Early forcing of narcissus: The effects of lifting date and stage of floral development at the start of cooling

Early Narcissus flowers may be obtained if bulbs are lifted early from the field, warm-stored (35°C) and then cool-stored (9°C) before forcing in a glasshouse. The earliest satisfactory forcing was investigated, in ‘Carlton’ and ‘Fortune’, by lifting weekly from 27 May to 22 June, and storing at 17°C for 0–7 weeks between warm- and cool-storage. Storage at 17°C is usually intercalated to allow the completion of flower differentiation prior to the start of cool storage.After warm-storage, the bulbs lifted on 27 May and 22 June had reached Stages Sp and A2 of flower differentiation, respectively; 5–7 weeks of 17°C-storage were then needed to reach complete flower differentiation (Stage Pc). Cool storage was therefore begun with bulbs ranging from Stage Sp to Stage Pc. The earliest cooled bulbs had progressed only to Stage A2, and all others to Stage Pc, after 14–16 weeks of cool storage. No floral defects (e.g., split paracorolla) were noted in any treatment, but in ‘Carlton’, about half the bulbs lifted on 27 May and stored for 0 or 1 week at 17°C did not yield a flower, due to failure of the scape to elongate and death of the flower bud within the spathe.Duration of the glasshouse period was reduced by later lifting and by longer 17°C-storage, but following lifting on 15 or 22 June and 2 or more weeks at 17°C, differences were trivial. For flowering within 30 days in the glasshouse, 5 or 6 weeks' 17°C-storage was needed with 27 May lifting, reducing to 1 week at 17°C after 22 June lifting. Flowering within 21 glasshouse days was achieved only after 15 or 22 June lifts followed by 4–5 weeks at 17°C. The earliest flowers in ‘Fortune’ (7 November) were produced following 3–5 weeks at 17°C after lifting on 27 May or 1 June, or following 1–2 weeks at 17°C after later lifting. In ‘Carlton’, the earliest flowers (23 November) followed 2–3 weeks at 17°C after lifting between 1 and 15 June, or 0–1 weeks at 17°C after the last lifting date (22 June). Following the use of 3 weeks' 17°C-storage, flowering date was about equal, irrespective of lifting date. However, further extension of 17°C-storage resulted in a delay in flowering date. Scape length increased irregularly with longer storage at 17°C; scapes were taller following later lifting (8–22 June) than following earlier lifting. Differences in flower diameter between treatments were relatively small.     

Effect of temperature manipulation during storage and ripening on firmness,extractable juice and woolliness in nectarines

‘Independence’ nectarines were stored at — 0.5°C for three or four weeks or at 3°C for four weeks or kept at room temperature for 18 h prior to storage for four weeks at -0.5°C. After cold storage, fruit from all treatments was ripened at 10°, 15°or20°C. In all treatments the percentage woolly fruit initially increased to high values and thereafter decreased with further ripening. The rate of increase and decrease in woolliness depended on the ripening temperature. A storage period of four weeks at — 0.5°C resulted more woolliness during subsequent ripening. Woolliness persisted longer after a four-week cold storage period than after a three-week one. When fruit was delayed at room temperature prior to cold storage, woolliness generally developed earlier and to a lesser extent during ripening. At all ripening temperatures initial storage at 3°C resulted in most woolliness extending over the longest period. In addition, browning of the meso- carp tissue occurred only in fruit cold stored at 3°C.-The delay period before cold storage decreased fruit firmness by 15.7 to 17.6 N. Except for fruit subjected to the delay period, the extractable juice in fruit of all treatments first decreased during ripening to low values then increased.     

Leatheriness and mealiness of peaches in relation to fruit maturity and storage temperature

