Biology B2 - Transpiration & Translocation

What do phloem tubes transport?

food substances (mainly dissolved sugars)

What are phloem tubes made of?

Columns of elongated living cells with small pores in the end walls to allow cell sap to flow through

Where are the food substances made?

leaves

Where are the food substance transported to in phloem tubes?

to the rest of the plant

When and how can food substance be used by the plant?

for immediate use (e.g growing regions) or for storage

What direction is food substances transported in phloem tubes

both directions

What is this process called?

translocation

What do xylem tubes transport?

Water and mineral ions

What are the walls of xylem tubes made from?

dead cells joined end to end with no end walls between them and a hole down the middle

how are the walls of xylem cells strengthened

with a material called lignin

Where do xylem tubes transport water and mineral ions from?

roots

Where do xylem tubes transport water and mineral ions to?

the stem and leaves

What is the movement of water from the roots, through the xylem and out of the leaves called

the transpiration stream

What is transpiration?

The loss of water from a plant

what is transpiration caused by?

The evaporation and diffusion of water from a plants surface

where does most transpiration happen?

at the leaves

What does the evaporation of water do?

creates a slight shortage of water in the leaf, and so more water is drawn up from the rest of the plant through the xylem vessels to replace it

What does this mean?

more water is drawn up from the roots, and so there's a constant transpiration stream of water through the plant

What is transpiration a side effect of?

The way leaves are adapted for photosynthesis

Why do leaves have to have stomata in them?

so that gases can be exchanged easily

How does water escape from the leaves?

Through the stomata by diffusion because there's more water inside the plant than in the air outside.