low concentration
- root hair cells provide a large surface area for absorption
- minerals absorbed by active transport
- requires ATP
- mineral ion concentration is smaller outside the root than inside
- through pump/carrier proteins
- proton pump transports hydrogen ions out of cell
In hot, dry conditions plants lose water rapidly due to transpiration. Explain how the structures and processes of the plant allow this water to be replaced. [8]
- Evaporation of water creates transpiration pull
- Water drawn through cell walls by capillary action
- Low pulling force in xylem
- Hydrogen bonds make water cohesive
- Xylem resists tension with lignified walls
- Water travels from the roots to the leaves in xylem
- Water absorbed in roots by osmosis
- Active transport of ions into roots enables osmosis
- many root hairs
- Thick, waxy cuticle reduces water loss
- Small/rolled leaves
- Few stomata
- Hairs on leaf surface
- CAM physiology (stomata opens at night)
Explain how a plant replaces the water it loses in transpiration. [3]
- transpiration causes tension
- water drawn out of xylem
- water move up in xylem
- due to transpiration pull
- cohesion of water
- movement from roots to leaves
- water enters root by osmosis
Explain the process of water uptake and transport by plants. [8]
- root hairs absorb water
- water absorbed in roots by osmosis
- water potential in root < soil
- active transport of ions into the root
- transport of water in xylem vessels
- flow of water from roots to leaves
- due to transpiration pull
- transpiration: evaporation of water from cell walls
- cohesion of water
- adhesion of water to cell wall to create tension
- lignin resists tension, prevents collapse
- passive process
Outline conditions needed for seed germination. [3]
- water to rehydrate
- suitable temperature (warmth) for enzyme activity
- oxygen for aerobic respiration
Explain how minerals move into plants. [8]
- minerals bound to soil particles
- e.g. phosphate/nitrate/potassium/calcium/magnesium
- minerals dissolve in water
- mass flow: movement of minerals with water through the soil
- diffuse down conc. gradient to roots
- active transport
- root hairs increase surface area
- root hairs have mitochondria to supply ATP
- export of H+ creates an electrochemical gradient
- causes positive mineral ions to diffuse into root cells
Explain how abiotic factors affect the rate of transpiration in terrestrial plants. [8]
Humidity
- low humidity, less transpiration
- air spaces in leaves are saturated with water vapor
- smaller conc. gradient with higher humidity
Temperature
- high temp. more transpiration
- faster diffusion
Wind Speed
- high wind speed more transpiration
- water vapor blown away from leaf
- increase conc. gradient of water vapor
Light Intensity
- more light more transpiration
- causes stomata to open
Outline the metabolic processes that occur in starchy seeds during germination. [6]
- water rehydrates seed
- activates metabolism
- gibberellin produced
- stimulates production of amylase
- digests starch to maltose
- maltase converts maltose to glucose
- glucose used in aerobic respiration
- glucose produces cellulose
Outline how and where energy is stored in plants. [4]
- glucose stored as starch
- starch stored as granules in chloroplast
- starch stored in seeds
- stored as lipids
- lipids store x2 energy per gram than starch
Describe how water is carried through a flowering plant. [6]
- active transport of solutes from soil to roots
- draws water by osmosis
- root hairs provide large SA
- carried through xylem vessels
- transpiration: loss of water vapor from leaves
- creates transpiration pull
- lignin resists tension
- water pulled up due to cohesion/adhesion
- transpiration stream
Describe how plants carry out the gas exchange in the leaves. [5]
- gases exit the leaf through stomata
- by diffusion
- photosynthesis maintains conc. gradient
- guard cells open stomata during the day
- gases move through air spaces in the spongy mesophyll
- CO2 dissolves in moisture in cell walls
Explain the role of limiting factors in photosynthesis. [8]
- factor nearing minimum is limiting
- increase in limiting factor with other factors constant increases rate
- increase in non-limiting factors does not affect the rate
Light Intensity
- limiting at low intensity
- required in light-dependent reactions
- photosynthesis directly proportional to light intensity
Temperature
- limiting at low and high temp
- low temp. limit rate of light-independent reactions
- RuBP cannot fix CO2 at high temperatures
CO2 conc.
- low CO2 limits carbon fixation
Outline pollination, fertilization, and seed dispersal. [4]
- pollination: transfer of pollen from anther to stigma
- pollen grain grows pollen tube down style to ovule
- fertilization: male and female gametes fuse
- ovary matures into a fruit
- seed dispersal depends on fruit
- e.g. animal eats fruit/wind dispersal
Angiospermophyta have vascular tissue (xylem and phloem) that bryophyta lack. Suggest advantages that vascular tissue confers. [4]
- easier to stand upright (structural support)
- leaves put higher in the air to get more sunlight
- transport of water/nutrients from roots to tissues
- efficient transport/translocation of sugars from leaves for storage
Explain how aphid stylets can be used to study the movement of solutes in plant tissues. [3]
- aphids tap into phloem with stylets to use sap as a food source
- plants grown in radioactive CO2
- phloem sap flows through stylet
- radioactive-labelled carbon can be detected
- stylets at different parts of the plant show rate of movement
