Biology Lab Salt Effect on Plant Growth Paper PDF

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Detailed paper with graphs for experiment performed on plant growth and the affects of salt. ...

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Sierra Monroe BIO 151L Thursday 11:30-1:00 Lynda Lafond Salt Effects on Plant Growth 3/29/17 Salt Effect on Plant Growth Abstract The effects on the plant growth of Brassica rapa s eeds from different levels of salt concentration in soil was observed in this experiment. Variables studied included: seed germination, number of buds and leaves produced, leaf area (mm2 ), mass (g), total plant length from root to tip (cm), plant length from stem to leaf(cm) and root to leaf (cm), and overall observations. Based off the results, concentrations from 6% to 1.5% had no seed germination, while concentrations from 0.75% to 0.045% all had seed germination, concluding that higher levels of salinity within the soil impedes plant growth. Introduction Salinity, as defined by Collins Dictionary of Biology, refers to the “degree of saltiness; the relative proportion of salt in a solution” (Collins, 2005). In the conducted experiment, the proportion of salt, or NaCl, within the soil was examined to determine its effects on plant growth. Soils with high salinity concentrations within the environment inhibit plant growth by depriving the plants from water, making them become dehydrated. This is due to the osmotic effect, in which, water flows from areas of low concentrations to high concentrations. As water flows from areas of the low salt concentrations to the high salt concentrations, plants are unable

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to obtain the necessary amounts of water needed for life due to being consumed by the high concentrations of salt (Seeling, 2000, pp 4-5). Adequate research has been conducted on the negative effects that high salinity of soil has on plant growth. The high salinity concentrations create stress on the plant, known as “salt stress,” in which all the major processes necessary for the plant to survive are compromised. The processes affected include: photosynthesis, energy and lipid metabolism, and protein synthesis. Without these processes being conducted due to “salt stress,” the plant growth is terminated, and may be resumed if salt concentration in the soil is lowered (Parida & Das, 2004). High salinity soil may occur in the region in which it is present in, for example, states within the Great Plains have naturally higher salinity soil due to the type of soil and bedrock (Franzen, Wick, Augustin, & Kalwar, n.d.). Although high salinity can occur naturally, humans also contribute by using salt as an ice control agent on highways, as a feedstock for chlorine, and in the agricultural industry for animal nutrition (Bolen, 2016, pp 63.1 - 63.4). The excessive amounts of salt are absorbed  into the soil, causing it to become of high salinity. The objective of this lab is to thoroughly examine the effects of salinity on seed germination, plant growth in the aspect of height and mass, and flower and leaf production. The prediction about the effects of salt on plants is that a higher concentration of salt in the soil will have a negative impact on plant growth. This negative effect is due to the salt causing osmosis to occur, which would restrict the plant from obtaining any water. The effects will be measured by planting four Brassica rapa, c ommonly known as “Wisconsin Fast plants” seeds into a concentrated salt soil and an unconcentrated, control soil, and observing their growth over several weeks. The variables measured of each plant will be whether the seeds germinated or not,

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number of buds and leaves produced, leaf area (mm2 ), mass (g), total plant length from root to tip (cm), plant length from stem to leaf (cm), and plant length root to leaf (cm). The results will be averaged and presented using Microsoft Excel line graphs comparing the plants grown in the concentrated salt soils and and the control soil. However, there is a possibility of human error or seeds not germinating for unknown reasons, which could ultimately alter the results. Methods The purpose of this lab experiment is to observe the effects of salt on plant growth over the time period of 3 weeks; the first week for preparing the experiment and the remaining 2 weeks for the data collection of the plant’s growth. To begin the first part of the experiment in week 1, prepare the soil with the following concentrations of salt: 0% (control), 0.045%, 0.095%, 0.18%, 0.37%, 0.75%, 1.5%, 3%, and 6%. One concentration of the prepared soils are assigned to each of the 8 groups, beginning with group 1 having the highest concentration of 6% and group 8 having the lowest of 0.045%. Each group will also have a control soil of 0% salt concentration. To prepare the soils, group 1, who is assigned the highest concentration, will begin by adding 15 mL of salt to 1 cup of plain soil and mixing thoroughly. The next group, group 2, will combine a ¼ cup of the 6% soil previously prepared with ¼ cup of plain soil, which will create the 3% salt concentration soil. The remaining groups, 3-8, will follow the exact procedure of combining ¼ cup of the previously made concentrated soil with ¼ cup of plain soil till the final soil of 0.045% is made. Each group will create a control soil by using ¼ cup of plain soil. Once each group has the assigned soil concentration, the next steps of the procedure can be performed. Collect 2 styrofoam “quads,” which contain 4 individual cells for each seed to be planted in. Use a marker to appropriately label the styrofoam quad with members of the group and the

