Science Research Project by: Tan Zhu Jia, Jamie Ow, Liu Jiang Feng, Amos Ng
Introduction
The aim of our project is to find out if the different pH values affects the growth of plants. We decided to grow green bean plants watered daily using different pH levels of liquids, they are, pH2, pH3.5, pH6.5, pH11, and for our control experiment, it is tap water with a value of pH7. This experiment helps us to understand what green bean plants better thrive in.
Hypothesis
According to some online research, we found that they like to thrive in pH levels of 6.0-6.2[1]. The closest pH value, though out of range, we think the plant that will grow the highest will be the one growing under pH6.5, and possibly our control experiment too.
Rationale for Hypothesis
The reason why we decided to research on this is since we were introduced to this topic in secondary school, and we were curious how plants would grow tall and strong. We researched and found out plants produces several substances such as amino acids, organic acids and phosphate groups, to maintain the necessary pH range[2].
Research
We found out that a change in the pH level can severely damage structures within the cells[2]. We also found out that large quantities of protons are used and produced in the process. Changes in pH levels are caused by an increase of the concentration of the protons in the cytoplasm. If the pH range is not maintained, structural deformities could occur, leading to the failure of processes and functions within a cell. We also found out that direct exposure to acidic water sources may be harmful to plants.
The pH value of the substance it's grown in(usually soil, in our case it's cotton), surrounding the plant can have a strong impact on plant growth. This is largely due to the reliance of plants on the soil for several nutrients and minerals. Acidic pH can also be detrimental to microorganisms in the soil that are beneficial to the plant. Most soils have a natural buffering capacity that keeps the pH at a level suitable for plant growth. However, not all soils are capable of maintaining a suitable pH level. Thinner soils, that can be found in the Northeastern regions of the U.S. have lower buffering capacities than thicker soils found in the Midwest of the U.S[2].
A high concentration of H+(Hydrogen) ions (low pH) in the soil can also lead to nutrient deficiencies. Acidic conditions can lower the levels of phosphorus, calcium magnesium and molybdenum, nutrients that are essential to plant growth.
Reasons for choosing Green Bean plant
Green beans, also known as string bean, snap bean in the northeastern and western United States, or ejotes in Mexico, are the unripe fruit of various cultivars of the common bean (Phaseolus vulgaris).[3] It is also that green bean plants are easy to grow, doesn't take too long for the sprout to come out and can give us results faster.
Independent variable
The pH level of the different liquids.
Dependent variable
The height of the plant(in cm).
Controlled variables
The amount of the liquid given daily(For the first day, 100ml, the rest of the days, 20ml). The type of plant grown Size of container it's put in The type of soil/growing media(cotton) Intensity of light The place it's grown at.
The experiment results
We conducted the experiment on a course of 9 days, and these are the results:
| pH 2 | pH 3.5 | pH 6.5 | pH 7 | pH 11 | |
|---|---|---|---|---|---|
| Day 1 | 0 | 0 | 0 | 0 | 0 |
| Day 2 | 0 | 0 | 0 | 0 | 0 |
| Day 3 | 0 | 0 | 0 | 2 | 0 |
| Day 4 | 0 | 0 | 3 | 5 | 1 |
| Day 5 | 0 | 0 | 11.5 | 12 | 1.5 |
| Day 6 | 0 | 0 | 16 | 17.5 | 4.5 |
| Day 7 | 0 | 2 | 18 | 19 | 6 |
| Day 8 | 0 | 3 | 21 | 23 | 7 |
| Day 9 | 0 | 4 | 22 | 24 | 8 |
| Positions | 5th with totally no growth |
4th | 2nd | 1st | 3rd |
References
- ^ Marie Iannotti, http://gardening.about.com/od/vegetables/p/GreenBeans.htm
- ^ a b c Miami University, Doug Bower, Doug Morgan, Koren Phillips, Brett Roeth, http://jrscience.wcp.muohio.edu/nsfall05/LabpacketArticles/TheEffectofpHontheGrotwho.html
- ^ Wikipedia, https://en.wikipedia.org/wiki/Green_bean