Contents
1.01-Focus Question – Will higher concentrations of sodium fluoride reduce the dry root mass and the dry mass of Phaseolus vulgaris (green bean)?
1.0.2- Hypothesis – The dry mass and dry root mass of Phaseolus vulgaris will be reduced in higher concentration of sodium fluoride.
.1.0.3- Theory – Sodium fluoride is a ionic compound between a single Na atom and a single F atom. This bond through a ionic bond to form Na-F. Sodium fluoride exists naturally is soil in concentrations from 0.5ppm to 1.5ppm. 8kg of sodium fluoride is lethal to a 70kg human (Unknown 2008). Technically sodium fluoride is a salt and therefore it is possible that it could affect plant growth. Ionic salts basically clog out water intake line in plant roots. It inhibits the plants ability to absorb water and nutrients from the soil. Therefore the plant cannot before photosynthesis as effectively. Photosynthesis is vital to the production of plant energy (starch). Without this energy the plant’s growth would be slower as it is vital for the production of new cells (R. Perry). Therefore if a plant is placed in an environment with an excess of an ionic compound such as Na-F it is highly possible that he plant will die. There are some exceptions to this however. Many plants such as mangroves thrive is high salt environments as they root systems allow them to absorb salts as nutrients. This however is not the case with the most crops. Crops normally have very thing stalks and have soft root systems. This makes them highly susceptible to many biotic such as weather and biotic factors such as pests. The state of the water itself is no exception. If crops where to be placed in high salt environment it is highly possible that they would die or not grow at all as the root systems would not be able to absorb nutrients and water (Australian Government 2008). Also if an area is made to be highly saline through treatment or removal of salt absorbing trees it is possible that he area will be lost forever as the salinity become so high that indigenous plants will no longer grow in that area. Many cities and councils in Australia have recently adopted a system in which Na-F will be added into water supplies as it will aid in dental hygiene. This Na-F is existent in trace amount and is very safe for human consumption. When human consume Na-F the compound will merely be absorbed and eventually excreted. However the same water that is used for drinking will also possible are used for the watering of plants. The soil however cannot “remove” the Na-F like humans can. Over time it is possible that the level of Na-F could build-up to such as level that plants in the area begin to die. On a side note when rain arrives, it will wash the Na-F in to rivers and eventually back into human water supplies, which could endanger human life. One of the most reliable ways to measure the development of a plant is to measure is dry weight. This means that water will not be a contributing factor to the weight and the only factor will be the actually plant mass and therefore the amount of growth. Another factor that is indicative of a healthy plant is the mass of the root system which can be measured by separating the root system from the seedling. (D, Timmers 2009)
- Experimental setup
1.1.1- Variables – (table 1)
1.1.2-Control Used for Comparison – Distilled water as it is pure and will not have any fluorine present
1.1.3- Apparatus and Materials (Table 2)
Materials-
1.1.4Safety Aspects – (TABLE 3)
1.1.5 Protocol and Protocol Diagram – (diagram 1 and 2)
How to do a dilution series (diagram 1)
Stock 90mls of pure water 20mls of pure water
Solution
100mls
1mg 0.1mg 0.08mg
How to acquire qualitative data (Diagram 2)
1.1.6 Experimental setup-(Diagram 3)
1.1.7 Procedure –
Preparation of solutions
- Draw 100mls of stock solution and place in a
- For 10ppm concentration draw 10ml of stock solution and place in 90ml of distilled water
- For 8ppm concentration draw 80ml of 0.1m solution and place ...
