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Module 3 Exchange and transport 9. 1 Xylem and phloem

Learning Objectives Success Criteria • Describe the structure and • Define xylem and phloem (Grade D – C) function of xylem vessels, sieve tube elements and • Describe the structure and companion cells function of a xylem and phloem (Grade C –B) • Compare the structure of xylem and phloem, linking it to their importance (Grade B – A)

Starter Using knowledge from KS 4 Write a definition of xylem and phloem Share defintions and add to them Xylem – plant transport tissue that carries water from roots to the rest of the plant. It consists of hollow columns of dead cells lined end-end and reinforced with lignin. Providing support. • Phloem – plant transport tissue that carries products of photosynthesis to the rest of the plant. It consists of sieve elements and companion cells • Define xylem and phloem • • (Grade D – C)

Transporting water and nutrients

Xylem and phloem • Using the textbook p 210 -211 describe in detail the structure and function of xylem and phloem • 20 mins

How is xylem adapted for transportation? Xylem vessels are dead cells and the inside of the cell is hollow. Xylem vessels have thick cellulose cell walls, strengthened & waterproofed by lignin. Lignin can form rings, spirals or solid tubes. There are lots of small unlignified areas called bordered pits, where water moves from one vessel to the next.

How is xylem adapted for transportation? Xylem vessels transport water and minerals from the roots to the shoot and leaves. This transport only occurs in one direction. The thick walls of xylem cells also help support plants. Xylem has to be very strong due to constant water flow like a straw there is pressure and this prevents the whole thing collapsing inwards

How is phloem adapted to transportation? Phloem is made of columns of living cells. They transport food, in the form of organic solutes, sugars and amino acids needed for cellular respiration and for synthesis of other molecules. Sugars are carried from the leaves to the growing and storage parts of the plants. This movement takes place in both directions.

How is phloem adapted to transportation? Phloem cells consist of sieve tubes. Cells are joined by small holes in the cell wall at the end of each cell, forming a continuous system. The end cell walls are called sieve plates. • Companion cells are linked to sieve tube elements by plasmodesmata, they carry out living functions for both themselves and sieve cells. They maintain their nucleus and all organelles. Providing energy from the active transport of sugars

Task complete the questions • Complete the questions