B7 - Plant Nutrition T10

Question 1

define photosynthesis

Answer 1

process of converying light energy to chemical energy (glucose)
CO2 + H2O -> C6H12O6 + O2

Question 2

where does photosynthesis occur?

Answer 2

chloroplasts -> chlorophyll absorbs light

leaves

Question 3

is photosynthesis an exothermic or endo thermic reaction?

Answer 3

endothermic
(take in heat from surroundings)

Question 4

equation for photosynthesis

Answer 4

light
carbon dioxide + water → glucose + oxygen
chlorophyll

Question 5

Balanced chemical equation for photosynthesis

Answer 5

CO2 + H2O → O2 + C6H12O6
light

Question 6

are plants autotrophs?

Answer 6

yes - they make their own food

Question 7

where can chloroplasts be found

Answer 7

• all plants
• some protoctists
• some bacteria have chlorophyll

Question 8

Structure of the leaf:

Describe the upper epidermis?

Answer 8

• few chloroplast cells tightly joined together
• few or no stomata
• covered in waxy cuticle
• transparent - lets light through

Question 9

why does the upper epidermis have few or no stomata?

Answer 9

prevents too much water loss

Question 10

why is the upper epidermis covered in a waxy cuticle?

Answer 10

1. reduces water loss by evaporation
2. prevents entry of pathogens

Question 11

Describe the palisade (upper) mesophyll?

Answer 11

palisade cells → elongated cells each containing 100s of chloroplasts (densely packed together)

main site of photosynthesis → absorbs light energy (lots of chloroplasts)

Question 12

Describe the spongy (lower) mesophyll?

Answer 12

• spongy cells → rounded, loosely packed cells with air pockets
• main gas exchange surface of leaf
• some chloroplasts

Question 13

Why does the lower mesophyll have lots of air pockets?

Answer 13

allow gases to diffuse in and out of cells faster, as it
increases the surface area to volume ratio

Question 14

Describe the lower epidermis and its function

Answer 14

lots of stomata (gaps) → has guard cells (allows for transpiration and lets in carbon dioxide)
covered in waxy cuticle
cells tightly joined together

Question 15

What is the function of the stomata in the lower epidermis?

Answer 15

1. allows gases to diffuse in and out of the leaf (gas exchange)
2. controls water loss

Question 16

When are the stomata open?

Answer 16

open during day
closed at night

Question 17

What is the function of guard cells?

Answer 17

open and close stomata by absorbing or losing
water.
When lots of water is available, the cells fill and open stomata

Question 18

[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.

Answer 18

Guards cells on upper surface in air, lower surface in water
allows for transpiration and water loss

Question 19

3 limiting factors for photosynthesis

Answer 19

1. temperature
2. light intensity
3. carbon dioxide concentration

Question 20

Define limiting factor

Answer 20

factor in shortest supply that limits rate of reaction

Question 21

Explain how temperature limits rate of photosynthesis

Answer 21

• 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.

Question 22

Explain how light intensity limits rate of photosynthesis

Answer 22

• 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

Question 23

Explain how carbon dioxide concentration limits rate of photosynthesis

Answer 23

• 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

Question 24

MINERAL IONS

Why is magnesium required for plant nutrition?

Answer 24

needed for chlorophyll production for photosynthesis

Question 25

Magneisum deficiency symptoms in plants

Answer 25

yellow plants (no chlorophyll)

Question 26

Why are nitrates required for plant nutrition?

Answer 26

required to make amino acids → used to make proteins for cell growth and repair

Question 27

Nitrate deficiency symptoms in plants

Answer 27

stunted growth (short, stubbly plants)

Question 28

Where are mineral ions absorbed and how are they transported around plants?

Answer 28

• aborbed by root hair cells
• transported by xylem

Question 29

Adaptations of root hair cells

Answer 29

1. large SA:V → absorb more minerals
2. lots of mitochondria → more efficient active transport as better aerobic respiration

Question 30

define active transport

Answer 30

movement of particles from a low concentration to a higher concentration using energy from respiration

Question 31

Practicals investigating photosynthesis:

Investigating starch production:

Answer 31

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)

Question 32

Results of practical to investigate starch production → starch present

starch =
leaf in light/dark =
variegated leaves green/yellow,white =

Answer 32

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

Question 33

Why does the leaf in light turn black?

Answer 33

plant needs light to photosynthesise
light made glucose, stored as starch

Question 34

Why does the green area in the variegated leaf turn black?

Answer 34

plant needs chlorophyll to photosynthesise
chlorophyll made glucose, stored as starch

Question 35

Practicals investigating photosynthesis:

Investigating the effect of light intensity:

Answer 35

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

Question 36

Practical: photosynthesis + oxygen

Answer 36

1. take shoots of a water plant
2. submerge them in a beaker of water underneath an upturned funnel
3. fill boiling tube with water and place it over end of funnel

Question 37

Practical: photosynthesis + oxygen

Answer 37

1. take shoots of a water plant
2. submerge them in a beaker of water underneath an upturned funnel
3. fill boiling tube with water and place it over end of funnel

Question 38

Practical: photosynthesis + oxygen

RESULTS

Answer 38

as oxygen is produced, bubbles of gas will collect in boiling tube and displace water

Question 39

Practical: photosynthesis + oxygen
LEAF RESULTS
leaf with CO2 =
leaf without CO2 =

Answer 39

leaf with CO2 = turns black
leaf without CO2 = stays brown

Question 40

Why does the leaf with CO2 turn black?

Answer 40

plants need CO2 for photosynthesis
using CO2, leaf made glucose -> stored as starch

Question 41

How to test for oxygen

Answer 41

glowing splint will relight

Question 42

How to remove CO2 from leaf

Answer 42

put in sodium hydroxide solution