A comparative study of onion varieties in relation to bolting and yield when grown from sets

Two trials are described, each of twenty-five varieties tested during two seasons and the intervening winter storage period. Sets were produced from seed in the-first season and planted to produce mature bulbs in the second. In the second seasons of both trials, the effects of time of planting of sets were also investigated as part of a factorial experiment. In the later trial the effects of set size were also tested. Data are presented of varietal differences in bolting, yield, earliness and of behaviour of the sets in storage. The effects of set size and of late planting on these characteristics are also recorded. Some practical recommendations are made: thus, among those tested, varieties were found which bolted little and gave high yields when grown from sets, but it is emphasized that names of varieties as listed in seedmen's catalogues may not be reliable. Efforts are being made to maintain and improve by selection the most satisfactory of these strains. Late planting of sets is not recommended, for, although bolting was effectively controlled by this means, the yields were much reduced. Plants grown from large sets tended to bolt more than those from small, as has been shown by earlier workers; while on the contrary the yields from large and small sets were on the average alike. Comparing different varieties, the highest gross yields of all were produced from the large sets of non-bolting varieties; but for highest yields of bulbs free from flower stalks small sets should be used and this is advisable for all varieties. During storage the large sets lost less percentage weight than the small but they sprouted much more, and this is considered the more serious defect. The storage data demonstrate an additional disadvantage of late planting, for this involves longer storage and both sprouting and weight losses increase rapidly during late spring.     

Storage of 'Gloster 69' apples in the preclimacteric state for up to 200 days after harvest

'Gloster 69' apples are unusual because they do not accumulate ethylene during storage at 2 kPa O₂ at 1.5–3.5°C with continuous ethylene removal. Their ethylene physiology and the extent of various ripening processes in storage were investigated. Ethylene production and l-aminocyclopropane-l-carboxylic acid (ACC) remained low for up to 200 days, and both increased on transfer of fruit to 15°C. The increase in ACC could be stimulated by ethylene treatment of apples after storage. In spite of this evidence that fruit remained preclimacteric, some softening and production of soluble pectin and volatile esters occurred at 3.5°C. These processes were suppressed at 1.5°C, but chlorophyll, starch, malate and sucrose losses and increases in glucose and fructose occurred at both temperatures.     

Opposite effects of temperature on breaking of dormancy and on induction of frost resistance in apple embryos

Apples ( Pyrus mains L., ev. Golden Delicious) were placed at 0, 12 and 35°C. At different intervals, seeds were taken from fruits, and the ability of isolated embryos to germinate was determined. In parallel, the survival of similar embryos frozen for 30 min at -7°C was estimated. Storage of apples at 0°C led to complete removal of embryo dormancy within ca 10 weeks. At 12°C, dormancy was only partly eliminated, and at 35°C breaking of dormancy did not occur. The onset of secondary embryo dormancy was thus evident as the result of 35 and 12°C treatments. On the other hand, the storage of apples at 35°C was the most effective treatment for induction of frost resistance in the embryos. At 12°C the same level of frost resistance was reached much slower. Even a prolonged storage of apples at 0°C did not allow frost survival of all embryos. The above relations were confirmed in experiments with transfer of fruits from one temperature of storage to another. The temperature of fruit storage affected the dormancy removal in embryos and induction of resistance to rapid freezing in opposite directions.     

Effect of chilling and subsequent storage at 20°C on electrolyte leakage and phospholipid fatty acid composition of tomato pericarp

Mature green tomato fruit ( Lycopersicon esculentum cv. Caruso) were stored at 1°C or 20°C and analyzed on day 0, 18 and 22 for electrolyte leakage, ripening-associated changes in pigmentation and phospholipid fatty acid composition. Chilled fruit were also analyzed 4 days after they were returned to 20°C. Fruit did not ripen significantly during chilling and subsequent storage at 20°C, and showed visible chilling injury symptoms only at 20°C. Electrolyte leakage increased in control and chilled fruit, indicating enhanced membrane permeability during both ripening and chilling. Returning the fruit to ambient temperature gave an apparent decrease in electrolyte leakage. Phospholipid and linolenic acid content and double bond index decreased during ripening at 20°C. The small changes in phospholipid fatty acid composition during chilling cannot account for the enhanced membrane permeability. The significant decrease in percentage of linolenic acid and in double bond index in the total lipids, but not in the phospholipids, upon returning the fruit to 20°C suggests loss of galactolipid polyunsaturated fatty acids     

Effect of growth conditions and storage on the specific activity of β-lactamases of Bacteroides spp.

