Dye Plants

plants whose organs (roots, stems, leaves, flowers, fruits, seeds) and tissues (wood, bark) produce and store dyes that are contained in the plastids or are dissolved in the cellular fluid.

Dyes are found in several thousand species of plants. How-ever, only those dye plants with a high concentration of colorfast dyes are used commercially. The dyes are extracted from most plants by hot water, acids, or basic solvents; they are obtained from some plants by pressing out the juice. The same dye may produce different colors on different materials; the color is also determined by the type of mordant used. Before the appearance of synthetic dyes, which are easier and less expensive to produce, plant dyes were used predominantly to color fabrics. For some purposes, plant dyes cannot be replaced even today—for example, in the carpet, food, and cosmetics industries.

The best-known dye plants of the tropics and subtropics include a number of species of Indigofera (which yield indigo and indirubin), logwood (hematoxyline), several species of oak in North America (quercitron), and turmeric (the yellow dye curcumine). Common dye plants in the USSR include a number of species of juniper having cones, or berries, with substances that yield a yellow, brown, greenish gray (khaki), or violet color. Other common dye plants include onion (an infusion of the skin gives a brown color), saffron (the stigmata contain an orange dye used for food products), larkspur (a bright yellow dye is obtained from the petals), woad (the sap of the fresh leaves contains indigo), woadwaxen (the flowers and leaves contain a yellow dye used in the carpet industry), milkweed (the extract from the stems and inflorescences is a khaki-colored dye), madder (the roots contain a red dye—alizarin—used in carpet-making), marigold (the flowers have a yellow dye used for coloring fats, such as margarine), safflower (the red dye carthamine is found in the flowers), henna (the roots contain the orange dye henna), and a number of species of lichen (litmus).