A Little Bit salty? I think so!

An investigation of Salinity resistance in Bean Plants.

By Christine Young and Michael he


The purpose of the experiment is to determine the tolerance and growth of bean plants on different salinity levels from salt water.


Excess salts in water or soil may cause plant growth consequences.

These photos were taken by the Experimenters in Coppell, Tx on December 1 2014


The dependent variable in this experiment is plant growth, measured in height of the plant and number of leaves of the plant.

The independent variable is the salinity of the water that the different plant groups are being watered with.

The control group is the bean plants that are being watered with tap water with no salinity.

The experimental group is the bean plants that are being watered with salt in them.

Some constants are the type of bean, the amount of water that they are being watered with, the sunlight they are exposed to, the temperature they are being grown in, and the moisture of where they are being grown


Salinity is the measure of the contents of salts in soil or water. It is usually produced by natural processes such as weathering of rocks by wind and rain. High concentrations of salt pose hazards for the environment by affecting agriculture and infrastructure. High levels of salinity in water and soil may cause native vegetation to become unhealthy and die. It can lead to a decline in biodiversity through dominance of salt resistant species, altering ecosystem structures. Despite the negative effects of salinity, some environments have adapted to a range of salt concentrations.

Click here to see more of the Background Research:



As the salinity of the water increases, the bean plants' health will disintegrate as the tolerance of the bean plants weaken through the increase of salinity in each experimental group.

These photos were taken by the Experimenters in Coppell, Tx on December 1 2014


In this experiment, the required materials will be needed:

  1. 400 plastic party cups to cultivate the bean plants in

  2. 400 bean seeds / seedlings

  3. 1 box of iodine table salt

  4. 1 tbsp to measure the salt

  5. 1 cup measurer

  6. mL measurer

  7. Plotting soil

  8. 1 measuring ruler

  9. Regular Tap water

  10. 1-5 measuring beakers, depending on how many bean seeds may be fit into each beaker.

These photos were taken by the Experimenters in Coppell, Tx on December 1 2014


  1. The night before , soak the beans overnight to make it easier to sprout.

  2. Label 100 cups for each group's name Control, 2% salinity, 5%, and 20%

  3. Line up the cups in 20 rows of 20

  4. Every 5 rows will be a different group, there'll be Control, 2%, 5%, and 20%.

  5. Place one cup of soil and a bean about one inch deep in each party cup.

  6. Water control group with 200 mL of water, slowly poured on the surface of the soil.

  7. For the 2% salinity, mix 5 g of table salt in 200 mL of water, and water each 2% salinity plant with 200 mL of the 2% saline water.

  8. For 5% salinity, repeat the procedure in step 9, but with 60 g of table salt.

  9. For 20% salinity, repeat the procedure again from step 9, with 90 g of table salt.

  10. Every day, water each plant with 100 mL of water, with no salt in the control group’s water, 2 g of salt in the 2% salinity, 5 g in 5%, and 20 g in 20%.

  11. Observe and record observations every day in the lab journal until the beans sprout

  12. When beans sprout, measure each sprout with a ruler every 3 days.

  13. When the first leaves grow, measure the height of the plant each day and keep all measurements in a data table and make calculations on Excel.


All Data Charts and Graphs created by the Experimenters.
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A positive growth trend was observed in the control, 2%, and 5% saline groups with 2% having the most growth at the end of 27 days;average ending height of 35.13cm. The data suggests that 2% salinity provides a good growing condition for bean plants. The maximum average height that the 20% saline plants reached was 2.1 cm which showed that the plants did not grow well at a high salinity. The average height control group reached 28.4 cm which was lower than the 2% saline plants. The average height of 5% grew to 25.91 cm which was also lower than the 2% saline plants. As a large concentration of salt is watered to the plants, it makes a hypertonic solution which causes the plant to shrink. The shrinkage was clear in the 20% saline plant group when the average height only reached 2.1 cm and did not survive the 27 days that the experiment was conducted. The 5% saline plant group averaged to be much taller than the 20% saline group at 25.91 cm, but was still less than the height of the 2% and control groups. However, the 2% saline plant group averaged to a height of 35.13 cm at the end of the 27 days of growth, surpassing the control group as well as the other two experimental groups. The data shows that an optimal growth condition for the bean plants is by watering them with 2% saline water.