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Solution
100mls
1mg 0.1mg 0.08mg
How to acquire qualitative data (Diagram 2)
1.1.6 Experimental setup-(Diagram 3)
1.1.7 Procedure –
Preparation of solutions
- Draw 100mls of stock solution and place in a
- For 10ppm concentration draw 10ml of stock solution and place in 90ml of distilled water
- For 8ppm concentration draw 80ml of 0.1m solution and place in 20mls of distilled water
- For 6ppm concentration draw 60ml of 0.1m solution and place in 40ml of distilled water
- For 4ppm concentration draw 40ml of 0.1m solution and place in 60ml of distilled water
- For 2ppm concentration draw 20ml of 0.1m solution and place in 80ml of distilled water
Collecting qualitative data
- Gently run plants under a tap
- Gently blot plants with a drying rag
- Heat plants in a 100deggree over night
- Place plants in a zip lock bag according to concentration and leave until cooled
- Weigh the dried plant on the scale(record data)
- Use knife to remove plant roots
- Weigh the plant roots on the scale (record data)
Bibliography
Unknown, Unknown, 2008, Sodium fluoride, viewed 16/07/2008-
Perry, R.P, 2008, Plant growth, viewed 16/07/2009
Australian government, Gov AU, Soil salinity, 16/07/2009
Queensland health, QLD H, 2004, Fluoride levels, 16/07/2009
Mrs Mandy- M M, 2009, Measuring plant growth, view 16/07/2009, published date unknown, accessed 16/07/2009
2.0- Data collection and processing
2.1.0- Raw data collection
2.1.1- Changes to experimental design- Because it required that at least one piece of data is taken over a period of days some changes had to be made. Because of this the fresh weight of each plant minus the original weight was taken on every 2nd day, and third day for two periods of time. The plants were also watered with 5mls of water instead of 3. 5mls every second day and 7.5 on three days periods. The dry weight which was originally planned to be considered will be disregarded. This is because the purpose of the fresh weight and dry weight is so they can be compared. However the mass of the dry seed before germination is unknown. The fresh weight is looking at the change in mass between the fresh seeds on different days, the dry mass however has no comparison so its change in mass cannot be found, and this applies for the dry root weight as well. The experiment was also allowed 14 days of growth instead of 10 days. To measure the fresh change in mass the mass was of the seed was taken (remove excess water and perlite) and measured on a electronic scale and then placed back into its environment. Perlite was used instead of vermiculite; there composition however is the same.
The new hypothesis is that- The change in mass of Phaseolus vulgaris between different days will be reduced as the concentration of sodium fluoride is increased.
The new focus question- Will the change in mass of Phaseolus vulgaris between different days will be reduced as the concentration of sodium fluoride is increased.
2.1.2- Qualitative data- All of the plants germinated on the same day, some samples in higher concentrations of sodium fluoride did not absorb all the water like samples in lower concentrations did. When samples began to grow they grew straight up and began to life the Petri dish lids, at this point they were removed which was contradictory to the controlled variable were samples were to be enclosed. When removing the plant they were brushed with a cloth, some water and vermiculite where left on this cloth. The experimenter who was performing a different experiment to mine had large amounts of harmful fungus on his samples, his samples were right next to mine so it is possible that some of those fungus spores could have affected my sample. The samples colour was generally green; however a seed in samples 2ppm, 8ppm and 10ppm turned brown and died. The actually roots and stem fell of the seed. Some samples lost their seed casings as they grew.
2.1.3- Quantitative data- Raw data table showing the fresh mass on different days. (Table 4)
2.2.0- Processing raw data
2.2.1 Calculations (table 5)
2.3.0- Presenting processed data
2.3.1 Overview- The data that was acquired was first averaged for all 5 samples on a particular day. This value was then subtracted by the value of the previous day. With this the average change in mass could be found. . The graph has the days of the experiment on the x axis while growth per day will be on the Y axis. With this the average mass increase between any set of days could be compared to other samples. It is important to note that in samples 2ppm, 8pm and 10ppm one of the germinate seeds died. This value was therefore not included in the averages because there death was most likely due to a random error and their effect on other values would be too great. This average’s standard deviation was also calculated, the standard deviation was that of the complementation of change in masses. Once the standard deviation was calculated it was found that if it was incorporated into the graph purposed to compare the change is mass between samples its effect would be to great and it could clutter the results. For this reason the standard deviation was calculated into multiple mini graphs that were interrelated purposed to comparing the standard deviation between samples.
