Transport in Plants :2Year 11: Biology

Stomates and transpiration

• The cuticle which covers the plant stops it drying out, by reducing water loss

• However water must be lost though the leaves to allow for water flow through the plant

• Water loss in leaves is also controlled by the stomates

• There are usually many more on the underside of the leaf than on the top.

• This reduces water loss since the underside of the leaf is more protected

• Water loss is controlled by the guard cells

• These can open and close the holes in the leaf

• They will open during the day to transport water needed for photosynthesis

• During times when the plant is losing too much water, and at night the guard cells will close

• The evaporation of water through the stomates in responsible for pulling the water up through the xylem vessels

Leaf- showing the stomates and guard cells

Glucose transport and phloem

• Glucose is produced in the leaves

• It is then converted to sucrose and transported through the phloem to other parts of the plant

Movement of water and sugars

• The transport of the sugars from the leaves is called TRANSLOCATION

• Sucrose can be changed back into glucose for respiration

• Excess sucrose can be converted into starch and stored in the roots

• Some plants such as potatoes store large amounts of starch in their roots

• When plants require energy which can not be supplied by photosynthesis this stored sucrose can be converted back to glucose

• The transport of sucrose back to where it is need is know as RETRANSLOCATION

Questions1. What are the main tubes through

which water and salts are transported in plants?

2. What are the main tubes through which sugar is transported

3.Xylem vessels provide much of the support in the stem of plants and in the woody trunks of trees. What special material in the walls of the Xylem provides them with support?

4.Draw your own diagram showing the movement of

a) Waterb) Sugarthrough a plant

5.What is the difference between translocation and retranslocation?

6. Explain the purpose of the stomates