Summary

`Huangjin' peaches (Prunus persica Batsch) were harvested at commercial harvest time (commercial) and 20 d before (early) or after (later) commercial harvest. Fruit from each harvest were stored at three temperature regimes (0, 5 and 10°C) at 95% r.h. After four weeks of storage at 0 or 5°C, early harvested fruit developed more leatheriness but less mealiness and later harvested fruit did not develop leatheriness but developed more mealiness comparedwith fruit from commercial harvest. Overall, fruit stored at 5°C developed more mealiness but less leatheriness than fruitat 0°C for the same period of storage. When stored at 10°C for two weeks, after which fruit were senescent, fruit did not develop any leatheriness or mealiness regardless of harvest times. Fruit with leatheriness were firmer (>30 N) thanjuicy or mealy fruit (<10 N) after the same period of cold storage and 4 d at 20°C. Mealy fruit were as soft as juicy fruit. 1-Aminocyclopropane-1-carboxylate oxidase (ACO) activity, 1-aminocyclopropane-1-carboxylic acid (ACC) content, and polygalacturonase (PG) and galactosidase (GAL) activities were lower, and insoluble pectin content was higher in leathery fruit than that in juicy or mealy fruit. ACO, PG and GAL activity, ACC, and insoluble pectin content were similar between mealy and juicy fruit.     

Prevention of hot-water treatment damage in narcissus bulbs by pre-warming

Summary

Hot-water treatment (HWT) used to control stem nematode in narcissus bulbs can lead to yield loss through damage to flower, leaf and root initials. Warm storage of bulbs, usually at 30°C, reduces this damage. The effects of two pre-warming treatments (18°C for two weeks or 30°C for one week before HWT) were investigated in bulbs hot-water treated at a range of dates (from early-July to late-September). Experiment 1 was conducted on bulbs of cv. Carlton lifted on three dates. In the year after HWT, flower numbers were much reduced when HWT was applied after mid-August following storage at ambient temperatures, or after late-August following storage at 30°C, but numbers were only slightly reduced even with late-September HWT when given after 18°C storage. Pre-warming was somewhat more effective after early lifting. Late HWT reduced yields of bulbs harvested after two years' growth, but 18°C treatment largely prevented these losses. In Experiment 2, the beneficial effects of 18°C treatment were confirmed in cvs Carlton and Golden Harvest but not in cv. Barrett Browning. These findings are discussed in terms of growth retardation by warm temperatures.     

Effects of high-humidity storage on quality,decay and storage life of cherry,lemon and peach fruits

Sweet cherries (Prunus avium (L.) ‘Lambert’ and ‘Blackboy’), lemons (Citrus limon (L.) Burm. f. ‘Lisbon’) and peaches (Prunus persica (L.) Batsch, ‘Summerset’) were stored at 77–83, 90–94 and 95–99% RH (high humidity) at near-optimal storage temperatures after harvest and treatment with fungicides. High-humidity storage did not increase the storage life of peaches held at 0°C, but the life expectancy of cherries (both cultivars) was extended by 7–10 days at 0°C, and of lemons by at least 4 weeks at 10°C when fruit were stored at 95–99% RH compared with levels below 95%. The beneficial effects of high humidity were attributed to retardation of peel desiccation and associated reductions in fruit deformation, peel de-greening, chilling-injury and decay in lemons and to the maintenance of a fresher stalk and a firmer, less shrivelled fruit in cherries. High humidity had no effect on decay in cherries or peaches, but it significantly reduced weight loss and delayed the appearance of shrivel in peaches stored at 0°C. However, after storage at high humidity for 4 weeks, peaches ripened with low rates of C₂H₄ evolution and showed severe low-temperature injury, slight peeling-injury and a poor flavour ex-store.     

A study of the effect of the environment during growth on sprouting of bulb onions in store

The partition of dry matter between leaf and bulb with sheath was studied in relation to the post-harvest physiology of cvs Bola and Robusta grown at three sites for two seasons and dried and stored under standardized conditions. Foliar fall-over was synchronous at all sites in each season but the effects of site showed that crops either partitioned dry matter to the bulb early, lost less fresh weight in drying and sprouted later in store, or partitioned dry matter late, lost more fresh weight in drying and sprouted sooner in store. Crops showing the former behaviour were associated with low rainfall and a high number of day degrees between 6° and 20°C during early growth. There was up to 10 days difference between the sites in 50% sprouting dates. Bulbs of cv Bola sprouted earlier than those of cv Robusta, and bulbs harvested when foliar fall-over was negligible sprouted before those from later harvests. There were no site effects on plant maturity, on bulb growth regulator content (cv Robusta one year only), on sugar content at harvest or during storage, on bulb respiration rates at the end of drying or in the spring, or on bulb weight loss during storage.     

