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Acidity Effects on Plant Growth

Author(s) - Bob Fiero, et al.

Question - What is the effect on varies levels of acidity (pH) on the growth of brassica species of 'Fast Plants'?

Science Standards

Structure and Function in Living Systems
  • The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
  • Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.
  • Students know organ systems function because of the contributions of individual organs, tissues, and cells. The failure of any part can affect the entire system.
  • Students know how bones and muscles work together to provide a structural framework for movement.
  • Students know how the reproductive organs of the human female and male generate eggs and sperm and how sexual activity may lead to fertilization and pregnancy.
  • Students know the function of the umbilicus and placenta during pregnancy.
  • Students know the structures and processes by which flowering plants generate pollen, ovules, seeds, and fruit.
  • Students know how to relate the structures of the eye and ear to their functions.
Background Information

Industries and motor vehicles produce gaseous oxides of nitrogen and sulfur. For example nitrogen and oxygen in the air can combine under high-temperature engine condi­tions to produce nitrogen dioxide (NO2). The equation for the reaction is:

N2 + 202 --> 2NO2.

Sulfides in fuels can combine with oxygen to make sulfur dioxide (SO2) and sulfur trioxide (SO3). Such oxides combine with water in the atmosphere to make acids. For example, nitrogen dioxide and sulfur trioxide combine with water. They form nitric acid (HNO3) and sulfuric acid (H2SO4), respectively. The equations for these reactions are:

  • 3NO2 + H20 ---> 2HNO3 + NO
  • SO3 + H20 ---> H2SO4.
The presence of these acids causes rain to be acidic. Acid rain damages trees, crops, and buildings. It can make lakes so acidic that fish cannot survive. Acid rain PH can vary of course and one extra task is to have students measure the pH of the rain in their region.

The acidity of solutions is measured using the pH scale, which extends from 1 to 14. The pH of a solution is defined as the negative of the logarithm of the hydrogen-ion concentra­tion (-log [H+]). For example, [H+] in pure water is 1.0 x 10-7. The pH of pure water is therefore -log (1.0 x 10-7), or 7. The pH of acidic solutions is less than 7, and that of basic solutions is greater than 7. The lower the pH below 7, the more acidic is the solution.

Investigation and Experimentation
Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
  • Select and use appropriate tools and technology (including calculators, computers, balances, spring scales, microscopes, and binoculars) to perform tests, collect data, and display data.
  • Use a variety of print and electronic resources (including the World Wide Web) to collect information and evidence as part of a research project.Communicate the logical connection among hypotheses, science concepts, tests conducted, data collected, and conclusions drawn from the scientific evidence.
  • Construct scale models, maps, and appropriately labeled diagrams to communicate scientific knowledge (e.g., motion of Earth's plates and cell structure).Communicate the steps and results from an investigation in written reports and oral presentations.
Design and conduct experiments to observe and describe developmental patterns in selected seed-bearing plants. Use mathematical analysis, scientific inquiry and engineering design, as appropriate, to pose questions, seek answers, and develop solutions.
  • Understand and apply scientific concepts, principles, and theories pertaining to the physical setting and living environment.
  • Design charts, tables, graphs, and other representations of observations to address hypothesis.
  • Interpret the organized data to answer the hypothesis.
  • Modify personal understanding of hypothesis based on evaluation of hypothesis.
  • The survival of an organism depends on its ability to sense and respond to its external environment.

    Experimental Design
    • Independent variable:  Acidity concentration (pH 3 & pH 5.6--common acidity of acid rain)
    • Dependent variables:  Plant growth (bottom of stem at soil surface to apical meristem)
    • Series: measured every day for three weeks.
    • Constants: temperature, humidity, soil type, fertilizer type and amount, light intensity, watering levels, plant type, planting time, measuring schedule procedure(using photgraphy against a grid).

    • Controls: neutral acidity (ph of 7)
    • Materials: Fast Plants species, potting soil, growing containers, full spectrum growing lights, slow release fertilizer pellets.
    • Procedures -

      After a four days of of planting to encourage germination the fast plant (Brassica rapa) apical meristems were visible above the soil surface. Until this point they were grown in quadrats under the same conditions of: lighting source and intensity; soil, amount of tap water; and temperature.  These seedlings were then separated into two groups: control  and two experimental. The 'control" group (one quadrat) were given the same treatment as before when they first germinated. That is tap water was used as a continuous feed (using a quadrat on a pad that absorbed water as it evapotranspired from the plants and soil).  One quadrat of seedlings were treated with a slightly acidic solution of pH of 5.6 and another quadrat was treated with pH of 3.0 solution pipeted onto the plants once per day.  The acid was acetic acid (vinegar) and not nitric or sulfuric for I do not have those available to me and can be more hazardous to handle. Each of these 'experimental" set of plants was grown under normal conditions as the control (the standard to compare the experimental plants to). Changes in growth and color were recorded for a 10 day testing period. Everyday, at the same approximate time of 2:30 pm, measurements of stem length  from base(soil surface) to apical meristem (tip) were taken and other qualitative observations were recorded for total period of 10 days using a photographic technique against a quarter centimeter grid background. 

