plant stem structure- lqc 2a

Question 1

structure of xylem vessels

Answer 1

-Cellulose microfibrils in cell walls
-Walls thickened with lignin (often in rings or spirals)
-Continuous column made of hollow, dead cells, with no end walls and no cell contents
-Pits in walls
-Vessels have open ends

Question 2

structure of phloem

Answer 2

-Has a cellulose cell wall
-Sieve tube elements have thin peripheral cytoplasm and very few organelles
-Have sieve plates with sieve pores
-A companion cell is linked to each sieve tube element by plasmodesmata
-Living tissue

Question 3

structure of sclerenchyma fibres

Answer 3

-Fibres/cells have cellulose cell walls which are thickly lignified
-Dead and hollow cells when mature
-Often have pits in their walls
-Long narrow cells, usually pointed at both ends

Question 4

function of xylem vessels

Answer 4

transport of water and dissolved mineral ions from roots to leaves, structural support

Question 5

function of phloem

Answer 5

transport of organic solutes from source to sink, in a process called translocation

Question 6

function of sclerenchyma fibres

Answer 6

structural support only (no transport)