Module 2 Flashcards
True or False
Water is important to the physiology of plants because of its crucial role in all physiological processes and because of the SMALL quantities that are required.
False
LARGE
How much water is found in the biomass in some non woody tissues such as leaves and roots?
70-95%
At the cellular level, ___ is the major medium for transporting metabolites through the cell.
water
True or False
Water readily dissolves LARGE quantities of ions and polar organic metabolites like sugars, amino acids, and proteins that are critical to metabolism and life.
True
___ is the medium that transports the raw materials (carbohydrates and nutrients) as well as the phytohormones that are required for the growth and development from one plant organ to another.
water
True or False
Living cells must maintain a NEGATIVE water pressure, or “turgor” to grow and function properly.
False
POSITIVE
True or False
Plants lose SMALL quantities of water in transpiration.
False
LARGE
___ is the evaporation of water from the interior of leaves through the stomata.
transpiration
How much (%) water do plants lose in one hour during transpiration?
100%
Why do plants rapidly lose water during transpiration?
Plants lose water rapidly during transpiration because of their large surface area and the high rate of evaporation in their leaves.
What is heat dissipation by leaves through transpiration?
Heat dissipation by leaves through transpiration is the process of plants losing water vapor into the atmosphere through their leaves, which helps to cool the plant.
How much heat by sunlight is dissipated by transpiration?
half
What is latent heat of vaporization?
Latent heat of vaporization is the amount of heat energy required to convert a unit mass of a liquid to a vapor at a constant temperature. It is a measure of the energy required to break the intermolecular bonds between liquid molecules and allow them to escape into the gas phase.
___, also referred to as low resistance pores, are biological membranes to which water passes through.
aquaporins
___ are proteins embedded in the cell membrane that regulate flow of water.
aquaporins
How do aquaporins regulate the flow of water in the cell membrane?
Aquaporins regulate the flow of water in the cell membrane by opening and closing their channels.
The opening and closing of stomatal pores are based on ___.
short distance intercellular transport
Water potential (🔱), or psi, measures the combined effects of : (2)
- solute concentration
- physical pressure (of the cell wall)
Water potential (🔱) is measured in ____.
MPa (megapascals)
1 MPa is equal to ____ of pressure.
10 atmospheres
What is the formula of water potential?
🔱w = 🔱s + 🔱p + 🔱g
🔱w —> water potential
🔱s —> solute potential
🔱p —> pressure potential
🔱g—> gravitational potential
___ is the effect of dissolved solutes on water potential.
solute potential
___ reduce the free energy of water.
solutes
___ is the hydrostatic pressure of a solution.
pressure potentail
Positive pressure ____ the water potential,
while negative pressure ___ it.
raises;
decreases
Positive pressure refers to ____,
negative pressure refers to ___.
turgor;
tension
___ is generally negligible; it is overcame by a transpirational pull.
gravity potential
____, ____, and ____ are all strongly influenced by water potential and its components.
cell growth, photosynthesis, and crop productivity
True or False
Water potential is a good indicator of plant health.
True
Water always moves from a ___ water potential to ___ water potential.
higher;
lower
____ is the passive movement of water from roots into soil layers with lower water potential, while other parts of the root system in moister soil layers, usually at depth, are absorbing water.
hydraulic lift
____ allows the survival of shallow-rooted plants during drought, or in arid environments.
hydraulic lift
The hydraulic lift is also referred to as the _____ or _____.
cohesion-tension theory;
transpiration pull theory
____ are responsible for increasing the surface area of the roots, which enhances their ability to absorb water and nutrients from the soil.
root hairs
____ are the most active in the water absorption process.
root hairs
Water enters the root most readily in the ____ part of the root that includes the root hair zone.
apical
What are the three (3) pathways for water uptake by the root?
- apoplast pathway
- symplast pathway
- transmembrane transport
What happens in the symplast, transmembrane, and apoplast pathway?
In the symplast pathway, water flows between cells through the plasmodesmata without crossing the plasma membrane.
In the transmembrane pathway, water moves across the plasma membranes, with a short visit to the cell wall space.
At the endodermis, the apoplast pathway is blocked by the Casparian strip.
At the endodermis, water movement
through the apoplast pathway is
obstructed by the _____.
Casparian strip
True or False
The Casparian strip breaks the continuity of the apoplast pathway. Hence, water movement across the endodermis occurs through the symplast.
True
What are the factors that affect water absorption? (5)
- availability of soil water
- concentration of soil solution
- soil temperature
- soil aeration
- transpiration
What are the factors that affect the rate of transpiration? (7)
- humidity of air
- temperature
- wind velocity
- light
- atmospheric pressure
- CO2 concentration
- root : shoot ratio
Give some of the significance of transpiration. (3)
- it helps in the ascent of sap
- it helps in the absorption of water and minerals
- it has cooling effects
____ occurs when water molecules are attracted to the walls of the vessel element.
adhesion
____ occurs when water molecules are attracted to each other. As some water molecules move up the vessel element, they pull other water molecules with them.
cohesion
True or False
Water molecules move up the xylem in MULTIPLE directions.
False
in ONE direction
According to the ____, transpiration is the main driver of water movement in the xylem.
cohesion-tension theory
True or False
Transpiration creates a POSITIVE pressure (TURGOR) equivalent to –2 MPa at the leaf surface.
False
NEGATIVE;
TENSION
Give a 5 step-by-step process of transpiration.
- Water and minerals are absorbed by the roots of the plant from the soil.
- The water and minerals are transported up to the leaves through the xylem.
- The water evaporates from the leaves through the stomata, which are tiny openings on the leaf surface.
- The evaporation of water creates a negative pressure in the xylem.
- This negative pressure pulls water up from the roots through the xylem.
____ was the first to suggest that the water flow in plants is governed by the C-T mechanism.
Stephen Hales
What did Stephen Hales mean in his book, in which he wrote: “ for
without perspiration the [water]
must stagnate, notwithstanding the
sap-vessels are so curiously
adapted by their exceeding
fineness, to raise [water] to great
heights, in a reciprocal proportion
to their very minute diameters.”
Stephen Hales’s quote about transpiration can be summarized as follows:
Transpiration is essential for the upward movement of water in plants, even though the xylem vessels are very narrow. Without transpiration, the water would pool in the roots of the plant.
___ is the damage that occurs to plant tissues when they freeze.
freezing injury
What happens when water freezes in a plant cell?
The sharp ice crystals cut cell membranes, resulting in fluids leaking from the cell, leading to cell and plant death.
What are some symptoms of freezing injury? (4)
- tissue browning
- tissue blackening
- tissue wilting, or
- curling of leaves and stems
____ is the damage that occurs to plant tissues when they are exposed to temperatures above freezing but below a critical threshold temperature.
chilling injury
In what threshold temperature does chilling injury occur?
from 32 to 55 F (0 to 10 C)
True or False
Plants from temperate zones are often chilling sensitive, while most tropical origins are not.
False
Plants from tropical origins are often chilling-sensitive, while most temperate zone species are not.
How do plants survive winter? (4)
- they create an anti-freeze
- they move water deeper
- they enter dormancy
- they drop their leaves
