Plant Structures and Functions

Question 1

What is the equation for photosynthesis?

Answer 1

6CO2 + 6H2O + light energy → C6H12O6 + 6O2

Question 2

What is photosynthesis?

Answer 2

A process that plants and algae use to produce their own food

Question 3

What are the limiting factors of photosynthesis?

Answer 3

• Low temperature
• Dim light
• Low CO2 concentration

Question 4

What are xylem and phloem?

Answer 4

Specialised plant cells

Question 5

How is phloem specialised?

Answer 5

• They contain sieve tube elements which have very little cytoplasm so there is lots of space to transport sucrose
• They have companion cells which have lots of mitochondria which supply energy from respiration for active transport for sucrose in and out of sieve tubes

Question 6

How is xylem specialised?

Answer 6

• They have no cytoplasm or cell contents which means there is more space for water containing mineral ions to move through
• They have holes in their walls called pits that allow water and mineral ions to move out
• Their walls are strengthened with lignin rings which makes them very strong and prevents them from collapsing
• They have no end walls so they form a long tube that water can easily flow through

Question 7

What is transpiration?

Answer 7

Movement of water from the roots of a plant to the leaves

Question 8

What is the process of transpiration?

Answer 8

• Water enters the roots through osmosis
• Water is drawn up the stem through the xylem from the roots
• Water is drawn out of the xylem and to the leaves
• Water vapour evaporates from the leaves mainly through the stomata

Question 9

Where are stomata normally located?

Answer 9

On the lower surface of the leaf

Question 10

What happens when guard cells of the stomata take in water by osmosis?

Answer 10

They swell up and the stoma opens

Question 11

What happens when guard cells of the stomata lose water by osmosis?

Answer 11

They become flaccid and the stoma closes

Question 12

What is translocation?

Answer 12

Transportation of sucrose around a plant

Question 13

What do xylem and phloem help with?

Answer 13

Transport of things around the plant

Question 14

How is sucrose transported in translocation?

Answer 14

In phloem

Question 15

Where is sucrose stored?

Answer 15

In storage organs (as starch)

Question 16

What adaptations do leaves have to assist with photosynthesis and gas exchange?

Answer 16

• Air covers most of the surface of each cell so gas exchange can take place
• Epidermis cells and waxy cuticle are transparent to allow light to pass through to the photosynthetic cells
• Leaf is flat to give larger surface area
• Xylem cells bring water for photosynthesis
• Phloem cells remove sugars produced in photosynthesis
• Stomata allow carbon dioxide from air into the leaf and allow oxygen to leave the leaf
• Internal air spaces increase surface area for diffusion of gases

Question 17

What do chloroplasts do?

Answer 17

Convert light energy from the sun into sugars

Question 18

What factors effect transpiration?

Answer 18

• Light intensity - increases the rate of transpiration because high light intensity causes the stomata to open which means more water evaporates from the leaf so more water is taken up to replace this
• Air movement - wind blows moist air away from the stomata keeping the concentration gradient high, the more air movement there is the higher the rate of transpiration
• Temperature - the higher the temperature the more energy the water molecules have so they move faster so the higher the rate of transpiration

Question 19

What is a potometer?

Answer 19

A piece of equipment used to measure the rate of transpiration

Question 20

How do you measure the rate of transpiration using a potometer?

Answer 20

Distance moved by the air bubble / time taken

Question 21

What adaptations do plants have for living in dry conditions?

Answer 21

• Waxy cuticle to reduce water loss
• Stomata sunk in pits to reduce water loss
• Leaves have hairs to trap moist air around stomata
• Rolled leaves to reduce air movement around stomata

Question 22

What adaptations do plants have for living in tropical conditions?

Answer 22

• Large leaves to take in as much light as possible
• Stems and leaves that climb up the trees to obtain more light
• Leaves with ‘drip tips’ so that water runs off them

Question 23

What adaptations to plants have for living in water logged soil?

Answer 23

• Spongy tissue in their roots that stores oxygen

- Fine surface roots that take oxygen in at the water surface

Question 24

What is a tropism?

Answer 24

A plant’s response to a stimulus (a change in the environment) by growing

Question 25

What is a positive tropism?

Answer 25

When the plant grows towards the stimulus

Question 26

What type of tropism do plant shoots show?

Answer 26

Positive phototropism, they grow towards light

Question 27

What type of tropism do plant roots show?

Answer 27

Positive gravitropism because they grow downwards towards the pull of gravity

Question 28

What are auxins?

Answer 28

Plant hormones that make cells grow longer

Question 29

Where do auxins stimulate cell elongation?

Answer 29

In the shoots, they inhibit cell elongation in the roots

Question 30

Give 3 examples of plant hormones

Answer 30

• Auxins
• Ethene
• Gibberellins

Question 31

What can auxins be used for outside of plants?

Answer 31

Selective weedkillers and rooting powder

Question 32

How do selective weedkillers work?

Answer 32

Broad-leaved weed plants absorb more of the auxins than narrow-leaved crop plants causing them to grow too quickly and die, this causes the crop plants to get more water and minerals so they grow better

Question 33

How does rooting powder work?

Answer 33

Gardeners take cuttings of plants to grow into new plants, they dip the stalk end of the cutting into rooting powder. Rooting powder contains auxins that cause the stalk to produce roots quickly, this helps the cuttings grow well into fully developed plants

Question 34

What can gibberellins be used for?

Answer 34

• To increase the yield of sugar from sugar cane, they can do this because it stimulates cell elongation
• They can also be used to stop seeds developing in fruit, many people prefer seedless fruit so they’re worth more