Bernard, Noël

Bernard, Noël

(b. Paris, France, 13 March 1874; d. Mauroc [near Poitiers], France, 26 January 1911)

botany.

During his short but productive career, Noël Bernard shed much light on the nature of the endophyticfungi found in orchids and their importance to the plant. His active research covered a period of only eleven years, cut short by his untimely death at the age of thirty-six. Moreover, the majority of Bernard’s work was done before he received a university professorship. He began in 1899 as a demonstrator at the École Normale, and in 1902 moved to Caen as a lecturer. Six years later he was called to take charge of the course in botany at the Faculté des Sciences at Poitiers, and in 1909 he was named professor of botany there. He was to have been the director of the experimental botany research institute he was planning at Mauroc for the university, but he did not live to see it established.

When he began his work it had already been known for some time that orchids were mycorhizally infected plants. But it was Bernard, in a 1900 paper and his doctoral thesis of 1901, who determined that the relationship was obligatory; the presence of the fungus, he found, had become necessary for the germination of the seed. Since this infection was chronic and always present, the morphological features characteristic of many orchids, such as a tuberous root and atrophied vegetal organs, were actually fungus-induced symptoms. In analyzing the life cycles of several orchids, Bernard found differing degrees of fungal infection present. In some, such as, the Ophrydeae, periods of noninfection and, therefore, morphological elaboration alternated with periods of infection and tuberization of the roots. In others such as the Neottia, the plant is never free of the fungus, and its vegetal apparatus is reduced to no more than a rhizome.

Bernard’s experimental work began with the isolation in pure culture for the first time of the endophyte. From more than twenty different orchid species three new species of fungus were isolated: Rhizoctoniarepens, widespread among the Orchidaceae, and two more localized species, Rhizoctonia mucorides and Rhizoctonia lanuginosa. As a verification, he inoculated previously sterile orchid seeds with the fungus and, in 1904, brought about germination in this artificially produced symbiont, inducing tuber formation. On the basis of these results, he was able to advise horticulturists as to how to ensure the germination in hothouses of orchids, until that time a very uncertain, seemingly capricious event. By contaminating the soil with Rhizoctonia repens, he was able to improve greatly the growers’ success.

Bernard announced this successful method for the germination of orchids at the international congress of horticulture held in Paris in 1905, only to find that his results were not unanimously confirmed by other workers; This disappointment led him to a reexamination of his fungal cultures, and therefore to the discovery of the phenomenon of attenuation of the fungi after having been cultured for lengths of time in vitro.

Further investigations revealed the physiological mechanism of the “disease” caused by fungal infection. From experiments, Bernard concluded that the fungus converted starch into sugar, and it was the increased osmotic pressure that stimulated growth and germination. In apparent verification of this, he found that tuberization could be produced in theorchid Bletilla without infection if the orchid were placed in a medium of high carbohydrate concentration. Similar results were obtained with the germination of orchids that normally required the presence of a virulent fungus. (It was later shown that the essential function of the fungus was to convert complex carbohydrates to simple sugars, and not necessarily to provide increased osmotic pressure.)

These results corresponded closely with observations made early in his career on potato tuberization, which is also dependent on the concentration of the medium. He was involved in further work on the potato tuber at the time of his death.

BIBLIOGRAPHY

I. Original Works. Works by Bernard include “Surquelques germinations difficiles,” in Revue générale debotanique, 12 (1900), 108–120; “Études sur la tubérisation,“doctoral dissertation (Paris, 1901), also published ibid., 14 (1902), 5–24, 58–71, 101–119, 170–183, 219–234 (mispaginated 139–154), 269–279; “La germination des Orchidées,“in Comptes rendus de l’Académie des sciences, Paris, 137(1903). 483–485; “Recherches expérimentales sur les Orchidées,“in Revue générale de botanique, 16 (1904), 405–451, 458–476; “L’évolution dans la symbiose. Les Orchidée set leur champignons commensaux,’ Annales des sciences naturelles (Botanique), set, 9, 9 (1909), 1–196 (a large work treating many aspects of the problem): La Matière et la Vie (Paris, 1909). Many of Bernard’s later researches can be found in Principes de biologie végétale, edited after his death by Mme. M. L. Bernard (Paris, 1921).

II. Secondary Literature. The only substantial biographical reference to Bernard is a memoir written immediately after his death by a friend, C. Pérez, in La Revue du Mois, 11 (1911), 641–657. No bibliographical detail is provided, and none is available elsewhere in any complete form. A portrait of Bernard can be found in Boissonade etal., Histoire de l’Université de Poitiers Passé et Présent(1432–1932) (Poitiers, 1932), facing p.424.

Alan S. Kay