Warm Storage of Narcissus Bulbs in Relation to Growth,Flowering and Damage Caused by Hot-Water Treatment

Three experiments are described on the effects on flowering of warm storage of narcissus bulbs before (and in some cases after) hot-water treatment (h.w.t.) against eelworm infection. Almost complete loss of the flower crop occurs if the bulbs are not warm stored, compared with the production of about 90% marketable flowers following warm storage. Optimum temperatures and durations of warm storage are not clearly defined; there is very little difference between the two recommended treatments, 34° C. for 3 days and 30° C. for 7 days, with the latter giving slightly better results. In another experiment, best results were obtained following 32·5° C. for 8 days or 35° C. for 5 days, with some varietal differences. These combinations were superior to most at 30° C., and to all of only 2 days duration. Higher temperatures and longer durations generally result in earlier flowering, with no adverse effect on flower quality. Bulb yield in the field following h.w.t. is higher when the bulbs are warm-stored before h.w.t. and, when forced in the following season, they give more flowers. Post-h.w.t. warm storage reduces flower quality and bulb yield in the field; although some minor benefits were observed, this treatment cannot be recommended. The possible mechanism for the protection afforded by warm storage is discussed.     

Induction of bulb maturity of Ornithogalum thyrsoides

The influence of bulb maturity at bulb harvest on growth and flowering response of Ornithogalum thyrsoides Jacq. ‘Chesapeake Starlight’ was investigated. Experiments were designed to determine if bulb maturity can be induced by bulb storage temperatures and whether bulb maturity can be evaluated by flowering responses. Bulbs with all senesced leaves at harvest were considered “mature” or with emerging young leaves and re-growing young roots were considered “immature”. Bulbs were potted after 0, 3, and 6 weeks of 30 °C or 2 weeks of 10 °C given either in the middle or at the end of 6 weeks of 30 °C. Mature bulbs, as compared to immature bulbs, took longer for leaves to emerge when control bulbs that did not receive any temperature treatment after harvest were planted upon harvest. Leaf emergence of the immature bulbs was significantly earlier than that of the mature bulbs. Mature bulbs which received 30 °C for 3 weeks (30 °C/3 week) flowered 31 days faster than immature bulbs and all bulbs flowered. Leaf emergence and flowering of mature and immature bulbs that received 30 °C/6 weeks or 2 weeks of 10 °C in the middle of 6 weeks of 30 °C (30 °C/2 weeks–10 °C/2 week–30 °C/3 weeks) did not differ from each other. Maturity can be induced by storing immature bulbs at 30 °C/6 weeks. Maturity, as evaluated by flowering percentage and days from leaf emergence to flowering, can be induced in O. thyrsoides. Immature bulbs can, therefore, be harvested for later forcing as long as bulbs are treated with 30 °C/6 weeks. It is proposed that maturity can be correlated with the speed of flowering and bulbs can be harvested at immature physiological state for forcing. Postharvest high-temperature treatment can be used to force immature bulbs that were harvested before the senescence of the leaves.     

Effect of bulb storage temperature on leaf emergence and plant development during scale propagation of Lilium longiflorum ‘White American’

Effects of temperature and duration of bulb storage on leaf emergence of scale bulblets and on the type of plant development were investigated in Lilium longiflorum ‘White American’. After the parent bulbs had been stored for 0, 5, 10 or 15 weeks at 30, 20, 10, or 0°C, scales collected from different parts of a bulb were scale-propagated at 25 or 14°C, or under the temperature regimes normally used in The Netherlands. Independently of the scale position, a higher storage temperature promoted leaf emergence from scale bulblets, whereas a lower temperature delayed it. Higher storage temperatures produced more epigeous type plants, especially from outer and middle scales. Sprouting of the parent bulb had no effect on leaf emergence from the scale bulblets nor on the type of plant development.     

High-Temperature Treatment (Blindstoken) of Bulbs of Tulip cv Rose Copland for Flower Killing and Yield Improvement

A three-year experiment on the high-temperature treatment of tulip bulbs established that yield could be increased by between 8 and 31 % for bulb weight or between 14 and 29 % for numbers of large bulbs, depending upon season, associated with a near-complete flower kill. The optimum pre-treatment storage temperature was 17°C, and the best date (of the five tested) for starting blindstoken at 33°C for one week was 20th-21st September.

