Saline Concentrations In Radish Seeds

Morgan McIver & Brooklynn Newberry

Final Proposal – Ecology Lab

The Effect Of Salt Concentrations In Water On Seed Germination

Introduction

Throughout the world, we are seeing a constant increase in salt concentrations in soil. The increase in saline concentrations in the water supplies for seedlings is a major concern because excess saltes hinder the growth of crops by limiting their ability to take up water, thus affecting their growth(USDA, 1998). This is supported by a study on the effect of saline water on seed germination and early seedling growth of the halophyte quinoa, “Salinization is increasing on a global scale, decreasing average yields for most major crop plants” (Panuccio, Jacobsen, Akhtar, and Muscolo, 2014). Salinization is the process by which water-soluble salts accumulate in the soil. This can occur naturally or because of conditions resulting from management practices(USAD, 1998). As salinity increases, we begin to see it affect agricultural productivity. The salinity in the soil affects soil physicochemical properties along with the ecological balance of the area(Shrivastava & Kumar, 2015). The negative impacts of the rising saline concentrations include low agricultural productivity, low economic returns and soil erosions (Hu and Schmidhalter, 2002). Crops that are grown in saline soils, tend to have high osmotic stress. In some cases, they are seen to have toxicities along with nutritional disorders. As the saline levels rise, the reason we see an increase in toxicity in plants is because some ions such as chloride are toxic to plants and as the concentration of these ions increases, the plant is poisoned and dies. Furthermore, the reduction in growth and reproduction can be directly linked to how salt interferes with the nitrogen uptake(Shrivastava & Kumar, 2015). In a study, it was found that seedling growth rate decreased drastically with increasing salinity (Powell, 2007). This was also supported in a different study when they stated, “With increasing salt concentration, the germination percentage decreased” (Panuccio, Jacobsen, Akhtar, and Muscolo, 2014). In order for crops to agriculturally thrive, the crops need to have moderate temperatures, sunlight, adequate precipitation and good soils. If salinization continues to rise, it is possible that we could eventually face a harmful decrease in crop production in the next few years leading to a decrease in human and animal food supply. Salinization increases at a rate of 10% annually. It is becoming a major threat to our food security. The purpose of this experiment is to test how different saline concentrations in water affect seed germination. We will begin by mixing three different saline concentrations: 0% (4 TBSP water + 0 TBSP salt), 25% (4 TBSP water + 1 TBSP salt), 50% (4 TBSP water + 2 TBSP salt). We predict that the seeds with 0% saline concentration will have a higher amount of seeds germinated compared to the seeds with 25% saline concentration and 50% saline concentration and seeds with 25% saline concentration will have a higher amount of seeds germinated than 50%. Essentially, as saline concentrations increase, the amount of seeds germinated will decrease. We made this prediction because salts in soil block the absorption of the water for seedlings. Seeds that are placed in water with higher saline concentrations will end up being deprived of the proper nutrients they need in order to grow and survive. Soil that is pure and has 0% saline concentration, will be able to grow. It is also known that an inner layer of tissue in the root of the crops can be sensitive to salts. This will cause crops that grow in higher saline concentration, to have high osmotic stress. The higher concentration of saline, will cause more damage and stress to the crop. This is why we predict that the 25% will still grow, but at a slower rate than the 50% saline concentration. The seeds with a 50% saline concentration will experience more stress and even could possibly have some nutritional deficiencies. It is also known that as water evaporates, salt will be left behind. As the crops with saline concentration continue to grow, it needs to be noted that the seed will not absorb all the water and some will evaporate. Osmotic stress occurs when there is a change in solute concentration in the cell. This causes a rapid change in water movement across the cell membrane and puts the crop in distress or even shock which prevents water from being taken in by the crop. As saline concentrations in water increase the amount of seed germination will decrease because salinity can affect germination by creating osmotic potential which prevents water uptake.

