9.1 - transport in the xylem of plants

Question 1

what is transpiration?

Answer 1

the loss of water vapor from the leaves and stems of plants.

Question 2

how do plants control water loss?

Answer 2

through the stomata using guard cells that control the aperture of the stomata.

Question 3

how is water replaced from transcription?

Answer 3

using transcription pull, water travels up the xylem vessels.
Xylem are strong bc of the lignin within the walls of the xylem.

Question 4

draw an annotated root and stem diagram

Question 5

what is a xylem

Answer 5

transports water and mineral ions around the plant.
long continuous tube of dead hollow cells

Question 6

xylem in young plants

Answer 6

thin wall and are freely permeable

Question 7

xylem in grown-up plants

Answer 7

undergoes lignification.
has think walls with lignin. strong walls that withstand low pressures.

Question 8

what is passive water movement in the xylem?

Answer 8

cohesion between water molecules.
adhesion with water and xylem wall.
this allows water to be pulled through the xylem in a continuous stream.

Question 9

how does a xylem work?

Answer 9

1. evaporation creates low pressure.
2. adhesion draws water into the leaf lowering the pressure
3. water is drawn from the roots into the xylem
   This is done by the transpiration pull.

Question 10

xylem model - capillary tube

Answer 10

cohesion between water molecules, and adhesion to glass.
water rises higher than the surrounding water level.

Question 11

xylem model - chromatography

Answer 11

cohesion between water molecules, and adhesion to paper. water rises up the paper.

Question 12

xylem model - porous pots

Answer 12

evaporation from pores. negative pressure draws up water from a tube by cohesion.

Question 13

active transport in the Roots

Answer 13

1. mineral ions actively transported into root cells
2. establishes a concentration gradient - water moves in by osmosis
3. seperate protien pumps for each mineral ion - potas, sodi, phos, nitr

Question 14

what is hyphae purpose?

Answer 14

some ions move to slowly so the hyphae absorb ion more quickly and pass them into the plant in exchange for glucose.

Question 15

what does the stomata do?

Answer 15

allows for effective gas exchange during photosynthesis because of the waxy cuticle.

Question 16

how does the transpiration pull occur?

Answer 16

1. water evaporates from mesophyll cells
2. water vapour diffuses through stomata pores
3. this increases the concentration in mesophyll cells
4. water from the xylem or vascular bundle moves into mesophyll cells by osmosis to replace lost water.
5. water climbs xylem by adhesion and cohesion
6. water from soil to roots by osmosis as minerals actively transported

Question 17

what does a potometer measure?

Answer 17

the uptake of water in plants
rate of transpiration

Question 18

how does a potometer work?

Answer 18

air bubble moves along a volume scale through a capillary tube as transpiration takes place in a cut shoot, water from stem to leaves

Question 19

what is mineral ion absorption - active transport

Answer 19

can only happen if ions contact the right pump protien
- this happens by diffusion by mass flow
- water carries ions through soil by relationship with fungus
- the fungus grows on roots to absorb mineral ions, in return gets sugars

Question 20

what are xerophytes?

Answer 20

plants that have adapted to grow in dry habitats.

Question 21

how do xerophytes adapt?

Answer 21

• reduce surface area of leaves even to spines to reduce evaporation
• a thicker waxy cuticle and low to the ground reduces water loss
• smaller no. of stomata
• use water storage tissue in stems
• stomata open at night instead of day
• tiny hairs used to stop or slow wind to reduce water vapour loss
• rolled leaves and stomata sit in pits to minimise opening.

Question 22

how is carbon dioxide used in xerophytes?

Answer 22

absorbed at night and stored as malic acid then used as carbon dioxide at day.
its called crassulacean acid metabolism - CAM

Question 23

what is a halophyte?

Answer 23

plants adapted to grow in saline conditions.

Question 24

how do halophyte adapt to their conditions? and an example.

Answer 24

• leaves are small scaly structures or spines
• leaves go when water is scarce - stem does photosynthesis
• water storage in leaves
• thick outer cuticle and muli layers of epidermis
• sunken stomata
• long roots
• have things to remove salt build up
  eg. ice plant