B7 - Plant Nutrition T10 Flashcards
define photosynthesis
process of converying light energy to chemical energy (glucose)
CO2 + H2O -> C6H12O6 + O2
where does photosynthesis occur?
chloroplasts -> chlorophyll absorbs light
leaves
is photosynthesis an exothermic or endo thermic reaction?
endothermic
(take in heat from surroundings)
equation for photosynthesis
light
carbon dioxide + water → glucose + oxygen
chlorophyll
Balanced chemical equation for photosynthesis
CO2 + H2O → O2 + C6H12O6
light
are plants autotrophs?
yes - they make their own food
where can chloroplasts be found
- all plants
- some protoctists
- some bacteria have chlorophyll
Structure of the leaf:
Describe the upper epidermis?
- few chloroplast cells tightly joined together
- few or no stomata
- covered in waxy cuticle
- transparent - lets light through
why does the upper epidermis have few or no stomata?
prevents too much water loss
why is the upper epidermis covered in a waxy cuticle?
- reduces water loss by evaporation
- prevents entry of pathogens
Describe the palisade (upper) mesophyll?
palisade cells → elongated cells each containing 100s of chloroplasts (densely packed together)
main site of photosynthesis → absorbs light energy (lots of chloroplasts)
Describe the spongy (lower) mesophyll?
- spongy cells → rounded, loosely packed cells with air pockets
- main gas exchange surface of leaf
- some chloroplasts
Why does the lower mesophyll have lots of air pockets?
allow gases to diffuse in and out of cells faster, as it
increases the surface area to volume ratio
Describe the lower epidermis and its function
lots of stomata (gaps) → has guard cells (allows for transpiration and lets in carbon dioxide)
covered in waxy cuticle
cells tightly joined together
What is the function of the stomata in the lower epidermis?
- allows gases to diffuse in and out of the leaf (gas exchange)
- controls water loss
When are the stomata open?
open during day
closed at night
What is the function of guard cells?
open and close stomata by absorbing or losing
water.
When lots of water is available, the cells fill and open stomata
[2 marks]
Water lillies float on the surface of ponds, Guard cells are found on the upper surface of a water lily rather than the lower surface.
Suggest a reason for this adaptation.
Guards cells on upper surface in air, lower surface in water
allows for transpiration and water loss
3 limiting factors for photosynthesis
- temperature
- light intensity
- carbon dioxide concentration
Define limiting factor
factor in shortest supply that limits rate of reaction
Explain how temperature limits rate of photosynthesis
- affects kinetic energy levels in particles → affects speed at which CO2 + water move through plant
- as temperature increases, the rate of photosynthesis increases
- as reaction is controlled by enzymes, this trend only continues up to a certain temperature until the enzymes begin to denature and the rate of reaction decreases.
Explain how light intensity limits rate of photosynthesis
- affects how much energy plants has to carry out photosynthesis
- higher the light intensity, faster the rate of photosynthesis
- trend will continue till another limiting factor prevents rate from increasing
Explain how carbon dioxide concentration limits rate of photosynthesis
- carbon dioxide needed to make glucose for photosynthesis
- more CO2 present, faster rate of reaction
- trend will continue till another limiting factor prevents rate from increasing
MINERAL IONS
Why is magnesium required for plant nutrition?
needed for chlorophyll production for photosynthesis
Magneisum deficiency symptoms in plants
yellow plants (no chlorophyll)
Why are nitrates required for plant nutrition?
required to make amino acids → used to make proteins for cell growth and repair
Nitrate deficiency symptoms in plants
stunted growth (short, stubbly plants)
Where are mineral ions absorbed and how are they transported around plants?
- aborbed by root hair cells
- transported by xylem
Adaptations of root hair cells
- large SA:V → absorb more minerals
- lots of mitochondria → more efficient active transport as better aerobic respiration
define active transport
movement of particles from a low concentration to a higher concentration using energy from respiration
Practicals investigating photosynthesis:
Investigating starch production:
1) Cover half of a small leaf with foil
2) Place the plant on a windowsill for 48 hours so that light can reach it
3) Put the leaf into boiling water to kill and preserve it.
4) Put the leaf in a boiling tube containing hot ethanol for 10 minutes (this removes the chlorophyll
pigment).
5) Dip the leaf in boiling water to soften it.
6) Put leaf in a Petri dish and cover with iodine solution.
7) The covered half of the leaf will remain orange-brown, whereas the exposed half will change to
blue-black (as iodine solution changes colour in the presence of starch, as photosynthesis
turned the glucose into starch for storage)
Results of practical to investigate starch production → starch present
starch =
leaf in light/dark =
variegated leaves green/yellow,white =
starch = iodine will go from brown → blue-black
leaf light = turns black
leaf dark = stays brown
variegated leaves green = turns black
variegated leaves yellow,white = stays brown
Why does the leaf in light turn black?
plant needs light to photosynthesise
light made glucose, stored as starch
Why does the green area in the variegated leaf turn black?
plant needs chlorophyll to photosynthesise
chlorophyll made glucose, stored as starch
Practicals investigating photosynthesis:
Investigating the effect of light intensity:
1) Place pondweed in water and set up a desk lamp next to alongside a ruler so that you can measure the distance between the light and the beaker
2) Move the lamp away by 10cm
3) Leave for 5 minutes to allow for the pondweed to adapt
4) Count the number of bubbles given off in 1 minute and record
5) Repeat steps 2-4
Practical: photosynthesis + oxygen
- take shoots of a water plant
- submerge them in a beaker of water underneath an upturned funnel
- fill boiling tube with water and place it over end of funnel
Practical: photosynthesis + oxygen
- take shoots of a water plant
- submerge them in a beaker of water underneath an upturned funnel
- fill boiling tube with water and place it over end of funnel
Practical: photosynthesis + oxygen
RESULTS
as oxygen is produced, bubbles of gas will collect in boiling tube and displace water
Practical: photosynthesis + oxygen
LEAF RESULTS
leaf with CO2 =
leaf without CO2 =
leaf with CO2 = turns black
leaf without CO2 = stays brown
Why does the leaf with CO2 turn black?
plants need CO2 for photosynthesis
using CO2, leaf made glucose -> stored as starch
How to test for oxygen
glowing splint will relight
How to remove CO2 from leaf
put in sodium hydroxide solution
