transpiration and translocation

What do xylem contain /describe structure

xylem tubes that are made up of dead cells joined end to end with no end walls between them. So tube is hollow. They’re strengthened with lignin

What do xylem tubes carry

Water and mineral ions up the plant from the roots to the stem and leaves

What is transpiration

The evaporation of water from leaves

What is the transpiration stream

The movement of water from the roots through the xylem and out of the leaves/the chain of water molecules.

What does the phloem contain/structure

Phloem tunes that are made of columns of elongated living cells with small pores in the end walls to allow cell sap to flow through

What do phloem tubes do

Transport food substances made in the leaves to the rest of the plant for immediate use or for storage. The transport goes in both directions from the roots down to the roots and from roots up to leaves process is known as translocation

More detailed describing the transpiration stream

Transpiration stream is the movement of water through plant from roots to leaves s

• water from inside a leaf evaporates and diffuses out of the leaf, mainly through the stomata

• This 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

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

What are the factors that affect the rate of transpiration

• light intensity

• Temperature

• Air flow

• Humidity

How does light intensity affect the rate of transpiration

The brighter the light the greater the transpiration rate. stomata begins to close as it gets darker. Photosynthesis can’t happen in the dark, so they don’t need to be open to let carbon dioxide in. When is the matter our Clothes very little Water can escape.

How does temperature affect the rate of transpiration

The warmer it is the higher the rate of transpiration because the particles of water will have more energy and are more likely to diffuse out of the stomata

How does air flow affect the rate of transpiration

The better the air flow around a leaf the greater the transpiration rate.

If air flow around a leaf is poor, the water surrounds the leaf and doesn’t move away.

This means there’s a high concentration of water particles outside the leaf as well as inside it, so diffusion doesn’t happen as quickly.

If there’s good airflow, the water vapour is swept away maintaining a low concentration of water in the air outside the leaf.

Diffusion then happened quickly from an area of high concentration to an area of lower concentration.

How does humidity affect the rate of transpiration

The drier the air around the leaf the faster transpiration happens. If the air is humid, there’s a lot of water in it already, so there’s not much of a difference between the inside and outside of the leaf. Diffusion happens fastest if there’s a really high concentration in one place, and I really low concentration