Y10 Transport In Plants

Question 1

What is the structure and function of the xylem?

Answer 1

The xylem is made up of dead cells and has no end walls - it carries water and mineral ions upwards from the roots to the leaves and stem

This creates a lumen down the middle which forms a narrow hole

Strengthened by a woody material called lignin - strong, waterproof and stiff

Question 2

What is the structure and function of the phloem?

Answer 2

Carries sugars and amino acids upwards and downwards

Nutrients are transported to new growing tissues and storage tissues (translocation)

Made up of living cells called sieve-tube elements joined end to end

The companion cells carry out the living functions for the sieve-tube elements (sieve-tube elements do not have a nucleus so they cannot survive on their own)

Sieve-tube elements contain end plates with holes (sieve plates)

This allows sugars and amino acids to flow more easily

Question 3

What do the xylem and phloem make up?

Answer 3

The vascular bundle

Question 4

What is transpiration?

Answer 4

The loss of water from the leaves of a plant through diffusion (as there is a high conc of water inside the leaves and low conc outside the plant)

Water becomes steam in the mesophyll cells and diffuses out of the stomata

It doesn’t move by osmosis since it becomes a gas in the mesophyll cells

Question 5

Describe the movement of water in the transpiration stream

Answer 5

Water moves upwards through the xylem

Evaporates in the spongy mesophyll

Diffuses out of leaf through stomata / guard cells

Question 6

How does water enter the xylem?

Answer 6

First, ions are moved into root hair cells via active transport, as there is a greater concentration of ions inside the cell than outside it

As the ion concentration in the root hair cells increases, the water concentration decreases, so water molecules can move in via osmosis

Then, the water travels from cell to cell in the root of a plant until it reaches the centre

It enters the xylem here and is transported upwards to the leaves and stem

Question 7

What features of a plant control gas exchange and water loss, and how?

Answer 7

The stomata and guard cells

The stomata are made of two guard cells which open and close the stomata

Guard cells have unevenly distributed cellulose, as the outer wall is thicker and the inner wall is thinner
this helps to open and close the stomata

Question 8

What is translocation?

Answer 8

Where nutrients are transported to new growing tissues and storage tissues (by the phloem)