The Utilization of Carbohydrate and Nitrogen Reserves in the Spring Growth of Lilac

The spring flush of growth and the utilization of reserve materials in this growth was studied in lilac plants 0, 2, 4 and 6 weeks after bud break. The influence of nitrogen applied the previous season on the storage and utilization of carbohydrate and nitrogen reserves was determined. The plants were separated into buds, stems and roots and analyzed for changes in total available carbohydrates, sugars, hemi-celluloses, total nitrogen, basic and non-basic amino acids and organic acids. The bulk of the carbohydrate reserves occurred as soluble sugars in the roots, although the reserves of sugars and hemicellulose in the stem was important during the first two weeks after bud break. The bulk of the nitrogen reserves were stored as non-basic amino acids in the stems and roots. However, the roots of plants grown under high nitrogen levels contained twice us much total nitrogen as roots grown under low nitrogen. This additional nitrogen which was stored in the roots of high nitrogen plants was released as arginine. The dry weight of buds increased 3–10 fold during the initial two week period and during the next four weeks doubled again. This bud growth was correlated with the stored nitrogen reserves. The high nitrogen plants grew twice as much and utilized more of the reserve carbohydrates in spring growth than low nitrogen plants. Carbohydrates were synthesized in this new growth and the high nitrogen plants utilized this carbohydrate for additional growth while low nitrogen plants transported it to the stems and roots.