HL Plant transport

What is water potential a measure of?

• The kinetic energy of water per unit volume

• The temperature of water per unit volume

• The potential energy of water per unit volume

• The density of water per unit volume

Answer explanation

Water potential is a measure of the potential energy of water per unit volume, making it the correct choice.

What is the water potential of pure water at atmospheric pressure and 20°C?

• 100 kPa

• 50 kPa

• 0 kPa

• -10 kPa

Answer explanation

The water potential of pure water at atmospheric pressure and 20°C is 0 kPa because pure water has the highest water potential, which is defined as 0 kPa.

In which direction does water move in terms of water potential?

• From lower to higher water potential

• From higher to lower water potential

• From higher to higher water potential

• From lower to lower water potential

Answer explanation

Water moves from higher to lower water potential, following the gradient to reach equilibrium.

What are the two main factors determining the water potential of a cell with walls?

• Pressure potential and kinetic potential

• Solute potential and pressure potential

• Pressure potential and temperature potential

• Solute potential and temperature potential

Answer explanation

The two main factors determining the water potential of a cell with walls are solute potential and pressure potential.

What is the formula for overall water potential (Ψw) in a cell with walls?

• Ψw = Ψs - Ψp

• Ψw = Ψs + Ψp

• Ψw = Ψp - Ψs

• Ψw = Ψs * Ψp

Answer explanation

The correct formula for overall water potential (Ψw) in a cell with walls is Ψw = Ψs + Ψp.

What happens to plant cells in a hypotonic solution?

• Water exits the cells, leading to plasmolysis

• Water moves into the cells, increasing turgor pressure

• Cells shrink due to water loss

• Cells remain unchanged

Answer explanation

In a hypotonic solution, water moves into the plant cells, increasing turgor pressure, which helps maintain cell rigidity and prevent wilting.

What process generates root pressure in xylem vessels?

• Evaporation of water

• Active transport of mineral ions

• Passive transport of mineral ions

• Diffusion of water

Answer explanation

Active transport of mineral ions generates root pressure in xylem vessels by creating a concentration gradient that drives water uptake.

What is the role of sieve plates in phloem sieve tubes?

• To provide metabolic support

• To allow the flow of sap between cells

• To reduce resistance to flow

• To store nutrients

Answer explanation

Sieve plates in phloem sieve tubes allow the flow of sap between cells, facilitating the movement of nutrients and other substances.

What is the function of companion cells in phloem?

• To transport oxygen

• To facilitate the loading and unloading of materials into sieve tubes

• To provide structural support

• To store water

Answer explanation

Companion cells in phloem facilitate the loading and unloading of materials into sieve tubes, aiding in the transport of nutrients and other substances.

What happens to plant cells in a hypertonic solution?

• Cells remain unchanged

• Water exits the cells, leading to plasmolysis

• Cells burst due to water intake

• Water moves into the cells, increasing turgor pressure

Answer explanation

In a hypertonic solution, water exits the plant cells, causing plasmolysis due to the higher concentration of solutes outside the cell.