Betalain

Betalain [ Biochemistry - Botany ]
Synonym: Betacyanin

Dictionary of botanic terminology - index of names


	The betalains are plants pigments that are yellow, orange, pink, red and purple in colour.

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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Holdfast roots [ Botany ]
Dictionary of botanic terminology - index of names

Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.

Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans), develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994