Nectarine

Nectarine, name for a tree (Prunus persica var. nectarina) of the family Rosaceae (rose family) and for its fruit, a smooth-skinned variety of the peach. The nectarine is a classical example of bud variation (see mutation). The nectarine tree occasionally produces peaches, and the peach tree nectarines. In appearance, culture, and care the nectarine is almost identical to the peach. It is cultivated in north temperate zones of both hemispheres, in America chiefly in the mild Pacific coastal area. The nectarine has been known for at least 2,000 years; in the 16th cent. it was called the nut of Persia. Nectarines are classified in the division Magnoliophyta, class Magnoliopsida, order Rosales, family Rosaceae.

Plant Differentiation From Other Kingdoms

Plants are multicellular eukaryotes—that is, their cells contain membrane-bound structures called organelles. Plants differ from other eukaryotes because their cells are enclosed by more or less rigid cell walls composed primarily of cellulose. The most important characteristic of plants is their ability to photosynthesize. During photosynthesis, plants make their own food by converting light energy into chemical energy—a process carried out in the green cellular organelles called chloroplasts (see Chlorophyll; Chloroplast). A few plants have lost their chlorophyll and have become saprophytes or parasites—that is, they absorb their food from dead organic matter or living organic matter, respectively—but details of their structure show that they are evolved plant forms.

Fungi, also eukaryotic and long considered members of the plant kingdom, have now been placed in a separate kingdom because they lack chlorophyll and plastids and because their rigid cell walls contain chitin rather than cellulose. Unlike the majority of plants, fungi do not manufacture their own food; instead they are saprophytic, absorbing their food from either dead or living organic matter.

The various groups of algae were also formerly placed in the plant kingdom because many are eukaryotic and because most have rigid cell walls and carry out photosynthesis. Nonetheless, because of the variety of pigment types, cell wall types, and physical attributes found in the algae, they are now recognized as part of two separate kingdoms, containing a diversity of plantlike and other organisms that are not necessarily closely related. One of the phyla of algae, the green algae, is believed to have given rise to the plant kingdom, because its chlorophylls, cell walls, and other details of cellular structure are similar to those of plants.

The animal kingdom is also multicellular and eukaryotic, but its members differ from the plants in deriving nutrition from other organic matter; by ingesting food rather than absorbing it, as in the fungi; by lacking rigid cell walls; and, usually, by having sensory capabilities and being motile, at least at some stage. See Classification.

Rice

Rice, plant that produces an edible grain; the name is also used for the grain itself. Rice is the primary food for half the people in the world. In many regions it is eaten with every meal and provides more calories than any other single food.

A kernel or grain of rice is a seed that contains an embryonic rice plant. The hull, a hard protective covering, surrounds the bran, which consists of layers of fibrous tissue that contain protein, vitamins, minerals, and oil. Beneath the bran is the endosperm, which makes up most of the rice grain. The endosperm contains starch, the energy source used by the germinating seed. The bran and endosperm are the edible portions of the grain.

A rice plant, a type of grass, has narrow, tapered leaves and grows from about 60 to 180 cm (about 2 to 6 ft) tall. Several flower stalks emerge from the plant, and in most varieties, a loose cluster of branching stems, called a panicle, radiates from the top of each stalk with small green flowers hanging from each stem. When the grain has developed, the panicle droops under the weight of the ripened kernels. Depending on the variety, one panicle provides about two handfuls of rice.

Scientific classification: Rice is an annual grass in the grass family, Poaceae (formerly Gramineae). Asian rice is classified as Oryza sativa and African rice as Oryza glaberrima.

Corn Plant

Corn or Maize, common name for the cereal grass widely grown for food and livestock fodder. Corn ranks with wheat and rice as one of the world’s chief grain crops.

The corn plant has an erect, solid stem, rather than the hollow one of most other grasses. It varies widely in height, some dwarf varieties being little more than 60 cm (2 ft) at maturity, whereas other types may reach heights of 6 m (20 ft) or more. The average is 2.4 m (8 ft). The leaves, which grow alternately, are long and narrow. The main stalk terminates in a staminate (male) inflorescence, or tassel. The tassel is made up of many small flowers termed spikelets, and each spikelet bears three small anthers, which produce the pollen grains, or male gametes. The pistillate (female) inflorescence or ear is a unique structure with up to 1,000 seeds borne on a hard core called the cob. The ear is enclosed in modified leaves called husks. The individual silk fibers that protrude from the tip of the ear are the elongated styles, each attached to an individual ovary. Pollen from the tassels is carried by the wind and falls onto the silks, where it germinates and grows down through the silk until it reaches the ovary. Each fertilized ovary grows and develops into a kernel.

