Plants

Question 1

What’s the function of xylem and phloem

Answer 1

Transports water and supports

Transports organic solutes

Question 2

Whats the function of sclerenchyma

Answer 2

Columns of stiffened cells to provide support

Question 3

Describe transpiration

Answer 3

Water diffuses out through stomata down a diffusion gradient
Water evaporate from the surface of cells lining substomatal cavities
Channels between microfibrils in cell walls act as capillaires they draw water up by capillary action caused by surface tension between capillary walls and water
Capillarry action replaces water
Minute channels in th cell walls creates a pull on water behind them which draws water up
Continuous stream

Question 4

How does xylem support a plant?

Answer 4

Lignin makes them stiffer and gives greater tensile strength

Laid down in spirals

Question 5

How does xylem transport? (properties)

Answer 5

Lignin which restricts entry of water and solutes impregnates the wall and causes autolysis of cell contents
tonoplasts breaks down
Organelles, cytoplasm and membrane broken down by enzymes and leaves hollow tubes
End walls highly perforated producing long tubes
Lateral pits
Made of large cells with thick walls

Question 6

Describe the cohesion tension theory

Answer 6

water is pulled up from the top of the plant waters under tension
water column isn’t broken due to cohesiveness

Question 7

Describe what nitrate ion are needed for?

Answer 7

Nitrogen to produce proteins as plants make their own amino acids
cytoplasm is made of protein cannot grow without
chloropyll, ATP

Question 8

What are calcium ions needed for?

Answer 8

Lack of them causes shunted growth as they help walls structure and permeability of the membrane

Question 9

What are magnesium ions neede for?

Answer 9

Unable to make chlorophyll without them and leaves become yellow and brownish

Question 10

Describe transfer cells

Answer 10

Cell walls and membranes have infoldings increasing SA, mitochondria for energy, plasmodesmata linking their cytoplasm with adjacent cells
Type of parenchyma cells

Question 11

Describe how solutes are actively transported into and out of phloem

Answer 11

Products actively unloaded from tubes into parts of plants where its being used but not produced ie roots

Question 12

Describe phloem sieve tubes

Answer 12

develops from a column of long, narrow cells in the growing stem
Remain alive however nucleus and most contents disintegrate during development leaving it as a liquid filled space called lumen

Question 13

What are sieve plates

Answer 13

End walls of sieve tube cell have holes that align with neighbouring cells to allow transfer of materials

Question 14

What are sieve tube elements?

Answer 14

section of phloem tube between sieve plates

Living cells and are joined end to end to form sieve tubes

Question 15

What is lumen

Answer 15

a vacuole that might stretch from a leaf at the top of a plant down to the end of branch and roots

Question 16

Whats a companion cell

Answer 16

alongside the tube
Nucleus, mitochondria, ribosomes and rER
perform metabolic functions that maintain the tube

Question 17

Describe sclerenchyma

Answer 17

lignin is deposited in their cell walls and die once lignified leaving hollow fibres

Question 18

Describe vascular bundles

Answer 18

Made up of xylem and phloem sieve tubes

Question 19

Describe sieve tube

Answer 19

Remain alive but nucleus and cell contents disintegrate only thin layer of cytoplasm remains
Perforated ends

Question 20

Describe translocation

Answer 20

Photosynthetic products diffuse from source cell to transfer cell
Actively pumped into the phloem sieve tube causing water to be drawn out of the xylem into the phloem by osmosis
Increases hydrostatic pressure
Transfer cell actively pumps solutes from phloem into their cell - diffuses into sink
Water moves back into the xylem
Reduces hydrostatic pressure
Difference in hydrostatic pressure