Methods

Study System

In this experiment we will examine the effects of different saline concentrations on seed germination. Our hypothesis is that As saline concentrations in water increase the amount of seed germination will decrease because salinity can affect germination by creating osmotic potential which prevents water uptake.We will begin by mixing three different saline concentrations: 0% saline concentration (control group), 25% saline concentration, and 50% saline concentration. The concentrations were mixed as follows: 0% (4 TBSP water + 0 TBSP salt), 25% (4 TBSP water + 1 TBSP salt), 50% (4 TBSP water + 2 TBSP salt). We then will place seeds on wet paper towels that have been soaked in their given saline concentrations in a 4×5 set up about 5 centimeters apart, totalling 20 seeds per concentration. The seeds that were taken from different packages allow us to randomize our sampling. We will then place the wet paper towels inside plastic bags and place them in indirect sunlight. The location of this study is in Highlands Ranch, CO and the plastic bags will be placed on a back patio counter in indirect sunlight. This study will be conducted over the next 6 days because for these specific seeds, the germination process typically takes 4-6 days. We will be using radish seeds. If they are not placed in ideal conditions, the seeds can take a few more days to fully germinate. Every 2 days (on days 2, 4, and 6), we will observe how many seeds have germinated in each given group and compare the three groups of seeds. The seeds will sprout at as low as 40 degrees fahrenheit and up to 85 degrees fahrenheit. Garden radishes can grow in even the smallest cities. They are generally fast-growing and can be planted during late summer or spring. After sowing, radishes will be ready to harvest after approximately 4 weeks. The study will be replicated by having two groups of each concentration, meaning we will have two groups of seeds at 0% saline concentration, two groups of seeds at 25% saline concentration, and two groups of seeds at 50% saline concentration. This will allow us to get a mean of each concentration and we will be able to compare the data using ANOVA. A one-way analysis of variance (ANOVA) is used when you have a categorical independent variable (with two or more categories) and a normally distributed interval dependent variable and you wish to test for differences in the means of the dependent variable broken down by the levels of the independent variable. Our independent variable is the different saline concentrations in water that will be given to the radish seedlings and our dependent variable is the amount of seeds that are germinated with each concentration. We predict that the seeds with 0% saline concentration will have more germination compared to the seeds with 25% saline concentration and 50% saline concentration. Below is a graph that represents our prediction on seed germination. 

Experimental design

The independent variable is the different saline concentrations in water that will be given to the radish seedlings. This is a continuous variable because we are measuring this by percentages. In the experiment, we will be randomizing the sampling by placing a population of 20 seeds in each bag, evenly placed. Each bag will contain a different percentage of saline concentration. Two bags will be given 0% saline concentration, 2 others will have 25% concentration and the last two will have 50% concentration of saline. They will be placed in rows of 4×5 approximately 5 centimeters apart.

Response variable

The dependent variable is the amount of seeds that are germinated with each concentration and this is a continuous variable as well because we are measuring this by interagers. Seed germination is the process of a seed sprouting. Once the seed is metabolically activated, the process of germination will begin and go through 3 stages. First, the seed coat will rupture. This will allow for the root to grow into the ground in order to get the nutrients. In the next step, we should begin to see the growing shoot’s first leaves. In the last stage, we will be able to see developing roots. Through this experiment, we will be monitoring these three stages of germination in order to access how the saline concentration is affecting the germination of the seeds.

Statistical analyses

We plan to count how many out of each sample germinated and compare the means of the samples. If a seed has begun the process of germination, we will be able to identify which stage the seeds are in and count it towards our data. This will be able to give us the data we need to determine how saline concentration affects the germination and growth of seeds in our population. The seeds we will be gathering are randomized because we will be taking a random sample of seeds from our package. From there we’ll be using the statistical test, ANOVA. A one-way analysis of variance (ANOVA) is used when you have a categorical independent variable (with two or more categories) and a normally distributed interval dependent variable and you wish to test for differences in the means of the dependent variable broken down by the levels of the independent variable.

References

1. M. R. Panuccio, S. E. Jacobsen, S. S. Akhtar, A. Muscolo, Effect of saline water on seed germination and early seedling growth of the halophyte quinoa, AoB PLANTS, Volume 6, 2014, plu047, https://doi.org/10.1093/aobpla/plu047
2. Hosseini, M., Powell, A., & Bingham, I. (2007, February 22). Comparison of the seed germination and early seedling growth of soybean in saline conditions: Seed Science Research. Retrieved July 16, 2020, from https://www.cambridge.org/core/journals/seed-science-research/article/comparison-of-the-seed-germination-and-early-seedling-growth-of-soybean-in-saline-conditions/7CB7F0789C00F46EA8AD6BFD9CB56EEF 
3. Lombardo, V., & Saladino, L. (1997, January 01). Influence of saline water on seed germination. Pt.2. Retrieved July 16, 2020, from https://agris.fao.org/agris-search/search.do?recordID=IT1998060603 
4. Shrivastava, P., & Kumar, R. (2015, March). Soil salinity: A serious environmental issue and plant growth promoting bacteria as one of the tools for its alleviation. Retrieved July 21, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4336437/

USDA Natural Resources Conservation Service. Soil Quality Resource Concerns: Salinization. 1998, http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_053151.pdf.