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|Economic Plant Photographs #18|
Grapes are one of the oldest cultivated plants. They are classified as true berries because the fruit wall or pericarp is fleshy all the way through. The cultivation of grapes dates back more than 5,000 years in Egypt, and they were highly developed by the Greeks and Romans. Today there are nearly 200 cultivated varieties. Modern cultivars have all been derived from two main species, the European (Mediterranean) Vitis vinifera (a tight-skin grape with wine-like flavor) and the North American V. labrusca (a slip-skin grape with Concord-type flavor). In the European tight-skins, which are used for wines, the skin does not separate readily from the pulp. North American slip-skin grapes are generally more hardy than the European. The fruit is round with a more watery flesh and a thin skin that slips off very easily. The North American V. labrusca is also called the fox grape and is the source of the famous cultivar discovered in Concord, Massachusetts. Concord grapes are the most important American grape for juices, jellies and preserves. They are also used for certain wines. Some of the best wines and popular eating grapes, such as 'Thompson Seedless' and 'Red Seedless' are cultivars of V. vinifera. Sterile, triploid cultivars have been developed that do not produce seeds because of synaptic failure during Meiosis I resulting in non-viable gametes. Several varieties of grapes are dried and used for raisins. The best raisin grapes are selected for flavor, reduced stickiness and soft texture. In the United States, most raisins are produced in California's Central Valley.
The fermentation of grapes is brought about through the action of wild yeasts which are present on the skins of the fruit (whitish powder). The maximum alcoholic content of natural wines is about 12 to 16% (24 to 32 proof). Higher alcoholic content will kill the yeast cells. Brandy is made from distilled wines and has a much higher alcoholic content (up to 140 proof). Red wines are made from grapes with colored skins (with anthocyanin), while white wines are made from white grapes (or red grapes with skins removed). In dry wines the sugar is almost completely fermented. In sweet wines fermentation is stopped before all the sugar is converted. Viticulture (the cultivation of grapes) and enology (the study of wine making) are enormous topics beyond the scope of this section of WAYNE'S WORD. They are discussed in more detail in the required textbook for Plants and People (Botany 115).
|Two popular varieties of seedless grapes in California: 'Thompson Seedless' (left) and delicious 'Red Flame' (right). Grapes are considered a true berry because the entire pericarp (fruit wall) is fleshy.|
|A native California wild grape (Vitis girdiana) that grows in canyon bottoms and along streams in southern California. This species often forms massive vines that drape over large trees such as coast live oak (Quercus agrifolia). It intergrades with the very similar V. californica of central and northern California. Unlike the tight-skin V. vinifera of Europe, this is a slip-skin grape in which the skin readily slips off of the juicy, seed-bearing pulp (see arrow).|
For years it has been known that people in France who consume red wines on a regular basis have a reduced risk of coronary heart disease compared with the United States. This data is paradoxical considering that the French also consume a lot of fatty foods, such as pastries. A phenolic compound in the grape skins called resveratrol was discovered that seems to inhibit the plaque build-up or clogging of arteries (atherosclerosis) by increasing the level of high density lipoproteins (HDLs) in the blood. Beneficial HDLs carry cholesterol away from the arteries so that it doesn't form plaque deposits in the arterial walls. Resveratrol also reduces blood platelet aggregation or clotting (thromboses) within blood vessels. Resveratrol belongs to a class of plant chemicals called phytoalexins. They are used by plants as a defense mechanism in response to attacks by fungi and insects. One interesting phytoalexin called psoralen comes from the leguminous herb Psoralea. It has a chemical structure similar to coumarin. Psoralen has been used in the treatment of certain cancers, including T-cell lymphomas in AIDS patients.
|Sprawling mass of wild grape (Vitis girdiana) in late fall, following a steep canyon on the desert escarpment of Mt. San Jacinto in southern California. The taller trees in distance are California sycamore (Platanus racemosa).|
Another potentially valuable herbal medicine from Vitis vinifera is grape seed extract, a mixture rich in bioflavonoids, specifically proanthocyanidins. The proanthocyanidins appear to enhance the activity of vitamin C through some unknown synergistic mechanism. Vitamin C protects cells from the damaging oxidation of free radicals, thus preventing mutations and tumor formation. The bioflavonoids in grape seed extract may also reduce the painful inflammation of swollen joints and prevent the oxidation of cholesterol in arteries which leads to fatty deposition (plaque) in the arterial walls.
