Grasses

-

Grasses, common name for a large family of flowering plants that is economically and ecologically the most important in the world. The grass family contains about 635 genera and 9000 species, making it the fourth largest family after the legume, orchid, and composite families (see Composite Flowers).

IMPORTANCE

All the world’s cereal crops are grasses, and thus the grass family is economically very important. The world’s 5 top crops produce more tonnage than the next 25 combined, and 4 of the top 5 are the cereals rice, wheat, corn, and barley. Human well-being depends on these few grasses, so even small crop failures of any one of them can produce widespread hunger and economic disruption. In addition, the family provides most of the world’s sugar (see Sugarcane). Another member of the family, bamboo, is an important construction material as well as a food source; it also has been used in papermaking. Citronella, used both in perfumery and as an insect repellent, is an oil distilled from the leaves of certain grasses.

Grasses are the primary source of food for domestic and wild grazing animals, which feed on pastures and grasslands and which are fed hay and silage harvested from them. The total land area devoted to these kinds of croplands is greater than the land area for all other kinds of croplands combined.

Another economically significant use of grasses is for the lawns maintained in many parts of the world. Perennial grasses are well adapted for use in lawns because their basal meristems (growing points) are not lost with mowing. Bermuda grass and zoysia are better adapted to the warm conditions of the southern states. Often special grasses are used where particular conditions of soil or exposure make the more common species unsuitable.

OTHER GRASSLIKE PLANTS

Plants of two other groups, the sedges and the rushes, are superficially similar to grasses and are often confused with them. The three groups are easily distinguished, however, by examining their flowers, stems, and leaves. Rushes have flowers with six-part perianths (floral whorls) and from three- to many-seeded fruits, whereas the flowers of sedges and grasses have no perianth and have single-seeded fruits. Sedges usually occur in moist habitats and have solid stems that are triangular and bear three rows of leaves. Grasses usually occur in dry habitats and have round, hollow stems with two rows of leaves.

Scientific classification: Grasses make up the family Poaceae (formerly Gramineae). Citronella is distilled from grasses of the genus Cymbopogon. Kentucky bluegrass is classified as Poa pratensis. Bent grasses are classified in the genus Agrostis. Fescue grasses are classified in the genus Festuca. Bermuda grass is classified as Cynodon dactylon. Zoysia grasses are classified in the genus Zoysia. Buffalo grass is classified as Buchloë dactyloïdes, carpet grass as Axonopus affinis, redtop as Agrostis gigantea, and annual bluegrass as Poa annua.

Comments

Post a Comment

Popular posts from this blog

Plant: Cell Structure And Function

-
Image
Plant Cell Plant cells contain a variety of membrane-bound structures called organelles. These include a nucleus that carries genetic material; mitochondria that generate energy; ribosomes and rough endoplasmic reticulum that manufacture proteins; smooth endoplasmic reticulum that manufactures lipids used for making membranes and storing energy; and a thin lipid membrane that surrounds the cell. Plant cells also contain chloroplasts that capture energy from sunlight and a single fluid-filled vacuole that stores compounds and helps in plant growth. Plant cells are surrounded by a rigid cell wall that protects the cell and maintains its shape. The tremendous variety of plant species is, in part, a reflection of the many distinct cell types that make up individual plants. Fundamental similarities exist among all these cell types, however, and these similarities indicate the common origin and the interrelationships of the different plant species. Each individual plant cell is at ...
Read more

Monocot and Dicot Seeds

-
Image
Monocotyledons (monocots) and dicotyledons (dicots) make up the two large groups of flowering plants, differentiated by their seed structures. Monocot seeds contain one cotyledon, or embryonic leaf. When these seeds germinate, the cotyledon remains below ground, absorbing nutrients from the endosperm, the starchy food supply in the seed. The coytledon transports these nutrients to the developing seedling. Dicot seeds contain two coytledons, which absorb and store the nutrients from the endosperm before the seed germinates. The cotyledons, thick with stored nutrients, emerge above ground during germination, and then transport the stored nutrients to the developing seedling. For a brief time, the cotyledons also serve as the first photosynthesizing leaves, but they wither and die when the true leaves emerge. related articles: flower flower variations in structure flower sexual reproduction flower pollination and fertilization flowering and the life cycle evolution of flowers angios...
Read more

Insectivorous Plants

-
Image
Insectivorous Plants, also carnivorous plants, plants that gain some of their nutrition from animals, especially insects, captured by the plants themselves. Most occur in bogs where the soil is acid and poor in available nitrogen; capturing insects is one way of getting nitrogenous compounds without manufacturing them. At the same time, the green leaves of these plants manufacture carbohydrates. The trapping mechanism of insectivorous plants is relatively small. Therefore, prey is almost inevitably limited to small insects. Insectivorous plants are diverse and represent members of three orders of dicots : Nepenthales, Scrophulariales, and Rosales. A majority are in the Nepenthales, including the pitcher plant , sundews and the Venus's-flytrap, and East Indian pitcher plants. Others include the bladderworts, butterworts, and the Australian pitcher plant. Discussed below are the sundews and bladderworts. Certain species of fungus are known to be carnivorous as well. Venus’s-Flytrap...
Read more