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Hydrangeas as chelators of aluminium in soil

Identifier

017792

Type of Spiritual Experience

Background

Delphinidin (also Delphinidine is an anthocyanidin, a primary plant pigment, and also an antioxidant. Delphinidin gives blue hues to flowers in the genera Viola and Delphinium. It also gives the blue-red color of the grape that produces Cabernet Sauvignon, and can be found in cranberries and Concord grapes as well as pomegranates. Delphinidin, like nearly all other anthocyanidins, is pH-sensitive.

From a gardening site

"The color of a hydrangea flower depends on the chemical makeup of the soil it is planted in. If the soil is high in aluminum and has a low pH, the hydrangea flower will be blue. If the soil has either a high pH or is low on aluminum, the hydrangea flower color will be pink.

If your hydrangea flowers are pink then either your soil does not have much aluminum, or your soil’s pH is too high and the plant can’t take up the aluminum that is in the soil.

If you know the soil is polluted with aluminium then the soil has to be more acidic for it to be able to chelate the aluminium. Lower the pH around the hydrangea bush by either spraying the ground with a weak vinegar solution or using a high acid fertilizer, like those made for azaleas and rhododendron. Pine needles seem to work too.  Remember that you need to adjust the soil where all the roots are. This will be about 1  to 2 feet beyond the edge of the plant all the way into the base of the plant."

A description of the experience

J Inorg Biochem. 2010 Jul;104(7):732-9. doi: 10.1016/j.jinorgbio.2010.03.006. Epub 2010 Mar 20.

The chemical mechanism for Al3+ complexing with delphinidin: a model for the bluing of hydrangea sepals.

Schreiber HD1, Swink AM, Godsey TD.

  • 1Department of Chemistry, Virginia Military Institute, Lexington, VA 24450, United States. HS@vmi.edu

Abstract

The blooms of many hydrangea cultivars can be red or blue, with the color depending on the soil pH.

This dependence reflects the availability of Al(3+) to the plant under acidic conditions, as Al(3+) changes the color of the anthocyanin pigment in hydrangea sepals from red to blue.

A chemical model, Al(3+) and delphinidin in acidic ethanol, was developed to understand the spectral characteristics and bluing of the hydrangea sepals.

Delphinidin as its flavylium cation leads to red solutions in the model system. In the presence of Al(3+), the Al(3+) removes H(+) ions from delphinidin, transforming delphinidin's flavylium cation to its blue quinoidal base anion which complexes with the Al(3+). To further stabilize this complex, a second flavylium cation stacks on top of the complexed quinoidal base anion, creating a bathochromic shift of the cation's spectral signature and accentuating the blue color. This Al(3+)-delphinidin entity forms in adequate concentration for bluing only if there is a sufficient excess of Al(3+), the exact excess being a function of pH and concentration.

The role of Al(3+) in bluing is not just to form a primary complex with delphinidin, but also to create a template for the stacking of delphinidin (or possibily co-pigments).

2010 Elsevier Inc. All rights reserved.

PMID:  20394986

The source of the experience

PubMed

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