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The betalains are plants
pigments that are yellow, orange,
pink, red and purple in colour. |
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Unlike the other three main classes of
plant pigments (chlorophyll,
carotenoids,
flavonoids ), betalains have a limited distribution,
they get their name from the red beets (the genus Beta in the
Chenopodiaceae), which are red in colour due to the presence of the
betalain, Certain betalains are responsible for the red to purple
colour of cacti
stems and
prickly pear
pads, particularly when under
stress.
Most red
colouration in plants is due to carotenoids and
flavonoids. The red
colour of most fruit and vegetables, such as strawberries and grapes is
due to anthocyanins, which are
in the flavonoid class of pigments.
Betalain are instead restricted exclusively to plants of the
order Caryophyllales the Carnations
order (e.g. in the
family
Cactaceae,
Aizoaceae,
Portulacaceae, Amaranthaceae
etc…) which differ by the presence of betalain and the absence of
anthocyanin as
pigments. This
unusual pigments are not found in any other plants. No currently
accepted plant family contains both anthocyanin and betalain producers.
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