Transport In Plants Flashcards
What factors may affect transpiration rate and why?
1 wind because water leaves faster
2 higher temperature because quicker evaporation
3 low humidity because more evaporation
4 more light intensity because (?)
What is the stomata and what do they do?
Stomata are small openings on the leaf surface
Water evaporates from stomata
Water diffuses out via evaporation
Stomata are closed to limit water loss
Carbon dioxide from the atmosphere diffuses into the air spaces and into the cells down the concentration gradient
At same time oxygen from photosynthesis is removed from the leaf by diffusion into surrounding air
What is transpiration?
The loss of water vapour from the surface of plant leaves
What are guard cells and what do they do?
Guard cells control the opening and closing of the stomata
They control gas exchange and water loss
Explain the transpiration stream?
- Water into roots from soil by osmosis - replacing water moving up stem
- Water moves up from roots into stem
- Water moves through stem into leaves to replace water lost by evaporation
- Water is lost from leaves by evaporation through stomata
How is water pulled up through the stem?
Through the xylem
Xylem consist of long tubes to carry water around the plant
Tubes are stiffened by rings of lignin
What are lignin?
Spirals and hoops that support xylem
What is the lower epidermis?
The layer of tissue on the bottom of a leaf
Made of irregular shaped cells that fit tightly together
Tiny holes called stomata are scattered around them
What are root hairs?
Long thin finger like structures designed to increase surface area of roots for absorbing water by osmosis and mineral ions by active transport
What is the upper epidermis?
Layer of tissue on top of leaf
Made of hexagonal cells which fit closely together
There are no stomata
What is a leaf section?
Different layers of different cells
One of the lower layers is spongy with visibile air spaces in it
What are phloem?
Long tubes which carry food around the plant
Sieve plates run across tubes at regular intervals
Look like dinner plates with lots of holes in them
What does phloem do?
Transports dissolved sugars made in photosynthesis in leaves through the stem including growing regions and storage organs
Active transport loads sugars into phloem
This is called translocation
Phloem are tubes of elongated cells with sap moving through pores in end walls
Small insects eg aphids feed from the phloem using sharp mouths
Root sugars are stored in branches and roots but are made in the leaf
What does xylem tissue do
Transports water and mineral ions from roots to stems and leaves
Composed of hollow tubes strengthened by lignin
Adapted for transport of water in transpiration stream
