The Cuticles of Cox’s Orange Pippin Apples from a Manurial Trial

The cuticles of fully-grown Cox fruits from a manurial trial were examined quantitatively. No differences attributable to fertilizer treatment were found in the weights of the cuticles per unit area of surface nor in their major components. This implies that the variations in susceptibility of fruits to storage rots that have been associated with nutritional differences in the manurial trial are not determined by variations in cuticle thickness or composition.     

The Effect of Conditions of Storage on the Respiration of Apples: III. The Effect of Modulation of Temperature on the Respiration of Cox’s Orange Pippin Apples,and on the Extent of Low Temperature Injury

When apples which develop low temperature breakdown (LTB) at 32° F. are moved from 32° F. to 65° F. for 3 to 5 days at about the 7th to 8th week of storage, they subsequently develop within a given period of storage less LTB than apples kept at 32° F. continuously.

The respiration of apples susceptible to LTB increases steadily during storage at 32° F. If these apples are warmed to 65° F. during the period of exposure to 32° F., the subsequent rate of respiration at 32° F. is lower than before warming, and continues at a lower rate than for apples kept at 32° F. continuously.

If the apples are moved to 38° F., without an intermediate treatment at 65° F., the rate of respiration is higher than for apples at 38° F. continuously, and this higher rate persists.

If there is an intermediate wanning period at 65° F., the respiration of apples moved from 32° to 38° F. is of the same order as that for apples kept at 38° F. continuously.

The respiratory quotient of apples at 32° F. or at 38° F., which is indicative of the type of respiratory activity, is typical for the temperature at which it is measured, and is not affected by the warming treatment. The effects of wanning on both the incidence of LTB and respiration are similar for apples stored in air and in 2% oxygen: 98% nitrogen.     

The Effects of Fruit Thinning on the Development of Cox’s Orange Pippin Apples in Relation to the Incidence of Storage Disorders

Severe hand thinning of fruitlets on Cox’s Orange Pippin trees five weeks after full blossom led to a doubling of fruit weight by harvest. Although the rate of cell division was stimulated slightly, the larger fruit size was due mainly to an increased rate of cell enlargement.

The respiration rate of whole fruits was slightly higher after thinning and the onset of the climacteric rise was advanced. Respiration per cell was correspondingly higher in the larger cells of the thinned fruit and respiration per unit protein was similar to that of fruit from unthinned trees.

Potassium, magnesium, and phosphorus contents, expressed on a fresh weight basis, were higher in the cortical tissue of the thinned fruits. Calcium per unit fresh weight was unaffected by thinning and the ratio of calcium to cell surface remained relatively constant throughout development in both types of fruit.

Senescent breakdown and bitter pit developed during storage only in the thinned fruit. Slight differences in the incidence of rotting and low temperature breakdown between the two types of fruit are attributed to the effects of maturity rather than of fruit size.     

Fruit-Thinning Effects on the Development and Storage Quality of Cox’s Orange Pippin Apple Fruits

Fruit-thinning treatments were applied in the three seasons 1963–65 to Cox trees to investigate the relationships between leaf : fruit ratio, fruit size, cell volume and cell number, and the incidence of rotting and disorders following air storage at 2·8° C. (37° F.) and o° C. (32° F.). Progressively more severe thinning was required, sis fruit development proceeded, to obtain a similar increase in fruit size. This declining response to thinning was accompanied by a progressively smaller increase in the cell numbers of fruits as the treatments were delayed. Thinning also caused an increase in cell-enlargement rate but the magnitude of the response varied between different experiments and did not appear to be related to the developmental stage at which the treatment was applied.

