Plant Structures And Their Functions

Question 1

What is the word equation for photosynthesis?

Answer 1

Carbon. + Water. —————————> glucose + oxygen

Dioxide Light energy

Question 2

Where does photosynthesis occur?

Answer 2

In chloroplasts which contain chlorophyll which traps light energy for photosynthesis

Question 3

Why is photosynthesis an endothermic reaction?

Answer 3

Since energy enters from the surroundings, the products of photosynthesis have more energy than the reactants

Question 4

What happens when glucose molecules are made?

Answer 4

They link together to form a polymer called starch which stays in the chloroplasts until photosynthesis stops.

Question 5

How is sucrose made?

Answer 5

When starch is broken down into simpler substances and moved into the cytoplasm which are then used to make sucrose, which is then transported around the plant

Question 6

What can sucrose be used to make?

Answer 6

Starch (in a storage organ e.g. potato)
Other molecules for the plant (e.g. cellulose,lipids,proteins)
Glucose for respiration (releases energy)

Question 7

In order from top of leaf to bottom, what cells are in the leaf?

Answer 7

Waxy cuticle
Upper epidermis 
Palisade Cell layer
Air space 
Spongy mesophyll
Lower epidermis 
Guard cell and stomata 
Waxy cuticle (again)

Question 8

How is the cuticle adapted?

Answer 8

It protects the cell from pathogens as it acts as a physical barrier
The waxy cuticle is water proof/water repellent

Question 9

How is the upper epidermis adapted?

Answer 9

It is thin so it allows a lot of light in for photosynthesis

Question 10

How is the palisade layer adapted?

Answer 10

They are packed with chloroplasts so they can absorb a lot of light for photosynthesis

Question 11

How are the air spaces/spongy mesophyll adapted?

Answer 11

Large surface area to allow for a greater amount of gas exchange

Question 12

How are the stomata adapted?

Answer 12

They can open and close to allow carbon dioxide to diffuse into the leafs but also allow less or more gas exchange

Question 13

How are the guard cells adapted?

Answer 13

Help the stomata open and close because when it is light (day time), water flows into the guard cells, making them rigid. This causes the stomata to open.
At night, water flows out of the guard cells so they lose their rigidity so the stomata closes, to prevent any gas loss or water vapour loss.

Question 14

What is it called when a factor prevents a rate from increasing?

Answer 14

A limiting factor

Question 15

What are some limiting factors for photosynthesis?

Answer 15

Carbon dioxide concentration, temperature and light intensity

Question 16

Once a factor is limiting, what does changing its supply change?

Answer 16

The rate of photosynthesis

Question 17

What does a straight line on a graph show?

Answer 17

A linear relationship

Question 18

What is the method for Core Practical: Light intensity and Photosynthesis?

Answer 18

1) Decide on the different distances between algae and lamp
2) For each distance you will need one clear glass bottle and an extra bottle
3) Add 20 algae balls to each bottle
4) Add same amount of indicator solution to each bottle and put caps on each bottle
5) Find our pH at start by comparing colour to pH scale
6) Set up a tank of water between lamp and area where you will place your tubes
7) Cover on bottle in foil so it’s in the dark
8) Put your bottles at the different distances you measured at start. Put bottle covered in foil next to the bottle closest to the lamp
9) Turn in lamp and wait until colour changes
10) Write down all your solutions pH
11) For each bottle calculate the ‘change in pH/hour’
12) Plot a graph of results

Question 19

What is water (absorbed by plant roots) used for?

Answer 19

Carrying dissolved mineral ions
Keeping cells rigid
Cooling the leaves
Photosynthesis

Question 20

How is a root hair cell adapted?

Answer 20

Have a large surface area so more water and mineral ions can be absorbed
Also have thin cell walls so the flow of water isn’t slowed down

Question 21

How does water travel in a root hair cell?

Answer 21

Water enters by diffusion - Water diffuses through cell walls

Water enters by osmosis - Tiny tubes join the cytoplasm of some cells together to allow water to be diffused

Question 22

How are mineral ions obtained in a plant?

Answer 22

Through active transport (against a concentration gradient)

Question 23

What is transpiration?

Answer 23

Water moves into the root hair cell by osmosis. This moves water from a high concentration to a low concentration.
Xylem vessels are continuous pipes running from root to leaf
Evaporation of water from the leaf pulls water up the xylem.
Water will then diffuse out of the leaf via the stomata.
From a high concentration to a low concentration, down a concentration gradient.

Question 24

What is translocation?

