Effect of Thallium on Growth of Tobacco Plants.

EFFECT OF THALLIUM ON GROWTH OF TOBACCO PLANTS IN view of the recent interest in thallium poisoningl' 2 the following preliminary report of the effect of this element on the growth of tobacco is given at this time. The previous papers3 dealing with the effects of this element report the death of the plant, but no mention appears to have been made as to its effects when present in smaller amounts than that causing death. In recent years an extensive search has been conducted as to the cause and the control of the so-called frenching disease of tobacco. Valleau and Johnson4 have reported that this disease is due to nitrogen deficiency, but our results have not substantiated their findings. In connection with a study of this disease trials were made of the toxicity of several of the heavy metals as possible causes of the trouble. Thallium in the form of the nitrate was included in this study and produced very decided effects on the growth of the tobacco plant. The element was applied in pot cultures at 35 and 75 p.p.m. based on the air dry weight of the soil after the plants had become established. Three typical sandy loam tobacco soils were used, two of which were held at two moisture contents. The severity of the effects of thallium differed to some extent in the different soils and was greater at the higher moisture contents. In many instances the stem was killed at the surface of the soil. This effect may have been due to the fact that the material was applied in solution and was not leached to any considerable extent from the surface layers. Thallium, when applied as the nitrate, was not leached from an inverted bell jar