Plant structures and Their Functions

Question 1

What happens during Photosynthesis?

Answer 1

Photosynthetic organisms, such as green plants and algae, use energy from the sun to make glucose.

Question 2

Some of the glucose is used to make…

Answer 2

larger, complex molecules that the plants or algae need to grow. Make up the organisms biomass.

Question 3

How are photosynthetic organisms the main producers of food?

Answer 3

The energy stored in the organisms biomass then works its way through the food chain as animals eat them and each other.

Question 4

What is the equation of photosynthesis?

Answer 4

Carbon dioxide + Water -> Glucose + Oxygen
Uses light energy.

Question 5

Is photosynthesis exothermic or endothermic?

Answer 5

Endothermic as energy is taken in during the reaction.

Question 6

What 3 factors affect the rate of photosynthesis?

Answer 6

Light intensity, the concentration of CO2 and the temperature.

Question 7

What is a limiting factor?

Answer 7

It stops photosynthesis from happening any faster

Question 8

As light level is raised…

Answer 8

the rate of photosynthesis increases steadily. Only true up to a certain point.

Question 9

Beyond the certain point the light intensity will not…

Answer 9

make any difference - it will either be the temperature or the CO2 level which is the limiting factor.

Question 10

How can you investigate light intensity in a lab?

Answer 10

By moving a lamp closer to or further away from your plant.

Question 11

If you just plot the rate of photosynthesis against “distance of lamp from the plant”…

Answer 11

you get a weird-shaped graph.

Question 12

The distance from the lamp and light intensity are…

Answer 12

inversely proportional. This means as the distance increases, the light intensity decreases.

Question 13

What is the inverse sqaure law?

Answer 13

light intensity is proportional to 1/(distance)^2

Question 14

The inverse square law means that…

Answer 14

if you halve the distance, the light intensity will be four times greater.

Question 15

Increasing the CO2 concentration increases…

Answer 15

the rate of photosynthesis up to a point.

Question 16

If temperature is the limiting factor…

Answer 16

its because its too low.

Question 17

The enzymes needed for photosynthesis work more slowly at…

Answer 17

low temperatures.

Question 18

What happens if the plant gets too hot?

Answer 18

The enzymes it needs for photosynthesis and its other reactions will be denatured. This happens at about 45 degree celsius.

Question 19

Why do plants have millions of microscopic root hairs?

Answer 19

It gives the plant a large surface area for absorbing water and mineral ions from the soil.

Question 20

What are Phloem tubes made of?

Answer 20

Columns of elongated living cells with small pores in the end walls to allow stuff to flow through.

Question 21

What do Phloem tubes transport?

Answer 21

Food substances made in the leaves to the rest of the plant for immediate use or for storage.

Question 22

What is this process of transporting food substances called?

Answer 22

Translocation

Question 23

What does Translocation require?

Answer 23

Energy from respiration.

Question 24

In Phloem tubes, does the transport go in both directions?

Answer 24

Yes.

Question 25

What are xylem tubes made of?

Answer 25

Made of dead cells joined end to end with no end walls between them and a hole down the middle.

Question 26

Why doe Xylem tubes require Lignin?

Answer 26

Provides strength and support so allows the xylem to withstand pressure changes as water moves through the plant.

Question 27

What do Xylem tubes carry?

Answer 27

Water and mineral ions from the roots to the stem and leaves.

Question 28

What is Transpiration?

Answer 28

The movement of water from the roots, through the xylem and out of the leaves.

Question 29

What is Transpiration caused by?

Answer 29

The evaporation and diffusion of water from a plants surface. Most transpiration happens at the leaves.

Question 30

In transpiration the loss of water creates...

Answer 30

a slight shortage of water in the leaf, and so more water is drawn up from the rest of the plant through the xylem vessels to replace it.

Question 31

What are Stomatas?

Answer 31

Tiny pores on the surface of a plant.

Question 32

Where is a stomata found?

Answer 32

On the lower surface of the leaf.

Question 33

What do Stomata allow?

Answer 33

CO2 and Oxygen to diffuse directly in and out of a leaf. Also allow water vapour to escape during transpiration.

Question 34

What are Stomata surrounded by?

Answer 34

Guard cells, which changes shape to control the size of the pore.

Question 35

When the guard cells are turgid (swollen with water)...

Answer 35

the stomata are open.

Question 36

When the guard cells are flaccid (low on water)...

Answer 36

the stomata are closed.

Question 37

What are the 3 factors which affect Transpiration rate?

Answer 37

Light intensity, Temperature, Air flow.

Question 38

The brighter the light...

Answer 38

the greater the transpiration rate.

Question 39

Because photosynthesis can't happen in the dark...

Answer 39

the stomata does not need to be open to let CO2 in.

Question 40

When the stomata are closed...

Answer 40

Very little water can escape.

Question 41

The warmer it is...

Answer 41

the faster transpiration happens.

Question 42

What happens to the water particles during transpiration when it is warmer?

Answer 42

Have more energy to evaporate and diffuse out of the stomata.

Question 43

The better the air flow around a leaf...

Answer 43

the greater the transpiration rate.

Question 44

What will water vapour do if air flow around a leaf is poor?

Answer 44

The water vapour just surrounds the leaf and doesn't move away. This means there's a high concentration of water particles outside as well as inside it, so diffusion doesn't happen as quickly.

Question 45

How can you estimate Transpiration rate?

Answer 45

You can use a special piece of apparatus called a potometer.

Question 46

What does potometer measure?

Answer 46

It actually measures water uptake by a plant, but its assumed that water uptake by the plant is directly related to water loss from the leaves (transpiration).