Plant stress is defined as any change in environmental conditions that produce a less than ideal plant response. We will look at Salt stress on plants and tour the campus to observe different factors influencing plant stress.
Abiotic Factors
Abiotic factors influencing plant stress describe non-biological factors.
These include:
1. Water
Water stress can be in the form of:

Drought – lack of water

Excess – flood situation creating an anaerobic environment where roots are unable to respire due to lack of available oxygen.
Plant/water relations are influenced by atmospheric conditions
(evapotranspiration) and will influence drought, cold, and salt stress.
2. Temperature
Temperature stress can be in the form of:

Extremely high temperatures.

Extremely low temperatures.

Extreme temperature changes.
3. Light
Light is a direct environmental factor influencing photosynthesis. Light affects the accumulation of certain pigments responsible for preventing photo-oxidation from UV light.

4. Soil (Edaphic) a. Salt Stress
For most plants, the presence of high salt concentrations in the soil is an important stress factor (Salisbury and Ross, 1985). Sodium chloride (NaCl) is ambiguously found in nature
– in deserts, coastal areas, and areas where road salts are used in the winter. Irrigation water contains dissolved salts that are concentrated as the water evaporates and builds up in soils over time. Millions of acres have been rendered unfit for agricultural production as a result of poor irrigation management (Hale and Oratt, 1987).
Two problems face plants in such conditions:

Obtaining water from a soil of negative osmotic potential.

High concentrations of potentially toxic Na + , carbonate and chlorine (Cl ) ions. Na + ions compete with potassium (K + ) ions. b. Nutrient Deficiency
A lack of one or more essential elements needed by plants for optimum growth can lead to plant stress.
Macroelements
Element Symbol
Nitrogen
Phosphorous
Potassium
Calcium
Magnesium
Sulfur
N
P
K
Ca
Mg
S
Microelements
Element
Chlorine
Iron
Boron
Manganese
Zinc
Copper
Molybdenum
Nickel
Symbol
Cl
Fe
B
Mn
Zn
Cu
Mb
Ni
5. Other Abiotic Stress Factors:

Chemical injury – pesticide or industrial chemical source.

Mechanical injury – “Weedeateritis”, “Bulldozeritis” (construction damage), car doors, vandalism.

Transplant shock
– planting nonacclimated plants.
All of the above abiotic stresses reduce plant vigor, predisposing plants to biotic stresses.

Biotic Factors
Biotic stress is caused by microorganisms (bacteria and fungal), virus, parasitic plants, and insects. Biotic factors can either be a primary or secondary stress.
Often plants will succumb to a secondary biotic stress factors considered saprophytic , already present in the environment that otherwise would not effect a healthy, vigorous plant (Schoeneweiss, 1981). Remedies for biotic stress that we can control are matching the plant to the site, and transplanting at the proper time of year with careful consideration of the plants status at the time of transplanting (Whitcomb, 1984).

Materials
1. 8 plants
2. Three different molar concentrations (moles/liter expressed as M) of sodium chloride (NaCl) solution. Concentrations are as follows:

0.1 M NaCl

1 M NaCl

5 M NaCl

Control (water only; no NaCl added)
Methods
Treatment One
Soak one plant in each of three concentrations of NaCl and one plant in water only (control). Place in the greenhouse in a sunny location.
Observe after one hour.
Treatment Two
Soak one plant in each of three concentrations of NaCl and one plant in water only (control). Place inside the greenhouse in a shaded location. Observe after one hour.

Name:_______________________________________Date:________________
Shade
Make observations on the plants. Note differences and similarities between the plants.
Salt
Concentration
(moles/L) Observations Treatment
Full Sun
0.1 M NaCl
1 M NaCl
5 M NaCl
Control
0.1 M NaCl
1 M NaCl
5 M NaCl
Control

Students will observe some of the plant stresses discussed in lab on and off-campus. Note observations on possible stresses at each site – both abiotic and biotic.

Answer the following questions.
1. Are some of the plants wilted? Which ones? Why do you think the plant(s) wilted?
2. What were the differences in effect between plants in Treatment One compared to plants in Treatment Two ?
3. What does water availability have to do with the plants condition?
4. What were some of the stresses you observed on the Plant Stress Walk?
5. What are some possible remedies to the stresses observed on the Plant
Stress Walk?