Topic 6 - Plant Structures And Their Functions

Question 1

What is photosynthesis?

Answer 1

An endothermic reaction that uses light energy to react CO2 and Water to produce Glucose and Oxygen.

Question 2

What type of reaction is photosynthesis?

Answer 2

Endothermic

Question 3

What are photosynthetic organisms?

Answer 3

Main producers of food and therefore biomass

Question 4

What is the effect of temperature on photosynthesis?

Answer 4

As temperature increases, the rate of photosynthesis increases. However, at high temperatures, enzymes are denatured and this will decrease the rate of photosynthesis.

Question 5

Effect of CO2 concentration on photosynthesis?

Answer 5

Carbon dioxide is one of the reactants in photosynthesis. If the concentration of carbon dioxide is increased, the rate of photosynthesis will therefore increase. At some point, another factor may become limiting and the rate of photosynthesis will become constant.

Question 6

Effect of light intensity on photosynthesis?

Answer 6

Increasing the light intensity increases the rate of photosynthesis, until a limiting factor becomes in short supply.

Question 7

How do you calculate inverse square law?

Answer 7

See how much the distance increases by (e.g x2)
This = 2/1.
Flip the fraction (1/2)
Square the fraction (1/2)(1/2)
This = 1/4
Divide your light intensity by 4 for your answer

Question 8

How are root hair cells adapted to absorb water and mineral ions?

Answer 8

Have a large surface area to increase the rate of absorption. Contain lots of mitochondria, which release energy from glucose during respiration to provide the energy needed for active transport.

Question 9

Explain each adaption of the leaf.

Answer 9

Leaves have veins to carry water into cells and carry glucose out.
Leaves are thin to allow gases to reach cells easily.
Leaves have stomata to let gases in and out.
Leaves are wide and flat to absorb as much light as possible.

Question 10

What is the internal structure of the leaf?

Answer 10

Waxy cuticle on top, with upper epidermis directly touching it. Underneath that, the palisade layer, then the spongy layer housing the leaf vein and air spaces. At the bottom, there is the lower epidermis with a stoma and guard cells.

W
U
P
S - leaf vein + air spaces
L
S + G

Question 11

Waxy cuticle

Answer 11

Protects the leaf and prevents excess water loss without blocking light.

Question 12

What does the epidermis do?

Answer 12

Allows light to pass through and is thin and transparent.

Question 13

Palisade layer

Answer 13

Column-shaped and packed with many chloroplasts. Arranged closely together so a lot of light can be absorbed.

Question 14

What does spongy mesophyll contain?

Answer 14

Contains internal air spaces that increases the SA to V ratio for the diffusion of gases e.g CO2

Question 15

What does the Vascular Bundle do?

Answer 15

Help transport water and sugars.

Question 16

Stoma and Guard Cells

Answer 16

Stoma are small holes on the underside of the leaf that allow gases to diffuse in and out and to reduce water loss.

Question 17

How do stomata open and close?

Answer 17

In day = light = photosynthesis. Stomata are open to enable gas exchange as the guard cells have taken in water by osmosis and are turgid. At night = no light = no photosynthesis, stomata close to prevent water loss from leaves, this is because the guard cells have lost water by osmosis and have become flaccid.

Question 18

NPK fertiliser

Answer 18

Nitrogen (N) - Phosphorus (P) - Potassium (K)

Question 19

Nitrate ions - use, deficiency symptoms, explanation

Answer 19

Use - to make proteins for growth,
Symptoms - poor growth, yellow leaves
Explanation - amino acids contain nitrogen. Amino acids are the building blocks of protein.

Question 20

Phosphate ions - use, symptoms, explanation

Answer 20

Use - respiration, growth
Symptoms - poor root growth, discoloured leaves.
Explanation - needed to make DNA and cell membranes.

Question 21

Potassium ions - use, symptoms, Explanation

Answer 21

Use - respiration, photosynthesis.
Symptoms - poor flower and fruit growth, discoloured leaves.
Explanation - must be present for photosynthesis and respiration enzymes to work

Question 22

Magnesium ions - use, symptoms, explanation

Answer 22

Use - photosynthesis
Symptoms - poor growth, discoloured leaves
Explanation - chlorophyll contains Mg ions. Mg makes chlorophyll green

Question 23

Minerals in soil

Answer 23

The concentration of minerals in the soil is very low. They dissolve in water and move around the soil in solution.

