COMPOSITION OF CURRENT AND PREVIOUS SEASON'S BRANCH GROWTH IN RELATION TO VEGETATIVE AND REPRODUCTIVE RESPONSES IN PYRUS MALUS L

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Abstract
The apple trees grown in metal cylinders were subjected to differential fertilizer treatments by application of different combinations of the pure salts NaNOa, CaH4(PO4) . H2O and K2SO4. The 5th season after planting samples of the season''s and previous season''s branch growth were taken periodically and analyzed. Glucose and sucrose decreased rapidly in all plants during the period of active growth and accumulated again when growth slowed down. The addition of N increased the amount of simpler sugars. The starch cycle in the wood lagged behind that of the bark. In relation to the different treatments the concentration of starch (and also of total available carbohydrates) followed the ascending series NPK < NP < NK < N < PK < P < Check. Storage of starch was intimately connected with cessation of active growth and appeared to be the cause of growth retardation in these experiments. The distribution of nitrogen throughout the cycle is similar to that previously found (Plant Physiology 2: 109-137; 245-271, 1927). The concentration of N in relation to the different treatments followed the descending series NPK > NP > NK > N > P > check. The concentration of N determined the utilization of accumulated starch. The C/N ratio under the conditions of this experiment proved to be the most sensitive index of physiological balance as determined by growth and blossom formation. The C/N ratio followed the descending series NPK > NP > NK > PK > N > P > check. A positive (and not a negative) correlation was found between the concentrations of K and N. Added N and potash increased the concentration of P. The starch/P2O5 and the available carbohydrate/P2O5 ratios indicate that P served as an accessory acceleration of respiration only when adequate supplies of N and K are present.