The effect of pH on the growth of beans (Draft 3)

This topic submitted by Dan Bower, Doug Morgan, Koren Phillips, Brett Roeth on 10/7/05. [Section: McCollum]
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Natural Systems 1 Syllabus---Western Program---Miami University


Vegetables are an important food source for humans around the world. Environmental conditions, such as the pH of water supplies, can affect plant and crop growth, thus affecting the food supply. This study will show how the acidity of a water source affects the growth of green beans.


How does the pH of a water source affect the growth patterns of green beans?


We predict that increased acidity of a water source will negatively affect the growth patterns of our plants. More specifically, low pH will decrease the overall health of the plants. Our definition of overall health considers attributes such as plant height, stem width, length between secondary stems, color, root mass, plants mass, overall mass, and reproductive structures.

Interesting Aspects of Research and Experiment

There are many factors that affect the pH of a plant's surrounding environment. One of the most prevalent attributors to aggregate pH levels is acid rain. Acidic pH, because it has a negative affect on plant growths, also has agricultural implications.

Background Information and References

1) Journal Articles
A) Correa, O. S., A. Aranda and A.J. Barniex. "Effects of pH on Growth and Nodulation of Two Forest Legumes." Journal of Plant Nutrition, Sept 2001: 1367-1375.: Documents the effect of acid pH on two species of forest legumes. Suggests that mycorrhizae are a major factor in determining a plant's tolerance to pH.
B) Rohyadi, A., et. al. "Effects of pH on mycorrhizal colonization and nutrient uptake in cowpea…" Plant & Soil, March 2004: 283-290: Documents how fungi affect cowpea plants when they are growing in low pH environments, and the relationship between fungi growth and pH.
C) Peet, Robert K. Jason D. Fridley and Joel M. Gramling. "Variation in Species Richness and Species Pool Size Across a pH Gradient…" Folia Geobotanica, Dec 2003: 391-401: Studies the association with plant species in acidic soils in the Blue Ridge Mountain Range
D) Hall, J.M., E. Patterson, K. Killham. "The effect of elevated CO2 concentration and soil pH on the relationship between plant growth and rhizoshpere dentrification potential." Global Change Biology, Feb 1998: 209-216: Ryegrass was subjected to different levels of CO2 concentration. Investigates the relationship between plant growth and rhizosphere dentrification potential and soil pH.

2) Books
A) Rengel, Zdenko. Handbook of Plant Growth: pH as the Master Variable. New York: Marcel Dekker 2002: Outlines the role of pH in plant growth. Describes the biological and chemical effects, as well as interaction of the plants with their encironments
B) Lane, Carter N. Acid Rain: overview and abstracts. Hauppauge, NY: Nova Science Publishers, 2003: Outlines the causes of acid rain, and describes its effects on ecosystems.
C) Abrahamsen, Guunear, Arne O. Stuanes and Bjorn Tviete. Long-Term Experiments with Acid Rain in Norwegian Forest Ecosystems: Describes the methods and results of an experiment that took place in Southern Norway. Shows the long-term effects of acid rain on forest ecosystems from the 1950's through the 1980's.
D) Styer, Roger C. and David K. Koranski. Plug & transplant production: a grower's guide. Batavia, Ill: Ball Publishers, 1997: Describes methods of plant propagation and what factors should be considered.
E) Forbes J.C., and R.D. Watson, Plants in Agriculture. New York, Cambridge University Press, 1992: Describes plant growth in detail, outlining the specific factors that influence growth and how the environment affects parts of the plant.

3) Internet Sources
A) Monitoring and Managing Soil pH
B) Acid Rain Experiments and Information
C) Acid Rain and its Effects
D) EPA Acid Rain Website
E) The Effects of Acid Rain on the Environment
F) Low pH and Container Plants

Experiment Design

We will observe100 green bean plants in our experiment. We will have 5 groups of 20 plants, each subjected to a different water source pH. We will measure a variety of characteristics of the plant to determine the effects of the water source pH on the plant.

Materials and Methods

100 green bean seeds
5 potting flats
Sulfuric Acid
Measuring cups
Containers for separate pH solutions
Soil and water pH testing kits
Digital scale
Microscope and slides
Digital camera
Data tracking sheets

Our experiment will take place over a period of six weeks in a stable environment (Boyd Hall greenhouse). Variables such as amount of sunlight and temperature will be the same for all plants. The only variable in our experiment will be the pH of the water-based solution applied to the plants.

Before planting our seeds, we will test the pH of the soil. During and after our experiment, we will continue to test the soil pH, to determine what affect the pH solutions have on the soil and to determine if the soil pH affects plant growth. Each bean seed will be planted in a separate container, each with the same amount of Metromix 360 soil. The containers will be grouped according to the solution they are exposed to, and the individual seeds will be numbered as well.

Five groups of 20 plants each will be observed during our experiment. Each group will be subjected to a solution with a different pH level – 7.0, 6.0, 5.0, 4.0, and 3.0. The solutions will be created by mixing sulfuric acid with water do obtain the desired pH level. The plants will be "watered" with the solution at least twice a week, possibly more depending on the rate of uptake by the plants and evaporation. All 100 plants will be watered with the same volume of water at the same time.

During our experiment, many observations will be taken every watering cycle. Photographs will be used to more completely document the experiment. The soil pH will be tested, and many characteristics of the plants will be documented. These include height, primary stem width, length of secondary stems, and color. When the plants start to flower, the number of buds, flowers, pods, beans in the pods, and stem splits will be documented. After the six-week period, the plants will be dug out of the soil. Before drying out, the root mass, stem mass and overall mass will be recorded for each plant. These measurements will be taken again after the plants have completely dried. All of the quantities measured during the experiment will be organized into data sheets. Five plants from every group will then be dissected and observed under a microscope for cellular characteristics, such as membrane and cell wall quality and chloroplast functionality.

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