| Explore | While the effects of a deficiency in zinc on the Arabidopsis thaliana have been tested thoroughly, the impact of an increased amount of zinc in this plant has not been explored as substantially. Over the course of our research however, the impacts of this were determined to consist of the following; Colombian Wild Type: This plant has been used in many different experiments across the globe because of its uncomplicated genome and relevance to the growth of other crops. When given an adequate amount of zinc, the plant is expected to grow without defects. Contradictory to these results is the growth of this plant when zinc levels are increased. Further, the plant should show signs of; stunted growth, smaller leaves, discoloration, modest germination and necrotic tips of its leaves. NCA1-1: Encodes a catalase chaperon and specializes in metal ion bonding and protein binding by controlling through the nucleus. In other words, this mutation allows the cell to have these skills through the nucleus rather than the Colombian Wild Type, where these skills are not as advanced. ZIP-2 : This gene allows the plant to appear as if it is maturing faster. This is done by a process of gene-silencing by multiple techniques in order to show these early vegetation signs. This gene also differs from the Colombian Wild Type in that it can move zinc around its membrane more efficiently. |
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| Research Question | To what extent does an increased amount of zinc impact the germination, chlorosis, condition of the leaves (color, strength, length, etc), and height of the wild type (Arabidopsis thaliana) and its mutants nca1-1 and zip-2? |
| Predictions | Controlled Group Colombian Wild Type is expected to grow relatively normally. Germination is expected to be relatively normal (at least 20 out of the 30). The colors of the plant and of the leaves are anticipated to be standard. The overall conditions of the plant are believed to be healthy and the height of the plant is expected to be uniform. The nca1-1 mutant is expected to be incredibly similar to the Colombian Wild Type, with the possibility of more growth due to advancements in its control. The zip-2 mutant is foreseen to grow less adequately than the Colombian Wild Type and nca1-1 mutant. This is because of the silencing of genes, which will lead to more unhealthy conditions in the plant. Other than that prediction, growth is anticipated to be similar to the Colombian Wild Type and nca1-1 mutant. Increased Zinc Groups Colombian Wild Type is expected grow in a less than adequate way. Germination is expected to be lower than the controlled groups due to the more acidic soil. The colors of the plants are expected to be discolored in a multitude of different ways (brown spots, etc). The overall health of the plants is expected to be substandard and the plant is expected to be stunted in growth. The nca1-1 mutant is expected to grow similarly to the Colombian Wild Type. However, the overall health of the plant is expected to be worse. This is because of its ability to metal ion bond as it will cause the plant to take in too much zinc and damage itself. The zip-2 mutant is also expected to grow similar to the Colombian Wild Type, however its overall conditions are expected to get worse as well. This is because of its already unstable silencing of genes to grow more quickly. |
| Experimental Design | Independent variable: The amount of zinc (toxic levels) available to the wild type nca1-1 and zip-2 Controls: Amount of water Temperature Light Air quality Same containers Amount of test subjects Other than the experimental amounts of zinc, same amount of micronutrients in the soil Amount of time to grow Dependent variables: Qualitative observations: Color of leaves (ex: brown spots, yellow spots, pale color etc..) Necrotic tips of leaves Quantitative observations: Height Number of plants germinated Size of leaves (should be smaller) Planned groups: Wild type with an adequate amount of zinc (Osmocote fertilizer that is being used contains 0.05% zinc) nca1-1 mutant with an adequate amount of zinc zip-2 mutant with an adequate amount of zinc Wild type with an increased amount of zinc (with taking into consideration the possibility of zinc poisoning) nca1-1 mutant with an increased amount of zinc zip-2 mutant with an increased amount of zinc Procedure 1. Let the seeds that are being used in the experiment sit in the refrigerator for a couple days to simulate a winter setting 2. Then remove them from the cold and place them in pods of dirt 3. These pods will then be grouped with other pods containing the same plant in green trays and labeled based on their type (Wild Type vs Mutant) 4. These trays will be grouped together in blue trays with two of the same treatment in the same tray and one that sits in a tray alone 5. These trays will be placed under a light source and left alone unless to;water, check their condition, or measure 6. Allow these plants to germinate and grow for a short time before adding the zinc solution (16.15 g/l and later 20.0 g/l) in the water and watering the controlled environments with tap water 7. Document their progression during this time; make note of their condition and measure 8. Allow them to grow until the end of the experiment without harm or interference 9. Once the experiment comes to a close, take the plants out of their pods and allow them to sit until they’re dry 10. After a few days, weigh them and calculate their average weight to calculate their biomass 11. Record all of the results |
