Which plant tissue transports water and minerals?
Xylem
Which plant tissue transports sucrose?
Phloem
How are xylem vessels adapted to their function?
Hollow, no end walls, lignified walls for strength/waterproofing.
How are phloem vessels adapted?
Sieve plates, companion cells provide energy (ATP) for active transport
What is transpiration?
Loss of water vapour from plant leaves via stomata
Which environmental factor decreases transpiration?
High humidity
Which factors increase transpiration?
High temperature, high wind speed, high light intensity
Why does high humidity reduce transpiration?
Smaller concentration gradient for diffusion of water vapour
Why does high humidity reduce transpiration?
Smaller concentration gradient for diffusion of water vapour
Write the word equation for photosynthesis.
Carbon dioxide + water → glucose + oxygen
Is photosynthesis endothermic or exothermic? Why?
Endothermic – it takes in light energy, products contain more energy than reactants
Name three limiting factors of photosynthesis
Light intensity, carbon dioxide concentration, temperature
What is the compensation point?
Light intensity where photosynthesis = respiration
Which hormone makes shoots bend towards light?
Auxin
How does auxin cause shoots to bend towards light?
Moves to shaded side, cells elongate more, shoot bends towards light
Which hormone ripens fruit?
Ethene (ethylene gas)
Why are auxin weedkillers effective on weeds but not grass?
Broad-leaved weeds absorb more auxin, grow uncontrollably and die; grasses less affected
Give one other use of auxins in farming.
Rooting powders to grow cuttings / promoting fruit growth
How are cacti adapted to desert conditions?
Thick stems store water; spines reduce water loss/protect from animals; deep roots absorb water
How are pine trees adapted to cold environments?
thick bark to insulate and keep tissue inside tree warm
spikey leaves to allow snow to fall off and prevent animals from damaging it
What is the dependent variable in the shoot curvature experiment?
Angle of curvature of seedlings
What correlation is shown in the auxin/agar experiment?
More shoot tips = more auxin = greater curvature
Why do scientists place a tank of water in front of a lamp in pondweed experiments?
To absorb heat so only light intensity changes (fair test)
Why do commercial greenhouses use heaters?
To keep enzymes at optimum temperature so photosynthesis doesn’t slow down in the cold