Scientific classification: Corn is classified as Zea mays. The perennial wild corn thought to be extinct and rediscovered in Mexico is classified as Zea diploperennis.

Wheat

Wheat, common name for cereal grasses of a genus of the grass family, cultivated for food since prehistoric times by the peoples of the temperate zones and now the most important grain crop of those regions (see Agriculture).

Wheat is a tall, annual plant attaining an average height of 1.2 m (4 ft). The leaves, which resemble those of other grasses, appear early and are followed by slender stalks terminating in spikes, or so-called ears, of grain.

CLASSIFICATION

Species of wheat are classified according to the number of chromosomes found in the vegetative cell. They are divided into three series: the diploid, or einkorn, containing 14 chromosomes; the tetraploid, or emmer, containing 28 chromosomes; and the hexaploid, containing 42 chromosomes. Wheat species crossbreed relatively frequently in nature. Selection of the best varieties for domestication took place over many centuries in many regions.

VARIETIES

According to the regions in which they are grown, certain types of wheat are chosen for their adaptability to altitude, climate, and yield. The common wheats grown in the former Soviet republics, the United States, and Canada are spring and winter wheats, planted either in the spring for summer harvest or in the fall for spring harvest. The color of the grain varies from one type to another; white wheats are mostly winter wheats, red are spring wheats. Closely related to the common wheats are the club wheats, which have especially compact spikes, and spelta (not grown in the United States), in which the glumes (reduced, scalelike leaves) tightly enclose the grains. Durum wheat (Latin durum, “hard”) is so called because of the hardness of the grain. It is grown in north-central regions of the United States. New high-yielding wheats were developed in the 1960s for use in developing countries, and research on them continued in the 1970s. Experimental programs have produced commercial wheat varieties for hardiness and disease resistance. In 1978 the identification of a drought-resistant, high-protein, ancestral species growing in the Middle East held promise of still more improved wheat varieties.

USES

The main use of wheat is in the manufacture of flour for bread and pastries. In general, hard varieties are used for bread flour and soft varieties for pastry flour. Wheat is used also in the production of breakfast foods and to a limited extent in the making of beer, whiskey, and industrial alcohol. Low grades of wheat, and by-products of the flour-milling, brewing, and distilling industries, are used as feed for livestock. A minor amount of wheat is used as a coffee substitute, especially in Europe, and wheat starch is employed as a sizing for textile fabrics.

Scientific classification: Wheat is a member of the family Poaceae (formerly Gramineae). It makes up the genus Triticum.

Plum

Plum (tree), fruit tree of a genus of the rose family, which also contains the other trees that produce drupes (hard-pitted fruits): peach, cherry, almond, and apricot. About 12 plum species are cultivated throughout temperate regions for their fruit and as flowering ornamentals. The trees are rarely more than 10 m (33 ft) high. The plum varieties, which are suited to both warm and cool climates, exceed the other drupes.

The common European plum, the most important species, has been cultivated since ancient times and probably originated near the Caspian Sea. It was introduced into North America, possibly by the Pilgrims, and is now mostly cultivated in the western United States. Fruits of varieties of this species range in color from yellow or red to green, but purplish-blue is most common. Dried plums, or prunes, are made from the varieties that are richest in sugar and solids.

The Japanese plum, probably originating in China, was introduced into the United States in 1870. The fruit is more pointed at the apex than that of the common European plum, and its varieties are yellow or light red but never purplish-blue. The Damson plum—a small, oval, sweet fruit used mostly in jams—was first cultivated in ancient times in the region of Damascus.

Scientific classification: Plums belong to the genus Prunus of the family Rosaceae. The common European plum is classified as Prunus domestica, the Japanese plum as Prunus salicina, and the Damson plum as Prunus insititia.

Apple

Apple, common name for certain related trees of the rose family, and for the pome fruit of the trees. The apple tree, a deciduous plant, grows mainly in the temperate areas of the world. The fruit is a firm, fleshy structure derived from the receptacle of the flower. Apple leaves are broadly oval in shape and are somewhat woolly on the undersides. The flowers in bloom have a rounded appearance. Some apple blossoms are white, but the majority of apple blossoms have stripes or tints of rose. A few apple species bloom with bright red flowers. Apple wood is hard, durable, and very fine-grained.

The physical characteristics of the fruit are subject to considerable variation. The skin color may range from green to a deep, blackish red. Shapes, also, are diverse and include oblate and oblong fruits and fruits of a size hardly larger than a cherry or as big as a medium-sized grapefruit.

Scientific classification: Apple trees belong to the family Rosaceae. They constitute the genus Malus.