ACCUMULATION OF FREE AMINO ACIDS AS A CHEMICAL BASIS FOR MORPHOLOGICAL SYMPTOMS IN TOBACCO MANIFESTING FRENCHING AND MINERAL DEFICIENCY SYMPTOMS

The chemical mechanism whereby plants respond to modifications in environment resulting in alterations in morphology has on the whole remained obscure. However, whatever the cause, it is clear that each change in environment may result in the appearance of a whole aggregate of symptoms characteristically specific for each condition. No change in environment can be said to cause only a single symptom. Though individual symptoms may to some extent resemble each other with various environmental variations, the aggregate of symptoms is usually characteristic of each particular environment and plant in question. The work discussed herein consists of studies on the chemical mechanism of symptom production in f renching and mineral deficiency of tobacco. The well defined aggregate of symptoms characteristic of these particular environments afford very favorable material for a study of the chemical mechanisms underlying morphological change. The condition of tobacco known as frenching is a well known deformity. Growth of the terminal bud of the plant slows or stops and the slowly ex-* panding new leaves develop a network type of chlorosis. In an extreme form the newly developed leaves become strap shaped because of the failure of the lamina to expand. Growth of axillary buds then starts but results only in the formation of similarly strapped leaves. Stem elongation whether of the main axis or of axillary branches is greatly inhibited in an extreme