Plant Structures and Their Functions - TOPIC 6

Question 1

what is photosynthesis

Answer 1

an endothermic reaction that uses light energy to react carbon dioxide and water to produce glucose and oxygen

Question 2

what are photosynthetic organisms

Answer 2

the main producers of food and therefore biomass

Question 3

what is biomass

Answer 3

the mass of living material in the organisms

Question 4

where does photosynthesis occur

Answer 4

in chloroplasts

Question 5

what is the word equation for photosynthesis

Answer 5

carbon dioxide + water —–> glucose + oxygen

Question 6

what is the symbol equation for photosynthesis

Answer 6

6CO2 + 6H20 ——> C6H1206 + 602

Question 7

what are the limiting factors on the rate of photosynthesis

Answer 7

effect of light intensity
carbon dioxide concentration
temperature

Question 8

how does light intensity affect rate of photosynthesis

Answer 8

as light intensity increases, rate of photosynthesis increases

Question 9

why does increasing light intensity after a certain point make no difference to the rate of photosynthesis

Answer 9

either the temp or carbon dioxide level will become the limiting factor

Question 10

how does carbon dioxide concentration affect the rate of photosynthesis

Answer 10

as carbon dioxide concentration increases, the rate of photosynthesis increases

Question 11

why does the amount of carbon dioxide only increase the rate of photosynthesis up until a point

Answer 11

temperature or light intensity will now be the limiting factor

Question 12

how does temperature affect the rate of photosynthesis

Answer 12

as temp increases, the rate of photosynthesis increases but if it gets too hot the reaction slows down or stops

Question 13

how do you investigate the effect of light intensity on the rate of photosynthesis

Answer 13

1. A source of white light is placed a specific distance away from a conical flask with pondweed
2. Leave the pondweed for a few minutes
3. Connect a gas syringe to the conical flask
4. Oxygen released will collect in the syringe
5. Repeat a few times with light source at same distance and calculate mean volume of oxygen produced

6, repeat experiment with light source at different distances

Question 14

what is the independent variable in the investigation

Answer 14

light intensity

Question 15

what is the dependant variable in the investigation

Answer 15

amount of oxygen produced

Question 16

what is a dependant variable

Answer 16

the variable you are measuring

Question 17

how do you calculate the rate of photosynthesis

Answer 17

total volume of gas produce / time taken

Question 18

what is the inverse square law

Answer 18

light intensity is proportional to 1/distance^2

Question 19

the rate of photosynthesis is directly proportional to ……..

Answer 19

light intensity

Question 20

what is the function of the phloem

Answer 20

phloem tubes transport food substances made in the leaves to the rest of the plant for immediate use OR for storage

Question 21

how is the phloem adapted to its function

Answer 21

it is made of living cells that are supported by companion cells AND have holes in the end cell walls which allow sugars and amino acids to flow easily through

Question 22

what is the function of the xylem

Answer 22

xylem tubes carry water and mineral ions up the plant from the roots to the stems and leaves

Question 23

how is the xylem adapted to its function

Answer 23

xylem tubes are made of dead cells joined end to end with no end walls between them and strengthened with lignin

Question 24

how are water and mineral ions transported through the plant by transpiration

Answer 24

1. water inside a leaf evaporates and diffuses out of the leaf, mainly through the stomata
2. This creates a slight shortage of water in the leaf, so more water is drawn up from rest of plant through xylem vessels
3. This means more water is drawn up from the roots, so there is constant transpiration stream of water through the plant
4. transpiration stream carries mineral ions dissolved in water

Question 25

how is the structure of root cells adapted to absorb water and mineral ions

Answer 25

the hairs give the plant a large SA to absorb water and mineral ions conc of mineral ions is higher in root hair cells than in soil, so mineral ions are absorbed by active transport there is more water in soil than in roots, so water is absorbed by osmosis

Question 26

what environmental factors affect transpiration rate

Answer 26

light intensity temperature air flow

Question 27

how does light intensity affect transpiration rate

Answer 27

the brighter the light, the greater the transpiration rate

Question 28

why is transpiration rate lower in the dark

Answer 28

in the dark, stomata begin to close and so very little water can escape

Question 29

how does temperature affect transpiration rate

Answer 29

the warmer it is, the faster transpiration happens

Question 30

why is transpiration rate faster when it's warmer

Answer 30

when it is warm, the water particles have more energy to evaporate and diffuse out of the stomata

Question 31

how does air flow affect transpiration rate

Answer 31

the better the air flow around a leaf, the greater the transpiration rate

Question 32

why is transpiration rate faster with better air flow

Answer 32

water vapour gets swept away, maintaining a low concentration of water in the air outside of the leaf and then diffusion happens quickly

Question 33

what is the function of the stomata

Answer 33

they allow carbon dioxide and oxygen to diffuse directly in and out of a leaf/gas exchange and allow water vapour to escape during transpiration

Question 34

where are stomata found

Answer 34

on the lower surface of leaves

Question 35

what is the structure of guard cells

Answer 35

they have a kidney shape which helps to open and close the stomata

Question 36

how do guard cells open the stomata

Answer 36

when the plant has lots of water, guard cells fill with water and go turgid. This opens the stomata.

Question 37

how do guard cells close the stomata

Answer 37

when the plant is short of water, guard cells lose water and become flaccid, closing the stomata

Question 38

why are stomata found more commonly on the underside of leaves

Answer 38

the lower side is shaded and cooler, so less water is lost through the stomata than if they were on the top

Question 39

what are the adaptations of guard cells

Answer 39

thin outer walls and thickened inner walls they are sensitive to light

Question 40

how is the leaf adapted to make photosynthesis efficient

Answer 40

epidermal tissues have a thick waxy cuticle upper epidermis is transparent leaves are broad xylem and phloem

Question 41

how does the waxy cuticle make photosynthesis efficient

Answer 41

it reduces water loss from the leaf by evaporation

Question 42

how does the transparent upper epidermis make photosynthesis efficient

Answer 42

light can pass through it to the palisade layer

Question 43

how do broad leaves make photosynthesis more efficient

Answer 43

large SA exposed to light

Question 44

how is the leaf adapted for efficient gas exchange

Answer 44

lower epidermis is full of stomata air spaces in spongy mesophyll increase rate of diffusion of gases

Question 45

what are the plant adaptations for extreme adaptations

Answer 45

small leaves or spines curled leaves thick waxy cuticle thick and fleshy stems only a few stomata stomata sunken in pits

Question 46

what are auxins

Answer 46

plant hormones which control growth near tips of shoots and roots

Question 47

what do auxins control

Answer 47

phototropism gravitropism

Question 48

what is phototropism

Answer 48

plant growth in response to light

Question 49

what is gravitropism

Answer 49

plant growth in response to gravity

Question 50

how do shoots grow towards light

Answer 50

when a shoot tip is exposed to light, auxins accumulate on the side in the shade so the cells grow faster on the shaded side, so the shoot bends towards the light

Question 51

how do shoots grow away from gravity

Answer 51

when a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxins on the lower side so lower side grows faster, bending the shoot up

Question 52

how do roots grow towards gravity

Answer 52

when a root is growing sideways, more auxins accumulate on lower side and the extra auxin inhibits growth so the cells on the top elongate faster and root bends down

Question 53

what are the commercial uses of auxins

Answer 53

selective weedkillers growing from cuttings with rooting powder

Question 54

what are the commercial uses of gibberellins

Answer 54

controlling flower and fruit formation controlling seed germination producing seedless fruit

Question 55

what is the commercial use of ethene

Answer 55

it is used in fruit ripening