Pigments in Plants




Дата канвертавання15.04.2016
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Pigments in Plants

1. The anthocyanins are common plant pigments. They are water-soluble glycosides with some or all of the sugar groups removed. The colour comes from a positive charge distributed over the chemical ring system. The colours of the charged anthocyanin pigments are dependent on the pH of the intracellular medium containing these pigments.

2

. Many leaves frequently develop red coloration during development, at maturity, and during senescence. Most plants produce anthocyanins (usually cyanidin glycosides) as the basis of this colour, but members of the Caryophyllales produce nitrogenous pigments, betacyanins.
3. The betacyanin pigment of beet roots is normally sequestered in the vacuole and, by means of the properties of the tonoplast and cell membrane, does not leak into the cytosol or the extra-cellular sap of the beet root. Of course if the beet root is cut cells are sliced open and the pigment spills out, but if the membrane is altered (phospholipid bilayer + proteins) more subtly leakage (diffusion) of betacyanin is induced.

Betalains: What are betalains?

Betalains are alkaloid pigments that are found in some families of plants belonging to the order Caryophyllales, but in no other plants.

Betalains are not found in plants containing anthocyanin pigments. Structurally they are unrelated

They have also been found in some fungi

They can be divided into betacyanins and betaxanthins based upon their molecular structure.

betacyanins generally appear red to red violet in colour

betaxanthins generally appear yellow in colour

They cause colour in both flowers, fruits and sometimes vegetative organs

They are found in the vacuole

They are aqueous in solubility

Betacyanins absorb in the 535-550nm range

Betaxanthins absorb in the 475-480nm range

Beetroot contains 2 Betacyanins Betanin and a derivative

Little is known about the role of betalains but it is thought they may protect against pathogens






The basic structure of betacyanins


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