Topic 6- Plants structures and their functions Flashcards
What are plants?
-Photosynthetic organsims
-Produce most of biomass (food)
What is photosyntheis?
-Endothermic + uses light
-Carbon dioxide + water —> Glucose + oxygen
6CO2 + 6H2O —> C6H12O6 + 6O2
What are limmiting factors?
-Limmit the rate of photsynthesis
-Light
-CO2
-Temperature
Core Practical: Investigate the effect of light intensity on the rate of photosynthesis
1) Use a light
2) Beaker filled with water (absorb heat)
2) Measure distance from light at equal distances
3) Place test tubes filled with same mass of algea
4) Add hydrocarbonate indicator (measure CO2 levels)
5) Wait for a certain amount of time
6) Indicator normally red:
- Yellow if rise in CO2
- Purple if drop in CO2 (more photosynthesis)
How does light intensity effect photosynthesis?
-inverse square law
-L= 1/d^2
-More light intensity the more photosyntheis
How are root hair cells adapt?
-Large SA (more space)
-Lots of mitochondria (active transport)
-No chloropllasts (saves room and energy)
-Thin cell wall (short diffusion distance)
How is the phloem adapt?
-Transport sucrose (translocation)
-Alive (energy for active transport of sucrose)
-Companion cells (supply ATP)
-No nucleus (more room)
-Seive plates (maintain pressure and sucrose flow)
How is the xylem adapt?
-Transport water (transpiration stream)
-Dead hollow cells (room for water)
-Lignin coating (strength + mantain pressure)
-No end cell walls (continuous)
What is transpiration?
-Evaporation of water through the stomata
-Cuases more water to be drawn up through the roots (transpiration stream)
What is the structure of a leaf?
-Wax cuticle (structure + barrier + impermeable)
-Upper epidermis (structure + allows sunlight through)
-Palisade mesophyl (chloroplasts)
-Spongy mesophyl (gas exchange)
-Lower epidermis (structure + stomata)
-Guard cells (thicker cell wall on one side = curve when filled witth water so turgid + open)
-Stomata (gas exchange)
-Wax cuticle (structure
What is translocation?
-Movement of sucrose through the phloem from the leaves to the rest of the plant
-To be stored and used
How does air movement affect transpiration?
-Windy = higher concentration difference so more transpiration
humid= less as equal concentration
How does temp affect transpiration?
-Higher temp = quicker evaporation + transpiration
How does light intensity affect transpiration?
-More as stomata open wider for gas exchange
-More photosynthesis
How to measure the rate of transpiration?
1) Potometer
2) Place in water + beaker of water at end of capillary tube
3) Introduce an air bubble through lifting capillary tube out of water
4) Use resovoir to position air bubble
5) Find starting position of air bubble
6) Wait
7) Measure where air bubble is now
How are plants adapted to desert conditions?
Thick waxy cuticle- prevent evaporation + water loss
Less stomata/ smaller leaves- Less transpiration
Curled leaves- Traps moisture + prevents air flow
Swollen stem- Stores water
Shallow roots- Absorb rain water quickly over longer area
Stomata open at night- cooler = less evaporation
e.g cactus
How are plants adapted to rainforest conditions?
Large SA leaves-Absorb more sunlight
Drip tip leaves- Prevent water accumilation + fungal growth
Thick waxy cuticle - impermeable to water + prevents fungal growth
Deep wide roots-Stability
Tall fast growing trees +straight trunks-More sunlight
Not much water loss as very humid
How are plants adapted to cold conditions?
Small tough leaves - prevents damage and freezing + reduces SA (less heat loss)
Grow short- prevents wind damage
Thick waxy cuticle-Prevents transpiration + damage
Dark coloured-Absorb sun heat
Stomata on underside- Less wind exposure and thus less water loss
E.g pine tree
What are the tropisms?
-Phototropism
-Gavititropism
Positive= towards
Negative= away
How are shoots grow with positive phototropism?
-Auxins are the growth hormone and cuase elongation
-Accumilate in shaded regions these cells elongate
-Plant bends towards light
How do roots grow with positive gravitropism?
-Auxins in the root inhibit growth and elongation
-Accumilate on underside of roots
-Underside grows slower than upper side
-Upperside grows faster + bends downwards
What hormones/chemicals are used commercially?
- Auxins
- Gibberellins
- Ethene
How are auxins used commercially?
Weedkillers- rapid, uncontrollable growth in broadleafed weeds which kills them
Rooting powders- Promotes growth in new plants
How are gibberellins used commercially?
Seedless fruit- induces fruits growth before fertilisation
Flower and fruit formation-Stimulates flower and fruit growth
Seed germination- Helpls break seed dormancy and promotes early germination
