Effect of Indoleacetic Acid on Thin Sections and Detached Segments of the Second Internode of the Bean

Abstract

1. Detached segments and thin sections of the second internode of the bean, smeared apically with indoleacetic acid in lanolin and placed with the basal ends in contact with a complete nutrient, respond in essentially the same way as similarly treated stems on the plant. In addition to apical swelling and root formation, the detached segments enlarge and produce roots at the bases. 2. When treated basally and placed with the apical end on the nutrient, only the basal end enlarges. When treated apically and placed apical end on the nutrient, only the apical end enlarges. 3. Treated segments or sections placed on White's nutrient lacking either sugar or nitrogen show no enlargement. 4. Segments placed with either the apical or basal end on nutrient to which 0.1 per cent of aqueous indoleacetic was added enlarge only at the end in contact with the nutrient. 5. The movement of the indoleacetic acid, or some derivative from it, takes place almost entirely in a basipetal direction with little acropetal movement. 6. When indoleacetic acid is applied to detached segments or thin sections in contact with a complete nutrient, there is digestion of the starch present, abundant growth and proliferation, and a direct absorption of foods and nutrients which are mobilized to the region of application and used in the development of additional cells and tissues. The cellular changes and responses in the detached segments and thin sections are similar to those which take place in intact treated second internodes.