Levels of nonstructural carbohydrate in leaves and roots and some characteristics of chloroplasts after application of different amounts of nitrogen fertilizer to peach seedlings

The effects of different amounts of nitrogen, applied in the soil, on the a ccumulation of nonstructural carbohydrate in leaves and roots were determin ed as well as on some characteristics of chloroplasts in one-year-old peach trees (Prunus persica) grown in 500-ml pots. The amounts of nitrogen, appl ied as NH4 NO3, were as follows: 0 mg/pot (N - 0), 75 mg/pot (N - 75), 150 mg/pot (N - 150), 300 mg/pot (N - 300), and 600 mg/pot (N 600). The weights of stems and leaves and shoot length were greatest in N - 150 and N - 300 trees, whereas root weights were heaviest in N - 75 and N - 150 trees. Shoo t and root growth was significantly reduced in N - 0 and N - 600 trees. Lea f chlorophyll content (mu g cm(-2)), total soluble sugar (% dry weight), an d nitrogen content (% dry weight) of leaves and roots increased with increa sed application of nitrogen, whereas starch content of leaves was inversely proportional to the amount of nitrogen administered. The amount of sorbito l (% fresh weight) in leaves was proportional to the growth rate of the tre es. Chlorophyll was stained more heavily by 4', 6-diamidino-2-phenylindole in N - 600 leaves than in N - 0 leaves; the staining concentrated at the pe riphery of chloroplasts, indicating an accumulation of starch. The level of the enzyme, ribulose-bisphosphate carboxylase-oxygenase (RuBisCO), increas ed with increased applied nitrogen, reaching maximum at N - 300 and N - 600 . Total soluble sugar in roots was high in vigorous trees, where root starc h content was inversely proportional to root growth.