Kids Research Express

Selecting Plants

Plants differ in their tolerance for heat, cold, and moisture, so when selecting plants, gardeners must take into account the climate of their region. Gardeners also evaluate the soil type and how much sunlight falls on the proposed site, factors that affect the types of plants that can be grown in a particular area. They consider, too, the plant’s life cycle—how long it takes a plant to grow, flower, produce fruits or seeds, and die. Annuals such as petunias bloom and produce seed the same year they are planted, then die when cold temperatures set in. Biennials—hollyhocks, for example—live for two years, producing just leaves the first year. In the second year they produce flowers, and die when the weather turns cold. Perennials, which include shrubs and trees as well as flowers, are plants that live for three or more years.

A gardener can experiment with a stunning diversity of interesting garden styles and types. Herb gardens may feature culinary herbs, medicinal herbs, and fragrant herbs. Flower gardens may combine a variety of flowering plants or focus on just one type, such as roses, white-flowered plants, or flowers that bloom only at night. Specialized gardens include rock or alpine gardens, which display plants native to mountains, and water gardens, which host plants adapted to wet conditions. Botanical gardens are designed to display plants for scientific and educational purposes, and in these gardens, the plants are often labeled with their names and their optimal growing conditions.

Gardening

Gardening, growing and caring for plants as an enjoyable leisure activity, to produce food, or to create beautiful landscapes with artfully arranged flowers, shrubs, and trees. For some, gardening is a form of exercise, a way to save money on food, or a way to ensure that fruits and vegetables are free from pesticides or other chemicals. For others, gardening is a profession: landscape gardeners design, install, and maintain gardens for a living. Unlike farmers, who typically produces large quantities of crops using complex equipment, such as tractors and combines, gardeners usually produce plants in smaller quantities, relying on manual tools, such as spades, rakes, and hoes, and small power tools, such as mowers and tillers.

See also: selecting plants; understanding soil; fertilizing; planting and transplanting; watering; controlling garden pests; harvesting and pruning

Cellophane

Cellophane, originally a trade name and now a common name for a flexible, transparent film made of regenerated cellulose and used principally as a wrapping material. Cellophane is produced by dissolving wood pulp or other cellulose material in an alkali with carbon disulfide, neutralizing the alkaline solvent with an acid, extruding the precipitate into a sheet, impregnating it with glycerine, and then drying and cutting the sheets to the desired size. Cellophane was invented about 1910 by the Swiss chemist Jacques Brandenberger, who in 1912 invented the first machines for large-scale production and established a factory near Paris.

Rayon

Rayon
Rayon, artificial textile material, composed of cellulose obtained from cotton linters or from the pulp of trees such as spruce.

Rayon can be made by either the viscose process or the cuprammonium process; both produce fiber classified by the U.S. Federal Trade Commission as rayon. In the viscose process purified cellulose is treated with sodium hydroxide, then with carbon disulfide, to form a viscous yellow liquid called viscose. In the cuprammonium process purified cellulose is treated with cuprammonium liquor, then with sodium hydroxide, to form viscose. The manufacture of rayon filaments—and all manufactured fibers—is done by means of an extrusion process called spinning. In this procedure the fiber-forming liquid is forced through tiny holes in a nozzle or spinneret into a liquid bath containing chemicals that produce filaments of pure cellulose, which can be spun into yarn. The filaments are drawn together to form both fibers and yarn in a single, continuous process.

Leaf mechanism

Leaf mechanism
When the stomata are open, carbon dioxide and oxygen pass either in or out—when carbon dioxide enters, it takes part in photosynthesis, the food-making process that releases oxygen as a waste product. This oxygen passes out of the leaf. At the same time, oxygen also enters the leaf, where it takes part in respiration, a process that forms carbon dioxide as a waste product. This carbon dioxide passes out through the stomata. Water also passes out of the open stomata in the form of a vapor. This process is called transpiration. Generally, there are more stomata on the under surface of a leaf than on the upper surface. This prevents water from evaporating too quickly or in excessive amounts from the leaf's upper side, which is exposed to the sun. Stomata close at night, providing another level of water conservation.

See leaf