Transpiration and Translocation

What do phloem tubes do?

Transport food substances (dissolved sugars) made in the leaves to the rest of the plant for immediate use or storage

What are phloem tubes made of?

Columns of elongated living cells with small pores in the end walls

Why do phloem tubes have small pores in the end walls?

To allow cell sap to flow through

What direction does the transportation of food occur in?

Both directions

What is the process of translocation?

The transport of sugars produced by photosynthesis to around the body via the phloem.

What do Xylem tubes do?

Transport water and mineral ions

Where do the Xylem tubes transport the water and mineral ions from and to?

From the roots to the stem and leaves

What are xylem tubes made up of?

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

What are xylem tubes strengthened with?

Lignin

What is the transpiration stream?

The movement of water from the roots through the xylem and out of the leaves

What is transpiration?

The loss of water from the plant

What is transpiration caused by?

The evaporation and diffusion of water from a plant's surface.

What does the evaporation for transpiration create?

A slight shortage of water in the leaf - more water is drawn up from the rest of the plant through the xylem vessel to replace it

Why is there a constant transpiration stream of water through the plant?

More water is drawn up from the roots due to the evaporation

What is transpiration rate affected by?

light intensity, temperature, air flow, humidity

How does light intensity affect the rate of transpiration?

The brighter the light, the greater the transpiration rate

How does temperature affect the rate of transpiration?

The warmer it is the faster transpiration happens

How does airflow affect the rate of transpiration?

The better the airflow (stronger winds) is around a leaf, the greater the transpiration rate

What happens to the rate of transpiration if there is a poor air flow around the leaf?

The water vapour surrounds the leaf = high concentration of water particles outside the leaf as well as inside, diffusion doesn't happen as quickly

How does humidity affect the rate of transpiration?

The drier the air around the leaf, the faster transpiration happens

What happens to the rate of transpiration if there is a high humidity level?

If the air is humid there's a lot of water in it = no difference inside or out, slow rate of diffusion

How can you estimate the rate of transpiration?

By measuring the uptake of water by a plant. This is because you can assume that the water uptake by the plant is directly related to water loss by the leaves (transpiration)