The larger fruits from thinned trees were more susceptible to bitter pit, breakdown, and rotting caused by Gloeosporium perennans, but were less susceptible to low-temperature injury than fruits from unthinned trees. Bitter-pit incidence was related to fruit size within each treatment and was more severe in fruit where the ratio between the potassium and calcium concentrations was high. Low-temperature injury was associated with fruit with low dry matter and potassium contents. Susceptibility to this disorder and to rotting was also influenced by fruit maturity as measured by the progress of the climacteric rise in respiration rate. There were no marked relationships between storage disorders and the numbers or size of cells in fruits produced by the various treatments included in these experiments.     

Routine Versus Post-Infection Sprays Against Apple Scab on Cox’s Orange Pippin

Routine sprays applied at regular intervals against apple scab on open-centred bush Cox’s Orange Pippin trees on M.IX rootstock were compared with curative sprays promptly applied after infection periods, as defined in terms of the Mills chart from instrument readings. A total saving of ten applications resulted from curative treatment over seven consecutive seasons. Routine interpretation of instrument data failed in only one marginal instance to detect an infection period, which arose from discontinuous wetting, but thereby jeopardized curative control in one season (1963).

With the one exception, both methods gave a high degree of scab control every year, although infection on the unsprayed controls was often severe. Some spray damage occurred in the form of reduced cropping or fruit russeting, particularly from phenylmercury chloride and didecyldimethyl-ammonium bromide as curative sprays, and from lime-sulphur applied post-blossom, either curatively or as routine. Captan with DNOPC (“dinocap”), however, gave superior crops showing relatively light russeting, and dodine acetate proved generally safe.

Although curative spraying proved generally successful on these relatively small, open trees, its exclusive use on an extensive scale is problematic. A feasible compromise is to reinforce a basic routine with curative sprays when desirable.     

Evidence of Clonal Variation and Latent Virus Effect on the Vigour of Cox’s Orange Pippin Apple Trees on M.9 Rootstocks

Apple trees on M.9 EMLA rootstocks free from known virus are at least 50% larger than those on M.9a containing latent virus. Evidence is presented that about half of this difference can be attributed to clonal variation and the rest to virus effects.     

Apple Rootstock Studies: Thirty-Five Years’ Results with Cox’s orange Pippin on Clonal Rootstocks

With the aim of obtaining information about light and temperature relationships during the early weeks of growth of young tomato plants, measurements of the weekly dry weight increments were made with plants up to six weeks old. Growth took place in natural light conditions during a number of winter periods (October to March). The daily light-time integrals (foot candle hours) were recorded throughout the investigation. In three experiments, each extending over a whole winter period, plants were grown at one-day temperature, but at three levels of night temperature, namely (a) 4° F. lower than the day, (6) equal with the day, and (c) 4° F. higher than the day. The day temperature was 6o° F. (15 ? 5° C.), 64° F. (68°C.) and 68°F. (20°C.) respectively for the three experiments. The results are summarized as follows :

1. With each day temperature, growth rates were lowest when night temperature was lower than the day.

2. Comparison of the effects of the constant temperature regimes with the high night temperature regimes showed that with the day temperature at 60° F. the growth rate was generally higher when the night temperature was high. With higher day temperatures, however, this was not the case.

3. There was little evidence that over this temperature range the temperature inducing maximum growth was related either to the light conditions or to the age of the plant.

4. The response to night temperature was small by comparison with response to that of the day.

5. The results suggest that in winter highest growth rates will be achieved if the night temperature is not lower than 64° F. and the day not lower than 68° F.

The results of an experiment designed to evaluate the separate effects of day and night temperatures showed that, over the temperature range 6o° F. to 68° F., dry weight increased with the night temperature. However, a much larger increase resulted with a comparable temperature rise during the day. Stem length was unaffected by the level of the night temperature but increased markedly with the day temperature.

The periods from pricking-out to both initiation and anthesis of the first two inflorescences were recorded for plants growing at 6o° F., 64° F. and 68° F. The temperature effect on the period to initiation was small. The inverse relationship between temperature and the period to anthesis was especially marked in low light conditions.

