Unit 4 Flashcards
What does a plant use water for?
Evaporation on leaf cools it Required for photosynthesis Needed for cell growth and expansion Keeps turgor Has to have it to live!
What is turgor?
Maintaining plant shape
What do plants use the most water for?
Transpiration
What are symptoms of water stress?
Purple color
Wilting
Foot printing
What are the stages a plant goes through during drought stress?
First it decreases photosynthesis,
Then it goes through a temporary wilting point,
Finally it enters a permanent wilting point = death
Transpiration usually keeps leafs below _______ degrees.
90 degrees
Describe a water molecule’s physical make up and how it’s formed.
2 Hydrogens are held at an angle…away from the 1 Oxygen.
Hydrogen Bonding means….
Water sticks together
Water freezes below _______ degrees Celsius?
0 degrees Celsius
Define adhesion:
The attraction of water Molecules to solid surfaces that also have an electrical charge.
How does water dissolve salt?
Water pulls the + and - atoms apart and “dissolves” them
Define cohesion:
The attraction of water molecules to eachother
Adhesion +Cohesion = ?
Capillarity
In regards to capillarity….the height of the rise is inversely proportional to what?
The radius of the tube
Capillarity can happen in any direction. True or False?
True
Define saturation:
Maximum amount of water that a soil can hold.
How do we measure moisture potential?
How many Bars
Is gravitational water available to plants?
No
Define gravitational water:
Amount of water held by the soil between saturation and field capacity. It is unavailable to plants
Define field capacity:
Max amount of water a soil can hold against the force of gravity.
There is plant available water once you reach ____________.
Field capacity
How long does it take to drain from saturation to field capacity?
24 - 48 hours
Saturation = how many Bars?
Field Capacity = how many Bars?
Saturation = 0 bars
Field Capacity = -1/3 bars
At Field Capacity…..Plant available water is about ?% - ?% of total soil volume?
25-40%
when draining…How much longer does clay loam take to reach field capacity compared to a sandy soil?
2 - 3 days longer
What are different ways that a soil dries?
Plant use
Evaporation
Water Moves out of root zone
What is the moisture potential at wilting point?
-15 bars
Is there still water in the soil when a plant reaches permanent wilting point?
Yes, but it’s being held so tightly in the micropores that the plant cannot use it.
Field Capacity has a moisture potential between ____ and _____ bars. Which means it is between ________ and _________.
-1/3 and -15 Bars
Saturation and Permanent Wilting Point
Why does water hold onto clay?
because clay is electrically negative
as far as water holding is concerned …..Why is Loam a prefered soil?
It maximizes the Plant Available Water.
what are the two ways water can be held in soils?
As a film on individual soil particles or in the micropores of the soil
Water stored in micropores is called__________.
Capillary Storage
What is a large determining factor in how much water a soil can hold?
Soil Texture because it influences pore spaces (aggregation) and types of particles (sand vs. silt vs. clay etc.) and amount of O.M.
define Infiltration:
the entry of water into a soil
define Percolation (permeability):
Movement of water through the root zone
define Saturated Flow:
Downward movement of water in response to gravity
define Unsaturated Flow:
Capillary movement of water (moving within the pores)
define Water Vapor movement:
Water moving as a gas
define Drainage:
Movement of water out of the root zone
Define Polarity:
Molecule is electrically neitral but has a + and - side.
define Cappilarity:
Adhesion + Cohesion….,,,,attraction of water to fine openings
