Plants With Desirable Traits example essay topic

Introduction I did my research on plant reproduction / breeding. What is PLANT REPRODUCTION / BREEDING How DO PLANTS REPRODUCE This information will be included in my report. I will tell you how many ways plants can reproduce. And I will give an example of each way of reproduction there is. Plant Reproduction Plant Reproduction is to make off springs. Plants reproduce two ways sexually and asexually.

Sexually means there are two sources and asexually means there is one source. Asexual plants reproduce by themselves. And sexual plants reproduce with another plant or source. A flower has 4 parts.

Sepals surround and protect the other parts of a developing flower before it opens. Petals make up the next whorl most animal pollinated flowers have brightly colored petals. The two innermost whorls of flower parts contain the reproductive structures. The male reproductive structures are stamens, each which consist of an anther and a filament.

An anther contains micro sporangia, which produce microspores that develop into pollen grains. A stalklike filament supports an anther. The innermost whorl contains the female reproductive structures, which are called carpels. One or more carpels fused together make up the structure called a pistil. The enlarged base of a pistil is called the ovary. A style, which is usually stalklike, rises from the ovary.

The tip of the style is called the stigma. Usually a stigma is sticky or has hairs, enabling it to trap pollen grains. Most species of flowering plants have flowers with both stamens and pistils. However, some species have flowers with only stamens (male flowers) or pistils (female flowers). Selection Individuals within a species vary widely in a number of characteristics.

Many of these traits ar heritable and can be passed on their progeny. In practicing selection, plant breeders choose plants with desirable traits for further propagation and discard plants that are inferior for that trait. By doing so, plant breeders can select and reselect for the trait through successive generations, shifting the population in the desired direction. Hybridization Hybridization involves crossing plants of different strains or types to join in the progeny the desirable traits of both parents. Undesirable traits also enter the combination, however, so hybridization is usually followed by several generations of selection. This allows breeders to discard undesirable plants, choosing for further propagation only those plants with the desired combination of traits.

Backcrossing is a common variation of hybridization. This technique is often used to transfer into a desirable variety a beneficial trait from an otherwise undesirable parent. First the hybrid between the two parents is made, then the hybrid is crossed with the desirable parent. The progeny from this backcrossing normally segregate widely, with individual plants showing a mixture of the characteristics of both parents. By continued backcrossing and selection the plant breeder concentrates the qualities desired, and, if all goes well, in six or seven generations the variety once again breeds true but now exhibits its new trait. Backcrossing is valuable for adding single gene characteristics to crop plants, particularly for resistance to specific insects and diseases.

When desirable characteristics are fully developed in a hybrid plant, and the plant can be propagated asexually by budding, grafting, or cloning, then no further selection is necessary. A hybrid apple, for example, is propagated by grafting, so all resultant plants are identical. Hybrids are often more vigorous than either parent. This phenomenon is called hybrid vigor and has been widely used by plant breeders to increase crop yield ers. Hybrid seeds have helped to double U.S. corn yields since the 1940's, and almost all the corn now grown in the United States and Europe is started annually from hybrid seed. Hybrid breeding has expanded in recent years, and hybrid varieties are now common in grain crops, vegetables, and many flower species.

Mutation Occasionally an individual plant shows an important change in one or more traits arising from a spontaneous mutatation. Usually a change in a single gene is involved. Most mutations are deleterious, bt occasionally one has a distinct advantage. The plant showing the mutation may be used directly as a variety, a common practice in apples and other fruits, or the new trait may be added to existing varieties through hybridization and backcrossing. Plant mutations caused by single-gene changes have found wide use in ornamentals, resulting in double-flowered forms, weeping stems, dwarfism or unusual. Mutations can be induced artificially by X rays or ultraviolet light.

Doubling the number of chromosomes is another plant-breeding technique that has been useful in improving some flower and crop plants, sometimes producing forms with increased vigor and with larger leaves, flowers, and fruits.

Bibliography

Lewis, Adele and Doris Killer. Fast - Track Careers for the 90's. Glenview, Illinois. NTC / Contemporary Publishing Company. 1999.
Mil more, Donna. "A Job In Finance More Than Math". Boston Globe. Internet source. web 32 - 34. Pearl stine, Norman. "Best Tech Stocks for 2001 and beyond".
MONEY. December 2000 Volume 29, Number 11.
58 - 71. Ring, Trudy. Careers in Finance. Illinois. NTC / Contemporary Publishing Group. 1999.
Steinberg, Jonathan. "The Ultimate Guide to Extreme Growth: Americas Fastest Growing Companies". Individual Investor. April 2001.
52, 53 & 60. Sumichrast, Michael. Opportunities in Financial Careers. Lincolnwood, Illinois. VG Career Horizons Publishing. 1998.