Transport in Plants

Question 1

What is transported in the xylum?

Answer 1

Water

Question 2

What is transported in the phloem?

Answer 2

Dissolved solutes such as sucrose

Question 3

How is the xylum formed?

Answer 3

It starts off as living tissue in the protoxylum which is flexiable.
As it ages, moe lignin is added and it becomes less flexiable and impermeable to water

Question 4

How is water transported from the roots to the leaves?

Answer 4

A transpiration stream

Question 5

What is the structure of the phloem?

Answer 5

Made up of sieve tube elements joined together linked to companion cells by a plasmodesmata

Question 6

How are companion cells adapted for their function?

Answer 6

Their membrane is highly folded to increase the surface area that they can transport sucrose into the cytoplasm
They have many mitochondria to supply the ATP needed for active loading

Question 7

What part of the root absorbs water?

Answer 7

The root tip as it has more root hair cells which increase surface area

Question 8

What is the purpose of root hair cells?

Answer 8

To increase surface area for osmosis into the plant

Question 9

How does water enter the root?

Answer 9

Through osmosis down it’s concentration gradient into the root hair cell

Question 10

What are the two routes that water can take from the root hair cells to the xylum?

Answer 10

Symplast pathway

Apoplast pathway

Question 11

What is the symplast pathway?

Answer 11

Water moves by diffusion down it’s concentration gradient through the cytoplams and plasmodesmata of cells

Question 12

What is the apoplast pathway?

Answer 12

Water is pulled between the cell walls due to it’s cohesive nature

Question 13

What is the casparian strip?

Answer 13

A waterproof layer of waxy tissue that controlls how much water enters the xylum. Water goes into the cytoplasm of cells temporerily.

Question 14

Is the movement of water a passive or an active process?

Answer 14

Passive

Question 15

Where does water go when it reaches the leaf?

Answer 15

Into the spongy mesophyll cells by osmosis where it evaporates and moves out of the stomata

Question 16

What is the transpiration stream?

Answer 16

When water evaporates, more water is pulled up into the leaf due to the cohesive nature of water. More water is then pulled through the xylum from the roots which creates a concentration gradient and means more water enters the roots through osmosis

Question 17

What factors affect transpiration?

Answer 17

Light
Temperature
Air movement
Humidity

Question 18

How does light affect transpiration?

Answer 18

Transpiration increases with light intensity as more of the stomata open

Question 19

How does tempreture affect transpiration?

Answer 19

Transpiration increases with tempreture. Tempreture ncreases the ammount of evaporation from the surface of the leaf and the ammount of waer vapour that the air can take. This means there is a steeper concentration gradient between the air and the leaf so transpiration increases

Question 20

How does air movement affect transpiration?

Answer 20

It reduces the shell of air around the leaf which keeps a steep diffusion gradient

Question 21

How does humidity affect transpiration?

Answer 21

High humidity lowers transpiration as the concentration gradient decreases

Question 22

What is the name given to the substances dissolved in the phloem?

Answer 22

Assimilates

Question 23

What is a source?

Answer 23

An area of the plant with high sucrose and loads sucrose onto the phloem

Question 24

What is a sink?

Answer 24

An area with low sucrose that removes sucrose from the phloem

Question 25

What is phloem loading?

Answer 25

The way that sucrose is moved into the phloem

Question 26

What are the two kinds of phloem loading?

Answer 26

Symplast pathway: Sucrose moves through the cytoplasm of the cells
Apoplast pathway: Sucrose moves through the spaces inbetween cells

Question 27

How is sucrose unloaded from the phloem?

Answer 27

Diffusion down it’s concentration gradient