Interrelation of Organic Materials in the Growth Substance Response

Intact tomato seedlings and cuttings in a mineral nutrient, kept in darkness during treatment, produced only a small response to the growth substances in 6 days. This was limited to slight enlargement of the cells and an increase in size of nuclei and nucleoli. 2. The reaction was almost completely inhibited when the leaves were removed. 3. Intact and defoliated cuttings cultured in sucrose in darkness produced the complete response obtained in plants in the light. Proliferations and root primordia were formed in abundance. Similar results were obtained with maltose, levulose, glucose, and lactose; mannitol was not effective. 4. Cuttings were left in the dark for 1-6 days before treatment. Those maintained on a sucrose nutrient showed no differences due to pretreatment, but those in the mineral nutrient alone showed progressively less response through the third day and none at all beyond that. 5. Cuttings treated with lanolin paste for 3 days while in the mineral solution were then transferred to the sucrose medium. Six days later, when harvested, the treated regions had proliferated and produced root primordia. The response was not so great, however, as in cuttings cultured in sucrose but not treated until the time the minus-sucrose plants were put into the sugar medium. 6. Bean cuttings in a mineral nutrient in the dark also showed decreased response to the growth substance and complete response when cultured in sucrose. 7. Galactose was toxic to both tomato and bean cuttings. 8. Tomato cuttings in a minus-nitrogen medium responded as vigorously to the growth substances as did those with nitrogen. Nitrogen-deficient plants and cuttings also proliferated and gave rise to root primordia. 9. The most obvious cytological change in response to the growth substances in both the bean and tomato was the great increase in size of the nucleolus. Under conditions of carbohydrate deficiency the nucleolus diminished in size and finally disappeared. No changes occurred in the nucleoli of plants cultured in a sugar medium in the absence of growth substances.