Topic 8

Question 1

Funtion of xylem

Answer 1

Transports water and minerals up the plant
-From the roots to the stem and leaves

Question 2

Function of phloem

Answer 2

Transport of sucrose and amino acids in both directions
- From the leaves to every cell

Question 3

Structure of xylem

Answer 3

Thick walls with lingin
No cell contents (dead hollow cell)
Cells joined end to end with no cross walls to form al long continous tube

Question 4

Why do plants need water?

Answer 4

Plants need water for photosynthesis, for cooling, transport of minerals and nutrients from the soil into the plant

Question 5

Where does water enter the plants

Answer 5

From the soil to the roots, by osmosis. It enters the root hair cells.

Question 6

Function of root hair cells

Answer 6

Absorption of water (osmosis) and active transport of ions

Question 7

Adaptations of root hair cells

Answer 7

• large surface area -> increases the uptake of water and mineral ions
  - large vacuole -> for storage of water
• mitochondria -> for active transport

Question 8

Pathway of water

Answer 8

Soil -> root hair cells -> root cortex cells -> xylem vessel -> travels in the xylem up the stem -> into palisade mesophyll cells

Question 9

What is transpiration

Answer 9

The loss of water vapour from plant that leaves by evaporation

Question 10

What is water needed for in plants

Answer 10

• it is a recatant for photosynthesis
• to mantain turgor pressure in cells, supports the plant

Question 11

Water evaporation (transpiration)

Answer 11

Water evaporates from the surface of mesophyll cells in the leaf to form water vapour. This moves through air spaces and diffuses out the leaf via stomata

Question 12

The transpiration pull (7)

Answer 12

1) evaporation and diffusion of water occurs from the leaves
2) shortage of water from the leaf
3) more water is drawn into the leaf from the xylem to replace this lost water
4) there are forces of attraction between water molecules, holding them tigether (water has conesive forces)
5) water is pulled up the xylem from the roots
6) water is drawn up from the roots
7) there is a contant transpiration pull of water through the plant

Question 13

How does leaf structure increase water loss?

Answer 13

• Leaves are adapted for photosynthesis and diffusion of gases
• This means that the mesophyll layer has a large surface area for diffusion of gasses, but also means more water can evaporate out the leaf

Question 14

How do guard cells influence water loss?

Answer 14

• Gurad cells can change the diameter of the stomata to control water loss
  -> the smaller the stomata, less water lost
  -> the greater the number of stonata, the more water is lost

Question 15

Factors that affect transpiration rate

Answer 15

Temperature
Humidity
Wind speed

Question 16

Factors that affect transpiration rate: temperature

Answer 16

• More kinetic energy
• Faster diffusion/transpiration

Question 17

Factors that affect transpiration rate:
Humidity

Answer 17

The higher the humidity, the more H2O around leaf -> slower transpiration
Lower concentration gradient

Question 18

Factors that affect transpiration rate:
Wind speed

Answer 18

• Faster/higher speed -> faster transpiration
  -> because wind sweeps evaporated water away
  -> and higher concentratin gradient

Question 19

What is translocation

Answer 19

The movement of sucrose and amino acids through the phloem from a source to a sink

Question 20

What is a source

Answer 20

Any part of the plant which releases sucrose or amino acids

Question 21

What is a sink

Answer 21

1) where sucrose and amino acids are stored
2) sucrose or amino acids are used up in respiration or growth

Question 22

Are the concentration of solutes higher at the source or the sink

Answer 22

Concentration of solutes are higher at the source than the sink

Question 23

Plants can be both sources and sinks: sources

Answer 23

• Plants growing -> leaves are photosynthesising
• Amino acids are made in the roots the transported to developing roots, flowers, leaves, seeds

Question 24

Plants can be both sources and sinks: sinks

Answer 24

• Winter -> storage in roots, tubers and bulbs
• Reproductive structures and stems during growth
• Newly growing leaves in spring, when they are fully grown they become sources again