plant water relations (ex 1) Flashcards
(19 cards)
What is the variable that quantifies the energy state of water?
water potential
The unit is Mpa (Megapascals)
What factors change the energy state of water?
- Osmotic potential: generated by the presence of solutes
- Hydrostatic pressure potential: generated by mechanical pressure
- Matric potential: generated by the adhesion of water to surfaces
- Gravitational potential: generated by the height of water against gravity
What is turgor?
Pressure inside a plant cell exerted by the cell wall against the internal pressure from the vacuole
Why is positive turgor important for land plants?
Maintains the structural integrity of the cell, keeps plant tissues rigid, and supports growth
What property of the plant cell wall makes turgor possible?
Provides structural support
What is saturation vapor pressure?
Pressure exerted by water vapor when it is in equilibrium with liquid water at a specific temperature
How does saturation vapor pressure relate to temperature?
Increases with temperature
What is the role of the plant epidermis?
Protective layer for the plant, preventing excessive water loss
What is the role of stomata?
Control the gateway for the exchange of H2O and CO2 = gas exchange
Name six factors that can affect stomatal aperture.
- Light intensity
- Carbon dioxide concentration
- Temperature
- Humidity
- Water availability
- Plant’s internal water status (turgor pressure)
What does the law of movement state?
Flow rate = Conductance × Energy Gradient
What does leaf wilting indicate about leaf water potential?
Indicates that the leaf’s water potential has become very negative, leading to a loss of turgor pressure
What happens to water potential when leaves wilt?
Water potential decreases, pressure potential inside the cells is low
How can wilted leaves regain turgor without receiving more soil moisture?
By absorbing water from neighboring cells or by reducing their osmotic potential
What are the two types of xylem conduits?
- Tracheids: long, skinny, lower hydraulic conductivity
- Vessels: shorter, wider, higher hydraulic conductivity
How do tracheids and vessels differ in terms of efficiency?
Vessels are more efficient at transporting water due to higher hydraulic conductivity
What happens to the hydraulic conductivity of xylem under drought conditions?
Decreases because xylem vessels may become embolized (blocked by air bubbles)
What is xylem embolism?
Air bubbles enter the xylem conduits, blocking water flow
What causes xylem embolism?
Negative pressure or tension within the xylem
