Xylem & Phloem

What is the function of transport systems in plants

To move substances over long distances because diffusion is too slow in multicellular plants

Why do plants need transport systems (3 reasons)

• multicellular

• have a low SA:V

• need long distance transport

What are the two main transport tissues in plants

Xylem and phloem

What is xylem

Plant tissue that transports water and mineral ions and provides structural support

What are xylem vessels

Long hollow tubes that make up most of xylem tissue

How are xylem vessels adapted (4 reasons)

• hollow

• lack organelles

• thick lignified walls

• pits for lateral movement

Why are xylem vessels hollow

To allow uninterrupted flow of water and minerals

What is lignin in xylem

Strengthening material that thickens walls and prevents collapse

What is the function of pits in xylem

Allow for sideways movement of water and ions between vessels and surrounding cells

What is phloem

Plant tissue that transports sugars and amino acids (assimilates) around the plant

What are sieve tube elements

Cells in phloem that form tubes for transport of sugars

What are sieve plates

Perforated end walls that allow movement of sap between STE

Why do sieve tube elements lack nuclei

To allow more space for transport of assimilates

What are companion cells

Cells that support STE and provide energy for active transport

Why do companion cells have many mitochondria

To provide ATP for active transport in phloem loading

What is the role of plasmodesmata in phloem

They connect CC → STE allowing exchange of substances

Where is xylem found in roots

In the central region forming a central cylinder

Where is phloem found in roots

Surrounding the xylem in the central region

Where is xylem and phloem found in stems

In vascular bundles near the outer region for support

Where are xylem and phloem found in leaves

In veins forming a network for transport and support

Identify F, E, G

F = phloem

E = cambium

G = xylem