Almost all high school labs will have access to pH paper. Everything else can be purchased at the grocery store.
Approximate Time Required to Complete the Project
Set-up is minimal, and can be completed in an hour, after purchasing supplies. Data collection is also minimal- 20 minutes every few days. The growth of seedlings, however, simply takes time, so budget for approximately three weeks.
This project hopes to determine whether pH- and by extension, acid rain- has any discernable effect on the germination and growth of seedlings, particularly aricultural crops.
The goals are to quantify growth of seedlings at various pH levels, and to speculate about the effect of acid rain in non-laboratory conditions.
- 1 bag of pinto ( or other agricultural) beans.
- Distilled vinegar or concentrated lemon juice
- Distilled water- at least two gallons
- Ziploc Baggies, medium size
- Paper towels
- Sharpie markers
- Metric ruler
- Plastic pipettes.
- pH testing strips All materials are available at the grocery store, with the exception of pH testing strips and pipettes, which are generally available in most school laboratories. Any type of eyedroppers, or even straws, can be substituted for pipettes. Links are provided below to purchase these materials should they not be available at school.
Acid rain is becoming more and more of a problem for our world. Outside of industrial pollutants, like nitrogenous and sulfuric oxides, even excess carbon dioxide can affect the pH of rainwater. One question that arises is ‘How will agriculture be affected?” plants rely on rainwater, and obviously have no control over its acidity.
We can explore one aspect of plant growth- germination and initial growth- fairly simply. Pinto beans ( phaseous vulgarus) are a major agricultural crop, and fairly easy test subjects to work with. We can moniter how many plants germinate and thrive under different acidic conditions in order to better determine the effect of acid rain will have on the agricultural sector.
- What is pH, and what does it measure?
- How is acid rain created?
- What is the normal pH of rain?
- How does acidity affect plant growth?
- What are some of the major agricultural staples throughout the world?
- What is germination?
- What is the ‘anatomy’ of a seed?
- What is the ‘anatomy’ of a seedling?
- What are the initial parts of a growing seedling?
Terms, Concepts and Questions to Start Background Research
Seed, seedling, pH, aciditiy, acid rain, commercial pollutants, air pollution, radicle, stem, cotylydon.
- Mix 3 parts distilled water with 1 part vinegar to make your first solution. Accuracy in mixing is not the most important part here- measuring the acidity is.2: Use the pH paper to determine the acidity of the solution.
- Add either water or vinegar to get the pH to a whole number. It’s easier to add vinegar than water, as you will need less- for instance if the initial mix has a pH of 3.5, it may be easier to add a little vinegar to get the pH to 3 than it would be to add a lot of water to get the pH to 4.
- Take approximately 1/10th of your initial solution and mix it with 9/10ths water.
- The second solution should be approximately one pH level more than your initial solution. For example, if you got the initial pH solution to 3, than this solution might be 4.2.
- Add either water or vinegar to get the pH to a whole number.
- Note: you don’t really need to get the pH to a whole number, as long as you are comfortable working with decimals. The goal is to get three solutions with three different pH values. The actual values don’t matter too much, as long as they are at close to I pH ‘point’ in difference. Or even more. Just not to close. Or too far. For example, three good pH’s might be 3.3, 4.7, and 6.0. Three bad ones would be 3.3, 3.4 and 6.9.
- Repeat steps 2-5 to get a third solution.
- Set aside one solution that is just distilled water to serve as a control for your experiment.
- You are now ready to set-up the experiment!
- Count out 40 pinto beans, 40 ziploc bags, and 40 paper towels or napkins.
- Label 10 bags for each pH solution with the sharpie, on the outside of the bag. For example, if you have pH solutions of 3, 4, 6 , and 7, you should have 10 bags labled “pH 3”, 10 bags labeled “pH 4” etc. etc.
- Place one bean in each of the 40 napkins and place one bean/napkin in each of the 40 ziploc bags.
- Add the correct pH solution to each bag, using a different ( or at least cleaned) pipette for each solution. The napkins should be mostly damp throughout, without being saturated- if there is solution collecting at the bottom of the bag, you’ve added too much. Iikewise, if most of the napkin is still dry, you’ve added too little.
- Place all the bags in a dark, warm place, like in a cupboard or under the kitchen sink.
- In three days, open the bags to take your first data!
To take data
- On day three, open up your baggies and record the length of all of your seedlings in cm. The first day you open them, they are bound to be very small, if they have even sprouted at all- some may not.
- If there is no growth, record the length as 0 cm.
- For the remainder of the experiment, measure from the tip of the primary root to the ends of the cotylydons (first leaves).
- The seedling is not likely to be straight- place a string against the plant and fit it into all the ‘bendy’ parts. Mark on the string where the seedling began and ended, and straighten the string out.
- Place the string against the ruler an measure.
- Do this for all plants, and record your data in a table.
- Repeat this procedure every two days for 14 days.
- At the end, graph your data and draw a conclusion!
You should take show all the data you took during the experiment in a table form. You should also include a graph of growth averages over time- a line graph should do nicely. Any other statistical analysis- percent change, X-squared or t-tests (high school only)- can be added as well, if you know how to do them.
While no diagrams are required, it is always a good idea to photo document the process so you have great visuals for your science fair board!
Seed and Seedling diagrams can be found at these websites:
pH strips can be purchased here: