Ph Bean Lab

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Florencia Rodriguez
October 20, 2010
IB Biology SLII

The effect of three different pH levels (4, 7, 10) on the rate of germination of spanish beans

Research Question:
What is the effect of three different pH levels (4, 7, 10) on the rate of germination of spanish beans? Independent Variable:
The different pH levels in the water would be the independent variable in this lab. Three different pH levels were tested, 4, 7 and 10, both 4 and 10 were chosen because they are 3 pH levels away from 7 which would be the regular pH level of water. We measured the different pHs by using pH buffer capsules. Dependent Variable:

The change in the rate of germination of the beans was measured and this was done by recording the size of the embryos after 4 days of germination (96 hours).
The bigger the embryo the more the beans had germinated, this happened mostly in the pH level 7. Six different samples of 15 beans were used so we could have two trials for each pH level. Background:

pH levels go from 1 through 14, 1 being the most acidic and 14 being the most basic, the pH level that is the most neutral is 7. (http://jrscience.wcp.muohio.edu/nsfall98/FinalArticles/Final.TheEffectofDifferen.html) When pH levels fall below 4 or above nine, usually the organism will die. (http://www.grc.nasa.gov/WWW/k-12/fenlewis/test.htm). Soil that is too acidic or too basic does not give plants a healthy environment to grow in, this is because in both cases the plants do not get enough nutrients, which is harmful to bacteria that is helpful. Hypothesis:

Therefore our hypothesis is that the further away the pH is from 7 the less germination the beans will go under. Although they will still go under germination since the numbers we chose were not below 4 or above 9 so therefore we just want to see how much the embryos will grow in levels 4 and 10.

Controlled Variables:
1. Germination Time
Each beaker with an amount of 15 beans in each, germinated for 4 days, the germination time had to be the same for all six beakers since the longer they were in the water germinating the more the embryos would have grown. This was done by taking the water out of the beakers while the beans were being measured so no beans had more time to germinate. 2. pH Buffer Capsules

The pH buffer capsules were all the same brand and all worked the same way. We used these pH capsules to controll the pH of the water and prefered to use these capsules since they were the most accurate. Even for the beaker that we wanted to be neutral which would just be normal water, we used a buffer capsule of pH 7 to control it. 3. Type of Bean

The beans used throughout the experiment were Spanish Beans, these were used in every single beaker so their way of approaching germination and embryo growth was the same. 4. Amount of Beans
Each beaker had 15 beans in it, this was measured because otherwise the amount of space and water each bean had would have altered the results if there were more beans in some beakers than others. 5. Amount of Water

Each 500ml beaker had 100 ml ± 0.5ml of water in it, this was measured in graduated cylinders. If the water had not been controlled some beans in different beakers would have had more water to succion. 6. Environment

All beans were kept in the same environment, this was inside a room so therefore the temperature was the same for all of them. The beakers were kept throughout the 4 days in a closet, so it was dark throughout the whole germination time so the light intake would not have an effect on the growth of the beans, since light affects photosynthesis which would make the beans have a higher photosynthetic rate. (http://www-saps.plantsci.cam.ac.uk/records/rec67.htm)

Materials:
1. 90 spanish beans
2. 6 500ml beakers ±25ml
3. Stirring rod
4. 100ml graduated cylinder
5. 6 pH buffer capsules (4, 7 and 10, two of each level)
6. 600 ml of water
7. 6 plastic cups
8. Parafilm
9....
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