The Sunflower Family Asteraceae

The Sunflower Family, with approximately 20,000 species, is the second largest of the flowering plant families in terms of number of species. The individual flowers are called florets. They are usually tiny and numerous but are arranged in a compact inflorescence so that they resemble a single flower. A sunflower or daisy, for example, consists of dozens if not hundreds of tiny flowers crowded together, with those around the margin having greatly developed corollas that extend out like straps, forming what appear to be the "petals" of the inflorescence (Fig. 24.24 gives details of a sunflower inflorescence). In dandelions, all the individual florets of the inflorescence have narrow straplike extensions.

Sunflower Inflorescence

Stern-Jansky-Bidlack: 24. Flowering Plants and Text Introductory Plant Biology, Civilization Ninth Edition

© The McGraw-H Companies, 2003

Chapter 24

stigma branches

— corolla stamens straplike extension of the corolla bristles or scales i representing the calyx

ovary straplike extension of the corolla

Disk Floret

ray floret disk floret receptacle ray floret disk floret

Xi receptacle

Figure 24.24 Parts of a sunflower. A. A section through a single floret. B. A section through an inflorescence.

Well-known members of this family include lettuce, endive, chicory, Jerusalem artichoke, globe artichoke, dahlia, chrysanthemum, marigold, sunflower, and thistle.

Santonin, obtained from flower buds of a relative of sagebrush that is native to the Middle East, is used as an intestinal worm remedy. Tarragon, used as a spice in meat dishes and pickles, comes from another relative of sagebrush. Pyrethrum is a natural insecticide obtained from certain chrysanthemum flowers. Fructose, a sugar, is obtained from the tubers of Jerusalem artichokes and dahlias. Dahlias are also renowned for their huge showy flowers, while Jerusalem artichokes are often eaten as a vegetable.

Marigolds are favorite plants of organic gardeners. Their roots are said to release a substance that repels nematodes, and the odor of the leaves repels white flies and other insects. Unfortunately, snails and slugs seem to be immune and voraciously consume the foliage.

Many members of this family were used widely by Native Americans. The dry fruits of balsamroot and mule ears were used for food. Balsamroot plants as a whole were eaten raw or cooked, and in the West, extracts of both mule ears and tarweeds were used to treat poison oak inflammations. Salsify and thistle roots were also used for food.

Young leaves and roots of dandelions have been eaten for centuries, and the flowers have been used to make wine. Roasted dandelion and chicory roots have been used as a coffee substitute. During World War II, chicory was grown as a crop specifically for use as a coffee adulterant.

The dried and boiled leaves of American yarrow are said to make a nourishing broth. European yarrow has become naturalized in North America. Its rhizomes contain an anaesthetic that, when chewed, numbs the tongue and gums, and it has been used to ease the discomfort of teething toddlers; the substance has also been used in suppression of menstruation. This plant is believed to have been used by Achilles in treating the wounds of his soldiers.

Sunflowers themselves were widely used by Native Americans for their dry fruits, which were ground into a meal for bread. They are grown commercially today primarily for the edible oil extracted from the seeds (after removal from the husks), but the seeds are increasingly being eaten by modern Americans.

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