Methods
This study was carried out in Dr. Ried's lab under the guidance of Dr. L. Kurepin in the Biological Sciences building at the University of Calgary.
In this study, the species of the plant (A. thaliana), the growing conditions (temperature, amount of light received, size of Petri dishes, method of sterilization of the seeds, method of agar preparation, pH of agar, MS media and gelrite) were all kept constant. The salt concentrations in the agar were varied (control, 25mmol/L, 50mmol/L, 75mmol/L) and the different plant hormone mutants (Wild type - Columbia (Col) (3), Ethylene insensitive - ein 2-1 (28), Ethylene overproducer - eto-2 (4), ABA deficient - aba 1-5 (15), Auxin resistant - axr 2-1 (10), BR insensitive - bri 1-201(1) and BR overproducer - BRI - GF(9)) were grown on agars of varying concentrations. Thus, the different plant mutants and the effect of salt stress on them could be examined through this experiment.
The salt used in this study was sodium chloride because sodium and chloride are the major ions in many soils and in seawater. Also sodium chloride is the salt that is used usually in deicing salts. Usually there tends to be a build up sodium chloride in the soil. Especially if the accumulation of the salt is combined with drought, then it can lead to a build-up of salinity in soils. Thus in this study only sodium chloride's effect on the plants will be studied, as it is the salt that is most likely to accumulate in the soil.
This study examined the effect of salt stress on primarily ethylene, a key
gaseous plant stress hormone, and its interactions with other hormones, such
as abscisic acid (ABA), auxin (IAA), and brassinosteroids (BRs), using hormone
mutants. Only ethylene, abscisic acid, gibberellins and brassinosteroids were
used in this study because of the important roles that they played in response
to stress, their ready availability at the place where the study was conducted,
and time constraints that limited the study from examining other hormones.
Also, not much prior studies have been done on these hormones in relation
to salt stress, thus it is good to study the hormones that have not been worked
on a lot previously.