• Question: are red cabbages the only vegetable you can use as an indicator?

    Asked by wookiee to Amelia, Clem, Izzy, Sarah on 12 Mar 2014.
    • Photo: Isabel Webb

      Isabel Webb answered on 12 Mar 2014:

      A chemical called an anthocyanin in red cabbage leaves is used to detect pH. Anthocyanins change colour in different pH conditions. Red cabbage is not the only plant with these – in fact, they are what gives many different fruit and vegetables their red and purple colours. I’ve never had a go, but maybe ask your teacher if you can try sensing pH with other red/purple plants – try blackberries, cherries, carrots or grapes – and apparently horse chestnut leaves as well.

      Some plants have pH indicator compounds in their flowers, and it makes the flowers change colour. The Hydrangea flower changes its petal colours depending on the pH of the soil, which is why the same seeds will give different colour flowers if planted in different places – and so can be used to tell what pH your soil is.

    • Photo: Amelia Frizell-Armitage

      Amelia Frizell-Armitage answered on 12 Mar 2014:

      This plant is called a Hydrangea : https://www.google.co.uk/search?q=hydrangea&espv=210&es_sm=93&source=lnms&tbm=isch&sa=X&ei=I0cgU9i3F_Sy7AbXkoGACA&ved=0CAkQ_AUoAQ&biw=1920&bih=951

      It’s petals change colour according to the PH of the soil! In soils that are alkaline the plants grow with pink petals. However, in acidic soils the petals are blue. The petals turn blue in acid soil because there is the chemical Aluminium in the soil. When the plants take up aluminium they grow blue petals instead of pink. This is often a good way for gardeners to know what type of soil they have in their garden.

      As Izzy said any plants containing the Anthocyanin chemical, which are usually a dark purple colour, will act as a PH indicator being red in acid solutions and blue in alkaline.

    • Photo: anon

      anon answered on 12 Mar 2014:

      Stinging nettles are known for growing and thriving in very very fertile nutrient rich soils. and so can be seen as an indicator of such soils

Comments

  • Photo: Izzy

    Izzy commented on :

    I just found out from a fellow scientist that eucalyptus trees can be used as indicators for gold! They put their roots very deep, and take up gold. This gold is stored in the leaves, so you can test the leaves for gold to find out if your soil has gold in it.

    I might have to plant some eucalyptus trees in my garden now! It just shows, even as a scientist you learn lots of new things every day

  • Photo: wookiee

    wookiee commented on :

    we are going to use the red cabbage water to test for acids and bases in science club, but i would like to test for gold