Yield increases were greater when the blindstoken treatment was applied to bulbs whose shoots were short; later treatment, or treatment after pre-treatments which allowed faster shoot growth, were less effective. For optimum flower kill and yield increase the shoot should be about 1 cm high at treatment. Bulb weight and large bulb number were correlated, suggesting that the treatment increases total bulb weight by increasing bulb size rather than by differentially affecting the growth of daughter bulbs.

No adverse effects of the treatments were observed when the bulbs were forced in a glasshouse the following season.     

Postharvest sprouting of onion bulbs grown in different temperature and C02 environments in the UK

Summary

The effects of different mean growing season temperatures and C0₂ concentrations during bulb production on postharvest bulb sprouting in a common storage environment at Reading, UK, was examined in two cultivars of the Rijnsburger type of onion (Allium cepa L.). Crops were grown in the field in temperature gradient tunnels maintained at either 374 or 532 ppm C0₂. At crop maturity, cohorts of bulbs were harvested, transferred to a constant temperature room (at an average of 11.6°C) and the subsequent duration to sprouting recorded. The duration to the onset of sprouting (expressed as days in storage until the first bulb sprouted) was not affected by cultivar, mean growing season temperature or CO₂ concentration, and was 165 d. The subsequent rate of sprouting (expressed as bulbs per day) was a positive linear function of mean growing season temperature, but no effects of CO₂ or cultivar were detected. Mean rate of sprouting increased from an average of 0.036 bulbs per day at 12.3°C to 0.093 bulbs per day at 18.6°C. Rapid sprouting in storage was associated with lower levels of total non-structural carbohydrate in the bulbs at the time of harvest. Thus, postharvest susceptibility of onion bulbs to sprouting in storage is expected to increase in warmer crop production temperatures.     

The Development of Adventitious Roots on Hardwood Cuttings of Gooseberries

Changes in percentage dry weight and in carbohydrate levels and distribution were followed in Golden Brown Lockyer onion bulbs for three months at storage temperatures of 4°, 15°, 25° and 37°C. The percentage dry weight within the bulbs increased from the outer to the inner leaf bases. Storage temperature and length of storage did not influence water loss. Sucrose concentrations increased from the outer leaf bases to become highest in the inner leaf bases, and in all leaf bases were higher at higher temperatures. Glucose and fructose levels also tended to increase from outer to inner leaf bases. After eight weeks fructose levels increased rapidly at the lower storage temperatures and this is attributed to low-temperature hydrolysis of fructans. The only fructan detected was the trisaccharide fraction, which was barely detectable in outer leaf bases and maximal in the inner ones. Trisaccharide levels were generally lower at the lower temperatures, thus supporting the suggestion of low-temperature hydrolysis of fructans. No information was obtained regarding storage temperature effects on fructans having a higher degree of polymerization than the trisaccharide. The results are discussed relative to temperature and time and the development of storage rots.     

Effect of the plant raising environment,transplant weight and date of transplanting on the subsequent growth and development of leeks (Allium porrum L.) grown for early production

Leek transplant weight at planting was greater for a given period of growth at 23°C than at 9°C but was unaffected by nutrition. A single line fitted to all the data, using a time-scale based on ‘effective day-degrees’ (with a base of 4°C and an upper limit of 23°C) accounted for over 76% of the variance in transplant weight at planting. Plant weight at harvest was positively related to transplant weight and fitting straight lines to each of the early and late harvest data sets from all the experiments accounted for 75% of the variance in plant weight at harvest. There were no ‘carry-over’ effects of temperature or nutrition from the plant-raising phase other than those on transplant weight. It was calculated, using data from two of the experiments where transplanting date was a factor, that yields fell by between 0.4 to 1.61 ha“1 for each week’s delay in planting over the period early April to mid-June. This loss in yield could be compensated by planting larger plants; 300 g plants could be produced in early August by planting 0.6 g, 0.9 g and 1.7 g plants in mid-April, mid-May and early/mid-June, respectively. The number of plants with flower initials at harvest increased with an increase in transplant weight and exceeded 10% with transplants of 0.5 g fresh weight or more and, for comparable transplant weights, was substantially greater from plants raised at 9° than 12°C. Flower initials were present even in crops from plants raised at 23°C. Transplants raised at 9°C produced up to 30% bolters at harvest but bolters were almost completely absent in crops established from plants raised at 12°C, 18°C or 23°C. Small plants (<0.4 g fresh weight) with 2-3 visible true leaves responded to cold.     