Answer 24

Glucose made in the leaf is turned into sucrose.
This is translocated(moved) in the phloem.
These are sieve tubes connected together by holes
Companion cells actively pump the sucrose and amino acids in and out of the siege tubes.
This requires energy.

Question 25

How is the xylem adapted for transpiration?

Answer 25

Contains dead cells with no cytoplasm and form an empty tube - this causes the water flow to be fast and not slowed down. Also, the lack of cell walls between cells mean the water flow isn’t slow also.

Tiny pores allow mineral ions and water to enter and leave the xylem vessels

Thick side walls and rings of lignin form rigid tubes that won’t burst or collapse - this provides support

Question 26

How is the phloem adapted for translocation?

Answer 26

Pores - where sucrose solution can be pumped

Holes in ends of cell walls - allows liquids to flow from one sieve cell to the next

Small amount of cytoplasm(no nucleus) in cells - allows more space for the central channel

Question 27

What is a potometer?

Answer 27

The air bubble moves along the tube as the plant loses water. The speed of the bubble gives a measure of the rate of transpiration

Question 28

Why did wind increase the rate of transpiration?

Answer 28

The water vapour is removed quickly by air movement, speeding up diffusion of more water vapour out of the leaf

Moves water molecules away from stomata

Question 29

Why does low humidity increase rate of transpiration?

Answer 29

There is a low water vapour in the air, increasing evaporation from the leaf so there is a higher concentration from the leaf to outside.

Question 30

How does a higher temperature increase the rate of transpiration?

Answer 30

Particles move faster so they diffuse faster

Question 31

Why does a high light intensity increase the rate of transpiration?

Answer 31

Cause the stomata to open wider allowing more carbon dioxide into the plant

Question 32

How are conifers adapted to their windy and cold climate?

Answer 32

Have needle shaped leaves with a small surface area but thick cuticle - creates less wind resistance then broad leaves allowing them to withstand high winds

Have stomata located in small pits where water vapour collects - Reduces water loss by trapping water vapour close to leaves which slows the rate of diffusion out of the leaves

Question 33

How are cacti adapted to their hot climate?

Answer 33

Spines instead of leaves - minimise the surface area so there is reduced water loss by transpiration and spines also protects from any predators

Stems store water and wide spread root systems that collect water from large areas

Question 34

What is the plant hormone that regulates growth?

Answer 34

Auxin

Question 35

What is phototropism?

Answer 35

Detects light (tropism that works towards light)

Question 36

What does auxin do in the shoots?

Answer 36

Auxin is produced in tip of shoots.

In the shoot, auxin promotes elongation causing negative geotropism (going against gravity). Then, as the shoot/plant bends towards the light, auxin moves to the darker side of the shoot. This results in positive phototropism.

Question 37

What is geotropism?

Answer 37

Detecting gravity ( tropism that acts towards gravity)

Question 38

What happens with auxin in the roots?

Answer 38

Auxins have an opposite affect to the that in the shoots.

In roots, auxin causes cells to stop elongating and this causes positive geotropism as the roots are growing towards gravity.

Question 39

What does gibberellin do?

Answer 39

Causes starch to turn into sugars which provides energy

Helps release energy for the seed to grow when germinating

Question 40

What does Ethene/Ethylene do?

Answer 40

Co-ordinates fruit ripening

Question 41

What is the hormone involved in Selective Weed Killer and how does it work?

Answer 41

Hormone: Artificial Auxins

Artificial auxins cause the plants to grow uncontrollably and this kills them. Weed killer uses this to kill plants with broader leaves e.g. dandelions, but not those with narrow leaves so farmers can kill weeds without damaging the crops.

Question 42

What is the hormone involved in rooting powder and how does it work?

Answer 42

Hormone involved: Auxin

How it works: The auxins cause plant cuttings to develop roots quickly. Large numbers of identical plants can be produced quickly using cuttings, compared to growing plants from seeds

Question 43

What is the hormone involved in seedless fruit and how does it work?

Answer 43

Hormone involved: Gibberellin

How does it work: Many plants only produce seeds after being pollinated which then allows egg cells to be fertilised, and seeds to be formed. Gibberellin causes plants to produce fruit without this, giving us seedless fruit

Question 44

What is the hormone involved in Ripening fruit and how does it work?

Answer 44

Hormone involved: Ethene

How does it work: Fruit producers often pick unripe fruit and then ripen it when needed using a plant hormone gas called ethene. This makes sure that fruit reaches the shops in a “just ripened” condition