Mass Transport In Plants Flashcards
Explain how water enters xylem from the endodermis in the root and is then transported to the leaves. (6)
- Active transport by endodermis;
- (Of) ions/salts into xylem;
- Lower water potential in xylem / water enters xylem by osmosis /down a water potential gradient;
(Xylem to leaf)
4. Evaporation / transpiration (from leaves);
5. (Creates) cohesion / tension / H-bonding between water molecules / negative pressure;
6. Adhesion / water molecules bind to xylem;
7. (Creates continuous) column of water
Root pressure moves water through the xylem. Describe what causes root pressure. (4)
- Active transport by endodermis;
- ions/salts into xylem;
- Lowers water potential (in xylem);
- (Water enters) by osmosis;
Name a factor that can affect transpiration
Light (intensity) / temperature / air movement / humidity
Why do plants need to absorb nitrate ions (NO3-) from the soil?
- They contain Nitrogen which make up amino acids for protein synthesis
- Nitrogen is required for the production of nitrogenous bases in nucleic acids (DNA and RNA)
Why do plants need to absorb Magnesium ions?
- needed for making chlorophyll
EXTRA - (plant turns yellow if not enough Magnesium)
Why do plants need to absorb Phosphate ions (PO4 3-)?
- for making nucleotides of DNA and RNA
- making ATP
- used to make phospholipids used in phospholipid bilayers
Give 2 features of root hair cells that are adaptations for uptake of water and minerals?
- Hair like projections which increase surface area to increase the rate of absorption of water and minerals
- Contain many mitochondria (release ATP for active transport of ions)
Why does a plant need to control entry of mineral ions into the xylem?
Some mineral ions are toxic if they are absorbed and accumulate inside plant tissues (e.g. Copper ions)
Why are potassium ions absorbed by plants?
- They are required for stomatal opening
Why does the plant actively transport mineral ions through the endodermis cell membrane?
Gives the plant control over which mineral ions are let through into endodermal cells and therefore through into the xylem
How is the water potential of the root hair cell initially lowered?
Mineral ions are transported from soil water to the root hair cell cytoplasm across cell membrane using carrier proteins and energy from ATP
What are Xylem adaptations?
- Xylems are dead hollow tubes (no cytoplasm)
- Walls contain lignin which makes them rigid and waterproof
- Thicc walls to withstand (negative) water pressure and are narrow to enable water to travel up them by capillary action
- Pits enable water to move laterally between xylem vessels
Give two precautions the students should have taken when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot
- Seal joints/ ensure airtight/ ensure watertight
- Cut shoot under water
- Cut shoot at a slant
- Dry off leaves
- Insert into apparatus under water
- Ensure no air bubbles are present
- Shut tap
- Note where bubble is at start/ move bubble to the start position
Describe the role of the sieve tube elements (2 marks)
- Living cells that form a tube for transporting solutes
- They have no nucleus and a few organelles
Describe the role of companion cells (1 mark)
- Contain many mitochondria to synthesize ATP through aerobic respiration for the active transport of solutes
