2.6.5 cell diversity in plants

Question 1

guard cells

Answer 1

in leaf epidermis, cells that surround stomata

Question 2

palisade cells

Answer 2

closely-packed photosynthetic cells within leaves

Question 3

root-hair cells

Answer 3

epidermal cells of young roots with long hair-like projections

Question 4

how are palisade cells adapted for photosynthesis

Answer 4

• long/cylindrical
  –> pack together closely & little space between so air can circulate & CO2 in these spaces diffuses into cells
• large vacuole
  –> chloroplasts are positioned nearer to periphery of cell = reduces diffusion distance for CO2
• many chloroplasts
  –> organelles that carry out photosynthesis
• contain cytoskeleton threads/motor proteins
  –> move chloroplasts closer to upper surface of leaf when sunlight intensity is low & further down if it’s high

Question 5

where are guard cells found

Answer 5

lower epidermis

Question 6

characteristics of the specialised cell: guard cells

Answer 6

• light energy used to produce ATP
• ATP actively transports potassium ions from surrounding epidermal cells into guard cells = lowers water potential
• water enters guard cells from neighbouring epidermal cells (osmosis)
• guard cells swell
  –> tips = cellulose wall is more flexible
  –> more rigid where thicker
  –> the tips bulge & the stoma enlarges
• when stomata open = air can enter spaces within layer of cells beneath palisade cells
• gaseous exchange can occur & CO2 diffuse into palisade cells
  –> (use it for photosynthesis) maintains steep conc. gradient
• oxygen produced in photosynthesis can diffuse out of palisade cells into air spaces & out through open stomata

Question 7

how are root hair cells specialised for their function

Answer 7

• hair-like projection increases SA for absorption of water/mineral ions (eg. nitrates) from the soil
• mineral ions are actively transported into root hair cells = lowers water potential in them & causes water to flow via osmosis (down water-potential gradient)
• root-hair cells have special carrier proteins in plasma membranes to actively transport mineral ions in
• cells produce ATP –> required for active transport

Question 8

what are root hair cells

Answer 8

epidermal cells on outer layer of young plant roots

Question 9

what do the xylem/phloem form

Answer 9

vascular tissue in plants

Question 10

what are present in vascular bundles

Answer 10

xylem vessels & phloem sieve tubes