1.7 THE TRANSPORT OF SUBSTANCES IN

PLANTS

Vascular tissue Vascular tissue

Phloem Phloem Xylem Xylem

Present in all organs of the plant and are continuous from organ to organ

RELATING THE STRUCTURE OF XYLEM TO TRANSPORT

Xylem Functions :Xylem Functions :

Transport water & dissolved minerals salts from roots to the stems & the leaves (one way)

Transport water & dissolved minerals salts from roots to the stems & the leaves (one way)

Provides mechanical support for the

plant Provides mechanical support for the

plant

Consist of :Consist of :

VesselVessel TracheidTracheid

Fibre(support & protection)

Fibre(support & protection)

Parenchyma(Food storage)

Parenchyma(Food storage)

Vessel

• Dead cells • forming hollow tubes

that connect the root to the leaf

• Lignin : substances that deposited on the vessels wall to strengthen it

Tracheid

• Dead cell • Long, slender cells with

tapered overlapping ends• thick lignified secondary

walls• Smaller lumen than

xylem vessels

PHLOEM

Phloem

Transports food from leaves & roots to other parts

Two way flow

• consist of :• Sieve tubes• Companion cells

• Made up of sieve tube cells

• Sieve plate : separate sieve tube

Sieve tube

Companion Cells

• has nucleus, ER, ribosomes & numerous mitochondria

• Provide metabolic support for the sieve tube cells in the transports of manufactured food

REVISION

Sample answer:

F1 : Xylem vessels are elongated cells arranged end to end

P1: to allows water to flow in continuous column

F1 : Xylem vessels are elongated cells arranged end to end

P1: to allows water to flow in continuous column

Sample answer:

F2 : (end) walls (of the vessels) have (broken down in the ) pits

P2 : to allow water to pass/diffuse/move from cell to cell

F2 : (end) walls (of the vessels) have (broken down in the ) pits

P2 : to allow water to pass/diffuse/move from cell to cell

Sample answer:

F3: The side walls of the xylem vessels are perforated by pits

P3 : to allow water to pass/move sideways/lateral movement

F3: The side walls of the xylem vessels are perforated by pits

P3 : to allow water to pass/move sideways/lateral movement

Sample answer:

F4: The lignified walls

P4 : prevent the xylem vessels from collapsing // for mechanical support

F4: The lignified walls

P4 : prevent the xylem vessels from collapsing // for mechanical support

Sample answer:

F5: The lumen of xylem vessels is narrow

P5 : increases the capillarity force / action

F5: The lumen of xylem vessels is narrow

P5 : increases the capillarity force / action