Lab Project: Testing the Effects of pH on Plant Growth PDF

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Testing the Effects of pH on Plant Growth Emily Zhou, Tatyana-Desire Brisard, Jason Starr, Samantha Stephens

Professor Klein BIOL 1001 April 25, 2017

Testing the Effects of pH on Plant Growth Emily Zhou, Tatyana-Desire Brisard, Jason Starr, Samantha Stephens Professor Klein BIOL 1001 April 25, 2017 The Abstract

The purpose of this experiment is to investigate the effects of pH on plant growth. Our experimental model involved the testing of kidney beans and corn kernels over a 5-week period. Following the experiment, major key findings included that a more neutral soil environment yielded more plant growth.

Introduction

Initially, our group believed that plants grew more favorably in more acidic settings. To test our hypothesis, we tested the experimental group of one bean plant and one corn plant with a diluted solution of hydrochloric acid. We expected to see greater height from this group, but instead saw opposite results. Information regarding plant growth and soil pH is most relevant to agribusinesses and farming. By regulating pH and other conditions of soil and growth environment, plants can predictably and reliably generate more yield. Furthermore, this knowledge is key in selecting optimal areas to farm since factors such as climate and water sources can dramatically impact plant growth.

Materials and Methods The materials required for this experiment include soil, kidney beans, corn, pots, beakers, deionized water, 1M HCl, litmus paper, area in sunlight, labels, and a ruler. To prepare, two kidney beans and two corn kernels were placed individually in four pot. The pots were filled three-quarters way to the top with soil and the beans and kernels were placed with a depth of approximately one to two inches. Next, each pot was watered with 65 mL of deionized water. Each pot was then labeled and placed together in a sunny lab. For the initial

week, no acid was added. Only after the first week was the experimental group watered with a solution of 50 mL deionized water and 15 mL of 1M HCl. The height of each plant was measured and recorded after each watering. The control group was watered with 65 mL of deionized water, a measured pH of 5. Results

6-Apr

10-Apr

14-Apr

18-Apr

21-Apr

A) Control (65 mL water, pH=5) bean

58.5 cm

63.8 cm

62.3 cm

61.0 cm

61.0 cm

corn

29.0 cm

30.3 cm

30.8 cm

31.0 cm

31.1 cm

B) Test (50 mL water, 15 mL 1M HCl, pH=2) bean

51.5 cm

52.5 cm

49.0 cm

44.0 cm

44.2 cm

corn

9.5 cm

10.5 cm

10.5 cm

10.5 cm

10.5 cm

Plant Growth 70

Plant Height (cm)

60 50 Bean A Corn A Bean B Corn B

40 30 20 10 0 1

2

3

4

5

Axis Title

Our results rejected our hypothesis since the plants in the control group fared better than those in the test group. In fact, the plants watered with the HCl solution started to wilt and lose

leaves, contributing to actual loss of height. We noticed that the corn in both groups grew significantly less than the beans, especially with the plateau in the growth of the test corn. Even with invariable volume of watering, the acidic solution had caused the test group plants to dehydrate and wither, essentially stunting growth.

Discussion

The collected data suggests that a neutral soil environment provides a more suitable and substantial environment for plant growth. According to an article from the SUNY College of Environmental Science and forestry, “extremely and strongly acid soils (pH 4.0-5.0) can have high concentrations of soluble aluminum, iron and manganese which may be toxic to the growth of some plants. A pH range of approximately 6 to 7 promotes the most ready availability of plant nutrients” (Bickelhaupt). Since we watered our plants with a solution that measured a pH of 2, it is evident that the soil must have had high concentrations of toxic elements that prevented healthy growth. Additionally, we suspect that the high acidic concentrations may have damaged the roots of the plants, inhibiting normal nutrient absorption.

Conclusion

Our group concludes that to maintain steady and healthy plant growth, it is crucial to preserve a nearly neutral soil environment. Strongly acidic and even perhaps strongly alkaline conditions can foment a soil setting that invites presence of toxic substances that harm plant growth. High levels of acidity not only contain significant levels of toxicity, but may also harm the roots of the plants. Continued exposure to acid can weaken roots, thus preventing the gathering of necessary nutrients.

References Bickelhaupt, D. (n.d.). Soil pH: What it Means. Retrieved April 25, 2017, from http://www.esf.edu/pubprog/brochure/soilph/soilph.htm Appendix

Showing evidence of withering and wilting.

Group Member Review

This project was much more manageable due to the availability of all the group members. This allowed each group member to water the plants on designated days to collect height data. Jay and I helped to titrate the acidic solution used in the experimental group and Tatyana helped to analyze the correct pH of our trial titrations....