The influences of growth conditions and cold storage on the specific activity of β-lactamases of four strains of Bacteroides spp. was studied. Interbatch variation was observed in extracts prepared in an identical way on separate occasions but less variation was observed in extracts prepared from bacteria grown on Brain Heart Infusion agar supplemented with yeast extract, haemin and menadione, than in similar extracts of bacteria grown in broth or on other solid media. The loss of enzyme activity seen during the stationary phase of growth of some strains in broth was minimal during incubation for 48 h on agar. Storage of enzyme extracts at 4°C was associated with loss of enzyme activity, but activity was retained during storage at—70°C for up to 32 days. Freezing and thawing had little effect on enzyme activity.     

Effects of chilling on tomato fruit texture

The effects of chilling on tomato ( Lycopersicon esculentum Mill cv. Caruso) texture were investigated using fruit stored at 22°C (nonchilled) or 5°C (chilled) for 28 days. or at 5°C for 15 days before transfer to 22°C to facilitate ripening during and additional 13 days (prechilled). Prechilled fruit exhibited symptoms of slight chilling injury, i.e. development of mealiness, accelerated softening relative to that of nonchilled fruit and nonuniform surface colour development. The firmness of all fruit decreased during ripening and chilled storage when measured by flat plate compression and puncture, especially during the early stages of ripening of nonchilled and prechilled fruit. The compression firmness of pericarp tissue similarly decreased during ripening of nonchilled and prechilled fruit, but was maintained during chilling. Total moisture content (ca 94%) of tissue, uronide content (32-35% w/w) and extracted β-galactosidase activity did not differ significantly ( P > 0.05) among fruit during ripening and chilled storage. The degree of uronide methyl esterification in ethanol-insoluble solids prepared from pericarp tissue (EIS) was relatively low for all fruit. i.e. <40%. EIS from which greater levels of pectinesterase were extracted (i.e. nonchilled>chilled>prechilled) exhibited decreased levels of uronide methyl esterification. Markedly elevated levels of β-glucosidase activity were extracted from prechilled EIS. Total polygalacturonase activity (mainly as PGI) and autolysis of enzyme-extracted EIS were inversely correlated ( P ≤ 0.05) only with the loss of nonchilled fruit and tissue firmness and prechilled fruit firmness. Results suggest a possible role for β-glucosidase in textural changes of prechilled fruit and tissue (e.g. loss of firmness, development of mealiness) and also implicate loss of skin strength in the softening of whole fruit during chilling.     

Efficacy of high sodium chloride concentrations for the destruction of Listeria monocytogenes

The effect of sodium chloride concentrations (6, 16 and 26% (w/v) NaCl) on the survival of Listeria monocytogenes at low temperatures (10°C and under refrigeration, average 2°C) and frozen (- 18°C) was investigated. All salt concentrations tested were ineffective in reducing numbers over 6 h incubation at low temperatures. Over a longer time (33 d) at low temperatures, the organism grew in 6% NaCl, numbers remained the same in 16% NaCl and numbers declined in 26% NaCl. Although L. monocytogenes was destroyed in 26% NaCl, numbers declined too slowly for immersion in cold brine at this concentration to be a useful bacteriocidal treatment. Storage at - 18°C for 33 d caused no significant reduction in numbers at any of the NaCl concentrations tested.     

Chilling Injury,Physicochemical Properties,and Antioxidant Enzyme Activities of Red Pitahaya (<i>Hylocereus polyrhizus</i>) Fruits under Cold Storage Stress

Low-temperature storage is extensively used to optimize the postharvest life of various fresh fruits. However, red pitahaya (Hylocereus polyrhizus) fruits are sensitive to chilling injury (CI), which leads to the limitation of low-temperature storage. In this study, red pitahaya fruits were stored at 2, 4, 6, 8, and 10°C, respectively, for 27 days to determine the appropriate storage temperature. During the storage of red pitahaya fruits, storage at 8°C was more effective in suppressing decay and maintaining quality than other low temperatures. Low-temperature (2, 4, and 6°C) storage decreased weight loss (WL) and maintained higher content of titratable acidity (TA), soluble sugars (SS), and total phenolics (TP) but different degrees of CI were detected. No CI was observed at 8°C and 10°C. Red pitahay as stored at 8 and 10°C were associated with better color evaluation, lower electrolyte leakage (EL), respiration rate, and lipoxygenase (LOX) activity, and higher fruit firmness, superoxide dismutase (SOD) activity, and catalase (CAT) activity. However, higher storage temperature (10°C) resulted in higher metabolic activity leading to lower quality and antioxidant capacities compared with 8°C. Therefore, our results demonstrated that red pitahaya stored at 8°C exhibited a protective effect on fruit quality and resisted CI development during storage.     

