|Why does the colour of flower petals change in pH?
|Question Date: 2004-10-22|
This is because the colors in plants come from
compounds called plant pigments, and these plant
pigments often have slightly different structures
when in acid (low pH) and when in base (high pH).
As a result of the different structures of the
pigment molecules, the colors are different.
The color of flower petals is determined by
pigments in the fluids inside of the flower's
veins (petals are modified leaves, and so have
veins just as normal leaves). Under different
chemical conditions, the pigment molecules might
switch to a different chemical state, changing
their color. pH is certainly one chemical
condition, and I would imagine that they would
change with temperature, concentration of salts,etc.
Different flower petals change color in different
pH conditions for different reasons. It all
depends on which pigments the flowers use to get
their colors. In general, very small changes to a
molecule (like a flower pigment) can cause it to
change color, and different pH conditions can
easily cause those changes. pH can change the
electrical charge of a molecule, or it can change
what the molecule can bind to. Both of these
things can change how the molecule interacts with
light, which means we see it as a different color.
This same principle is how pH indicators work, by
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