Young Apples Research Articles

The Relation of Thrips to Pansy Spot on Apples

AbstractPansy spot, a discoloration of the skin of McIntosh and Spartan apples, was shown to be a reaction of the apples to the egg punctures of thrips. Periodic sampling of apple blossoms and native hosts associated with apple orchards showed that Frankliniella occidentalis (Pergande) was the dominant species. The adult thrips moved from host to host as each came into flower, and apples were but one of several hosts attacked during the early spring.The thrips were most numerous in apple blossoms during the bloom period, and oviposited in the flower parts. The adult thrips left the apples after the bloom period, and the nymphs that hatched from the eggs developed in the calyx end of the young fruit. When the nymphs matured they oviposited in the young apple before leaving for other hosts. The area of apple skin surrounding the thrips egg developed the typical pansy spot symptoms. Other apple varieties were also attacked, but did not develop pansy spots.It was evident that the best time to apply control measures was at the petal fall period, when nymphal thrips were present but before damage was caused to the young apples.

Electron microscopy of ribosomes isolated from young green fruit of the apple tree

Many studies have been made on ribosomes both in plant and animal material, on account of their importance in the proteosynthesis of protein. In plant material, studies have been made on the pea by Ts'o andBonner (1956), Ts'o,Bonner andVinograd (1958),Setterfield et al. (1960) andSisakyan et al. (1963). Ribosome from spinach were investigated byLyttleton (1962) andMurakami (1963) and fromClivia byMikulska et al. (1962). As part of a wider study of the mechanism of biosynthesis of nucleic acids in apple trees, we isolated ribosomes from the young green fruit and studied them by means of electron microscopy. Young apples were selected because cell division is very intense at this stage of growth of the apple.

Quinic and shikimic acids in fruits

There are relatively large amounts of quinic acid in young apples and small amounts of shikimic acid in senescent apples. The possible significance of these acids in the biosynthesis of the aromatic ring is discussed. The widespread occurrence of varying amounts of these acids in edible fruits (pears, gooseberries, blackberries, strawberries, cherries, bananas) and in tanning extracts is described and the origin of these alicyclic acids is considered.

The Oxidation of Quinic Acid

SUMMARY 1. It is shown by means of filter-paper chromatograms prepared at intervals during the oxidation of quinic acid by hydrogen peroxide that at least six acids appear in the reaction liquid. 2. One of these acids is shown to be citric acid, and the oxidation of citric acid is shown to account for a further two of the acids resulting from the oxidation of quinic acid. 3. After prolonged oxidation (by H2O2) of both quinic and citric acids one acid predominates. This acid is proved by isolation and characterization to be malonic acid. 4. Evidence is produced which suggests that acetonedicarboxylic acid is an intermediate in the oxidation of citric acid (and, therefore, of quinic acid) to malonic acid. IN the course of the isolation and identification of quinic acid from the young fruits of the Worcester Pearmain apple, filter-paper chromatograms were run at intervals during the oxidation of the quinic acid with hot H2O2 (Hulme, 1951). These chromatograms showed that, while the reaction as a whole is a complex one involving at least six acids in addition to the original quinic acid, two acids emerged as the main products of the reaction. One of these was found to be citric acid, which was the acid obtained by Fischer and Dangschat (1934) on oxidation of quinic acid by periodic acid followed by bromine water. The work described in the present paper was carried out primarily to identify the second acid. The results also illustrate the value of paper chromatography in following the course of a complex series of reactions. The large amount of quinic acid present in young apples—recent work has shown that young Worcester Pearmain apples (average weight 15 g.) contain rather more quinic than malic acid—poses the question of its function in the metabolism of the fruit as indeed in other plant tissues where it is known to exist. For this reason a more complete knowledge of its chemistry is desirable than at present exists. Small-scale oxidations (~ 20 mg. quinic acid and 1 ml. 100 vol. H2O2) yield, as oxidation proceeds, chromatograms having the patterns shown in Fig. 1. Fig. 2 (upper portion) is a photograph of a chromatogram taken after 25-30 hours' oxidation in the large-scale preparative experiment to be described later; it is included to show the streaking effect produced by the continuous state of flux of the system. Although it does not follow that the acid-reacting spots on the chromatogram represent a sequence of events commencing at the acid of lowest RF—during

Effect of a Temperature Gradient on Distribution of Water in Apples

1. Mature apples (variety Wealthy) exposed to a temperature gradient show a fairly rapid rate of water movement across the fruit (from the warmer to the cooler side) for the first 3 days and then a slower rate of movement. Gradient treatment of apples caused significant amounts of water to move across the fruits in less than 48 hours. 2. After a 31/2 day gradient treatment plugs from mature apples showed a greater percentage of water in the middle, next highest on the cool side, and lowest on the warm side. The controls also showed a higher percentage of water in the middle. 3. After 3 days of treatment a small but measurable difference in percentage of water was found between the warm and cooler sides of young (1-17/8 inch diameter) apples. 4. Mature apples subjected to alternating 12-hour gradient and nongradient treatments showed water movement from the warmer to the cooler sides. 5. Wealthy apples on the tree, during a sunny summer day, showed a maximum temperature gradient of 9.7⚬ C. between the sunny and the shaded sides.

Hormones and Fruit-Fall

THE year 1939 marked the publication by F. E. Gardner, P. C. Marth and L. P. Batjer of their important discovery that the spraying of synthetic growth-substances on young apples prevented the natural shedding of fruit, which often reduced the crop quite substantially. These findings have been confirmed and expanded by many workers, and Dr. M. C. Vyvyan, of East Mailing, has summarized the large amount' of research which has been done on the subject*.