Effect of fruit type and storage treatments on the biodeterioration of African pear (Dacryodes edulis (G. Don.) H. J. Lam.)

The storage potential of the African pear (Dacryodes edulis (G. Don.) H. J. Lam.) (Burseraceae) was investigated using four fruit types. At ambient temperatures (28·5–30°C), those enclosed in either paper or polythene bags could be stored satisfactorily for 3–8 days, after which they deteriorated rapidly. Storage life was increased at lower temperatures, but injury due to chilling was observed at −5°C. At 15°C, fruits dipped in palm oil before being packaged were of better quality and retained their firmness longer than fruits dipped in a 500 ppm benlate solution. Storage in moist sawdust, wood-shavings or water were the least effective in extending shelf-life. Variation among fruit types in their response to storage treatment was observed.     

Peroxidase: Changes in soluble and bound forms during maturation and ripening of apples

Peroxidase (POD) enzymes, both soluble and bound, have been implicated in the ripening process of a number of fruits. However, their roles are poorly understood. The aim of this study was to define clearly the classes of POD activity in apple parenchyma tissues on the basis of their solubility in salt solutions, to determine the subcellular localisation of ionically‐bound POD activity, and to determine whether soluble‐ or ionically‐bound POD activities exhibit any relationships with maturation and ripening. The cortical parenchyma of apples ( Malus domestica Borkh cv. Cox's orange pippin) was investigated for changes in POD activity during maturation and post‐harvest storage at 0, 4, and 8°C at 100% relative humidity (RH), and controlled atmosphere (CA) storage (4°C in 1.25% O₂ and 0.5% CO₂). The parenchyma cells contained both soluble and ionically‐bound POD activity. The ionically‐bound POD was located in the cell wall in the middle lamella, plasmodesmata and cell corners, and could be extracted quantitatively with 0.4 M CaCl₂ at neutral pH to leave a POD‐free residue. During maturation, both forms of activity increased on a 'per apple' basis, but decreased as a function of fresh weight. Under all conditions of storage, soluble POD exhibited a peak of activity at approximately the mid‐point of ripening‐related softening; this event may constitute a biochemical marker. In contrast, ionically‐bound POD generally decreased during ripening, except under CA storage. CA storage inhibited ripening‐related softening after an initial loss of firmness. However, softening resumed after transfer of apples to normal atmosphere storage at 8°C. This may provide a new insight into controlling tissue softening.     

Significance of temperature and preincubation temperature on survival of Listeriamonocytogenes at pH 4·8

Listeria monocytogenes is a food-borne pathogenic bacterium that can be found in softcheese. At the beginning of cheese ripening, the pH is about 4·85–4·90. The aimof this work was to study the influence of temperature, preincubation temperature (temperature atwhich the inoculum was cultivated) and initial bacterial concentration on the survival of L.monocytogenes (strain Scott A) at pH 4·8. It was demonstrated in an earlier study thatthese factors did influence growth kinetics. Survival studies of L. monocytogenes weredone in a laboratory broth simulating cheese composition. Four test temperatures (2, 6, 10 and14°C) and two preincubation temperatures were studied (30°C or the test temperature). Listeria monocytogenes (strain Scott A) was unable to grow at pH 4·8 under allconditions tested. The time for 10% survival was about 11 and 2 d, at 2°C with preincubationat 2°C and 30°C, respectively; 9 d at 6°C with preincubation at 6°C; 4 d at 6°Cwith preincubation at 30°C; and 1 d at 14°C with preincubation at 14°C or at 30°C.The results show that survival of L. monocytogenes (strain Scott A) at pH 4·8 is notdependent on initial bacterial concentration but on both the test and preincubation temperatures.     

