CARYOPHYLLALES

pink order of dicotyledonous flowering plants, a division of the subclass Caryophyllidae. also called Centrospermae, the pink order of flowering plants, belonging to the class called dicotyledon (characterized by two seed leaves). It consists of 12 families and some 10,000 species, distributed throughout the world. Although most of the species are annual or perennial herbs, various families have shrubs, vines, and trees. Herbaceous members include ornamental flowers, weeds, and vegetables. Pigweed (Chenopodium album). The majority of the food-producing plants of Caryophyllales belong to the goosefoot family (Chenopodiaceae), including spinach (Spinacea oleracea), the sugar beet (Beta vulgaris), and Swiss chard (Beta vulgaris variety cicla). Lamb's-quarters (Chenopodium album; see photograph), a cosmopolitan weed, is useful as a potherb when young. Another edible member of the order is poke (Phytolacca americana). Many weedy genera make up the pigweed family (Amaranthaceae). Amaranthus retroflexus, the re-rooted, noxious pigweed, has spread northward from the tropics of the Americas and Africa into most agricultural areas of the world. Many persons are allergic to its pollen. Ornamental plants belong to several families in Caryophyllales. The family Nyctaginaceae is known for the four-o'clock (Mirabilis jalapa), which flowers late in the day, and Bougainvillea. Portulacaceae includes the rose moss (Portulaca grandiflora), widely grown as a garden annual, and spring-beauty (Claytonia virginica), a wildflower of eastern North America. The pink family (Caryophyllaceae) has many genera of ornamentals. Members of the cactus family (Cactaceae) are cultivated throughout the world for their unusual forms and sometimes striking blossoms, and various species are grown for food. (Some authorities place this family in a separate order, Cactales.) Although a few families in this order reproduce by means of rhizomes (i.e., vegetatively), the major means of reproduction is sexual. The production and dispersal of seeds is very efficient. Inflorescences (flower clusters) of various structural types consist of small, short-stalked, compactly arranged flowers. In the Amaranthaceae and Chenopodiaceae, sepals are five in number, petals are lacking, and stamens (male) may number up to five. The pistil (female) consists of two carpels as shown by the two terminal, pollen-receptive stigmas and two styles. The swollen, basal ovary is one-chambered and contains a single ovule. After pollination and fertilization, the ovule becomes the seed and the ovary the fruit, which is very small; it ripens dry to become a closed nutlet or an achene. Variations in number of flower parts occur among the thousands of species constituting these two families. In some, male and female parts appear in different flowers, generally on the same plant. Most members of the Caryophyllales develop a perianth consisting of sepals only. Another attribute of this order is a one-chambered, superior ovary. The developmental patterns of stems and leaves, resemblances of tissues and cells at the microscopic level, and synthesis of unique cell products are used to ascertain relationships. In most flowering plants, colours ranging from nearly red to nearly blue are dependent on the presence of chemical compounds called anthocyanins; colours ranging from yellow to reddish orange are dependent on compounds called anthoxanthins. A distinct but parallel group of pigments, known as betalains (betacyanins and betaxanthins) occurs only in a large number of Caryophyllales. Because the betalains are apparently restricted to this order, their presence has assumed some taxonomic significance. Additional reading The cacti are described in Willy Cullmann, Erich Gtz, and Gerhard Grner, The Encyclopedia of Cacti (1986; originally published in German, 5th rev. ed., 1984); Arthur C. Gibson and Park S. Nobel, The Cactus Primer (1986); J. Rha and R. ubk, The Illustrated Encyclopedia of Cacti & Other Succulents (1981); Gnter Andersohn, Cacti and Succulents (1983); and Lyman Benson, The Cacti of the United States and Canada (1982).