Mass Transport in Plants Flashcards
What is mass transport?
The bulk movement of a substance(s) from 1 area of an organism to another a similar rate
Diagram of a root? (6)
How are root hair cells adapted?
- Extensions that increases surface area to increase uptake of water + increase area for channel & carrier proteins
- Thin cellulose cell walls so shorter diffusion pathway
What is the structure + function of the xylem tissue? (4)
- Dead cells which form hollow tubes with no organelles for faster water flow
- No end walls so a continuous columns of water can form
- Cells walls are strengthened with lignin to make xylem waterproof + provides support to withstand tension
- Xylem pits to allow water to move laterally to get around blocked vessels
Describe the cohesion-tension theory of water transport in the xylem? (6)
- Water is lost from the leaf due to transpiration
- This water loss lowers water potential of leaf cells
- Water is pulled up the xylem
- Water molecules cohere together by hydrogen bonds
- Which forms a continuous column
- Adhesion of water to walls of xylem
Explain how water enters the xylem from the endodermis in the root + is then transported to the leaves? (5)
IN THE ROOT
- Active transport of ions into xylem
- Decreases water potential in xylem/ water enters xylem by osmosis
XYLEM TO LEAF
- Transpiration
- Creates tension/ cohesion
- Adhesion/water molecules bind to xylem
- Creates continuous column of water
Root pressure moves water through the xylem. Describe what causes root pressure? (4)
- Active transport by endodermis
- Ions into xylem
- Lowers water potential
- Water enters by osmosis
Describe how high pressure is produced in the leaves? (3)
- Water potential becomes lower
- Water enters phloem by osmosis
- Increased volume of water cause increased pressure
Factors affecting rate of transpiration? (5)
- Light Intensity - more stomata opens which increases RoT
- Temperature - increases KE, diffusion, evaporation + RoT
- Humidity - decreases
- Wind Speed - increases
- Stomatal Density - increases
Give 3 precautions the students should have taken when setting up the photometer to obtain reliable measurements of water uptake by the plant shoot?
- Seal joints/ensure watertight
- Dry off leaves
- Ensure no air bubbles are present
- Cut shoot at a slant
Diagram of phloem?
Describe the transport of carbohydrate in plants? (5)
- Sucrose is actively transported into the phloem
- By companion cells
- Which lowers water potential + water enters (from xylem) by osmosis
- This produces a higher pressure
- Which causes mass flow to respiring cells
Describe the mass flow hypothesis for the mechanism of translocation in plants? (5)
- Sucrose actively transports into the phloem by companion cells
- Lowers water potential of sieve cell
- Water enters by osmosis
- Increase in pressure causes mass movement
- Sucrose used/converted in root for respiration for storage
LOOK AT QUESTIONS FROM QUESTION PACK TO ADD
What is the ringing experiment?
For? (2)
Against? (3)
If a ring of bark is removed then a budge form as phloem is also removed
FOR
- Fluid from the bulge has higher conc. of sugars as sugar can’t move past
- Conc. of sucrose is higher in leaves than roots
AGAINST
- Sieve plate function unclear
- Not all solutes move at the same rate
- The sieve plates would create a barrier to mass flow
