Transpiration And Translocation Flashcards
1
Q
What do the phloem transport
A
- they transport food substances (mainly dissolved sugars) made in the leaves to the rest of the plant for immediate use (e.g. in growing regions) or for storage
- The transport goes in both directions
- This process is called translocation
2
Q
What is the xylem made out of
A
- dead hollow cells joined end to end
- They’re strengthened with a material called lignin
3
Q
What is the phloem made out of
A
- elongated living cells with small pores in the end walls
- to allow cell sap to flow through
4
Q
What does the xylem transport
A
- they carry water and mineral ions from the roots to the stem and leaves
- the movement of water from the roots, through the xylem and out of the leaves is called the transpiration stream
5
Q
What is transpiration
A
- the loss if water from the plant through he leaves
- it is caused by evaporation and diffusion of water from a plant’s surface
6
Q
Describe how the transpiration stream works
A
- transpiration causes a shortage if water in the leaf, so more water is drawn up from the rest of the plant through the xylem vessels to replace it
- this in turn means more water is drawn up from the roots, and so there’s a constant transpiration stream of water through the plant
7
Q
What 4 things can affect the rate of transpiration
A
- light intensity
- Temp
- Air flow
- Humidity
8
Q
How does light intensity affect the rate of transpiration
A
- The brighter the light, the greater the rate
- Stomata begin to close as it gets darker. Photosynthesis can’t happen in the dark, so they don’t need to open to let CO2 in. When the stomata are closed, very little water can escape.
9
Q
How does temp affect the rate of transpiration
A
- the warmer it is, the faster transpiration happens
- When it’s warm the particles have more energy to evaporate and diffuse out of the stomata
10
Q
How does air flow affect the rate of transpiration
A
- The better the air flow around a leaf (e.g. stronger wind), the greater the transportation rate
- If air flow around a leaf is poor, the water vapour just surround the leaf and doesn’t move away. This means that there is a high conc of water particles outside the leaf as well as inside it, so diffusion doesn’t happen as quickly
- If there’s a good air flow, the water vapour is swept away, maintaining a low concentration of water in the air outside the leaf. Diffusion then happens quickly, from an area of higher conc to an area of lower conc
11
Q
How does humidity affect the rate of transpiration
A
- the drier the air around a leaf, the faster transpiration happens
- this is like what happens with air flow. 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 the outside of the leaf
- Diffusion happens fastest when there’s a really high conc in one place, and a really low conc in the other
12
Q
What is the basic function of the guard cells
A
To open and close the stomata
13
Q
What is the shape of the guard cells
A
They have a kidney shape
14
Q
What do the guard cells do if there’s lots of water in the plant, why do they do this
A
- The guard cells fill with it, and go plump and turgid
- this makes the stomata open so gases can be exchanged for photosynthesis
15
Q
What do they guard cells do when the plant is short of water, and why
A
- they lose water and become flaccid, making the stomata close
- this helps stop too much water vapour escaping
