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- Author or Editor: D. H. Dewey x
- Journal of the American Society for Horticultural Science x
Abstract
The disorder known as Jonathan spot commonly observed on ‘Jonathan’ apples actually consists of 2 spot types which must be distinguished in order to define the affecting factors and to resolve the confusing and contradictory evidence in the literature. The spots which occur in the epidermal tissues without definite relation to lenticels are considered as Jonathan spot. Those which occur directly around the lenticels are defined as lenticel spots.
Histologically, the epidermal tissues afflicted with Jonathan spot showed a significant radial compression of the collenchyma cells in the 4 to 7 subepidermal tiers; whereas, such modification was not always apparent in tissues affected with lenticel spot. For the latter, some degree of rupture of the epidermis and the 3 to 5 subepidermal collenchyma tiers was usually noted. Jonathan spot development was inhibited by high temperature (70°F). It was favored by delayed harvest, yet none was observed until the fruit was stored at low temperature for several months. Conversely, lenticel spot often was present at harvest time and its development was accelerated at high temperature and inhibited at low temperature. High relative humidity (90%) enhanced lenticel spot development, whereas, humidity level had no effect on Jonathan spot.
Abstract
Apple (Pyrus malus L.) seedlings or rooted layers growing in nutrient solution in the greenhouse were used to determine the role of xylem and phloem in the accumulation of Ca in the leaves. 45calcium accumulation increased with increasing rates of transpiration as measured by water losses. Girdling experiments demonstrated that the phloem was the primary route of translocation. Young leaves accumulated more 45ca than old leaves even though the water losses for plants bearing only young leaves or only old leaves were similar. 45calcium accumulation in mature leaves was decreased when the shoot tips were removed. Apparently, in young apple trees Ca moves primarily in the phloem, but leaks into the xylem at increasing reates in the younger stem and near the growing apex.
Abstract
Ca infiltration into the flesh of mature ‘Jonathan’ apples (Malus domestica Borkh.) from a postharvest dip was enhanced by increasing the CaCl2 concentration, decreasing the temperature and surface tension of the cooling solution, increasing the initial fruit temperature, and increasing the submersion duration. Increases of fruit Ca to levels normally adequate to control storage disorders were achieved by cooling fruit at 21°C for 10 minutes in 4% CaCl2 plus 0.1 % surfactant L-77 at -1°. The results suggest that hydrocooling apples with a refrigerated CaCl2 solution would offer a practical means of postharvest Ca enrichment.
Abstract
Dipping ‘Jonathan’ apples in CaCl 2 solution prior to storage greatly reduced the development of internal breakdown (IB) and retarded flesh softening during 19 weeks at 2.2°C plus 1 week at 23°C. Infiltration of fruit with sorbitol produced IB symptoms, whereas glucose caused a dissimilar browning coloration and sucrose yielded no visible damage. Infused Ca inhibited IB symptoms and browning, retarded respiration, reduced the metabolism of endogenous substrates, and increased the oxidation of exogenous substrates. The results suggest Ca inhibits IB by enhancing the uptake and compartmentation of substrates, particularly sorbitol.
Abstract
A continuous gas flow system is described which utilizes a paramagnetic O2 analyzer and an infra-red CO2 analyzer to automatically sample, analyze, and record respiratory gas exchange of plant material. The system monitors gas exchange of up to 96 plant samples sequentially, repeatedly, and over extended time periods.
Abstract
The production of CO2 by apple and pear fruit was measured during and after alternating 12-hr exposures to air and N2 atmospheres. Typical stimulation of CO2 evolution in the absence of O2 was observed. Five or more anaerobic cycles imparted a permanent reduction on the subsequent aerobic respiration rate. The differences between control respiration and aerobic CO2 evolution by fruit exposed to cyclic anaerobiosis indicated that the capacity for aerobic respiration was reduced by the early anaerobic cycles. Suppression of the anaerobic stimulation of CO2 production was observed after several cycles suggesting that the capacity for fermentation was accumulatively impaired. Subsequent measurements of physical characteristics showed that flesh softening and chlorophyll degradation, processes which generally coincide during ripening, were differentially affected by cyclic anaerobiosis. Apple scald was induced by anaerobiosis. Pear fruits subjected to anaerobic cycles or continuous anaerobiosis did not ripen during the 14-day poststorage period at 21°C.
Abstract
In a collaborative study at 5 North American locations, treatment with 12% CO2 and 3 to 5% O2 for 2 weeks at 0° to 3°C at the beginning of controlled atmosphere (CA) storage significantly delayed softening of ‘McIntosh’ apples (Malus domestica Borkh.). Softening was retarded further when treatment time and CO2 concentration were increased, and when fruit was harvested less mature. The effect was diminished by treatment at 0°, and was nullified by delayed treatment and slow cooling during treatment. Softening response to CO2 was not influenced by O2 concentration or storage humidification during treatment. CO2 treatment reduced the rates of CO2 and ethylene evolution from the fruit, even after 4 to 5 months of subsequent CA storage, but affected neither soluble solids nor titratable acidity of fruit after storage. When taste panelists could distinguish CO2-treated from nontreated CA apples, they preferred the treated fruit.
These beneficial results were usually accompanied by external CO2 injury, and occasionally by internal CO2 injury; 30 to 50% of the fruit were injured in some tests. Treatment in a non-humidified room reduced CO2 injury without also reducing treatment benefits. We conclude that for ‘McIntosh’, the potential for injury outweighs the benefits obtained from CO2 pre-treatment in CA storage.