Agronomie, Chimie et Botanique (1755-1805) en France: L'exemple des maladies des plantes : principe chimique ou plante microscopique parasite ?

International audienceThis paper deals with the development of interpretations of plants' diseases by analyzing early notions and texts describing these phenomena. The authors on agriculture are classified into three groups: the agronomists-magistrators, the agronomists-chemists, and the agronomists-botanists or agronomists-naturalists. During the "Ancien Régime" at first the "physiocratics" and magistrators interested mainly in technical, economical, social, and law's aspects tried to improve the productivity of French agriculture? Their approach to the life phenomena of useful plants was dominated by their ideas on the nature in general and the usefulness of agriculture. The plant, the corn grains and the flower were only stages of a big process including natural, economic, technical, and social aspects. The most important science supporting and furthering this process seemed to be chemistry. therefore, the agronomists of the 18th century emphasized the chemical processes in nature: the continuous movement of the elements composing living substances of plants by help of the ground and the water dropping from "the sky". The "economical chemistry" and the "chemical agriculture" were higher estimated than the botany treated in the Linnean style. At the same time some botanists thinking more in physiological categories refused to recognize the significance of chemical plant analyses with the methods of the years around 1800. They stated rightly that the "conditions" of life surrounding and affecting the plants like weather during the growing period or even during transports of the corn may effect significant modifications of the quality of plants' products