1. Natural pH indicators

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    Locate  and contribute to a catalogue of plants whose parts -- fruits, flowers, stems, leaves or roots -- contain substances with the properties of acid-base indication.

    Research question

    Do the intracellular fluids of the majority of the plants contains indicator substances? 


    • Plastic or glass containers (e.g., baby food jars or medicine containers). You will need at least five of those for the preparation of solutions.
    • Syringe (2-5 ml, without a needle) for sampling – 1 pc.
    • Citric acid
    • Baking soda
    • Boiled water
    • Spirituous solution of boric or salicylic acid (25 ml)
    • Empty chewing gum blisters (plastic plates with the wells)
    • If no blisters are available, ice molds or a clean painting palette will also be suitable.
    • Camera or a mobile phone with a camera
    • Plants for the preparation of the indicators
    • Botanical atlas or a plant identification guide.

    You can use plant keys available in the internet.

    Why use data from multiple participants?

    There are various agricultural and wild plants in different regions. Joint GlobalLab research allows us to identify a significant number of plant species which have the properties of pH indicators.

    Investigation Protocol

    • 1. Prepare acidic and alkaline solutions. You will need baking soda and citric acid, both available in a grocery store. It is better to make the solutions in small containers (e. g., baby food jars or medicine containers). To prepare a acidic solution, add one teaspoon of citric acid to 50 ml of cold boiled water. To prepare an alkaline solution, add one teaspoon of baking soda to a clean container and add 50 ml of boiling water; you will observe foaming during that process. The container must be labelled with waterproof markers or sticky labels “citric acid solution”, “baking soda solution”. For better preservation, the containers must be tightly closed.
    • 2. Choose the plants for your investigation. You can choose as many plants as you like (ideally at least five.)  Later you will fill in a Project Report for each of them.
    • Give preference to the plants that are specific for your region such as local berries, herbs, trees or shrubs. However, it is not a problem if you would like to use more easily available plants such as agricultural or house plants.
    • If you cannot decide about a plant to test, perform the first experiment with some commonly used plants. You can make teas (brew it) of it and/or prepare juice from the root.
    • 3.Take a photo of the plant and those parts you are going to use for the extraction of the intracellular fluid. Try to take a photo in a way that the plant is clearly recognizable, i.e. display its parts: flowers or fruits (if available), leaves, and stems.
    • 4. For the experiment, it is necessary to extract intracellular fluid from the plant.  Try not to repeat already conducted work.
    • If you investigate the succulent parts of the plant (fruits, thick leaves, root-crops), you can simply squeeze the juice from them. In some cases, it will be necessary to grate them, or to grind with a blender, or simply to cut into small pieces. If the juice contains some plant tissue debris, it has to be filtered through a fine sieve, gauze, or a dense white fabric. If the colour of the juice is too intensive, it can be dissolved with some boiled water.
    • If you want to extract the substances from dry plants or their hard and leathery parts (leaves, stems), you can prepare an infusion or a decoction. To make them, the relevant parts of plants must be chopped and covered with hot water (for infusion), or cooked for a few minutes (for decoction) at the boiling temperature, until the colour of the liquid is sufficiently intensive.
    • Using leaves, stems, or flowers, one can make a tincture. You will need ethanol: spirituous solutions of boric or salicylic acids can be purchased at the drugstore and are suitable for this purpose. Put the chopped parts of the plants into a small tin, add ethanol, and close the tin tightly to prevent evaporation of the ethanol. The tincture will be ready in 1-3 days.
    • The petals can be used without a preliminary preparation. Put them into a blister and try to grind, e.g. with a back side of a plastic pen or a pencil.
    • 5 ml of solution, decoction, infusion or tincture is enough for the analysis; therefore, you should not use too much of the vegetable material: 2-3 berries, 1-2 flowers or leaves, a few grams of fruit or root etc. will be enough. The prepared sample of intracellular juice must be used for the experiment immediately or stored in a closed container in the refrigerator for no longer than 2 days.
    • 5. Fill three wells of the blister each with 1 ml of the solution for investigation. Then add to the first well 1 ml of citric acid solution (Ac), to the second well – 1 ml of the distilled water (N), to the thirdwell – 1 ml of bakingsoda solution (Alk).
    • 6. In 5-10 minutes, assess the result and take a photo of the blister on a white background. The wells must be labelled according to the character of the medium: Ac (acid), N (neutral), Alk (alkaline). Please notice: if the colour/color of the intracellular fluid did not change, this is not necessarily a failure! This is also a result which must be documented in the project, so that the other participants do not repeat the experiment with this plant.
    • 7. Fill in the Project Report for each investigated plant.
    • 8. Follow the progress of the project, and take part in the discussion of the results obtained by other participants.

    Safety tips

    Be careful during the work with acidic and alkaline solutions, as well as with the tinctures: avoid their contact with skin, eyes, mouth and nose. If you feel a burning sensation (A SIGN OF ACID) or feel your hands soapy, (A SIGN OF A BASE), wash them with a large amount of water; soap can be used afterwards. In case of contact with the inside of the nose, wash the area with cold boiled water.

    Be careful, also, during the work with hot and boiling water. Work only with cooled solutions. If you are not sure that you can prepare an infusion or a decoction yourself, ask an older person to help you.

    Report Form Before filling in the Report Form, please read the Investigation Protocol