L1 - Transport systems in dicotyledonous plants

Why do plants need specialised transport systems?

Large multicellular organisms creates a low surface area:volume ratio

Diffusion too slow to meet the metabolic needs

What does Xylem transport?

• The movement of water molecules and dissolved mineral ions only up the plant

• Passive process

What does Phloem transport?

• The movement of sugars (sucrose) and amino acids up and down plant

• Active process

What are two other tissues associated with xylem?

Parenchyma tissue (packing tissue) - stores food and contains a bitter tasting chemical tannin.

• Prevents attack by herbivores

Tracheids - Elongated lignified cells - transport water and hold it against gravity

Features Of Xylem

• Made of dead cells

• Carries water and minerals to leaves

• Cell wall made of lignin

• Thick cell wall

• Cross walls absent

• Flow is upward

• Impermeable cell walls

• Transports water and minerals

• Parenchyma stores food and tannins

Phloem

• Made of living cells

• Carries food to the growing parts and storage organs

• Does not contain lignin

• Cell wall made of cellulose

• Thin cell wall

• Cells lined with cytoplasm strands

• Permeable cell walls

• Flow is Up and Down

• Perforated cross walls

• Tissue also has companion cells that provide energy