Flowering was induced in the sweetpotato cultivar, ‘Allgold’, by growing plants with a N level of 280 mg/1 in a peat moss-perlite medium. Plants grown with other factorial combinations of N and K failed to flower. Analyses of plants from treatment N2K0 prior to and after flowering showed these plants to contain the highest percentage of N, the lowest total sugars, and the lowest starch in both tops and roots as compared with plants that failed to flower.
The levels of total free amino acids, arginine, aspartic acid, glutamic acid, serine and protein were determined in the roots of apple plants grafted with (a) rootstocks of MM 111, MM 106 or EM IX or (b) rootstock MM 111 plus interstems 1, 3, 5, or 7 inches long of ‘Red Delicious’ (RD), MM 106 or EM IX; all scions were RD. The levels of free amino acids and protein in the rootstocks were not related to their dwarfing effect. The level of free amino acids was very low in MM 106. The levels of free amino acids in the roots of plants with MM 106 interstem increased as the interstem was increased in length. Plants with EM IX interstem had high and nearly equal levels of free amino acids in the roots when the interstem was 3, 5, or 7 inches long, but there was a much lower level in the roots of plants with a 1-inch interstem. The levels of protein in the roots of plants with MM 106 or EM IX interstem showed smaller differences but followed the same pattern as that of free amino acids. Among control plants free amino acids and protein were lower in roots of plants with 2 grafts than in those with 1 graft, and free amino acids were lower in the roots of those with 5- and 7-inch interstems than in those with 1- and 3-inch interstems. The levels of individual amino acids were variable, but the levels of aspartic acid and serine followed a pattern similar to that of total free amino acids.
Comparisons were made of MM.111, MM.106 and EM.IX as rootstocks and ‘Red Delicious’ (RD), MM.106 and EM.IX as 1-, 3-, 5- and 7-inch interstems. The dwarfing effects of the rootstocks were greater than those of the interstems. Interstems reduced the growth of most plant parts in direct proportion to the degree of dwarfing of the interstem and there were few significant differences among plants with different interstem lengths. However, plants with interstems of 1 and 3 inches had higher percentage increases in root weight than those with 5 and 7 inch interstems. Plants with EM.IX interstems showed similar patterns of total plant, leaf and new growth weights. Weight increases of RD interstems were lower than those of MM. 106 and EM.IX interstems. The EM.IX rootstock weights were 101 percent of the weights of the plant tops, whereas rootstock weights were approximately 50 percent of the weights of plant tops for all other treatments.
Leaves, shoots and flower buds of 3 peach cultivars differing in cold hardiness were compared biochemically throughout the year. The analyses included starch, reducing and total sugars, total protein, and total and individual amino acids, (a) Starch in leaves and shoots was low in early spring, but increased to peak concentrations in fall. Flower buds were devoid of starch, (b) Reducing and total sugars in leaves and shoots were high in early spring and decreased to a minimum in fall, but increased to a maximum in the shoots during winter. In flower buds reducing and total sugars were relatively high during winter and increased to peak concentrations in early spring, (c) Protein in leaves was high in spring but decreased to a minimum in summer, then steadily increased to a peak concentration in fall. A similar but less pronounced trend occurred in shoots. In flower buds a steady increase in protein occurred during dormancy and reached a maximum in early spring, (d) Total free amino acids in leaves was high in the spring, but decreased rapidly to a minimum in the fall. In shoots the level was relatively high in the spring, decreased in early summer, but increased to a maximum in late summer, then gradually leveled off during the fall and winter. In flower buds the level was relatively high in winter, but increased rapidly in early spring.
Some correlation existed between the levels of the biochemical constituents and the degree of hardiness in the 3 peach cultivars.
Levels of soluble sugars in bark, leaves, leaf buds and flower buds of 2 cultivars of peach (Prunus persica (L.) Batsch) differing in cold hardiness were compared throughout the year. Thirteen sugars — galactose, glucose, fructose, xylose, stachyose, sucrose, raffinose, rhamnose, maltose, trehalose, arabinose, ribose and mannose — were present in measurable and variable concentrations. In general, oligosaccharides accumulated, particularly in the bark, during fall and winter, whereas monosaccharides accumulated during periods of active growth. These data do not show significant differences between the 2 cultivars regarding the accumulation of these sugars and cold hardiness.
Fruit buds of 5 peach cultivars—‘New’, ‘Daroga’, ‘Redskin’, ‘Mayflower’, and ‘Loring’—grown in Kentucky and exhibiting varying degrees of cold hardiness, were compared biochemically. Fruit bud analysis for total and reducing sugars, starch, total protein, and total and individual free amino acids indicate some correlation between the degree of hardiness and the biochemical make-up of these cultivars. Generally, a high sugar and protein content, and a low total free amino acids were associated with increase in hardiness. Specifically, significant correlation was found between hardiness and a high sugar and protein content when buds were frozen at −2½° F. Significant correlation was also found between 2 amino acids (arginine and γ-NH2 butyric) and hardiness at both −2½° and −5°.