Plants of cocklebur were grown with a complete nutrient culture medium and in one lacking calcium. One-half of these plants were treated with alpha-naphthalene acetamide. 2. Symptoms of calcium deficiency, such as short upper internodes, downward cupping of the leaves, brown areas on the surface of the leaves and darkening of the margins, and drying of the stem tips, soon appeared on plants grown without calcium Treatment with alpha-naphthalene acetamide had only a slight effect on delaying symptoms of calcium deficiency at a temperature of 65⚬ F. At 75⚬ F., on the other hand, treatment of the plants with the acetamide greatly delayed the appearance of symptoms of calcium deficiency. At a temperature of 75⚬ F. plants grown without calcium were dry except for a few of the lower leaves after 46 days. Seventy-four days from the start of the treatment plants grown without calcium but treated with the acetamide first began to show slight symptoms of calcium deficiency. 3. The fourth internode of plants grown without calcium had smaller and thinner-walled cells at both 65⚬ F. and 75⚬ F. than the normal plants. When treated with alpha-naphthalene acetamide at 75⚬ F., the cells of calcium-deficient plants more nearly resembled those of the normal plants in size and degree of lignification, but at 65⚬ F. the treatment was less effective; some of the cells had collapsed, giving necrotic-appearing regions. Stems of plants given a complete nutrient and treated with the acetamide had an active cambium and a greater number of xylem elements than the controls. 4. Sections of the stems were incinerated. As compared with control sections those from calcium-deficient plants contained the least ash. Sections from calcium-deficient plants treated with alpha-naphthalene acetamide contained nearly as much ash as the controls and those from the complete nutrient culture plus the acetamide appeared to contain more than the controls.
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Β. Esther Struckmeyer (1949) studied this question.