Properties and Uses of Water

Property of WaterPermitting this Use
polar solvent dissolves soil minerals, sugar, etc.
widest range of any liquid!
hydraulic fluid cell: turgor pressure
xylem: transpiration
phloem: translocation
reactive reactant: photosynthesis
product: respiration
high specific heat good heat buffer
1 Calorie = 1 Liter 1° C
high heat of fusion (vaporization) liquid→gas removes energy
=evaporative cooling

Sources of Water

precipitation: fog, mist, rain, snow, sleet, hail
runoff: brook, creek, stream, river
water table: puddle, pond, lake (Ocean is not freshwater)
soil water: capillary space...most useful for plants!
aquifers: porous rock, wells, artesian springs

Soil Water

Mud ----> ______________ ----> ______________ ----> Absolutely Dry Soil
\ \ \
\ \ \
________________ ________________ ________________
water water water

The water that is available to plants is: ________________ water.

When this water is present the soil is called ________________.


Methods of Irrigation

Sprinkler: wastes water
kills zygotes and larvae!
Surface: furrow = trenches with water between rows
flood = one trench in un-level field
Trickle: Less wasteful at each pot
Computer programming helps!
Wick: Capillary mat + ebb-flow pump
plants take only as needed
Natural: 4 inches of rain per month
irrigate only if short!

What time of day is best for irrigation? Early AM       Noon       PM       Evening

How can you tell if your plant needs to be watered or not? (Hint: no green thumb needed)

Touch surface of soil in pot with finger...
if cold, wet, dirty: don't water now!
if warm, dry, clean: water now.

Symptoms of Poor Irrigation

Symptioms of Overwatering
Organs swell, crack open
Fungi thrive (Damp-off)
Yellowing of leaves
Root death by asphyxiation
Symptioms of Underwatering
Growth inhibition (dwarfing)
Leaves with brown tips + edges
Blueing of leaves
Abscission of leaves

One symptom is shared by both problems it is: _____________________
and this leads to many failures in home and landscape gardening.

These symptoms are easily explained by Osmosis which is:
Osmosis: The passive movement of water from purer area to more "polluted" area

When a cell is placed in a hypotonic solution...
Water moves into the cell
Cell gains weight
Cell gets larger
Cell develops turgor pressure
Stops when it cannot overcome wall pressure
When a cell is placed in an isotonic solution...
Water movement into the cell
...is balanced by water movement out of the cell
Cell has no weight change
Cell stays same size
Cell has no turgor pressure
But cell remains full
When a cell is placed in a hypertonic solution...
Water moves out of the cell
Cell loses weight change
Cell loses volume
Cell loses turgor pressure
Cell membrane pulls away from wall: plasmolysis
hypertonic solution fills space between cell membrane and cell wall
Stops losing water when concentration of cytosol matches solution

When these conditions prevail the plant needsmore waterless water
It is a seedling   X
It is growing rapidly X  
It is reproducing (flowers and fruits) X  
It is dormant   X
It has succulent leaves   X
It has waxy leaves   X
It has hairy leaves   X
It has thin, fine, dissected leaves X  
It has deep roots   X
It is in a clay soil   X
It is in a sandy soil X  
The temperature is hot X  
The wind is blowing X  
The humidity is high   X
The sun is bright (no clouds) X  

This page © Ross E. Koning 1994.

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Send comments and bug reports to Ross Koning at koningre∂gmail⋅com.