Josef Gottlieb Köhlreuter

views updated

Josef Gottlieb Köhlreuter


German Botanist

Josef Gottlieb Köhlreuter was a German botanist who, in the mid-eighteenth century, made a number of extremely important discoveries about plant genetics and reproduction. His work in many ways foreshadowed that of Gregor Mendel (1822-1884) and helped to establish that plants, like animals, could be thought of as having two distinct sexes. He also made important progress in developing plant hybrids, and studied plant pollinization.

Köhlreuter was born in the city of Sulz in 1733. Educated at the universities of Berlin and Leipzig, he earned a degree in medicine from the latter. He was not, however, to make his reputation as a physician but, rather, as a botanist.

Beginning in 1761, Köhlreuter published a number of landmark papers on plant breeding that, unfortunately, were to go unrecognized until many years after his death. In his first papers, he reported the existence of sex in plants, noting that, like animals, plants have distinct sex organs that can be considered male and female. This was important because it helped show a link between reproduction in all forms of life, demonstrating that the gap between plants and animals was not too great after all.

In this context, it must be remembered that sexual reproduction simply means that two "parents" combine genetic information to form offspring. It is this combination of genes in a random fashion that gives such diversity to life. This is how, for example, a child can have some characteristics from her mother, some from her father, can resemble her aunt in other respects, and be completely unlike any relative in still other factors. This mixing of genes also helps species to evolve since it guarantees that every individual will be genetically unique.

Later in his career, Köhlreuter continued his work with plants by showing that plants could be artificially fertilized and by creating fertile hybrids between different species of plants. Both of these were important discoveries, and both are in common use in modern agriculture. In fact, some commercial crops are fertilized almost exclusively artificially, and hybridization is one of the more important tools used by horticulturists and plant breeders to develop plants with a combination of traits to make them more nutritious, hardier, more aesthetically pleasing, and so forth.

Köhlreuter was also the first to realize the importance of insects and the wind in helping plants pollinate. This realization followed almost directly his understanding of the existence of sexes in plants, and led him to the realization that plant pollen carried the genetic information from a male plant to the female. All of this helped to not only increase knowledge about genetics, but it also helped farmers and horticulturists develop new plants in a scientific manner, rather than by simple hit-or-miss. Also, by realizing how pollination normally takes place, Köhlreuter was able to use this knowledge to help make more consistent hybrids. For example, by placing a bag over a particular plant, he could keep it from being fertilized by insects or the wind. He could then collect pollen from a specific plant with desirable traits and spread this pollen on the plant he had isolated. The seeds, then, would have only the pollen from a known plant with known characteristics, and the plants they produced could be studied. By doing this with many plants over many years, he was able to better determine how certain traits were transferred from plant to plant, as well as selectively breeding plants with specific desired traits. This same method of plant breeding continues to be used today, with a high degree of success.