The value of adjusting both the day and night temperatures in accordance with the day-to-day fluctuations of the natural light was assessed by comparison with other temperature regimes having the same mean over each 24 hours. In general, flowering and fruiting was earliest when the day and night temperatures were equal. No evidence was found to justify the technique of adjusting the temperature in accordance with the natural light.     

The effect of boron upon leaf development and growth of the apple cultivar ‘Cox’s Orange Pippin’

One-year-old ‘Cox’s Orange Pippin’ trees planted in pots in sand culture in the spring of 1970 were (during the growing seasons of 1970–72) watered with nutrient solutions containing 0, 0.12, 0.23, 1.2, 3.5 or 7.0 mg boron per litre.

With increasing boron supply, the boron concentration of the leaves increased, the growth of current year’s shoots and to some extent of other plant parts increased, and summer leaf-fall and the occurrence of necrotic leaf spots (‘Cox spots’) decreased. The percentage of healthy leaves was greatest when boron in leaf dry matter was about 30 ppm.

In 1972 the trees with highest boron supply suffered from incipient boron toxicity and increased incidence of ‘Cox disease’ flowering was delayed, and the percentage of dead buds was increased. In the latter part of the summer the leaves curled upwards, turned purple and became brittle.     

The Effect of Frequent Spraying with Calcium Nitrate Solutions on the Mineral Composition and the Occurrence of Bitter Pit of the Apple Cox’s Orange Pippin

In several commercial orchards the percentages of Ca and K in the leaves and fruit of the cultivar Cox’s Orange Pippin were determined at intervals during one or more years. The values for a series of untreated trees were continually compared with those of a comparable series of trees which were sprayed at about seven-day intervals with a Ca(NO₃)₂ solution. At the end of each experiment the fruit was placed in storage and later examined for the incidence of bitter pit.

The Ca contents of leaves and fruit and the quotient (K+Mg)/Ca in the leaves of untreated trees showed only a moderate relationship with the percentage of bitter pit. The K content of the fruit was more closely correlated, however.

The level above which much bitter pit was unlikely to occur was found to be approximately 7.5–8 mg Ca in a fruit of 140 g fresh weight.

The total amount of Ca in the untreated fruit increased in a rather regular and comparable fashion in the various experiments. The rate of increase was somewhat higher during the first period of development, until the fruit reached about 20–40 g in weight, than during its subsequent growth.

Spray treatments increased the Ca content of the leaves by 0.2–0.5% of the dry weight; a maximum of 4 mg Ca was added to the fruit, an increase of 47% on the basis of the amount already present. In general the Ca level increased progressively during the season with successive spray applications, and 9–15 sprays reduced bitter pit incidence to about 5%.

The permeability of the fruit tissue to ions diminished as a result of the sprays, and it is suggested that an increase in cell membrane permeability may be involved in the development of the disease.

For commercial orchards, more frequent sprays may need to be applied than are recommended at present to provide effective control of bitter pit.     

The effect of summer pruning and nitrogen on growth,cropping and storage quality of Cox’s Orange Pippin apple

Pruning in late summer was compared with winter pruning on mature 23-year-old spur pruned trees of Cox’s Orange Pippin on M.2 rootstock. Two nitrogen treatments were superimposed, namely a standard dressing of 126 units N (sulphate of ammonia) applied in March as compared with 288 units N (nitrate of soda) applied in mid-August at the time of summer pruning. Summer pruning reduced trunk girth increment, advanced blossom development, increased the amount of red colour on the fruits and drastically reduced the incidence of bitter pit in stored fruit. The treatments did not affect cropping. Nitrogen treatments had no overall effect upon the incidence of bitter pit, but in the first season, when bitter pit was most prevalent, high levels of N applied in August reduced the amount, a similar trend being recorded the following year.     

The Relation Between Time of Picking and Storage Disorders in Cox’s Orange Pippin Apple Fruits

In four successive seasons. Cox’s Orange Pippin apples were picked at weekly intervals and stored under various conditions to assess the effect of time of picking on wastage from different causes.

