transport in plants

Question 1

features of xylem

Answer 1

-carries water and minerals from roots to photosynthetic parts of plant
-movement always upwards
-long tubular xylem vessels main functional units of xylem

Question 2

features of phloem

Answer 2

-living tissue
-made of phloem cells that transport dissolved product of photosynthesis from leaves to where its needed for growth or storage as starch
-flow up and down within a plant

Question 3

whats the cambium

Answer 3

layer of unspecialised cells that divide giving rise to more specialised cells that form both xylem and phloem

Question 4

first xylem formed

Answer 4

protoxylem

Question 5

features of the protoxylem

Answer 5

capable of stretching and growing because walls not fully lignified

Question 6

how does the protoxylem strengthen

Answer 6

-cellulose microfibrils of xylem vessels laid down vertically in stem increasing strength of tube and allows it to withstand compression forces from weight of plant pressing down on it

Question 7

what happens as the xylem stem ages and the cell stop growing

Answer 7

-increasing amount of lignin are laid down in the cell walls

Question 8

result of increase in lignin in protoxylem developing

Answer 8

-the cells become impermeable to water and other substances
-tissue becomes more strong and supportive but contents of cell die

Question 9

metaxylem

Answer 9

increased lignified tissue

Question 10

what happens after metaxylem is produced

Answer 10

-the end walls between the cells largely break down so the xylem forms hollow tubes running from roots to the tip of stems and leaves

Question 11

how does water move out of xylem into surrounding cells

Question 12

role of lignified xylem vessels

Answer 12

very strong and play important supportive role in stems of plants, particularly larger plants

Question 13

what supports smaller non woody plants

Answer 13

-from turgid parenchyma cells and schlrenchyma and clychryma cells

Question 14

how can shoot in dye be evidence for water transport through xylem

Answer 14

if you cut end of shoot placed in eosin dye, the dye can be seen carried into transport system into vascular tissues of xylem

Question 15

how would removing a complete ring of bark give evidence for water transportation in plants

Answer 15

destroys living phloem cells but not xylem cells
-eosin dye placed in water shows upward movement of water through plant is unaffected

Question 16

steps of audioradiography

Answer 16

-plant given radioactive labelled version of substance being studied
-radioactive plant taken up in same way by plant as normal isotope
-tracked with photographic film, labelled substance causes photographic film to shadow revealing areas it has accumulated
-labelling can be traced by examining each area of plant seperatly using scintillation counter

Question 17

what are the sieve tube elements made of

Answer 17

of many cells joined together to make very long tubes that run form the highest shoot to the end of the roots

Question 18

why to the phloem cell contents remain living

Answer 18

because they do not become lignified

Question 19

how are sieve plates formed

Answer 19

walls between cells become preforated

Question 20

what do the phloem contents flow through

Answer 20

the holes in the sieve plates

Question 21

what happens as gaps in sieve plates form

Answer 21

nucleus, tonoplast and other organelles break down

Question 22

why do phloem sieve tubes survive

Answer 22

-sieve tubes becomes tube filled with phloem sap and mature phloem has no nucleus
-survive because of companion cells

Question 23

features of companion cells

Answer 23

very active cells
-linked to sieve tube elements by plasmodesmata

Question 24

adaptations of companion cells

Answer 24

have many infoldings that increase the surface area over they can transport sucrose into cell cytoplasm
-have mitochondria to supply ATP for Active transport