2.3.2 Processed data table
Table showing processed data (table 6)
Standard deviation between plant mass on different days (Table 7)
2.3.3 Processed data graphs
Graph 1- This graph show the comparison of the different masses of growth on different days at different concentrations of sodium fluoride,
The results were highly linier, control and tap water had the highest changes in mass while in respect to the sodium fluoride concentrations 2PPM had the most growth with each subsequent increase in concentration having less growth. The first four samples (Control, tap water, 2ppm, 4ppm) all followed a very similar pattern. The increase in mass increasing constantly until the 12th day. A drop then occurs. It is important to note that day 9 to day 12 was 3 days of growth and 12 to 14 was two days of growth however, this also applies for day 2 to day 5 were a extra day was allowed before measuring. Naturally it is expected that growth would be greater as there is an extra day for growth. Despite this the graph tends to be exponential, the amount of mass increase between subsequent days increases through the course of the experiment. Simply as the days move on the amount of mass increase increases. Samples 6ppm, 8ppm and 10ppm followed the same trend as control, tap water, 2ppm and 4 ppm until the 9th day, instead of the rate of mass increase booming like the other samples did the rate of mass increase decreased substantially , despite 3 days of growth, this suggest that something occurred on day nine to spawn this occurrence. The drop between days 12 and 14 is not as sharp as the drop samples (control, tap water, 2ppm, 4ppm) however. Looking at the samples there apparent order is highly linier. Control remains on top tap water which remains atop 2ppm which remains on top of 4ppm and so on. This is with the exception of 2ppm and tap water on day 9 where this order is reversed and then corrected on day 12. This suggests some sort of random occurrence as no other samples reflect this occurrence. From this table 2 distinct similar groups can be identified. Group 1 being control, tap water, 2 ppm and 4ppm, group 2 being 6ppm, 8ppm and 10ppm. The groups are relatively close together in their change in mass, Tap water, 2PPM and 4PPM and 6PPM,8PPM,10PPM are close together.. One exception to this however is the control . Its difference in average increase in mass is much larger than that of the previous samples which reflect a negligible difference between samples.
Graph 2, 3, 4, 5, 6, 7, 8 - These graphs are all inter related and serve as a comparison between standard deviations, they are separate because as a single entity they are simply too cluttered.
Although the actual deviations for each individual sample were all different a very distinct trend could be seen. This is that as the change in mass the size of the standard deviation grew as well. This is with the exception of samples in the 6PPM sample (table 6) which grew exponentially. Singular samples in tables 2 and 3 also defied this trend. Otherwise this trend is evident and static throughout the other samples .This suggest that as the change in mass rises for some reason the standard deviation rises as well. The standard deviation itself would prove to be problematic in the experiment. The difference between many samples in table 1 was quite small, if the standard deviation error bar was included it means that some samples could cross above or below others, this means the actual data could be somewhat invalid as some samples may switch places if the standard deviation is taken into account.
3.0- Conclusion and evaluation
3.0.1- Conclusion
The hypothesis “the change in mass of Phaseolus vulgaris between different days will be reduced as the concentration of sodium fluoride is increased” was proven to be correct on the surface but this statement is somewhat questionable, the change in mass was reduced in higher concentration of sodium chloride with samples with no sodium fluoride having the highest change in mass and those with the most sodium fluoride having the lowest change in mass. From table one it could be seen that as the day’s move on the plants change in mass increases as well, it gradually gets larger. The samples with the biggest changes in mass are those without with the least present sodium fluoride. The largest was the control sample, then tap water; in respect to fluoride 2PPM had the highest growth with each subsequent increase having less change in mass. The sample with by far the most change in mass was the control sample which contained no fluoride, the second highest was tap water and the third highest was 2ppm of fluoride, the lowest was 10ppm of fluoride. This trend was static with the exception of tap water and 2PPM on day nine where 2PPM was for a brief period had higher growth then tap water, this was the only factor that denied the trend and therefore it is most likely a random occurrence. The general sentiment is that when the concentration of sodium fluoride is increased the change in mass of Phaseolus plants over a period of days decreases compared to samples with higher sodium fluoride concentrations... There are a few possibilities to why this might occur. Sodium fluoride may act as a toxin to the Phaseolus Vulgaris plant; it is possible that as the sodium fluoride concentration increases the toxicity in the plants increases as well. However it could be fluoride or sodium as a signal entity that is causing the issue and not the sodium fluoride compound as a whole. Sodium fluoride is in essence as ionic salt, it is possible that as the levels of sodium fluoride increased the plants ability to draw liquid from its surroundings decreased as well, this would