gas exchange in plants

Question 1

plants during the day

Answer 1

they photosynthesise and need to take more carbon dioxide into their cells than they produce by respiration

Question 2

plants at night

Answer 2

take in oxygen and release carbon dioxide for respiration all the time

Question 3

what provides large surface area externally

Answer 3

large leaves

Question 4

site of gas exchange in plants

Answer 4

spongy mesophyll

Question 5

what increases surface area inside plant

Answer 5

irregular shapes
-with large air spaces between them

Question 6

feature of surface of spongy mesophyll cells

Answer 6

they are moist
-gas exchange can occur freely between cells of leaf and air spaces by diffusion

Question 7

function of spongy mesophyll during day

Answer 7

carbon dioxide for PH moves by diffusion into cells and oxygen moves out
-water passes by evaporation from cells into air spaces

Question 8

features of waxy cuticle

Answer 8

-impermeable
-acts as barrier to diffusion of gases
-evaporation of water barrier
-thick barrier can eliminate evaporation
-

Question 9

why do gases and water still move out of plant

Answer 9

to maintain conc gradient so more gases can diffuse into plant

Question 10

stomata- stoma

Answer 10

gases move in and out of the leaf itself by diffusion through stomata

Question 11

stomata

Answer 11

specialised pores mainly found in epidermis on underside of leaf

Question 12

transpiration through leaves

Answer 12

• to maintain steady flow of water from cells in leaf
  -process requires stomata to be open

Question 13

guard cells

Answer 13

stomata bordered by two guard cells
-specialised examples of epidermal cells

Question 14

features of guard cells

Answer 14

-sausage shapes
-contain sap vacuole
contain chloroplast and cellulose of cell wall uneven unlike other epidermal cells

Question 15

how are stomata opened and closed

Answer 15

by turgor

Question 16

guard cells controlling stomata closing

Answer 16

-respond to co2 levels in leaf
-when turgor guard cells low
-thick cellulose closes cell
-cellulose uneven distributed around cell

Question 17

how guard cells open stomata

Answer 17

potassium ions
-moved into guard cells by active transport
-water moves into guard cells
-turgor pressure increases
-stomatal pores open
-because of uneven cellulose

Question 18

what happens to potassium ions at night

Answer 18

stop pumping around guard cells and excreted from cells
-water leaves cell by osmosis
-turgor decreases
-guard cells become flaccid
-stomatal pore closes

Question 19

lenticels

Answer 19

spongy areas with loosely packed cells that are site of gas exchange for woody stems and roots

Question 20

function of lenticels

Answer 20

-link inner tissue of trunk or woody stem with outside world so gas exchange can take place
-can also form on roots so can exchange gases with air in soil