trasnport in plants

Question 1

where does Absorption of water and dissolved mineral salts takes place mainly in ?

Answer 1

Absorption of water and dissolved mineral salts takes place mainly in the zone of root hairs.

Question 2

y does water enter the root hair cell

Answer 2

The sap in the root hair cell is a relatively concentrated solution of sugars and salts. Thus the cell has a more negative water potential than the soil solution.

Question 3

how does water molecules make it from the outer layer to the xylem

Answer 3

Water molecules pass by osmosis from cell to cell in the cortex region of the root until they reach the xylem vessels.
osm from soil to root, osm from root thru cortex. AT from cortex into xylem

Question 4

how is dissolved mineral salts taken into the plant

Answer 4

Active transport is the main mode of absorption of dissolved mineral salts by root hair cells.

Question 5

how does mineral salts get to the xylem

Answer 5

After being absorbed the dissolved mineral salts diffuse from cell to cell until they are actively transported into the xylem vessel.

Question 6

what are three main ways in which water moves up a plant:

Answer 6

Capillary action / capillarity
Root pressure
Transpiration pull (cohesion-tension theory)

Question 6

what is capillary action

Answer 6

water will rise due to the attraction of water molecules to the cellulose in the wall of the xylem vessel (adhesion) and the attractive forces between water molecules (cohesion). Adhesion and cohesion are due to hydrogen bonds.
only for small plants

Question 6

what is root pressure

Answer 6

 The living cell around the xylem vessels in the root use active transport to pump ions into the vessels. The accumulation of dissolved mineral salts in the stele makes its water potential more negative than cells in the root cortex.
 Water flows from the cells in the root cortex down a water potential gradient by osmosis and enters the xylem vessel with sufficient force to generate a hydrostatic pressure that forces fluid up the xylem vessel. This upward push of xylem sap is called root pressure.

Question 7

what is Transpiration pull (cohesion-tension theory)

Answer 7

ranspiration pull: Main force pulling water up to leaves.
Transpiration: Loss of water vapor from stomata.
Spongy mesophyll: Cells with air spaces; water forms a thin film.
Steps of Transpiration:
Evaporation: Water from mesophyll cells to air spaces.
Diffusion: Water vapor through stomata to outside air.
Tension: Evaporation creates a pulling force, lowering water potential.
Water Movement:
From mesophyll cells to surface film.
From deeper cells to veins (xylem vessels).
Transpiration Stream: Continuous upward movement of water and minerals.
Cohesion: Water molecules stick together, forming a continuous column.

Question 8

what happens when transpiration is higher than the rate of water absorption

Answer 8

Excessive transpiration that is higher than the rate of water absorption is harmful to the plant because it causes cells to lose their turgor pressure, leading to the plant wilting.

Question 9

3. transpiration benefits

Answer 9

1. The suction force (tension) due to transpiration is the main factor in transporting water and dissolved mineral salts up the plant from the roots to the leaves for photosynthesis.
2. It allows water to flow through the plant, making the cells turgid and keeping the plant upright.
3. As water coating spongy mesophyll cell walls evaporates, latent heat of vaporisation is removed, thereby *cooling** the leaves.

Question 10

y is trabspiration inevitable

Answer 10

photosynthesis is needed for the plant to produce ATP to survive. Carbon dioxide diffuses into the leaf via the open stomata for photosynthesis to occur. At the same time, water vapour also diffuses out via the stomata in transpiration.

Question 11

what influences the rate of transpiration

Answer 11

Humidity of air
Temperature of the air
Air movements
Light intensity