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salt concentration. Place wicks, which will be used by the plants for obtaining water, into each of the 4 styrofoam cells and be sure that they are elongated out the bottom. Fill the cells of one of the “quads” approximately half full with the correct salt concentration assigned and the other will the control soil. Next, add 2 fertilizer pellets to all 8 cells. Once pellets are placed, fill the cells with the correct and remaining soil to the top. Using your finger, make a slight indentation into the soil of all 8 cells and place 2 Brassica rapa  seeds into each. Use just enough soil to fully cover the seeds. Next, use a plastic dropper to water all cells. It is important to watch closely and once water begins to drip off the wick emerging from the bottom of the styrofoam quad, stop watering. Fill the provided Rubbermaid container ⅔ full with water and place an “anti-algae” square inside. Dampen the felt mat and lay on top of the Rubbermaid container lid. Place both of the styrofoam quads on the felt mats in the arranged planting scheme. All plants will be equally provided with light 24 hours a day and kept on a “growth chart.” Once all styrofoam quads are placed correctly on the moist felt mats, appropriately dispose of the leftover soil and clean up all areas used in experiment. For the second part of the experiment, observe the plants and the variables being tested, such as height and germination, over the allotted time period and record all necessary data. Results The first variable tested in the experiment was seed germination, in which all Brassica rapa s eeds germinated in salt concentrations of 0.045%, 0.09%, 0.1875%, 0.37%, 0.75% and the control 0%, but not in concentrations of 6%, 3%, and 1.5%. These results are presented in Figure 1 under the “Figures” section. Figure 2 presents the results of the average number of buds produced: 0% = 5.7, 0.045% = 3.25, 0.09% = 4, 0.1875% = 8.5, 0.375% = 10, 0.75% = 5.35, 1.5% = 0, 3% = 0, and 6% = 0. The remaining results in Figure 3 are: 0% = 4.75, 0.045% = 5.75,