Viability of rape (Brassica napus L.) seeds following selection on the basis of newly-emerged radicles then subsequent drying and storage

Germinating rape seeds selected on the basis of newly-emerged radicles (1 ± 0.5 mm) were dried to an equilibrium moisture content (c. 11%) in air at 20°C and 80% relative humidity without loss of viability. Storage life of these low-moisture-content germinating (LMCG) seeds at 15°C was limited to 7 days before viability was significantly reduced. However, viability of LMCG seeds was maintained for 84 days in storage at -20°C. Longer periods in store reduced viability, but 96% of seeds still remained viable after 336 days at - 20°C. Increasing periods of storage at -20°C reduced the subsequent seed longevity at 15°C, indicating a reduction in vigour during storage. Storage under reduced pressure or in a nitrogen atmosphere had little significant effect on seed longevity. Reduction of moisture content below 11% using vacuum drying at a range of temperatures reduced seed vigour.     

Water temperature fluctuations and territoriality in the intertidal zone: two possible explanations for the elevational distribution of body size in Graus nigra

On the central coast of Chile, distribution of body size in Graus nigra varied with tidal pool height. With the objective of determining whether environmental temperature is one of the possible causes which explains the observed distribution pattern, two behavioural responses were analysed during an experimental period of increasing water temperature: number of opercular movements (an indirect measure of energy expenditure) and activity levels. The interactions of temperature × time and body size × time had a significant effect on the number of opercular movements. At low temperatures (13–15° C), large fish reached a maximum number of opercular movements, while small fish reached a maximum only at high temperatures (23–25° C). The interaction temperature × time had a significant effect on activity levels of different body sizes. In general, large fish appeared to be less active than small fish, however, at very high temperatures (24–26° C) all individuals increased their activity levels. These data indicate that small fish are acclimatized to live in a wider range of temperatures (13–23° C), and, for fish of all body sizes, the highest temperatures (23–26° C) probably constitute a suboptimal microhabitat. Strong territoriality was observed, with large individuals displacing smaller individuals. These data suggest that temperature is an important factor in explaining why large individuals are not present in high tidal pools (high temperatures), whereas territoriality explains why small individuals are not in low tidal pools (habitat of large individuals).     

Nitrite loss and spoilage microflora development in chub-packed luncheon meat

Residual nitrite was lost from chub-packed luncheon meat during storage through both chemical breakdown and microbial consumption. The relative importance of these mechanisms in this pasteurized product was determined by the speed of development of the spoilage microflora, which is influenced by storage conditions. The nitrite half-life due to chemical loss was 13 d at 25°C and 36 d at 10°C. When microbial growth occurred these half-lives were reduced to 2.6 d and 21 d, respectively. Qualitative differences in the microflora that developed at these two temperatures (denitrifying Bacillus spp. at 25°C and non-denitrifying Streptococcus spp. at 10°C) account for the large temperature effect. Growth of Streptococcus spp. increased the rate of chemical nitrite loss in chubs by reducing the pH value. Nitrite did not inhibit the aerobic growth of either Bacillus or Streptococcus species associated with spoilage but did inhibit the anaerobic growth of Bacillus spp. This bacteriostatic effect of residual nitrite in anaerobic conditions will decrease during storage as nitrite level falls and oxygen penetrates the chub pack. Nitrite-mediated bacteriostasis does not obviate the need for refrigerated storage but does afford a real, if ephemeral, safeguard against spoilage occurring during short periods of temperature abuse.     

Free Sulfhydryl Groups in Ripening Fruits

Ripening was found to be accompanied by an increase in sulfhydryl (SH) group content in several fruits. In ripening, climacteric,tomato fruits, this increase was due mostly to an increase inthe glutathione level. In orange, a non-climacteric fruit, therelatively high SH levels did not change during developmentand maturation. Non-ripening tomato mutants, e.g., rin and nor,were characterized by low and constant SH levels during fruitgrowth and senescence. Ripening-inducing storage conditions,such as high temperature (30?C) and ethylene treatment, concomitantlyhastened the increase in SH level in fast-ripening tomato varieties.Storage conditions that slowed down the ripening process, suchas low temperatures (2, 12?C) and low oxygen levels (5%), sloweddown the increase in SH content. Storage of red tomatoes at30?C caused an increase in the SH content in comparison withlower temperature treatments (2, 12, 20?C). SH compounds (reducedglutathione, cysteine), dithiothreitol and an SH-binding compound(n-ethylmaleimide), did not affect the ripening process of greentomatoes. The results suggest that the increase in SH groupsaccompanies the ripening processes rather than regulating them. (Received April 26, 1982; Accepted September 6, 1982)     

