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Watermelon

Watermelon

Watermelon (Citrullus lanatus) is a plant species in the family Cucurbitaceae, a vine-like flowering plant originating in West Africa. It is a highly cultivated fruit worldwide, having more than 1000 varieties.

Watermelon is a scrambling and trailing vine in the flowering plant family Cucurbitaceae. There is evidence from seeds in Pharaoh tombs of watermelon cultivation in Ancient Egypt. Watermelon is grown in favorable climates from tropical to temperate regions worldwide for its large edible fruit, which is a berry with a hard rind and no internal divisions, and is botanically called a pepo. The sweet, juicy flesh is usually deep red to pink, with many black seeds, although seedless varieties exist. The fruit can be eaten raw or pickled, and the rind is edible after cooking. It is commonly consumed as a juice or as an ingredient in mixed beverages.

Considerable breeding effort has developed disease-resistant varieties. Many cultivars are available that produce mature fruit within 100 days of planting. In 2017, China produced about two-thirds of the world total of watermelons.

Description

The watermelon is an annual that has a prostrate or climbing habit. Stems are up to 3 m long and new growth has yellow or brown hairs. Leaves are 60 to 200 mm long and 40 to 150 mm wide. These usually have three lobes which are themselves lobed or doubly lobed. Plants have both male and female flowers on 40-mm-long hairy stalks. These are yellow, and greenish on the back.

The watermelon is a large annual plant with long, weak, trailing or climbing stems which are five-angled (five-sided) and up to 3 m (10 ft) long. Young growth is densely woolly with yellowish-brown hairs which disappear as the plant ages. The leaves are large, coarse, hairy pinnately-lobed and alternate; they get stiff and rough when old. The plant has branching tendrils. The white to yellow flowers grow singly in the leaf axils and the corolla is white or yellow inside and greenish-yellow on the outside. The flowers are unisexual, with male and female flowers occurring on the same plant (monoecious). The male flowers predominate at the beginning of the season; the female flowers, which develop later, have inferior ovaries. The styles are united into a single column. The large fruit is a kind of modified berry called a pepo with a thick rind (exocarp) and fleshy center (mesocarp and endocarp). Wild plants have fruits up to 20 cm (8 in) in diameter, while cultivated varieties may exceed 60 cm (24 in). The rind of the fruit is mid- to dark green and usually mottled or striped, and the flesh, containing numerous pips spread throughout the inside, can be red or pink (most commonly), orange, yellow, green or white.

A bitter watermelon has become naturalized in semiarid regions of several continents, and is designated as a “pest plant” in parts of Western Australia where they are called “pig melon”.

The species has two varieties, watermelons (Citrullus lanatus (Thunb.) var. lanatus) and citron melons (Citrullus lanatus var. citroides (L. H. Bailey) Mansf.), originated with the erroneous synonymization of Citrullus lanatus (Thunb.) Matsum. & Nakai and Citrullus vulgaris Schrad. by L.H. Bailey in 1930. Molecular data including sequences from the original collection of Thunberg and other relevant type material, show that the sweet watermelon (Citrullus vulgaris Schrad.) and the bitter wooly melon Citrullus lanatus (Thunb.) Matsum. & Nakai are not closely related to each other. A proposal to conserve the name, Citrullus lanatus (Thunb.) Matsum. & Nakai, was accepted by the nomenclature committee and confirmed at the International Botanical Congress in 2017.

Cultivation

Watermelons are plants grown in climates from tropical to temperate, needing temperatures higher than about 25 °C (77 °F) to thrive. On a garden scale, seeds are usually sown in pots under cover and transplanted into well-drained sandy loam with a pH between 5.5 and 7, and medium levels of nitrogen.

Major pests of the watermelon include aphids, fruit flies and root-knot nematodes. In conditions of high humidity, the plants are prone to plant diseases such as powdery mildew and mosaic virus. Some varieties often grown in Japan and other parts of the Far East are susceptible to fusarium wilt. Grafting such varieties onto disease-resistant rootstocks offers protection.

The US Department of Agriculture recommends using at least one beehive per acre (4,000 m2 per hive) for pollination of conventional, seeded varieties for commercial plantings. Seedless hybrids have sterile pollen. This requires planting pollinizer rows of varieties with viable pollen. Since the supply of viable pollen is reduced and pollination is much more critical in producing the seedless variety, the recommended number of hives per acre (pollinator density) increases to three hives per acre (1,300 m2 per hive). Watermelons have a longer growing period than other melons, and can often take 85 days or more from the time of transplanting for the fruit to mature.

Farmers of the Zentsuji region of Japan found a way to grow cubic watermelons by growing the fruits in metal and glass boxes and making them assume the shape of the receptacle. The cubic shape was originally designed to make the melons easier to stack and store, but these “square watermelons” may be triple the price of normal ones, so appeal mainly to wealthy urban consumers. Pyramid-shaped watermelons have also been developed and any polyhedral shape may potentially be used.

Production

In 2017, global production of watermelons was 118 million tonnes, with China alone accounting for 67% of the total.Secondary producers included Iran, Turkey, and Brazil.

 

Food and beverage

Watermelon is a sweet, commonly consumed fruit of summer, usually as fresh slices, diced in mixed fruit salads, or as juice. Watermelon juice can be blended with other fruit juices or made into wine.

The seeds have a nutty flavor and can be dried and roasted, or ground into flour. In China, the seeds are eaten at Chinese New Year celebrations. In Vietnamese culture, watermelon seeds are consumed during the Vietnamese New Year’s holiday, Tết, as a snack.

Watermelon rinds may be eaten, but their unappealing flavor may be overcome by pickling, sometimes eaten as a vegetable, stir-fried or stewed.

The Oklahoma State Senate passed a bill in 2007 declaring watermelon as the official state vegetable, with some controversy about whether it is a vegetable or a fruit.

Citrullis lanatus, variety caffer, grows wild in the Kalahari Desert, where it is known as tsamma. The fruits are used by the San people and wild animals for both water and nourishment, allowing survival on a diet of tsamma for six weeks.

Nutrients

Watermelon fruit is 91% water, contains 6% sugars, and is low in fat (table).

In a 100 gram serving, watermelon fruit supplies 30 calories (125 kJ) and low amounts of essential nutrients (see table). Only vitamin C is present in appreciable content at 10% of the Daily Value (table). Watermelon pulp contains carotenoids, including lycopene.

The amino acid citrulline is produced in watermelon rind.

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