Fruit ID #5

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Fruit Identification Photos #5

Achenes Of The Sunflower Family

Sunflower Family (Asteraceae)


The largest family of flowering plants is the ubiquitous sunflower family (Asteraceae or Compositae). According to James L. Reveal of the University of Maryland (personal communication, 2000), the family contains nearly 1550 genera and 24,000 species. The sunflower family is rivaled in size only by the orchid family (Orchidaceae) with approximately 20,000 species and the legume family (Fabaceae) with about 18,000 species. [Judd, W.S. et al. 2008 Plant Systematics: A Phylogenetic Approach lists 23,000 for Asteraceae, 19,500 for Orchidaceae and 18,000 for Fabaceae.] In fact, if all the known species of flowering plants on earth were randomly lined up, every fourth one would belong to the sunflower, orchid or legume families. The sunflower family includes a great diversity of species, including annuals, perennials, stem succulents, vines, shrubs and trees. It is well-represented in parks and gardens throughout the world, with bedding plants, ground covers and shrubs. Familiar common names, such as daisies, marigolds, zinnias, gazanias and chrysanthemums all belong to this family. Throughout San Diego County and the southwestern United States (where Wayne's Word is based), this family is usually represented by the largest number of wild species in coastal mountain and desert regions. In many areas of the world, members of this family comprise 10 to 20 percent of the total flora. The family also includes numerous endemic species that only grow on one isolated mountain range or island, such as the remarkable silver sword (Argyroxiphium sandwicense var. macrocephalum) endemic to Haleakala Crater on the Hawaiian Island of Maui and the beautiful Panamint daisy (Enceliopsis covillei) endemic to California's Panamint Range. In addition, the family includes many economically important herbs and vegetables, and has some of the world's most widespread and successful weedy species with very effective hitchhiker seeds and seeds dispersed by air currents.

The large head of a sunflower (Helianthus annuus). The darker center of the head is composed of hundreds of disk flowers, each with an immature achene at the base. The disk is surrounded by yellow, petal-like ray flowers and leaflike bracts called phyllaries.

Go To Article About The Sunflower Family

The blossom of a typical sunflower is called a head. Since it is technically composed of numerous individial flowers rather than a single flower, it is called an inflorescence. In the common sunflower, the outer yellow petals are called ray flowers, and the center is composed of numerous disk flowers crowded together. The entire head is subtended by numerous green bracts called phyllaries. Each disk flower produces a one-seeded achene at its base, and these achenes are the source of sunflower seeds. Sunflower seeds used for eating usually come from achenes with a striped pericarp, while seeds used for sunflower oil come from solid black achenes.

Close-up view of a portion of the large flowering head of a sunflower (Helianthus annuus) showing an outer ring of large, strap-shaped (petal-like) ray flowers surrounding a dense mass of small, tubular disk flowers. The ovaries of the disk flowers ripen into the striped achenes sold in markets as sunflower seeds. The entire head is subtended by green, overlapping bracts called phyllaries.

Left: Mature seed head of a sunflower (Helianthus annuus) after the disk flowers and ray flowers have fallen off. The head is 12 inches (30 cm) in diameter and contains hundreds of seed-bearing achenes. Right: Close-up view of a portion of the head showing many achenes embedded in the receptacle. Each achene is subtended by a small, green, chaffy bract (red arrow).

The large seed-bearing head of a sunflower.

Safflower oil comes from the spiny, thistlelike heads of the safflower plant (Carthamus tinctorius). Like the sunflower, the seeds are produced inside one-seeded fruits called achenes. Because of its degree of polyunsaturation, the use of safflower oil as an edible oil has declined. The oil oxidizes readily and must be kept at low temperatures to preserve its flavor and freshness. Today, health conscious people have switched to monounsaturated oils, such as olive oil (Olea europea) from the olive family (Oleaceae) and canola oil (B. napus) from the mustard family (Brassicaceae). The specific epithet "tinctorius" refers to the blossoms which were originally grown for their deep orange pigment called carthamin. This ancient pigment was used for dyeing 2,000 years ago.

Achenes of the sunflower (Helianthus annuus). One achene has been sectioned to reveal the single seed inside. The seed is essentially free within the pericarp wall, except where it is attached at the placenta. Sunflower seeds of this variety with striped pericarps is used primarily for food. Seeds from achenes with solid black pericarps are used for sunflower oil.

Read About The Chemistry Of Plant Oils

Other edible members of the sunflower family include the dandelion (Taraxacum officinale), globe artichoke Cynara scolymus, cardoon or thistle artichoke (C. cardunculus), Jerusalem artichoke (Helianthus tuberosus), lettuce (Lactuca sativa), endive (Cichorium endiva) and numerous other species. The following table contains links to some of the economically important members of this remarkable plant family:

See The Root Of Japanese Burdock Or Gobo
See Photograph Of The Herb Called Absinthe
See Photograph Of The Herb Called Tarragon
Chicory: A Dandelion Relative Used In Coffee
See Photo Of Rubber-Producing Guayule Plant
See Photograph Of The Herb Called Echinacea
See Flower Head & Seeds Of Thistle Artichoke
See Photo Of Jerusalem Artichoke Or Sunchoke
Photo Of The Flowers & Leaves Of A Dandelion
See Photograph Of The Herb Called Milk Thistle
See Edible Flower Heads Of The Globe Artichoke

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