Parietin is the predominant cortical

Cortex (botany)

In botany, the cortex is the outer layer of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the endodermis. It is composed mostly of undifferentiated cells, usually large thin-walled parenchyma cells of the ground tissue system. The outer cortical cells...

 pigment

Pigment

A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

 of lichen

Lichen

Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...

s in the genus Caloplaca

Caloplaca

Caloplaca is a lichen genus, composed of a number of distinct species. The distribution of this lichen genus is world wide, extending from Antarctica to the high Arctic. It includes a portion of northern North America and the Russian High Arctic. There are about thirty species of Caloplaca in the...

, a secondary product of the lichen Xanthoria parietina

Xanthoria parietina

Xanthoria parietina is a foliose, or leafy, lichen. It has wide distribution, and many common names such as common orange lichen, yellow scale, maritime sunburst lichen and shore lichen. It can be found near the shore on rocks or walls , and also on inland rocks, walls, or tree bark...

, and a pigment found in the roots of Curled Dock

Curled Dock

Curled Dock , also known as Curly Dock, Yellow Dock, Sour Dock, Narrow Dock, sometimes as "narrow-leaved dock" , and ambiguously as "garden patience", is a perennial flowering plant in the family Polygonaceae, native to Europe and Western Asia.The mature plant is a reddish brown colour, and...

 (Rumex crispus). It has an orangy-yellow color and absorbs blue light.

It reacts with KOH

Potassium hydroxide

Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

 to form a deep, reddish-magenta compound.

It has also shown anti-fungal activity against barley powdery mildew and cucumber powdery mildew, more efficiently in the latter case than treatments with fenarimol and polyoxin B.