Pictures and Calculations


Annual percent growth Formula=| [(Final-Initial)/Initial] x 100 | /27

Percent Growth rate= [(Final-Initial)/Initial] x 100

Observations (Pictures are above)

Throughout the experiment, the salinity rates of water given to the plan subjects have played a major role to the plant’s growth. During the 27 day experiment ,Control and experimental groups one and two, had been seen to grow well with the salinity rates of 0, 2, and 5%. The control group of 100 bean plants grew a normal and healthy rate as average pinto bean plants. Meanwhile the 2% experimental group was not affected by the salinity and grew as well as thrived more compared to the control, causing itself to sulk from the weight of it’s leafs. Experimental group 5% grew steadily throughout the 27 days at a constant rate that was approximately 15% slower that the control group and 2%. By the end of the experiment, the 5% group was 3 cm shorter than the control group and 10 cm shorter than the 2% group; tending to be the most solid and stable plant that did not sulk. Thus proving that experimental groups 2 and 5 percent may have adapted to the amount of salt infused water that was given. Finally the 20% experimental was the most affected from the salinity rates, thus resulting in the death of all 100 bean plants by the 24-27th day. During the experiment, the health and growth of the salinity was extremely poor due to the high concentration of salt in the water. Salt water being a hypertonic solution, was observed to have sucked most of the water from the vacuole of the plants rather give them the nutrients of water that they needed. This caused the plants to shrink and barely grow, having a maximum height of only 3.3 cm.


After the 27 day experiment, it can be concluded that the purpose was achieved through the implementation of 400 bean plants, testing each 100 group with a certain amount of water that had been infused with a certain percentage of salt. By testing the resistance of the bean plants and measuring the growth to see how the rate of salinity may affect the groups. The hypothesis in which, as the salinity rate of the water given to the plants increases, the higher the salinity rate, the worse the bean plants’ health will become as the tolerance of the bean plants weakens from it, was proven partially correct with evidence according to the results from the data selection. In the graph and calculations, the 2% experiment group was known to be the most successful group out of all 4 groups. Despite the fact that there was an increase in the amount of salt given to the plants, compared to the control group, this experiment group adapted and benefited from the salt instead and grew better instead. Other experimental groups such as 5% and 20% followed the hypothesis statement and decreased in growth and health as the rate of salt given increased. Nevertheless, the 2% experiment group was the only 100 bean plants to contradict the hypothesis and prove it invalid.

These photos were taken by the Experimenters in Coppell, Tx on December 1 2014

Sources of Error

As the beans were originally being placed into the cups with soil, some of the cups fell over and soil spilled out. An attempt was made to put as much soil back into the cup as possible, but the spills caused some cups to have less soil than others when the amount of soil was supposed to be a constant. While placing the beans in the cups with soil, there were a few times when the placement of the cups was confusing and beans may have been misplaced or forgotten. This could have caused a few cups without beans or a few cups with more than one bean. One other problem that could have affected the experiment is that the scale that was used to measure the salt. The amounts of salt that were needed had decimals into the thousandths, but the scale only measured up to the tenths, which could have caused a difference in salt levels of each experimental group.


The experiment could be improved by using a more accurate scale to measure the amount of salt used in each experimental group. In order to find a more accurate measurement of the optimal growth condition, more experimental groups should be used such as watering the plants with 1% saline water or 3% saline water. The experiment also could be conducted using another species of plant to test if the same concentration of salt provides the optimal growth condition.


The experiment can be applied to growth of other bean family vegetables. The data showed that with 2% salinity, the plant would grow more in the long term of 27 days. That result opens a possibility for bean plants to be able to grow more in the presence of a very small amount of salt, but not too much.


Agdex 518-17. "Salt Tolerance of Plants." Salt Tolerance of Plants. Alberta Agriculture

and Rural Development, 1 Nov. 2001. Web. 27 Sept. 2014.


Bohnert, H. J. "Adaptations to Environmental Stresses." The Plant Cell Online 7.7

(1995): 1099-111. Web. 28 Sept. 2014.

Department of Sustainability, Environment, Water, Population and Communities.

"Salinity and Water Quality Fact Sheet." Department of the Environment. Commonwealth of Australia, 2012. Web. 26 Sept. 2014.


Painter, Tammie. "The Development of a Pinto Bean Plant." Home Guides. Demand

Media, n.d. Web. 28 Sept. 2014.


Warrence, Nikos E J., and James W. Bauder. "The Basics of Salinity and Sodicity Effects

on Soil Physical Properties." The Basics of Salinity and Sodicity Effects on Soil Physical Properties. Ed. Krista E. Pearson. University of Montana, 19 Aug. 2009. Web. 27 Sept. 2014. <http://waterquality.montana.edu/docs/methane/basics_highlight.shtml#EffectsofSalinityonPlantGrowth>.