    • Side note: this experiment was run twice with the first trial resutling in bolted (etiolated) seedlings possibly due to the fact the growing light was not utilized until a couple days after the sedling emerged.  Also on thinning the seedlings to other quadrats as recommended by the publishers of 'fast plants" many of them we lost or badly damaged.  

                            • Sample data and graphs.
                              Growth of Brassica rapa "Fast Plants" in various acidic to neutral solutions.
                              Height --base to apical meristem (cm)--**Control growth data is average of all plants in quadrat.            
                              Time  Control**  Exp. Exp.
                              (daily growth) pH 7.0 pH 5.6 pH 3.0
                              4 1 0.8 0.9
                              5 2.4 3 2.2
                              6 5 5.3 4
                              7 6.3 6.8 0
                              8 7.1 8.1 0 Zero  "0" indicates the plant(s) died.
                              9 8.5 9.4 0
                              10 10.3 10 0
                              Measurements began on day four after the seedlings emerged from the soil strata and the solution treatments were applied.
                               To see spreadsheet with graph see attachment --the link at bottom of page.
                            • Slide show of sample pictures.

                              PicasaWeb Slideshow


                              Results--Data Analysis

                              The plants that grew in acidic solution of 3.0 lived only three days from first application of the acidic.  Probable reason os on the growth setup they get water continuously fed to them as it evaporates from soil and plants which may dilute the concetration of acid also they showed signs of stress as they paled to yellow and then collapsed dead.  The plants in the experimental treatment of  the pH 5.6 solution applied daily continued to live though only one seed germinated and it seem to bolt and remain very pale gree to yellow. This matches well with observations of plants general responses to acid rain which this acidity is to simulate. The control did very well and grew in deep green and robustly (thicker stems)  as expected and at the rate predicted or described by the 'fast plant" distributer. Acidity
                              Using photography with a 0.25 centimeter grid background to measure plants was probelmatic even though we attempted to use a platform for the plants, grid, and the camera at a standard height and at the same time of day.  The setting of focus was not always the same and the camera was not perfectly set even with the height of the soil giving a perfectly level perspective.  Fortunately the plants were measured using a standard ruler and/or string as well especially as they became longer and drooped some.


                              Velikova V., Yordanov I., Kurteva  M., and T. Tsonev, "Effects of simulated acid rain on the photosynthetic characteristics of Phaseolus vulgaris L.," Photosynthetica, Volume 34, Number 4 / November, 1997
                              Web resources related to project 
                         is a website all about Wisconsin Fast Plants and includes lots of resources for students and teachers
                         is a link to Carolina biological supply, for ordering materials and other info
                         offers a virtual tour of a recirculating aquaponics facility that recycles 99.7% of all its water and
                         is a link to interactive K-12 lesson plans for the International Space Station
                         is the Educational Resource page of the U. S. Environmental Protection Agency

                              Textbooks available to teachers

                              Using Fast Plants & Bottle Biology in the Classroom (published by NABT)

                                   Duckweed Unlimited (Using common duckweed to measure water quality)
                                   pH...Potential Horrors of Acid Rain (assessing the effects of pH on growth and development of Fast Plants)
                                   The Salty Solution (A study of the effects of salinization on plant growth and development)
                                   The Neighborly Effects of Atrazine (A study of the environmental effects and plant tolerances to atrazine)
                              Bottle Biology (published by Kendall/Hunt)
                                   Bottle Basics (Collecting, cleaning and cutting)
                                   Decomposition Column (When is the end a beginning?)
                                   Predator-Prey Column (Who eats whom?)
                                   Terraqua Column (What is the land-water connection?)
                                   Water Cycle Column (Is rain pure?)

                              Spiraling Through Life with Fast Plants (published by Kendall/Hunt)     Germination

                                  Growth and Development
                                  Fertilization to seeds
                              Exploring with Wisconsin Fast Plants (published by Kendall/Hunt)
                                  Where do Fast Plants come from?
                                  Growing Fast Plants
                                  Life Cycle of Fast Plants
                                  Influence of the environment on plant growth
                                  Variation, heredity, evolution
                                  Energy and Nutrient Recycling
                                  Stories, Modeling, Games
                                  Environment, lighting, alternative growing systems
                              Wisconsin Fast Plants Manual (published by Carolina Biological Supply Company)     Germination
                                  Plant Responses to light and gravity
                                  Gibberellic Acid/Rosette plants
                                  Plant Nutrition
                                  Mendelian/Non-Mendelian Genetics
                                  Effects of Salt, Acid Precipitation on growth
                              Robert Fiero,
                              Dec 1, 2009, 12:08 AM
                              Robert Fiero,
                              Nov 22, 2009, 5:12 PM
                              Robert Fiero,
                              Nov 22, 2009, 5:12 PM