9 Transport in Plants

Question 1

What are the metabolic demands of plants (transport) (2)

Answer 1

-hormones in plants need transporting
-mineral ions absorbed by the roots need to be transported to all cells

Question 2

why do plants need a transport system (3)

Answer 2

-metabolic demands
-size = plants don’t stop growing
-surface area = leaves have a large SA:V ratio, but plants overall have a low SA:V ratio

Question 3

what is the series of transport vessels running through the stem, roots and leaves called ….

Answer 3

The vascular system

Question 4

what does the xylem carry (2)

Answer 4

-water
-soluble mineral ions

Question 5

which direction does the xylem carry its items

Answer 5

-upwards , roots to leaves

Question 5

what does the phloem carry (2)

Answer 5

-sugars
-amino acids

Question 6

which direction does the phloem carry its items

Answer 6

up + down

from the leaves to the rest of the plant

Question 7

what are vessels

Answer 7

tubes with thick lignified walls and no cross walls or living cell contents

Question 8

what does lignin do (6)

Answer 8

-waterproof
-strong
-causes cell death
-prevents tube collapse
-flexible, its shape is a spiral, ringed, broken rings
-water can enter and exit though irregular breaks in the lignin

Question 9

is the xylem or phloem in the centre

Answer 9

xylem = centre

Question 10

what are the functions of the pits in xylem (2)

Answer 10

-allow water + solutes to move from the xylem to the cells
-bypass a blockage

Question 11

explanation for xylem structures + processes (big)

Answer 11

The xylem is lined with lignin which kills of the cells surrounding it. This forms a spiralled column in which the mass flow of water and solutes can be transported in. Bordered pits are on the walls of the xylem and these allow water and solutes to pass from the xylem to the cells. The companion cells are there for loading and unloading sugars into the cavity of sieve tube members.

Question 12

Explanation for the phloem’s structure + processes

Answer 12

phloem carry ions, water and sugars. The structure is made up of sieve tube elements which are long cells containing no nucleus or cytoplasm. The phloem tissue contains perforated sieve plates, which allow substance’s to pass though.

Question 13

Hydrostatic pressure in plants is called ……. its caused by ……

Answer 13

turgor pressure

osmosis

Question 14

what does turgor pressure do

Answer 14

-drives cell expansion

(the force that enables plants roots to force their way through tarmac + concrete)

Question 15

what is a root hair

Answer 15

a long thin expansion of a root hair cell, a specialised epidermal cell

Question 16

facts for root hair cells (structures for processes) (4)

Answer 16

-microscopic size = penetrate easily between soil particles
-large SA:V ratio = thousands of root hair cells on root tip
-thin surface layer = diffusion + osmosis can take place quickly
-concentration of solutes in the cytoplasm = maintains water potential gradient between the soil water and the cell.

Question 17

apoplast pathway

Answer 17

travels through cell walls by cohesion

Question 18

Symplast pathway

Answer 18

Travels though cytoplasm + plasmodesmata

Question 19

Vacuolar pathway

Answer 19

travels though the vacuole + plasmodesmata

Question 20

what is plasmodesmata

Answer 20

• these are almost gaps in cell wall + membrane pf a plant cells when together, for easier paths that water can take (faster)

Question 21

Casparian strip

Answer 21

-surrounds the endodermis cells
-stops flow in apoplast pathway

( looks like a cube with a dark strip all around its outside)

Question 22

information card for how water travels from soil to xylem

Answer 22

-Enters root cell via osmosis down the concentration gradient due to the higher volume of minerals inside the cell and a lower water potential than the soil. (active transport maintains the concentration gradient, by taking the mineral ions in)
-Water travels by 3 pathways symplast, apoplast and vacuolar.
- When water reaches the endodermis cells which are surrounded by casparion strips the apoplat pathway no longer works. Water then travels into the endodermis cell by vacuolar and symplast pathways.
-Water now enters the xylem through the endodermis cells.

Question 23

what does root pressure do

Answer 23

moves water through the xylem

Question 24

how is root pressure caused

Answer 24

endodermis cells use active transport to take mineral into the xylem, this then lowers the water potential in the xylem causing water to enter. The lower the water potential in the xylem making it more negative.

Question 25

what is cohesion

Answer 25

water molecules stick together due to hydrogen bonding

Question 26

what is tension

Answer 26

‘suction’ pulls more water into the leaf

Question 27

What is adhesion

Answer 27

hydrogen bonds in water stick to cellulose on inside of the cell wall

Question 28

what us transpiration

Answer 28

the continuous pull of water through a plant

Question 29

what is capillary action

Answer 29

water will pull adhere to the dies of a vessel and move upwards in confined spaces, caused by the adhesive properties of water.

can observed in glassware, the narrower the glassware diameter the more the water creeps up.

only contributes minimally to overall movement up the xylem

Question 30

wyas leaves/ plants conserve water (9)

Answer 30

-root adaptations
-thick waxy cuticle
-sunken stomata
-reduced leaves
-reduced number of stomata
-hairy leaves
-curled leaves
-succulents
-leaf loss

Question 31

why are root adaptations good

Answer 31

can penetrate several metres deep, shallow roots to absorb water before it evaporates

Question 32

why are sunken stomata good

Answer 32

stomata located in pits, reduce air movement, produce microclimate + collects water that would’ve left

Question 33

why are hairy leaves good

Answer 33

create a microclimate of still humid hair. Some plants such as marram grass have micro hairs in sunken stomata pits.

Question 34

why are curled leaves good

Answer 34

Con fines all of the stomata within a microenvironment of still humid air to reduce diffusion of water vapour from the stomata, creates a smaller SA:V ratio e.g. marram grass

Question 35

structures of hydrophytes (3)

Answer 35

-buoyancy = air spaces
-stomata on the upper endermis, so they are exposed to air for gas exchange
-leaf stem has many air spaces, helps with buoyancy and quick diffusion of oxygen to roots for aerobic respiration.

Question 36

info card how does water move from a source to a sink (5 steps)

Answer 36

1
Sucrose is actively loaded into the sieve tube element and reduces the water potential

2
Water flows by osmosis and increases the hydrostatic pressure in the sieve tube element

3
Water moves down sieve tube from higher hydrostatic pressure at source to lower hydrostatic pressure at sink

4
Sucrose is removed from the sieve tube by the surrounding cells and increases the water potential in the sieve tube

5 Water moves out of sieve tube and reduces the hydrostatic pressure.