Mean fruit weight increased by up to 20% over the 6 to 10 weeks of the picking periods.

The maturity of the fruit when picked was assessed by following the respiration pattern of samples kept at 12°C.

The results for successive pickings of fruit kept at 37°-38° F. (2.8°-3 ·3° C.) (normal cold storage temperature for Cox) and all removed from store at the same time, showed more core flush in early-picked apples, and more senescent breakdown and rotting in late-picked apples. There was no sudden change in liability to any of these disorders which could be associated with any particular stage of maturity. There were no consistent effects of time of picking on the amount of bitter pit or on weight loss during storage.

Storage at 32° F. (o° C.) (below the recommended temperature for the storage of Cox’s Orange Pippin) resulted in low temperature breakdown. This disorder tended to be less severe in apples picked just before the climacteric rise in respiration rate.

It is concluded that, for any particular orchard, picking date should be based not only on maturity as judged by colour and size, but on the expected liability of the fruit to disorders, such as core flush and rotting due to Gloeosporium, and on the type and period of storage required.     

Effect of part-tree flower thinning on fruiting,vegetative growth and leaf photosynthesis in ‘Cox’s Orange Pippin’ apple

Flower clusters were removed at full bloom from ten year old ‘Cox’s Orange Pippin’ trees on M.9 rootstocks, over the whole tree, on alternate branches or on whole sides. Mean fruit weight per tree at harvest was linearly dependent on leaf area per fruit and on light interception per fruit, both relationships accounting for over 90% of the variance. These relationships did not differ between treatments, implying either a mobile pool of carbohydrate or photosynthetic adjustment within the tree to crop load. Measurements of leaf photosynthesis in July and September showed no statistically significant differences in photosynthetic rate of spur or extension shoot leaves on bearing or non-bearing branches. Although the treatments caused no overall effects on shoot growth or leaf area per tree, sides of trees without fruit had greater leaf area and shoot growth than did sides bearing fruit. Fruit mineral composition and percentage dry weight were not affected by treatment except where the treatments significantly altered fruit size. In the following spring, although the treatments did not affect the total number of flower buds produced, branches that were deflowered in the previous spring carried significantly more flower buds than did branches which had cropped.     

The long-term effects of pre-planting soil fumigation on the growth and cropping of cvs Laxton’s Fortune and Cox’s Orange Pippin on M.2 rootstock,planted on land affected with a replant disease of apple

Soil fumigation of land affected by apple replant disease, using chloropicrin at 281 1 ha^-1 before planting-out, caused increases in shoot numbers, trunk girth and of 35% in total crop accumulated over 10 years for cv Cox’s Orange Pippin on M.2 rootstock. Chloropicrin at 1121 ha^-1 gave rise to a smaller response, and DD at 5621 ha^-1 was ineffective. Cv Laxton’s Fortune on M.2 showed little response to any treatment.     

Prediction of storage quality of ‘Cox’s Orange Pippin’ apples from nutritional and meteorological data using multiple regression models selected by cross validation

Summary

An experiment was carried out over a six year period to relate the storage quality of ‘Cox’s Orange Pippin’ apples to the mineral composition of leaves, fruitlets and fruits and to the climatic conditions during development. The apples were sampled from 24 orchards over a wide geographic area. The extent to which physiological disorders, bitter pit and low temperature breakdown (LTB), and quality attributes, greenness and firmness, of stored fruit could be predicted either before or at harvest was determined. For each response variable, a short-list of up to 12 potential explanatory variables was selected from an initial set of up to 54 possible explanatory variables, using stepwise regression techniques. Predictive models were generated by selecting variables from the initial short-list using a cross validation technique. The average incidence of bitter pit in controlled atmosphere (CA) storage at 1.2% O2 (<1% CO₂) was 4% compared with 12% for similar samples stored in air. Predictive models accounted for up to 67% of the variance in bitter pit in air-stored fruit but the percentage was lower (39%) for fruit stored in CA. The concentrations of calcium and potassium in fruit were particularly important for predicting bitter pit in air-stored fruit but less so for fruit stored in CA where more explanatory variables were required for prediction. Fifty one per cent of the variance of LTB in fruit stored in CA was accounted for by a nine-variable model incorporating three climatic variables. A simple three-variable model (leaf nitrogen concentration, harvest firmness and fruit dry weight) accounted for 67% of the variance in ex-store firmness and the addition of other nutritional and climatic variables increased the percentage variance accounted for to 76%. Seventy-one per cent of the variance in the greenness of fruit after CA storage was accounted for by a six-variable model. The possible physiological significance of the explanatory variables in each model is discussed.     