also explain why not all the water was absorbed in some of the higher sodium fluoride concentrations. Another possibility is that perlite (the compound the seeds were grown in) could bond with one of the alloys in the sodium chloride compound, this means that as the levels of sodium fluoride increased more of the hydrogen and oxygen atoms required for plant development would be held onto the perlite, this is unlikely however because the composition of perlite is mostly silicon dioxide which is a covalent bond and therefore neutral in its electron charge, the entire purpose of perlite is to prevent water loss by reducing evaporation without affecting other chemicals in the compound. The rise in the change in mass was exponential between days, each subsequent gap gave rise to an increase in change in mass over the previous set of days, this trend is not evident in days 12-14 which is excusable becume day 9-12 had 3 days of growth instead of 2. Two definable trend groups could be identified. The first was the samples control, tap water, 2PPM and 4PPM. These all grew gradually until day 9 to 12 where they had large changes in mass dropping from day 12 to 14. It should be noted that the drop in day 12 to 14 could have been higher than the previous day 9-12 sample if the data reading was taken on the 15th day. Due to timing issues the period’s 2-5days and 9-12 days were taken 3 days apart instead of 3. The overall trend of this group is that the rise in the change in plant mass is exponential; it is increasing between each subsequent reading. This suggests that a plant or in particular Phasoeolus Vulgaris will develop slowly at first and then begin to speed up in its development. Or possibly the mass is increasing because the plants are absorbing more and more water, for instance the plant was watered once and it absorbs the water from its surroundings, it is then watered a second time and it will once again absorb that water plus the water it absorbed originally, or possibly a combination of both the plants developing and retention of more water. The control group which contained no sodium fluoride has noticeably more growth then tap water, 2ppm and 4ppm (graph 1). 2PPM is twice then generally accepted limit for sodium fluoride, however the change in mass tap water samples was only a little above 2PPM, this may suggest that tap water sample may be above that of the legal limit. This is unlikely however because tap water also contain many other chemicals such as chlorine which could inhibit plant growth. The second trend group (6ppm, 8ppm, 10ppm) followed the same trend as the first group until day 9. At this point the change in mass plummeted whereas in group 1 the change in mass grew. This occurred across all of the samples but they still retained their order of change in mass (6ppm highest, 8ppm medium, 10ppm lowest). This suggests that the sudden drop in rate of growth is linier across all three spectrums and it is most probably not due to error. The drop occurred between days 9 and 12 to all of the higher concentration of sodium fluoride samples. The plants were watered every 2 days (3 days on days 2-5 and 9-12). It can be hypothesized that on day 9 the seeds reached a “saturation point” were the plant simple y begin to “die” and its change in mass reduced. This could be contributed to the plants reaching a point where the sodium fluoride compound has reached a point where the toxicity has become too high, or possibly that the build-up of sodium fluoride over the period of nine days have lead to the plant being severity inhibited in its ability to draw liquid. Also possible is that on day 9 the plants literally “drowned”. As stated before sample in the large sodium fluoride concentration sometimes had water left over from previous treatment, to remain true to the experimental procedure these plants were watered anyway, perhaps on day 9 this saturation had reached such a high point that the plant simple could not grow efficiently. Even if the plants drowned however it could be attributed to their inability to draw moister due to the effects of sodium fluoride. In conclusion the cumulative effect of sodium fluoride reduces the change in mass of the Phaseolus Vulgaris plant when it is in excess. Change in mass of a plant is indicative of it development, if the change in mass is reduced the relative development of the plant is being reduced as well. Sodium fluoride is being implemented into human water supplies, if these levels cumulative they could have disastrous effects on the plants that the water is used to nurture. In the tap water sample the change in mass and therefore the development of the plant was lower than that of the control, and if the sample was to be calibrated it is possible it could be larger than the standard of 1ppm (0.01ml). However it has to be considered that tap water is a concoction of different chemicals that may have an effect on the deployment of plants, not just sodium fluoride. In tables 2-9 it can be observed that apart from the exception of 6PPM the standard deviation increased as the change in mass increased. This suggests that each that as the change in mass increases there is more differentiation between the samples. This can be contributed to each individual seed being different, some will naturally grow better than others, it was concluded before the increase in change in mass is largely exponential, 5 replications were done. These replications could have fallen any ware in this exponential increase, therefore as the change in mass increases the size of the sample that each replication “could be”” increases, and therefore as the change in mass increases the standard deviation increase s as well.
