3.3 Organisms exchange substances with their environment - Mass Transport in Plants Flashcards
What is transpiration?
The loss of water vapour from the stomata by evaporation.
Transpiration plays a crucial role in water movement and temperature regulation in plants.
What are the four factors that affect the rate of transpiration?
- Light intensity
- Humidity
- Temperature
- Wind
These factors influence the evaporation of water from the plant’s surface.
What is the relationship between light intensity and transpiration?
There is a positive correlation.
Higher light intensity leads to more open stomata, increasing the surface area for evaporation.
How does humidity affect transpiration?
There is a negative correlation.
Increased humidity raises the water potential outside the leaf, reducing the water potential gradient and evaporation.
What is the effect of temperature on transpiration?
There is a positive correlation.
Higher temperatures increase kinetic energy, leading to faster-moving molecules and increased evaporation.
How does wind influence transpiration?
There is a positive correlation.
Wind removes humid air from around the leaf, maintaining the water potential gradient and promoting evaporation.
What is the cohesion-tension theory?
It explains how water moves up a plant against gravity through three principles: Cohesion, Capillarity (adhesion), and Root Pressure.
This theory is essential for understanding how plants transport water from roots to leaves.
Fill in the blank: The more _______ there is, the more kinetic energy, leading to faster-moving molecules in transpiration.
[temperature]
True or False: A higher water potential gradient increases evaporation.
True
A steeper water potential gradient facilitates the movement of water from areas of higher potential to lower potential.
What role do stomata play in transpiration?
They are the openings through which water vapour is lost from the plant.
Stomata can open and close to regulate water loss and gas exchange.
What is capillarity in the context of the cohesion-tension theory?
It refers to the adhesion of water molecules to the walls of xylem vessels, aiding in water transport.
Capillarity allows water to rise against gravity in narrow tubes.
What is root pressure?
It is the pressure within the roots that helps push water upwards through the plant.
Root pressure is generated by the active uptake of minerals and water from the soil.
What is a dipolar molecule?
A molecule with a slight negative charge on one end and a slight positive charge on the other end
Water is an example of a dipolar molecule.
What enables hydrogen bonds to form between water molecules?
The dipolar nature of water
The oxygen atom carries a slight negative charge while the hydrogen atoms carry a slight positive charge.
What is cohesion in the context of water molecules?
The sticking together of water molecules due to hydrogen bonds
Cohesion allows water to travel up the xylem as a continuous water column.
What role does adhesion play in the movement of water in plants?
Water sticks to other molecules, helping to hold the water column up against gravity
Adhesion occurs when water molecules form hydrogen bonds with the xylem walls.
How does capillarity affect the movement of water in narrow xylem?
The narrower the xylem, the greater the impact of capillarity
This is because more water molecules adhere to the walls, requiring less pull to draw up the liquid.
Fill in the blank: Water adheres to the xylem walls due to _______.
hydrogen bonds
This adhesion is crucial for water transport in plants.
True or False: Cohesion allows water to move upward through the xylem.
True
Cohesion creates a continuous water column that facilitates upward movement.
What is the effect of straw width on the required pull to draw up liquid?
The narrower the straw, the less pull is required
This demonstrates the principle of capillarity in water movement.
What is root pressure?
The pressure inside the root that increases as water moves in by osmosis, forcing water upwards.
What causes positive pressure in plants?
The increase in volume of liquid inside the root due to water entering by osmosis.
What is the effect of water vapor evaporating from stomata?
It creates a lower pressure inside the leaves, leading to more water being pulled up the xylem.
What is negative pressure in the context of plant water transport?
The pressure created when water is lost by transpiration, pulling more water up the xylem.