|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,
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 the
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