On April 27, 1733, German botanist Joseph Gottlieb Kölreuter was born. Kölreuter was a German botanist who pioneered the study of plant fertilization, hybridization and was the first to detect self-incompatibility. He was an observer as well as a rigorous experimenter who used careful crossing experiments although he did not inquire into the nature of heritability.
Joseph Gottlieb Kölreuter was the son of an apothecary in Karlsruhe, Germany. From early age, Kölreuter collected local insects and began to study medicine at the University of Tübingen. There, Kölreuter studied under the physician and botanist Johann Georg Gmelin who was highly interested in floral biology and reprinted a work by Rudolf Jakob Camerarius. The latter is best known for first demonstrating sexual reproduction in plants.
When Johann Georg Gmelin died in 1755, Kölreuter took up his position and was appointed at the Imperial Academy of Sciences at St. Petersburg. As part of his work, Kölreuter curated the fish and coral collections, and from 1759 he also experimented on plant hybridization. In Karlsruhe, Kölreuter was professor of natural history and briefly director of the botanical garden at Baden.
In his research, Joseph Gottlieb Kölreuter followed the idea of the period of plants and nature personified by a Creator. Probbaly influenced by C. F. Wolff the works of Kölreuter believed in epigenetic influences. According to Kölreuter there had to be two uniform fluids, male and female semen which combined in the process of fertilization. He further believed that equal quantities of the male and female fluid were needed and he therefore examined how much pollen was needed in fertilization of a given number of seeds. Kölreuter examined the action of stigma fluid on pollen. described many plant species, and studied pollen and its transfer.
It is believed that Kölreuter conducted around 500 different hybridization experiments across 138 species and examined the pollen characteristics of over a 1000 plant species. In 1763, Kölreuter first documented male sterility, and he was the first to report self-incompatibility in Verbascum phoeniceum plants. Further, the botanist observed heterosis, that hybrids surpassed their parents.
While Joseph Gottlieb Kölreuter’s experiments included repetition and control to test if hybrids across species could be fertile, Buffon used the idea of sterility of crosses as a method of testing species from In one experiment he sat beside a flower from dawn to dusk and shooed away all insects to find that the flower remained unfertilized. In order to test the hypothesis by Jan Swammerdam that honey was nectar that underwent fermentation in the crop of a bee, Kölreuter collected nectar from many hundreds of orange trees and kept them in vials to evaporate and he reported that it thickened and tasted like honey with time. Then, Linnaeus through his student J. J. Hartmann reported the possibility of new “species” arising from hybridization but Kölreuter was skeptical of the results. Kölreuter then produced interspecific hybrids, hybrids showed male sterility. However, even though Kölreuter conducted a variety of repeated crossing experiments much in the manner of Gregor Mendel, he had no interest in examining the nature of heritability or the particulateness of heritable traits.
Joseph Gottlieb Kölreuter’s major scientific works were published as four reports between 1761 and 1766: Vorlaufige Nachricht von einigen das Geschlecht der Pflanzen betreffenden Versuchen und Beobachtungen, Fortsetzung, Zweyte Fortsetzung, and Dritte Fortsetzung. Many parts of Kölreuter’s work have not yet been completely translated into English.
At yovisto academic video search you can learn more about “The Roots of Plants” in a talk by Stefano Mancuso.
References and Further Reading:
-  Joseph Gottlieb Kölreuter at the Online Enzyclopedia Britannica
-  Joseph Gottlieb Kolreuter’s Contributions to Biology by Ernst Mayr
-  Comte de Buffon and his Histoire Naturelle, SciHi Blog
-  Jan Swammerdam – Microscopist, SciHi Blog
-  How a Cobbler became the ‘Princeps Botanicorum’ – Carl Linnaeus, SciHi Blog
-  Joseph Gottlieb Kölreuter at Wikidata