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0.09% = 4.5, 0.1875% = 6, 0.75% = 6, 1.5% = 0, 3% = 0 and 6% = 0. Figure 4 represents the average results of leaf area measured in millimeters, which as follows: 0% = 174.2 mm, 0.045% = 245.25 mm, 0.09% = 87.81 mm, 0.1875% = 384.825 mm, 0.375% = 202.4 mm, 0.75% = 178.375 mm, 1.5% = 0 mm, 3% = 0 mm, and 6% = 0 mm. The mass measured in grams for the Brassica rapa seeds in Figure 5 average results were: 0% = 0.395 g, 0.045% = 0.375 g, 0.09% = 0.175 g, 0.1875% = 0.825 g, 0.375% = 0.2 g, 0.75% = 0.425 g, 1.5% = 0 g, 3% = 0 g, and 6% = 0 g. Figure 6 shows the results for the average total plant length, measured in cm, which were: 0%,= 16.57 cm, 0.045% = 14.1 cm, 0.09% = 14.65 cm, 0.1875% = 23.375 cm, 0.375% = 20.925 cm, 0.75% = 17 cm, 1.5% = 0 cm, 3% = 0 cm, and 6% = 0 cm. The effect of salt concentration on leaf to stem length is displayed in figure 7 and had the average lengths of: 0% = 13.01 cm, 0.045% = 11.4 cm, 0.09% = 10.6 cm, 0.1875% = 18.75 cm, 0.375% = 17.78 cm, 0.75% = 11.875 cm, 1.5% = 0 cm, 3% = 0 cm, and 6% = 0. The last variable tested of the effect of salt concentration is on the leaf to root length, which has the following results of: 0% = 3.56 cm, 0.045% = 2.7 cm, 0.09% = 4.05 cm, 0.1875% = 4.85 cm, 0.375% = 2.98 cm, 0.75% = 5.125 cm, 1.5% = 0 cm, 3% = 0 cm, and 6% = 0. The average results of each of the variables were calculated by adding up all the numbers of that specific variable tested and dividing by the total number of plants within that concentration group. Overall observations of the plants varied as one plant grown in the 0.1875% salt concentration was yellow and had dried leaves, while the other 3 plants grown in that concentration were green and healthy. Other observations recorded were the plants grown in the control soil had uniform budding and production of numerous leaves and those in the 3% salt concentration had a salt crystal that formed sitting on top of the soil. Discussion

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The concluded findings of this experiment indicate that salt concentrations below 1.5% had optimal plant growth, while concentrations from 6% to 1.5% had no growth, as there was no data for any of all 8 of the variables tested. However, the salt concentrations from 0.75% to 0.045% had data in all 8 of the variables, except for those that did not germinate due to natural or human cause. This data suggests that a small percentage, preferably between 0.75% and 0.045%, of salt concentration in the soil can have a positive impact and contribute to plant growth. Using the calculated averages, there is a trend that the variables follow. Based off the results, bud production was highest at 0.375% salt concentration and lowest from 6% to 1.5%. The number of leaves produced resembles the average bud production, as there the highest production level was at 0.375%, which was 6.25 leaves. Comparing these two variables to leaf area (mm^3), the trend of the results being highest at 0.37% concentration was ended as the highest average was at 0.1875% and 0.37% had the second to lowest average. The mass of the plant also had very similar results when compared to the leaf area, as the peak concentration for the average was at 0.1875% and the lowest was at 0.09%. Total length of the plan Soil salinity has became a major concern in recent years due to the fact that it is harming agricultural crop production, which eventually can lead to economic distress. With salinity having numerous effects on different variables, such as the environment region, the type of soil, the amount of precipitation, etc., plant breeding programs have been focused on creating a crop that is completely salt-tolerant. Although there has been some success in determining the genetic traits that can make a crop salt-tolerant, there still is not a definite plant that can sufficiently grow in high salinity soils plus the numerous variables (Shrivastava & Kumar, 2015, pp 123–131). As for now, the main approach to solving high soil salinity soil problems is to use “site-specific”

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management” by planting certain plants, such as hay or alfalfa, or deep-rooted crop species that help with retention of soil water (Nickel, 2016). Many other experiments have been conducted by researchers to determine whether salt concentration has an effect on plant growth. An experiment performed on Sesuvium portulacastrum, which is a type of perennial herb that grows on coastal regions, tested the long-term effects that salinity has on water relations, nutrient status, growth, and proline accumulation. The experimental method was performed by using individual rooted cuttings from mother plants and placing them into 2 liter pots filled with 0.30 mmol of sodium (Na+ ) and 0.95 mmol of potassium (K+ ) per 100 grams of soil. The plants then were divided into 2 lots: the first lot was watered with a nutrient solution without salt and the second lot was watered with a nutrient solution with an addition of 100 milliliters of salt. The plants were placed in a greenhouse under the appropriate growing conditions and were left to grow for several weeks. The results found that high soil salinity has a detrimental effect on Sesuvium portulacastrum plant growth. Although the plant grew, the roots, leaf surface area, mass and leaf numbers were significantly different compared to the control, which was grown in unconcentrated soil and watered with a nutrient solution excluding salt (Slama, Ghnaya, S  avouré, & Abdelly, 2008, pp 442-451). This experiment with the S esuvium portulacastrum  plant relates to the one performed with Brassica rapa p lants as they both were grown in a salt concentrated soil and were tested to find the variables that were affected. However, there were some differences, such as the Sesuvium portulacastrum plants were watered with a nutrient solution containing 100 milliliters of salt, whereas the Brassica rapa p lants were watered with just plain water. Both experiments