Carbohydrate changes in flowers,leaves, shoots and spurs of ‘Cox’s Orange Pippin’ apple during flowering and fruit setting periods

Summary

Changes of carbohydrate concentrations in different parts of the flower and the surrounding tissues (leaves, spurs and shoots) were measured in apple (Malus pumila) in 1987 and 1988, during the periods of flowering and fruit setting, to investigate their importance for fruit setting. HPLC was used for soluble sugar and sorbitol analysis. Starch was hydrolysed to glucose enzymatically and glucose concentration was determined colorometrically to estimate starch concentrations. Soluble sugars plus sorbitol (the soluble pool) increased rapidly in all parts of the flower from bud burst until full bloom. In contrast, in the same period, starch concentrations decreased rapidly and reached about zero at full bloom in the storage organs (shoots and spurs), indicating starch conversion to sugars and their movement to the growing flowers. Sorbitol was the most abundant carbohydrate in all apple tissue measured, with the exception of sepals, in which glucose concentration was the highest from full bloom onwards. Sepals had much higher glucose and fructose concentrations than leaf laminae but much lower sorbitol concentrations. Although dry weight, soluble pool and starch concentrations and total soluble pool content increased in the receptacle after petal fall, sucrose concentrations and total sucrose content dramatically decreased. These results suggest a preferential mobilization and utilization of sucrose rather than sorbitol during the fruit setting period and probably an important role of sucrose metabolism in fruit setting.     

Effects of rate of establishment of storage conditions and ethylene removal on the storage performance of ‘Cox's Orange Pippin’ apples

The use of rapid establishment of temperature and CA storage conditions, as well as ethylene removal to reduce loss of firmness and ground colour, during storage of apples (Malus domestica Borkh, ‘Cox's Orange Pippin’) in <1% CO₂ + 1.25% O₂ at 3.5°C was investigated. Samples subjected to rapid establishment (RE) of storage conditions had a higher peel chlorophyll content after 5 months storage, but not after 8 months, than samples from containers where the conditions had been established at a rate typical of normal, well-maintained commercial stores (CR). RE samples were considered firmer than CR by a sensory panel in February but not in May, while penetrometer readings were the same on both occasions. RE samples which had additionally been subjected to a pre-harvest daminozide spray and ethylene removal during storage (LE) were firmer, had a higher peel chlorophyll content and, on the green parts of the surface, a lower Hunter “b” value in February than both CR and RE samples. The effects of LE on chlorophyll and ground colour were maintained until May, but in both February and May only the ground colour effect was maintained during a simulated marketing period of 14 days at 10°C in air following storage.     

The Minimization of Variability in Experiments on Apples Planted on the Site of A Previous Orchard: I. The Effect of Cultural Treatments Associated with Three Years’ Arable Cropping

Most of the frequency distributions of onion bulb weight throughout the growing period were found to be significantly and positively skewed. The positive skewness was significantly greater at high density than at low and increased significantly with time from sowing. A nomogram relating yield of various onion grade sizes to plant density was derived. For a particular cultivar grown in a known environment such a nomogram enables the plant density for optimum yield of a specified grade to be predicted.