||Grape seed extract: to enhance the antioxidant activity of vitamin C and an anti-inflammatory to treat arthritis and allergies. Also a powerful antioxidant to prevent free radical assault on capillary walls; to prevent oxidation of blood lipids (such as cholesterol) that lead to fatty deposition in arterial walls; and to block free radical attack on molecules within cells that might lead to mutations and tumor formation. The efficacy and mechanism of all these claims is not completely understood or agreed upon by experts in the medical field.|
The sea grape (Coccoloba uvifera) belongs to the buckwheat family (Polygonaceae), along with rhubarb (Rheum rhaponticum), wild rhubarb (Rumex hymenosepalus), buckwheat (Fagopyrum sagittatum), and a huge genus of California herbs and shrubs called wild buckwheat (Eriogonum). Although it is not related to grapes or even a member of the grape family (Vitaceae), the sea grape produces clusters of edible berries that greatly resemble true grapes. The sea grape is native to the Florida Keys, islands of the Caribbean region, and the Caribbean shores of Central America. On exposed, windy shores it grows as a sprawling shrub but in more sheltered areas it grows as a tree, reaching a height of 50 feet (15 m). The ripe fruits are sour, but they contain large amounts of pectin which makes them especially useful for jellies and jams. Some historians have suggested that the sea grape was one of the first beach plants encountered by Columbus when he arrived in the Caribbean region in the fifteenth century.
|Sea grape (Coccoloba uvifera), a member of the buckwheat family (Polygonaceae). Photographed at Cahuita National Park on the Caribbean shore of Costa Rica.|
Blackberries and raspberries are classified as aggregate fruits because they are clusters of one-seeded drupelets, each cluster of drupelets developing from a single flower. The drupelets are typically eaten as a cluster, and not individually. Like other fruits, the origin of blackberries and raspberries is very complicated and there are numerous cultivated varieties that have been developed through the centuries. The main red raspberries grown commercially come from Rubus idaeus, a widespread North American species. The origin of many cultivars of true blackberries include the North American black raspberry R. occidentalis, the European cut-leaved blackberry (R. laciniatus), and the Pacific blackberry or dewberry (R. ursinus). The latter species is also the source of the 'Loganberry,' 'Youngberry' and 'Boysenberry.' Actually, a cross between an octoploid California blackberry (possibly R. ursinus) and a European raspberry, first discovered in the garden of Joshua Logan, gave rise to the loganberry, a popular fruit in the western United States, where it is used for pies and jams. North American blackberries are also the source of an edible purple dye used to label meats with the familiar USDA ratings.
|Aggregate fruits of a blackberry (Rubus ursinus) in coastal northern California showing the individual drupelets, each with a separate style. Although the one-seeded drupelets represent separate ripened ovaries, each aggregate cluster of drupelets develops from a single white flower. [Note: This species might be a hybrid blackberry; the widespread weedy R. procerus also grows in the area.]|
Another introduced blackberry called the Himalayan blackberry (R. procerus) is harvested for edible fruit in the Pacific northwestern United States. [Note: In The Jepson Manual of California plants (1993), this species is listed as R. discolor.] It is a rampant, weedy vine that forms impenetrable, prickly thickets along roadsides and in vacant fields. An attractive western North American shrub with simple (undivided) leaves and without prickles is called thimbleberry (R. parviflorus). Although mulberry fruits superficially resemble blackberries, they are very different. Mulberry trees (Morus species) belong to the mulberry family (Moraceae). The fruits are called multiple fruits because they are composed of many drupelets, each arising from separate, small flowers without petals. They do not arise from a single flower as in aggregate fruits like raspberries and blackberries.
|Flower and aggregate fruit of thimbleberry (R. parviflorus), a native shrub in the mountains of the western United States. This photo was taken on Palomar Mountain in San Diego County, California. Although the one-seeded drupelets represent separate ripened ovaries, each aggregate cluster of drupelets developed from a single white flower.|
|Aggregate fruits of the raspberry, a commercially-grown hybrid of (Rubus idaeus). Although the one-seeded drupelets represent separate ripened ovaries, each aggregate cluster of drupelets develops from a single white flower. Note the individual hair-like styles that arise from each of the numerous drupelets. The most obvious difference between these fruits and blackberries is their red color.|
The strawberry is another very beautiful aggregate fruit that develops from a single white flower. It is composed of numerous, small, yellowish-brown, one-seeded fruits (called achenes) which are embedded in a swollen, fleshy, red receptacle. The tiny achenes are only found in the outer (surface) tissue of the strawberry receptacle, and produce the slight, gritty texture of the fruit. Most of the common cultivated varieties come from Fragaria x ananassa, a hybrid between Virginia strawberry F. virginiana of eastern North America and the widespread beach strawberry F. chiloensis of North and South America. The generic name Fragaria is derived from the Latin fragrans, referring to the sweet fragrance of the fruit. Strawberries are an attractive and delicious fruit with a high content of vitamins A and C.
