M3 - VASCULAR BUNDLE, XYLEM AND PHLOEM

Question 1

What forms a vascular bundle

Answer 1

Xylem and phloem vessels grouped together
cambium are in vascular bundles and provides structural support

Question 2

Arrangement of vascular bundle in the stem

Answer 2

Vascular bundles are arranged in a circle around the stem
Xylems are on the inside and provide structural support to the stem in wind
Phloem found in middle and sclerenchyma found on outside

Question 3

Vascular bundle in roots

Answer 3

Xylem forms a cross structure in centre
Surrounded by phloem vessels
This makes the root strong as it’s pushed through the soil

Question 4

Vascular bundle in leaf

Answer 4

Xylem vessels found towards the top of the vascular bundle
Phloem vessels found underneath the xylem

Question 5

What does the xylem do

Answer 5

Xylem transports water and mineral ions from the roots to the rest of the plant

Question 6

What is the Xylem made of

Answer 6

Dead hollow cells with no end cell walls
This forms one continuous tube when the xylem cells are stacked on top of each other

Question 7

Xylem cell structure

Answer 7

Xylem cells have no organelles or cytoplasm which creates more space in the vessel for transporting water
Cell wall contains pits which allow water and mineral ions to move in and out of vessel
Cell well contains lignin which strengthens vessel and provides structural support

Question 8

Phloem and sink/source function

Answer 8

Phloem transport dissolved substances such as sucrose from parts of plant where they’re made (source) to the parts of the plant where they’re used (sink)

Question 9

What two types of cells are phloem made of

Answer 9

Sieve tube elements and companion cells

Question 10

sieve tube elements structure and function

Answer 10

They are living cells joined end to end to form sieve tubes
Ends of each cell has sieve plate which has small holes to allow solutes to move from cell to cell
Side tube has no organelles and very little cytoplasm to create more space for transport

Question 11

Companion cells and function

Answer 11

Sieve tubes don’t have organelles so need companion cells to provide energy
They have nucleus and packed with mitochondria
Mitochondria provide energy fir active loading of sucrose
Connected to sieve tube element from plasmodesmata

Question 12

Source to sink cell process

Answer 12

1. Source cell photosynthesises - produce sucrose and lower water potential
2. Water therefore moves from xylem to source cell and hydrostatic pressure increases
3. Sink cell is respiring and uses up sucrose - water potential increases
4. Water leaves sink cell via osmosis and hydrostatic pressure decreases
5. Source has higher hydrostatic pressure and solution is forced to sink via phloem