Make your own free website on Tripod.com
Home | Acids, Bases and Neutral Substances | What is pH? | Plants and the Effects of pH | My Experiment | Results and Photos Trial 1 | Results and Photos Trial 2 | Discussion, Conclusion and more | Science Experiment Ideas | Links Page
* * * Plants and pH * * *

Discussion, Conclusion and more

From this experiment a lot of conclusions could be drawn and patterns spotted. I have included all of this below as well as a discussion, which would have been included in a normal scientific report. however I decided to add it in anyway. 

 

Patterns and Trends

 

From both trials of this experiment trends and patterns can be seen, with the exception of plant 4 (pH 7.5) in trial one which did not grow as well as it should. All other plants grew very similarly in both trials and the results were almost the same, this is one pattern that is very obvious. Another visible and obvious pattern is that Plant 3 (pH 7.0) strived the best in both trials. By looking at the results table and photos for each trial and by comparing the two, patterns or trends can be spotted. By observing these patterns in the growth of each plant generalisations or conclusions can be made. These patterns made it easy for me to see that:

        The plant that was watered with a neutral substance grew the best.

        The plants that were watered with acidic substances did not grow. Instead they began to shrivel up, leaves feel off and no progress was made.

        The plants that were watered with basic substances made progress. Both grew, but not as well as plant 3 that was watered with a neutral substance. The closer the pH of the substance was to pH 7.0 (neutral), the better it grew. This means that plant 4 (pH 7.5) grew better than plant 5 (pH 8.5), as the pH is closer to 7.0 (neutral).

 

These were the three main patterns or trends that can be gathered from this experiment and helped draw the most accurate conclusions possible. By looking at these three patterns I can say that the closer the substance is to neutral the better the plant will grow, however acidic substances, no matter what pH make no progress.

 

By comparing each plant’s growth individually in both trials other patterns or trends can be found. Such as:

        Plant 1 (pH 4.5) stayed almost stable, it shrunk slightly and some leaves died.

        Plant 2 (pH 6.0) shrivelled up and many leaves feel off. This is due to the fizzing of the Eno.

        Plant 3 (pH 7.0) grew very well with no problems.

        Plant 4 (pH 7.5) grew differently in both trials. However if pond water was used for both they would grow very similarly. It grew very similarly to plant 3, but not as good.

        Plant 5 (pH 8.5) grew, but was slightly stunted from the substance, as the pH was further away from 7.0.

 

These are patterns as the same thing happened in both trials, with the exception of plant 4 (pH 7.5). This means that the relationship in data collected from each trial was very similar.

neutralplants1.jpg
The plant watered with a neutral substance grew the best in both trials

acidicplants1.jpg
The plants watered with acidic substances made no progress in both trials

basicplants1.jpg
The plants watered with alkaline substances made progress in both trials

 

Discussion

 

From the results of this experiment I concluded that broccoli plants grow best when being watered with a substance that had a pH of 7.0. When doing my experiment I also observed that the broccoli plants did not grow when watered with acidic substances, but did when watered with basic substances. Plant 4 (pH 7.5) grew the second best out of the five plants, as it was the closest to pH 7.0. Plant 5 (pH 8.5) followed as the substance was basic and plant 1 and 2 did not make any progress in both trials as both plants were watered with acidic substances.

 

According to experts most plants, including broccoli plants grow best when watered with rainwater, however pure water is slightly better. This is why Plant 3 (pH 7.0), which was neutral water grew the best. Rainwater is slightly alkaline which is the reason why Plant 4 (pH 7.5), grew very well when pond water (also slightly alkaline) was used in trial 2. As the other plants were watered with different substances of different pH levels they made less progress, and some not at all. The plants which were watered with acidic substances did not grow as acidic substances are corrosive. This ate away the roots of the plants and stunted their growth.

 

Two trials were done for this experiment, as trial one was slightly unsuccessful. Plant 4 (pH 7.5) did not make much progress in trial 1. Seeing as it was closer to pH 7.0, than plant 5 (pH 8.5) was it should have grown better. This however did not happen. For trial one of the experiment toothpaste was used as the substance for plant 4 (pH 7.5). Although the toothpaste was diluted with water like all other substances it was still very thick and most of the substance stayed above the soil. Very little of it soaked through the soil and watered the roots. This stunted the plant’s growth and introduced a new variable as all other substance soaked into their plants roots, whereas very little of the toothpaste substance did. For trial two I changed the substance used for plant 4 (pH 7.5) to pond water from my backyard, which also had the same pH. All other substances and variables were kept the same. The outcome of trial two was successful, as plant 4 (pH 7.5) grew a lot better. Plants 1 (pH 4.5), plant 2 (pH 6.0), plant 3 (pH 7.0) and plant 5 (pH 8.5) grew very similarly in both trials. By attempting two trials I could achieve a more accurate result and a more accurate conclusion could be drawn.

 

The independent variable in this experiment was the substances used and the dependent variable was the height of the plants. Despite the failure of plant 4 (pH 7.5) in trial one all other variables were controlled in both trials to ensure I received the most accurate results possible from the experiment. The controlled variable in this experiment are: the plants, the substances, the quantity of the substances, when the plants were watered, measuring cup, measuring tape, watering cups, the way the plants were measured, the position of the plants and the length of each trial.

 

Although it was an overall successful experiment, there is room for modification and improvement. If I were to repeat the experiment I would conduct a third trial as this would be even more accurate and a better average can be drawn. However seeing as each trial went for a duration of three weeks I did not have enough time to do so. To improve the experiment further I would also have tested the substances on a variety of plants. This would have modified the experiment a lot because if three different types of plants were used, then there would be three plants tested with each substance of a different pH. If this were so I would need a total of 15 plants. This would involve a lot more work and recording. However many different conclusions could be drawn from that conclusive experiment.

 

Conclusion

 

Broccoli plants grow best when watered with a neutral substance. Broccoli is able to grow when it is watered with basic substances, however when broccoli is watered with acidic substances it can’t. The closer the basic substance is to neutral the better the broccoli plant will grow. Therefore plant 3 (pH 7.0) grew the best followed by plant 4 (pH 7.5), then plant 5 (pH 8.5) and last were the two acidic substances plant 1 (pH 4.5) and plant 2 (pH 6.0), which made no progress.

 

 

 

bestworst.jpg
Plant 3 (pH 7.0) grew the best, where as the plants watered with acidic substances made no progress

Intel Young Scientist 2004