|Aggregate fruit of a hybrid strawberry (Fragaria x ananassa) showing the individual yellowish-brown, one-seeded achenes embedded in the red, fleshy receptacle. Although the one-seeded achenes represent separate ripened ovaries, each strawberry is produced from a single white flower.|
The heath family (Ericaceae) is known for many native shrubs in the chaparral and subalpine regions of North America and Eurasia, and for some of our most beautiful ornamental shrubs, such as azaleas, rhododendrons and mountain laurels. It is also known for some popular berries that come from shrubs of the genus Vaccinium, including blueberries (V. corymbosum and V. angustifolium) and cranberries (V. macrocarpon and V. oxycoccos). Most commercially-grown huckleberries belong to the closely-related genus Gaylussacia. There are also many other native species called blueberries, cranberries, bilberries and huckleberries that are relished by bears and other animals in the Sierra Nevada, Cascade Range and Rocky Mountains of North America, including V. occidentale, V. ovatum, V. nivictum, V. caespitosum and V. globulare. In general, they all have dark blue or purple, many-seeded berries that develop from an urn-shaped or bell-shaped corolla.
|Globe huckleberry (Vaccinium globulare), a native huckleberry in the Rocky Mountains of North America. The fleshy, tart berries are a favorite food of bears and people.|
|Hawaiian huckleberry or "ohelo'ai" (Vaccinium reticulatum), an endemic huckleberry that colonizes lava flows on the island of Hawaii. The fleshy, tart berries were a favorite food of the native Hawaiian people. This colorful shrub was photographed near the rim of Kilauea Crater.|
|Cranberry (Vaccinium macrocarpon), a prostrate, North American shrub that grows in acidic, boggy soils. A number of cultivated varieties are grown commercially. The fruit is a fleshy, many-seeded berry that is too acidic to be eaten raw. It is used in drinks, jellies, pies, muffins, puddings, ice cream, and the traditional "cranberry sauce" of Thanksgiving dinners.|
The heath family also includes mazanita (Arctostaphylos), a very large genus of shrubs. One attractive species is bearberry (A. uva-ursi), a common prostrate shrub of the Rocky Mountains with bright red berries relished by bears and other wildlife of the region. The fleshy berries were collected by native Americans for food. A yellowish dye was also obtained from the leaves.
|Bearberry (Arctostaphylos uva-ursi), a native shrub in the Rocky Mountains, Sierra Nevada and Cascade Ranges of western North America.|
|Strawberry tree (Arbutus unedo), a native species in southern Europe and Ireland. The sweet, mealy fruits are eaten raw and are made into sherbets, preserves and alcoholic drinks. It is closely related to the madrone tree (A. menziesii) of the Pacific coastal region of the U.S.|
|Summer holly (Comarostaphylis diversifolia), a chaparral shrub in the coastal mountains of southern California. It belongs to the heath family (Ericaceae), along with manzanita (Arctostaphylos), mission manzanita (Xylococcus), madrone (Arbutus), azalea (Rhododendron) and blueberries (Vaccinium). The bumpy, red fruits (berries) resemble small versions of the strawberry tree (Arbutus unedo).|
Currants and gooseberries belong to the genus Ribes in the saxifrage family (Saxifragaceae). This large North American genus is sometimes placed in its own family, the Grossulariaceae. In the California mountains, the prickly Ribes shrubs with nodal spines are called gooseberries, while the unarmed shrubs are referred to as currants. In both groups, the sepals, petals and stamens arise from the rim of a tubular calyx tube or hypanthium above the ovary. The shriveled hypanthium often remains attached to the berry after it has ripened.
|Mountain gooseberry (Ribes roezlii) from Cuyamaca Peak in San Diego County, California. The fleshy berries are covered with slender spines. The withered hypanthium tube (from which the petals, sepals and stamens arise) is still attached to the berries. Unlike the unarmed wild currants, the gooseberry shrubs have nodal spines and may be painfully prickly if you attempt to walk through them.|
|Fushsia-flowered gooseberry (Ribes speciosum), a native California shrub with spiny branches, shiny green leaves, and bright red pendant flowers. This chaparral species in common in shaded canyons of coastal mountains.|
|Mountain currant (Ribes nevadense) from Palomar Mountain in San Diego County, California. The glandular-hairy, blue-black berries have a whitish bloom or powder that readily wipes off. The withered hypanthium tube (from which the petals, sepals and stamens arise) is still attached to the upper side of the berries.|
|Left: Oregon grape (Berberis aquifolium), one of several species of barberry in the Pacific northwest region of the United States. It is often classified in the genus Mahonia. The berries are used in pies, jellies, jams, beverages and confections. Fermented berries are made into barberry wine. Right: Zereshk (zirishk) or Indian barberry (B. aristata). The dried fruits (known as zereshk or zirishk) are used like raisins in desserts and rice dishes in the Middle East.|
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