Cell size and cell number in Sturmer Pippin apple fruits from trees receiving different fertilizer treatments have been determined. N fruit contained larger cells than U, P, NP, or NPK fruit of the same weight (K = 2 lb sulphate of ammonia, P = 4 lb superphosphate, and K = 1 lb sulphate of potash per tree per year: U = no fertilizer). Fruit from the latter four treatments did not show any consistent differences in cell size. In fruit of the average size for each treatment, differences in cell number per fruit were present,, N fruit containing fewer and larger cells than fruit from all other treatments. Cell number of NPK fruit was greater than that of U fruit. Mean cell volumes for fruit from the various treatments were significantly correlated with the incidences of internal breakdown in storage in each of three years. IS fruit of varieties Cox's Orange Pippin and Dunn's Favourite contained larger cells than U or SPK fruit of the same size. Delicious SPK fruit contained smaller cells than U or IS fruit), the cell sizes of which did not differ.

The respiration rates and tissue contents of nitrogen, phosphorus, and titratable acidity were determined for apple fruit from trees receiving differential fertilizer treatments U, N, P, NP, and NPK (U, no fertilizer; N, 2 lb ammonium sulphate; P, 4 1b superphosphate; and K, 1 Ib potassium sulphate, per tree per year). The results obtained (expressed on a dry weight basis) are summarized as follows: Respiration rate: N > NP = NPK = U > P. Total nitrogen content: NPK > NP = N > U = P. Ethanol-insoluble nitrogen content: NPK = NP = N > U = P. Ethanol-soluble nitrogen content: NPK > NP = N > U = P. Phosphorus content : P > NP = NPK > U > N. Titratable acidity content: NPK > N > NP = U > P. The incidence of internal breakdown in stored fruit from these treatments has positively correlated with respiration rate per cell and negatively correlated with phosphorus content. Phosphorus content was negatively correlated with cell volume and respiration rate. Mechanisms by which phosphorus content might regulate the incidence of internal breakdown are discussed.

The contents of total phosphorus, ethanol-soluble phosphorus, ethanol-insoluble phosphorus, magnesium, calcium, and potassium were determined in tissue of apple fruits from trees receiving no fertiliser (U) and from trees receiving the fertiliser treatments N, P, NP, and NPK (N=2Ib sulphate of ammonia, P=41b superphosphate, and K=llb sulphate of potash per tree per year). In comparison with tissue from U fruit, tissue from P fruit possessed higher total, ethanol-soluble, and ethanol-insoluble phosphorus contents and a slightly lower potassium content. Treatment N resulted in increased levels of calcium and potassium but a markedly reduced phosphorus content. Calcium, magnesium, and phosphorus levels were elevated as a result of treatments NP and NPK; the latter treatment also resulted in a higher potassium content. Incidence of internal breakdown was negatively correlated with total and ethanol-soluble phosphorus contents, but not with the contents of magnesium, calcium, or potassium.