EFFECTS OF CARBON ARC LIGHT ON THE CHEMICAL COMPOSITION AND VEGETATIVE PROPAGATION OF TOMATO PLANTS GROWN WITH A LIMITED SUPPLY OF NITROGEN

When succulent plants growing under favorable conditions of light, temperature, and moisture, are deprived of nitrogenous fertilizer their chemical composition and growth habits generally change. These responses usually include an increase in the carbohydrate content, particularly in the case of the polysaccharides, followed by a decrease in moisture content and percentage of total nitrogen, which is especially noticeable in the soluble nitrogenous compounds (5, 8, 9). Vegetative growth is retarded, particularly in the above-ground portion, the new leaves produced are small and light green in color, and fruiting is often checked when the plants become stiff and woody. In propagating many varieties of plants vegetatively, cuttings often produce roots more quickly and grow more vigorously when taken from the "harder" portion of a plant or when made from a plant that exhibits the above characteristics. Typical symptoms of nitrogen deficiency and carbohydrate accumulation are not easily obtained in tomato plants by limiting the external nitrogen supply when they are grown during the dark cloudy periods of winter or early spring. This is due mainly to the small amount of carbohydrate synthesized under these conditions. Various changes in the growth and chemical composition of tomato plants occur when they are transferred from natural illumination of low intensity during the winter to artificial illumination from a carbon arc lamp of somewhat greater intensity and grown with a nitrogen-free nutrient. Root production by stem cuttings from tomato plants under such conditions are discussed.