Kids Research Express

Aconite, common name for certain perennial herbs and for a preparation derived from them that was formerly used in medicine. More than 100 species belong to the aconite genus and are native to temperate regions of the northern hemisphere. Several species, including the helmet flower, a well-known European species, are cultivated as garden plants in the United States. The common aconites have fibrous or tuberous roots, mostly erect stems, and palmately divided or cleft leaves. The flowers in most species are blue or purple, although some species have yellow or white flowers. The outer, showy parts of the bilaterally symmetrical flower are five in number, and the uppermost is shaped like a large, downward-opening hood. Because of this hood, which immediately distinguishes aconite from larkspur, aconites are commonly called monkshood. They are also known as wolfsbane. Aconites contain highly active alkaloids, especially aconitine, and are poisonous to both humans and animals. The hel

Lichens are common food for insects and slugs. In the arctic tundra, reindeer and caribou rely on lichens during the winter, when no other food is available. Several species of lichens that sprout up through the snow are called reindeer mosses. Humans rarely eat lichens except in cases where no other food is available. The Bible may chronicle one such example: Some scholars believe that the manna or bread that the ancient Israelites ate in the desert when they fled Egypt was made of lichen. In Japan, where algae as well as fungi are prized foods, certain lichens are eaten as delicacies. Although lichens have been used in folk medicine as purported cures for many ills, from headaches and toothaches to tuberculosis , diabetes , and asthma , their use in modern medicine is recent. The discovery in the 1940s that some fungi produce potent antibiotics stimulated an extensive screening of fungi and lichens. Since then, lichen extracts have found limited use in Europe, where lichen a

Lichens lack roots, but they are usually firmly attached to the surfaces where they grow by hyphae. Lichens grow excruciatingly slowly, adding a few millimeters to their length or diameter in a year. The fastest growing varieties may add no more than 30 mm (1.2 in) to their length in a year. Lichens may have long life spans—a lichen found in West Greenland in the Arctic is more than 4,500 years old. Scientists have used the sizes of large specimens to estimate how long it has been since glaciers covered arctic and mountain areas.  During prolonged dry periods, lichens survive by retaining a small amount of water and reducing their growth and metabolic processes to the barest survival levels. After a rain, the fungal partner is able to soak up water like a sponge, absorbing two to three times its weight in water. A moist internal environment is critical for the alga, which needs water, along with carbon dioxide and sunlight, to manufacture food through photosynthesis. During dry pe

About 18,000 to 20,000 species of lichens have been identified. Scientists typically classify lichens based on the fungal partner, and the lichen name is the same as the scientific name of the fungal partner. By far the most common fungi found in lichens are sac fungi, or ascomycetes, which produce reproductive spores in special cells shaped like sacs. In about two dozen tropical lichens, the fungal component is a club fungus, or basidiomycete. The club fungi, which include common mushrooms and toadstools, produce their reproductive spores in special cells that are shaped like clubs.  The algal partner of a lichen is usually composed of green algae in the form of single cells or chains of cells. Green algae contain chlorophyll , the primary light-absorbing pigment necessary for photosynthesis. This pigment is housed in saclike structures called chloroplasts , the sites of photosynthesis. In some dark-colored, gelatinous lichens, cyanobacteria (also known as blue-green algae) are

Vegetative Reproduction, method by which plants reproduce asexually—that is, without the union of cells or nuclei of cells—thus producing individuals that are genetically identical to the parent. Vegetative reproduction takes place either by fragmentation or by special asexual structures. Parts of liverworts and mosses fragment from the parent and grow into new individuals, as do plant cuttings. Asexual structures in plants include specialized stems such as tubers, stolons (runners), rhizomes, and corms, and specialized buds such as bulbs. Roots and leaves can also give rise to new plants. Thus, new individuals generate, for example, from the eyes of potatoes, the cloves of garlic bulbs, and the stolons of strawberry plants. See also Plant ; Plant Propagation .

Some plants produce special underground stems such as tubers, bulbs, and corms that enable them to reproduce asexually. Like all stems, these structures have buds, or nodes, from which new stems branch. Tubers are swollen, fleshy stems with several buds called eyes that produce new plants; an example of a tuber is the potato. Bulbs, such as those found in onions, lilies, hyacinths, and tulips, are short, wide, teardrop-shaped underground stems surrounded by scaly leaves. Corms, such as crocuses and gladioli, are similar, but lack the scaly leaves. Both bulbs and corms make clumps of new bulbs or corms, called offsets, which can be divided and buried in the soil to generate new plants. Irises and ferns produce rhizomes, fleshy stems that grow horizontally beneath the soil, with new plants developing from the tip of the rhizome and from each node on the stem. Stolons, specialized stems found in strawberries and many lawn grasses, are similar to rhizomes but are usually thinner and grow

Also called micropropagation, tissue culture is the production of plants under sterile laboratory conditions. A variety of tissue culture techniques are used to propagate plants. In one method, growers remove a tiny piece of leaf or stem from a plant and place it in a sterile test tube on a gel-like medium enriched with hormones and nutrients. A yellow-brown mass of cells called callus develops from the piece of plant. Small chunks of the callus are separated, and each piece is placed in a petri dish with a hormone and nutrient mix that stimulates the development of the callus pieces into plants. The young plants are removed from the petri dish and placed in pots with soil, or into the ground, where they grow to maturity. Tissue culture enables researchers and growers to rapidly generate numerous clones year-round in greenhouses. In nature, strawberry plants typically produce their fruits in summer. Commercially grown strawberries, however, are propagated throughout the year by ti