Question 24

How can minerals be absorbed regarding diffusion and osmosis?

Answer 24

Can’t be absorbed by osmosis (movement of water) or diffusion (minerals are low concentration).

Question 25

Mineral absorption (active transport)

Answer 25

Root hair cells have carrier molecules on their surface that pick up minerals and move them into the cell against the concentration gradient. Requires energy -> active transport.

Question 26

How does water get transported around the plant?

Answer 26

Water travels from the soil to the roots by osmosis. Once in the roots it travels into the xylem where it will travel up the plant to the cells that need water. Xylem vessels are water proofed by lignin which stops water leaving the vessels by osmosis as it passes up the plant. This is so not all the water gets used up straight away by cells at the bottom, and therefore let some get to the top.

Question 27

Translocation description

Answer 27

Another type of transport vessel in plants are called the phloem. The phloem transports sugar and other nutrients from the leaves, where they are produced, (in the form of Sap) to places in the plant where they are needed. This process is referred to as translocation. We say that in plants transport is always up the xylem and down the phloem.

Question 28

Xylem Vessel

Answer 28

One-Way only
Transports water and minerals
No end walls between cells
Thick walls stiffened with lignin

Question 29

Phloem Vessel

Answer 29

Transports water and food
Cells have end walls with perforations
Two-way flow

Question 30

Xylem Summary -

Answer 30

Function - carries water and minerals
Structure - hollow tubes
Dead
Support - thickened with cellulose and lignin

Question 31

Phloem Summary -

Answer 31

Function - carries dissolved sugars
Structure - tubes have sieve plates
Alive
Support - companion cells provide energy for active transport.

Question 32

Definition of translocation

Answer 32

Movement of dissolved sugars up and down the plant through the phloem.

Question 33

Definition of transpiration

Answer 33

Movement of water up the xylem vessel.

Question 34

Factors which affect the rate of transpiration

Answer 34

1) Temp - the warmer it is, the faster water evaporates from the leaves
2) Humidity - the lower, the faster water evaporates.
3) Wind speed - windier, the faster moist air is taken away from the leaf surface.
4) Light intensity - transpiration is faster when the stomata are open in the light.

Question 35

Potometer

Answer 35

Measures rate of transpiration (cm3/min)

Question 36

What is a hormone?

Answer 36

Chemical messengers that co-ordinate systems.

Question 37

What is controlled by hormones in plants?

Answer 37

Growth - roots and shoots, seed germination, leaf fall, disease resistance, fruit formation and ripening, flowering time, bud formation.

Question 38

A tropism

Answer 38

Responding to a stimulus by growing towards or away from it is called a tropism.

Question 39

Phototropism

Answer 39

A tropism caused by light

Question 40

Positive tropism

Answer 40

A tropism towards a stimulus

Question 41

Positive phototropism

Answer 41

Shoot tips growing upwards towards light

Question 42

Negative phototropism

Answer 42

Roots growing downwards into dark soil

Question 43

Positive geo/gravitropism

Answer 43

Roots growing downwards

Question 44

Gravitropism

Answer 44

Growth towards the direction of gravity

Question 45

Negative geotropism

Answer 45

Shoots growing upwards

Question 46

Auxins effects

Answer 46

Auxins are produced in the shoot tip.
They have different effects depending where it is.
• In the shoots any concentration promotes growth.
• At the root, high concentration inhibits growth, small concentration promotes growth.

Question 47

Why do auxins make plants bend?

Answer 47

The Sunlight breaks down auxins, therefore the shoot tip which has direct sunlight will have the least amount of auxins. This means the area of the plant which is shaded has a higher concentration of auxins, and so more growth occurs, this leads to lop sided growth and the plant bends towards the light

Question 48

Gibberellins

Answer 48

Plant hormones released inside of a seed to start germination.

Question 49

Uses of auxins

Answer 49

Rooting powder
Selective weed killers

Question 50

Uses of gibberellins

Answer 50

germination, fruit and flower formation and the production of seedless fruit

Question 51

Uses of ethene

Answer 51

Fruit ripening