Introduction
Elodea is a genus of 6 species of aquatic plants, often called the waterweeds, described as a genus in 1803. (Wikipedia contributors, 2023) Elodea is native to the Americas and is also widely used as aquarium vegetation and laboratory demonstrations of cellular activities.
Elodea leaves are only two cell thick(very thin), making the microscopic observations of plant cell structure simple. Also, aquatic plants can be used to demonstrate oxygen production in the process of photosynthesis because they are specialized to produce oxygen while submerged under water. These traits make Elodea a very easy plant to grow, which becomes a good choice for many lab experiments. Thus, my experiment is to measure plant growth.
Elodea Canadensis has a wide range of conditions in which it can grow. It can grow in very shallow to deep water and slightly mineralized and acidic water in siliceous sediments to heavily mineralized water in calcareous sediments. However, it prefers mesotrophic (Reservoirs and lakes that contain moderate quantities of nutrients and are moderately productive in terms of aquatic animal and plant life.) waters (CABI, 2005). This species can grow slowly under ice cover and survive inside the ice (Bowmer et al., 1995). Dense stocks can also partly survive when the water level sinks and the plants on the banks are exposed to dryness for several weeks.
“In its native habitat, Elodea resides in surface-standing waters and surface-running waters: shallow lakes, ponds, pools, ditches, and streams with slow-moving water. In its invaded habitat, it can survive in the same environments; however, it can survive in up to 3 meters of water depth in slow-moving water and, in exceptional cases, up to 16 meters in depth.”(GISD) It tolerates pH values from 6.0 to 7.5 and temperatures from 1 to 25 degrees Celcius (Gollasch, 2006). The foliage can stand much battering by turbulence, but, being poorly anchored or not at all, this species will not persist in waters with a continuously fast flow and favors still or sluggish conditions (Rodwell, 1998).
The experiment
My research question is how do different water types(distilled water, salt water, and lake water) affect the growth of elodea? I hypothesize that Elodea will grow more in lake water because a lot of dissolved minerals and natural fertilizers produced by life in the lake benefit Elodea.
The independent variable of this experiment is the different water types - distilled water, salt water, and lake water. The dependent variable is Elodea's growth(height) measured in centimeters. The controlled variables are factors that may affect the growth of Elodea - the amount of light each receives. The same volume of liquid and container it is in. The control group in the experiment is the elodea within the lake water. The experimental group will be Elodea with the other water types( distilled water, salt water).
Materials list:
● Elodea x3
● Gloves
● Tongs
● Cylinder container(500ml)
● Lake water, Saltwater, distilled water
● Ruler
● Scale
● Beaker
● Plastic plates
Method
Extract three same types of Elodea plants, then measure the initial length of each Elodea. Then prepare the three types of water. Lake water from Elodea's natural environment (Blair’s Lake). Distilled water. Saltwater (17.5g of salt in 500ml distilled). Place the three Elodea in each 500ml cylinder container. Add the different liquids and leave the lid open for the water to exchange oxygen, which keeps the Elodea respiring. Put the four-cylinder under a light bulb or an area exposed to sunlight. Because the sunlight will evaporate the solution, on each day 1 of the experiment, refill the water level to 500ml. After the experiment(3 weeks), remove the Elodea from the container. Measure the length and see which Elodea has the most growth or if it did not survive.
Prior Studies
As mentioned above, Elodea Experiments are often related to photosynthesis measures. Photosynthesis and Elodea is an experiment by Mathew Abolafia to see photosynthesis on a plant. In the experiment procedure, he put two similar Elodea in two different cylinder lids tightened - so no new oxygen with being in the water - in water with drops of Bromothymol
Blue indicator. Then he wrapped one Elodea with tin foil so no light would read the plant(Plant with tin foil, group A. Plant without, group B). He put a heat light, placed the two cylinders under it, and waited for a day. After unwrapping, he compares her result. After one day of photosynthesis, group B Elodea uses the carbon dioxide in the solution. More carbonic acid dissociates to form more carbon dioxide and water. Thus, the solution becomes more basic. The pH indicator, Bromothymol Blue, reacts to the basic solution by turning it green and eventually blue. Group A does not change color as there is no photosynthesis occurring.
Abolafia, Mathew. “Elodea Photosynthesis Lab.” DataClassroom, about.dataclassroom.com/ready-to-teach/elodea-photosynthesis-lab. Accessed 24 Jan. 2023.
Significance
My experiments measure the growth of Elodea in different water. Although it does not have real-world significance, it may explain why Elodea prospers in some water areas over others. It could also affect the aquatic life there in that area as it provides suitable habitat for aquatic invertebrates, fish, and amphibians.
Results
figure 1: The table shows the measurement before, after, and change of each elodea in salt, distilled, and lake water.
figure 2: The graph shows Elodea growth in different water types. The blue represents salt water, red represents distilled water, and yellow represents lake water. On the x-axis is the measurement of elodea before, after, and change. The Y-axis is the length of Elodea in cm.
