anthocyanins

Kenneth J McNeil mcnei002 at maroon.tc.umn.edu
Sat Feb 17 01:00:09 EST 1996


markwell at unlinfo.unl.edu (john markwell) writes:

>>>i'm doing a phase two of a science fair project on anthocyanins, a
>>>flavonoid found in roses, red cabbge and african violets.  i read that
>>>they can change the plant's color when subjected to acids or bases, but
>>>my results last year were inconclusive...this year, i'm doing a better
>>>job, but i really don't have enough data on anthocyanins; i guess
>>>they're pretty obscure.

>>Many purple pigments in plants are anthocyanins.  In general, they
>>are more red in acid solutions, and blue in basic solutions.  You
>>can observe this for yourself by taking some water from cooking 
>>red cabbage or beets, and observe the color change when you add
>>vinegar or baking soda.

>Actually, it is a little more complex than that.  Red cabbage and many
>flowers and leaves do contain anthocyanins.  THey generally are red or
>blue below pH 4 and will be colorless around pH 5 to 7 and at higher 
>pH values (more basic) will turn blue and then fade.  Beets (beet 
>root) contains a betalain or betacyanin that does not change color 
>with these pH changes.

>>To change the color of the plant (or its flowers), you will have to
>>change the pH of the solution the anthocyanins are in within the plant
>>cell.  This may well kill the plant!

Hydrangeas sold at Easter usually come in three colors, pink, blue or 
white. The colored forms are the same variety just grown under acidic or 
basic conditions. Some growers even add acidic fertilizer to 1/2 of a pot 
and basic to the other half to produce flowers of mixed colors.

Ken




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