transport in plants

Question 1

what are the main substances transported in plants

Answer 1

water and organic substances

Question 2

structure of the roots

Answer 2

in the roots the vascular bundles are arranged different to the stem and leaves
the xylem is a star shape the pholem is in the middle of the star shape

Question 3

structure of the stem

Answer 3

xylem = inner edge of the bundle
pholem = outer edge of the bundle
combodium is a meristematic tissue contains actively dividing pluripotent cells

Question 5

structure of the leaf

Answer 5

in the leaf the vascular bundles runs down the centre of the leaf and contains both xylem and pholem tissues

Question 6

pholem

Answer 6

lateral sieve area = assist in the mass transport of floras they are dependent on companion cells to provide ATP
companion cells = provide ATP required for active transport of organic substances
sieve tube element = living cells no nucleus contains few organelles

Question 7

xylem

Answer 7

xylem cells are dead and hollow
they do not contain any organelles or end walls they stack on top of each other to make a j=holow column
it is strengthen with lignin

Question 8

transport of water into the plant

Answer 8

water is absorbed into plants through the root hair cell by osmosis
root hair cells are adapted to maxisme osmosis it then travels to the xylem by either to simplest pathway or the apoplast pathway

Question 9

symplast pathway

Answer 9

the symplast pathway is through the cytoplasm of a cell the water moves from cell to cell towards the xylem by osmosis
through the cytoplasm and through gaps in each cell wall called plasmodesmata
each successive cell cytoplasm has a lower water potential and this is why the water is able to move by osmosis through

Question 10

the apoplast pathway

Answer 10

the apoplast pathway is through cell walls, water can enter the cell wall and move due to cohesive force of water
the water molecules stick together forming a continuous stream of water which move toward the xylem. this pathway transports the water faster so there is little resistance to the water in the cell.

Question 11

adaptation of plants

Answer 11

plants exchange gases through the stomata which are tiny pores that open or close depending by the guard cells surrounding them.
this is a mechanism to help prevent excessive water loss by evaporation

Question 12

xerophytes

Answer 12

xerophytes are plants with adaptations to reduce water loss and therefore found in locations with limited water e.g. the dessert
marram grass is found on sand dunes and despite being next to the ocean there is limited water

Question 13

xerophytes have :

Answer 13

• curled leaves to trap moisture to increase local humidity
• sunken stomata to trap moisture to increase humidity
• hairs to trap moisture to increase local humidity
• thick cuticle to reduce evaporation
• longer root network to reach more water

Question 14

hydrophyte

Answer 14

hydrophytes are plants that live in/on water so they require adaptations to survive in an excess of water e.g. water lilies

Question 15

hydrophytes adaptations

Answer 15

adaptations : short rots , very thin/ no waxy cuticle , stomata permanently open
to ensure no additional water is retained in the plant and enough light is still absorbed for photosynthesis
adaptations: large leaves, wide leaves, and they are on the surface of the water

Question 16

transpiration definition

Answer 16

the loss of water vapour from the stomata by evaporation, can be measured by a potometer

Question 17

the rate of transpiration can be be effected by :

Answer 17

• light intensity , more light , causes more stomata to open ( positive correlation )
• temperature , more heat means more kinetic energy means faster moving molecules therefore more evaporation ( positive correlation)
• humidity more water vapour in the air makes the water potential more positive that will reduces the water potential negative correlation
• Wind , more wind will blow away humid air containing water vapour therefore maintaining water potential gradient positive correlation

Question 19

 how does water move up the plant?

Answer 19

Water moves up the plant from the roots against gravity due to cohesion tension theory
cohesion + adhesion p+root pressure = cohesion tension theory

Question 20

cohesion

Answer 20

water is a dipole molecule which enables hydrogen bonds to form between the hydrogen and oxygen of different water molecules this creates co cohesion between water molecules they stick together and therefore water travels up the xylem as a continuous water column. Water molecules adhere to the lighting in xylem wall

Question 21

capilarity

Answer 21

adhesion of water is when water sticks to a molecules the narrow the xylem the bigger the impact of capilarity

Question 22

Root pressure

Answer 22

as water moves into the roots by osmosis, it increases the volume of liquid inside the room and therefore the pressure inside the root increases. This is known as root pressure , the increase in pressure in the roots forces water above it upwards (positive pressure)

Question 23

Explain movement of water up the xylem

Answer 23

1. water evaporates out of the stomata on leaves which creates a lower pressure because of the loss of water
2. When this water is lost by transpiration, more water is pulled up the xylem to replace it
3. Due to the hydrogen bonds between water molecules, they are cohesive stuck together which creates a column of water
4. Water molecules adhere stick to the walls of xylem this helps to pull the water to column upwards
   as this column of water is pulled up the xylem accurate tension pulling the xylem in to become narrower

Question 24

trans location

Answer 24

 the transport of organic substances, e.g. sucrose and it requires energy

Question 25

source to sink relationship

Answer 25

Mass flow from the source of production (the leaves ) to the sink the site where organic substance is such as sucrose and amino acids are used up in

Question 26

how sucrose transfers from the source to the sieve tube element

Answer 26

1. Active transport of hydrogen ions occurs from the companion cell into the photosynthesis cell of the source. 2. This creates a concentrated gradient and therefore the hydrogen ions move down their concentration gradient via carrier proteins back into the companion cells. 3. Call transport of sucrose with the hydrogen ions occurs via protein co transporters to transport the sucrose into the companion cells , sucrose then diffusers through plasmodesmata into the sieve tube elements