This is the result of the experiment. The blue represents salt water, red represents distilled water, and yellow represents lake water. On the x-axis, the graph shows the measurements in cm, and on the y-axis, the graph shows the measurement before, after, and the overall change. The graph trends show that the yellow bar line had the most overall change reaching 14cm, meaning Elodea has the most growth in lake water. Following lake water is distilled water at 12.3 cm in change. Saltwater, as shown in a graph and pictures, has a reduction in change and size, meaning it had the least growth.
Conclusion
My hypothesis was correct as I predicted that Elodea would thrive best in its natural environment, lake water, as it provides Elodea with various amounts of minerals that benefit its growth. Elodea grew slower in distilled water as it did not contain the same amount of rich minerals as lake water. This is shown in the graph. The Eldoea in distilled water is 8.7cm and 8cm in lake water. At the end of the experiment, the Elodea in lake water reached 22cm, whereas distilled only reached 21. However, Salt water has a negative effect on Elodea because it is undergoing a process called plasmolysis. Osmosis is a biological process where the water in a hypotonic solution(lower concentration of solute, therefore, higher water concentration) moves to a hypertonic solution(higher concentration of solute, lower water concentration.)Plasmolysis is the process by which the internal contents of a plant cell shrink and aggregate when the cell is placed in a hypertonic solution because the water in the cell is moving out. This is shown on the graph of a negative change and also in picture three, where the elodea has turned transparent/white and had a significantly smaller size.
Limitations
The limitation or drawback of this experiment is that I only had one trial of the experiment. This meant I only had 1 Elodea tested for each water type; therefore, I cannot be sure my results are accurate because it might be a coincidence. Next time, I would add more Elodea in each Jar to make sure my experiment is accurate as possible.
References
Simpson, P. S., et al. “The Influence of Environmental Factors on Apparent Photosynthesis and Respiration of the Submersed Macrophyte Elodea Canadensis.” Plant, Cell and Environment, vol. 3, no. 6, Dec. 1980, pp. 415–423, 10.1111/1365-3040.ep11586879.
Jones, J.Iwan, et al. “The Effect of Changing Environmental Variables in the Surrounding Water on the Physiology of Elodea Nuttallii.” Aquatic Botany, vol. 66, no. 2, Feb. 2000, pp. 115–129, 10.1016/s0304-3770(99)00069–8. It was accessed on 25 Nov. 2020.
Ozimek, Teresa, et al. “Growth and Nutrient Uptake by Two Species of Elodea in Experimental Conditions and Their Role in Nutrient Accumulation in a Macrophyte-Dominated Lake.” Nutrient Dynamics and Retention in Land/Water Ecotones of Lowland, Temperate Lakes, and Rivers, 1993, pp. 13–18, 10.1007/978-94-011-1602-2_2.
Thouvenot, Lise, and Gabrielle Thiébaut. “Regeneration and Colonization Abilities of the Invasive Species Elodea Canadensis and Elodea Nuttallii under a Salt Gradient: Implications for Freshwater Invasibility.” Hydrobiologia, vol. 817, no. 1, 13 Mar. 2018, pp. 193–203, 10.1007/s10750-018-3576-1. Accessed 15 Oct. 2020.
“GISD.” Www.iucngisd.org, www.iucngisd.org/gisd/species.php?sc=290#:~:text=In%20its%20native%20habitat%2C%20E Gollasch, Stephan. “National Checklist for Aquatic Alien Species in Germany.” Aquatic Invasions, vol. 1, no. 4, 2006, pp. 245–269, 10.3391/ai.2006.1.4.8. Accessed 23 Nov. 2019.
Duenas-Lopez, M. A, et al. “Elodea Canadensis (Canadian Pondweed).” CABI Compendium, vol. CABI Compendium, 7 Jan. 2022, 10.1079/cabicompendium.20759. It was accessed on 13 Dec. 2022.
Wikipedia contributors. (2023). Elodea. Wikipedia. https://en.wikipedia.org/wiki/Elodea
Notes
What will be your week one plan?Ensure I have all the material, an experiment overview, and know what I am doing. What will you hope to accomplish in the first class?Setting up my experiment
What materials will you need for week 1? Can you all compile the materials you will need?
● Distilled water
● Saltwater (tap water + 35g/liter)
● Lake water(Blair’s lake water)
● 1-liter transparent cylinder container x 3
● Elodea plant
Experiment measurement:Saltwater container:500ml + 17.5 g of salt Lake water container: 500mlDistilled water: 500 ml
Measurements:
Salt:8.7cm Distilled: 8.1cm Lake:8cm
Week 2:
Week 1:
Day 1: Setup experiment and measure Elodea
Day 2: Observe
Day 3 Observe
What did you accomplish last week?Setting up my experiment and recording the data
What will be your detailed plan for this week? Day 1: Refill to 500mlDay 2:observeDay 3:observe
Week3:
Day1: Refill to 500ml Day2: observeDay3: Conclude experiment Results:
Salt: 8cm Distilled: 21 Lake water: 22
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