Dual induction control of flowering in Leucanthemum vulgare

The perennial herb Leucanthemum vulgare (oxeye daisy) has a dual induction requirement for flowering. The primary induction is a typical low temperature vemalization response. Temperatures up to 15°C are effective, and the optimum is 6–9°C. Short days (SD) during low temperature exposure enhanced primary induction, but SD could not fully substitute for low temperature in primary induction. At optimum temperatures about 6 weeks exposure were required for 100% flowering, but the flowering response increased with increasing exposure up to 12 weeks, especially at higher temperatures. Seedling have a short juvenile phase of about 4 weeks. Populations with origin ranging from 59 to 69°N in Norway did not vary in their primary induction requirements. Long days (LD) were required for inflorescence initiation and stem elongation at 9°C. At 21 and 15°C some plants initiated and developed inflorescences in SD, but the inflorescences were sessile and their development strongly delayed. More than 16 LD cycles were required for normal stem elongation (bolting).     

Prediction of the shelf-life of pasteurized milk at different storage temperatures

Initial psychrotroph counts determined by a Most Probable Number technique were correlated with shelf-lives of pasteurized milk determined at a number of storage temperatures. The initial psychrotroph count was also correlated with a bacterial count carried out on milk agar containing crystal violet penicillin and nisin after previous incubation of the milk at 15°C for 25 h.
Pre-incubation counts carried out at a variety of temperatures and on a variety of media were examined for their relation to shelf-life. Shelf-lives at four pre-set temperatures (2, 6, 10 and 14°C) could best be predicted by pre-incubation of pasteurized milk at 15°C before inoculation on milk agar.
An equation which allows prediction of shelf-life of pasteurized milk at any storage temperature is described.     

Allocation of carbon to growth, storage and respiration in the vegetative barley plant

Abstract. It is proposed that the growing plant can be divided into three compartments with reference to carbon: soluble, storage and structural. Experiments carried out at 10, 15, 20 and 30°C in the light followed changes in size of these compartments in barley plants 10–24 days old. The redistribution of ^I4C photo-assimilated by 10 day old plants was monitored simultaneously. The soluble and storage compartments are a higher percentage of plant weight at lower temperatures, and are turned over rapidly at all temperatures; they form the source of respired ¹⁴C. About 30% of the ¹⁴C fixed enters structural material; in the first 24 h after labelling, for each unit of ¹⁴C entering the structural compartment, between 0–9 (at 15°C) and 3.2 (at 30°C) units of ¹⁴C are lost by respiration. At 15°C in the dark, respiratory loss of ¹⁴C is initially from soluble and storage compartments; thereafter respiration of ^I4C occurs at the expense of structural material.     

Synergistic effect of relative humidity and temperature on the survival of rhizobia in inoculant carrier

Six strains of Rhizobium , three temperature-tolerant (U1, C13 and A19) and three temperature-sensitive strains (U10, C10 and A4) selected on the basis of previous study were used to screen the synergestic effect of different relative humidities (r.h. 50%, 65% and 90%) and temperatures (28°, 35°, 40° and 45°C) on the survival of rhizobia in inoculant carrier. At a particular temperature all the three r.h.'s were maintained. At a storage temperature of 28° and 35°C, the r.h. had little effect on the population of any of the rhizobial strains tested, but at 40° and 45°C, marked differences were observed and it was concluded that higher r.h. in conjunction with higher temperature resulted in low viable counts. The effect was similar but less obvious with the temperature-tolerant strains. It was found that 50% r.h. at different storage temperatures extended shelf life of rhizobial strains of blackgram, cowpea and arhar crops which were tested in this study in inoculant carrier.     

The influence of temperature on weight loss from stored onion bulbs due to desiccation, respiration and sprouting

When onion bulbs were stored for 9 months at 2, 7.5, 15 or 25 °C and 70% r.h., the losses due to desiccation increased with temperature but less than 20 % was due to respiration at any of the storage temperatures. Respiration rates of onion bulbs transferred from 2 to 25 °C were higher from February onwards than those of bulbs stored continuously at 25 °C. Conversely, bulbs transferred from 25 to 2 °C respired less from February onwards than those kept at 2 °C. Sprouting, at the final assessment in June, was highest at 15 and 7.5 °C and lowest at 2 °C. Total weight loss was above 45 % in all the storage treatments except at 2 °C (12%). Storage at 7.5 °C is suitable until March but long-term storage until June requires low temperatures.