3.0.2- limitations of experimental design
When the experiment germinated they grew too large to be covered by the Petri dish cap, at this point they were removed, this means that the greenhouse effect would be lost which may have had an effect on growth as more water was lost to the air and the inside temperature was decreased. This could be reprimanded by using larger containers to accommodate the growth of the seeds. When the weights were recorded the seeds were removed from their environment and lightly dabbed with a cloth to remove excess water and perlite, this could possibly have damaged some samples. This could be reprimanded by perhaps using a compound other then perlite that did not stick to the plant itself, or by finding the mass of each individual granule of perlite and subtracting the given weight by the number of attached perlite grains, the best solution would be to find the mass of the perlite + container and then measure the entire mass and then subtract weight of the environment by the mass of perlite and Petri dish, this would give the mass of the plant. The experimenter next to this one had a lot of fungus growing on it, it is possible that some of these fungal spores could have infected the seeds and effected growth; this is a possibility as the samples which received the least growth (10ppm) were the ones closest to the fungal experiment. This could be reprimanded by performing the experiment in an area away from other people’s experiments. The standard deviation of some of the samples was very large, so large in fact that in some samples by moving in either direction would break the order and trend of the graphs. This suggests that the data may not be completely correct as it could change it order. Reducing the standard deviation is difficult, especially in plant growth; seeds contain different amounts of potential energy which means that there will almost always be some difference in growth. Standard deviation refers to the deviation between averages, as the change in mass increases there is larger pool of possibilities. If the number of replications are increased the pool will remain the same and theoretically the standard deviation will not change, if the number of replications is reduced the standard deviation may fall but then the experiment would lack ecological validity, all seeds are of different specifications, and all will grow slightly better or worse than others. It is near impossible to eliminate standard deviation in plant development unless each seed was completely identical to its counterpart. The standard deviation could possibly be reduced by studying smaller changes in masses, perhaps by using a plant that grows slowly or has a low change in mass, this way the size of the deviation pool would be reduced. During the experiment 3 of seeds died, these were in sample 2ppm, 8ppm and 10ppm. Considering that all seeds are different and some may simple have been received in bad condition these deaths were not included in the results as there death may have been caused by a random error such as damaging of roots when they were weighed out. This is why many replications are performed so that other data can be sued to compensate for issues like this, if more replication are performed the dead values could still be included as their effect would be minimum, this would improve validity and reduce random chance errors. The tap water sample was used so drinking water (often used in plant care) could be compared to the concentration data, this comparison however is highly invalid because water contain many other compounds that could damage plant development, a sample prepared to the exact concentration of sodium chloride of tap water should have been prepared so the sodium fluorides individual effect could be examined. Some sample had more perlite then others, since it was chemically inert is was assumed that it would not have any effect on the samples, however it is possibly that those with more perlite would have held more fluid then those with less perlite and would have given a large surface for the plants to grab on to possibly effect the change in mass. Perhaps it would be more logical for the samples to have the same amount perlite. Samples in the high fluoride did not absorb all the water they were given but where continued to be watered, this could have led to their decline in development as they were being saturated. This could be reprimanded by water all plant samples less frequently or in lower volumes of water to make sure that samples do not become saturated. In the end this experiment only touched on the effect of fluoride on the Phaseolus Vulgaris plant, its effect other plants may have been different. Also only the factor of fresh weight was considered, thesis only a single measure of plant development and other factors should be considered because if the experiment is to be valid a multitude of the factors effecting growth such as high and root mass be performed for if the experiment is truly correct then these values will reflective of the fresh mass. The experiment performed was too focused to be considered completely valid as only one point was considered. The whole is the sum of its parts and change in fresh mass is only one of these sums. Perhaps most questionable is the composition of sodium fluoride itself, it is possible that a singular factor such as just sodium or just fluoride is the cause of the inhibited growth and not the compound as the whole, and even if it is the compound it is possible that in tap water it bonds with other molecules negating it chemical properties. A test should be done with each singular component of sodium fluoride to discover if it is only singular components affecting plant growth, these data sets could be compared to that of sodium fluoride, This present a limitation however because it is regular state fluoride is a gas.