| Conclusion | In all, the research conducted in this experiment indicates that the Colombian Wild Type and zip2 mutant were deeply impacted by zinc toxicity, however the nca1-1 mutant did not depict a significant difference through the use of stem height and biomass. Colombian Wild Type The results of the experiment indicated their superiority in stem height, as both the controlled plants and plants with increased zinc grew taller than all other mutants and were similar to our initial ideas While the Wild Type in both conditions grew taller than the mutants, the plants treated with increased zinc had a height that differed from the controlled plants by an average of 5.18 centimeters This growth difference was most likely caused by a reaction to the increased zinc, as signs of premature growth were present in; premature flowering, small comparative biomass (Wild Type controlled plants vs zinc treated plants) and spike in growth seen on the graph zip2 mutant The results from this experiment contradicted our initial thoughts that this mutant would be able to sustain itself in a toxic environment (increased zinc) as their stem height in both the control and zinc treated plants had the shortest averages of the test subjects This height difference was also expressed between the controlled plants and zinc increased plants with a difference of an average of 2.06 centimeters Zinc toxicity symptoms can be found in this mutant through the stunting of the plant, in which the root cells are damaged by the zinc and can no longer take up nutrients or water very well, hence their small size and underdeveloped leaves This mutant’s ability to transport zinc across membranes was thought to be beneficial, however this ability is now believed to be the reason that the plants suffered as much as they did because the toxicity was spread across the plant more quickly This stunting is also identified in their biomass, as there is 0.635 grams in difference between their weight (the largest difference between the biomass of any two plants in the experiment) nca1-1 mutant The outcome of this experiment also contradicted our initial thoughts on the ability for this plant to survive in toxic environments (zinc) as they did better than the zip2 mutant and not far from the Wild Type The difference between the height of the control and zinc increased also displayed this similarity as there was only an average of 0.18 centimeters difference in their height This mutant’s ability to bond more specifically with metal ions led us to initially believe that zinc would build up and kill the plant, but actually aided it in adapting to the extra zinc. There were also many little hairs on their leaves and this is where the extra zinc was distributed to, causing zinc toxicity to not impact its growth While there was some difference in their biomass that could indicate some impact from the zinc, the impact seen in the biomass is far less impactful than the zip2 mutant and the Wild Type Future experiments that could be done from these results would more specifically include the nca1-1 mutant. This is because this mutant has the most evidence from this experiment to suggest its stronger immunity to zinc than the Wild Type or zip2 mutant. Therefore, more experiments could be conducted at a larger scale testing the abilities of this mutant that allow it to be more adaptable to these toxic environments. |
| Investigation Theme | ARABIDOPSIS |
| Grade Level | High School Students (Grades 9,10,11,12) |
| Session | Fall 2019 |
| About this Project | The Zinc (Zn) Team had a challenging project ahead of them, which leveled up with postgraduate research work. Not only they were testing an environmental variable that was very subtle and difficult to control (Zn nutrition status), but they increased the complexity of their experiment by testing the effect of increased Zn levels (relative to control) on Arabidopsis plants with different genetics. They compared different mutant lines, where particular genes and processes were not functioning, to Columbia wild-type plants. The team initially developed a research proposal, and allowed time for mentor feedback, showing that they put some time and effort planning their project. The long-term plant physiology experiment also required a lot of dedication, since plants required daily monitoring of plant growth and development, water status and Zn toxicity symptoms. While the students faced setbacks in their experimental setup (i.e. fungal contamination and drought) which are normal when performing a pilot study, they were fast in detecting issues and reporting them in the PlantingScience platform, as so to ensure their experiment was not lost. Finally, the Zinc Team also produced a nice poster to report their findings and conclusions to their school community. In this poster, they also made sure to realistically point out the setbacks faced, and came up with possible research directions based on their observations and overall research experience. Absolutely great work! |