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came to the conclusion that salt concentration within soil can have negative impacts on plant growth. The hypothesis predicted that as the concentration of salt in the soil increased, there would be negative effects on the Brassica rapa plant growth. Although the hypothesis is partially correct, it also is incorrect in the aspect that there was no prediction as to the “specific” concentration or concentrations that would seize plant growth. From the results, the concentration of 1.5% was the “starting” concentration that had serious effect of no growth at all on the Brassica rapa p lant. The other 2 concentrations of 3% and 6% also had no growth. The remaining concentrations of 0.045% to 0.75%, plus the control of 0%, all had growth but the results fluctuate depending on the variable being tested. Some of the variables, such as mass and leaf area had similar averages at 0.1875%, while 0.375% had the highest averages in bud and flower production. In conclusion, the results show that high concentrations of salt, specifically from 1.5% to 6%, completely inhibits plant growth and the lower concentrations from 0% to 0.75% had minimal effects on plant growth. Some results even suggest that a slight addition of a small concentration of salt may actually benefit plant growth. The results found in this experiment compare to those of other experiments, and conclude that plants have optimal growth in low salt concentrations rather than in high concentrations.

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References Bolen, W.P. (2016, October). US Geological Survey Minerals Yearbook 2014: Salt [Advance Release]. U.S. Department of the Interior U.S. Geological Survey. 6 3.1 - 63.4. Retrieved March 20, 2018, from https://minerals.usgs.gov/minerals/pubs/commodity/salt/myb1-2014-salt.pdf Franzen, D., Wick, A., Augustin, C., & Kalwar, N. (n.d.). S  aline and sodic soil. NDSU Extension Service. Retrieved March 20, 2018, from https://www.ndsu.edu/soilhealth/wp-content/uploads/2014/07/Saline-and-Sodic-Soils-2-2 .pdf Nickel, R. (2017, November 29). How to Manage Soil Salinity. Retrieved March 21, 2018, from https://www.agriculture.com/crops/cover-crops/how-to-manage-soil-salinity Parida, A. K., & Das, A. B. (2004, August 07). Salt tolerance and salinity effects on plants: A review. Retrieved March 20, 2018, from https://www.sciencedirect.com/science/article/pii/S0147651304000922 Salinity. (2005). In Collins Dictionary of Biology  (3rd ed.). Glasgow, Scotland: HarperCollins. Seeling, B. D., (2000, May). Salinity and sodicity in North Dakota soils. NDSU Extension Service. 1 -15. Retrieved March 20, 2018 from https://www.ag.ndsu.edu/langdonrec/soil-health/salinity-and-sodicity-in-nd Shrivastava, P., & Kumar, R. (2015). Soil salinity: A serious environmental issue and plant growth promoting bacteria as one of the tools for its alleviation. Saudi Journal of Biological Sciences , 22( 2), 123–131. h ttp://doi.org/10.1016/j.sjbs.2014.12.001 Slama, I., Ghnaya, T., Savouré, A., & Abdelly, C. (2008, April 23). Combined effects of long-term salinity and soil drying on growth, water relations, nutrient status and proline accumulation of Sesuvium portulacastrum . Comptes Rendus Biologies , 331( 6), 442-451. Retrieved March 20, 2018, from https://www.sciencedirect.com/science/article/pii/S1631069108000814

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