Effect of gibberellic acid and Vapor Gard on ripening,amylase and peroxidase activities and quality of mango fruits during storage

Post harvest application of gibberellic acid at 200 mg 1^?1, Vapor Gard (di-l-p-menthene) at 2.5% and their combination was studied on ‘Mallika’ mangoes (Mangifera indica L.) stored at ambient temperature (37 ± 2° maximum and 34 ± 2°C minimum) and at 15°C. Significant delay in the ripening of mango fruits was observed when gibberellic acid was applied with or without Vapor Gard. Gibberellic acid significantly retarded the degradation of ascorbic acid and chlorophyll in the peel, and reduced a-amylase and peroxidase activities during storage. Loss of weight decreased following treatment with Vapor Gard either alone or with gibberellic acid during storage at both ambient temperature and at 15°C. A pronounced retardation of ripening was observed when fruits were treated with gibberellic acid and Vapor Gard and stored at 15°C. The study thus suggests that mango fruits can be successfully stored for 20 d by application of gibberellic acid (200 mg 1^?1) in combination with Vapor Gard (2.5%) and stored at 15°C.     

The effect of 4 storage treatments on seed yield components of 3 onion inbreds

Onion bulbs of 3 inbred lines were stored during the winter in 4 different storage temperature regimes. Traits directly and indirectly associated with seed production were studied the following summers. The inbred lines differed in their responses and many traits were affected by the storage treatments. The storage treatment of 10°C for 12 weeks followed by 2° C for 12 weeks resulted in a significantly higher seed yield than did storage at 2° C throughout the entire period. Inbred 2399 had a higher seed yield than the other inbreds. Associated with high seed yields of 2399 was early flowering, a high number of leaves/bulb, tall seed stalks and a high number of florets/bulb.     

Quality of raisins under different packaging and storage conditions

We determined the effect of different storage systems and packaging on the quality of ‘Sultana Seedless’ raisins. The fruit were packed in plastic boxes and kept under controlled atmosphere (1% O₂ and 3% CO₂) at 0°C and 75–85% RH for 12 months (CA), packed in vacuum bags and kept under normal atmosphere (21% O₂–0.03% CO₂) (NA) and packed in thin plastic bags + carton boxes and kept under ambient condition (semi-refrigeration), at 0°C and 90% ± 5 RH for 12 months (AC). Fruit kept under CA or NA had acceptable fruit quality in terms of general appearance and taste for 10 months, whereas fruit quality was unacceptable at that time under AC. Fruit under NA had less weight loss than fruit under the other conditions. Differences in skin colour were relatively small, apart from the h° values. Concentrations of ochratoxin A were generally higher with AC. External appearance and taste were better with CA and NA. As a result, raisins can be stored for 10 months with good quality in vacuum package in NA (0°C and 90% ± 5 RH) and CA (1% O₂–3% CO₂) at 0°C and 75–85% RH.     

Effect of low-pressure storage on the quality of green capsicums (Capsicum annum L.)

Green capsicums (Capsicum annum L.) were stored under low pressure (4 kPa) at 10°C for 5 and 11 days with 100% RH. The results showed that the incidence of stem decay under low-pressure storage for 5 and 11 days and storage at ambient atmosphere at 20°C for 3 days was lower compared to fruits that were stored at regular atmosphere at 10°C. Fruit that had been stored at low pressure at 10°C had no symptoms of flesh rots for up to 11 days, whilst fruit which had been stored at regular atmosphere at 10°C had 6% flesh rots after 11 days storage at 10°C.There was no difference in flesh firmness and colour retention between fruits stored at low pressure and regular pressure at 10°C. Capsicums stored at low pressure had higher overall acceptability compared to fruit that were stored at regular atmosphere at 10°C. These results demonstrate the potential of low pressure storage as an effective technique to manage capsicum fruit quality, however, there was no additional benefit when fruits were stored at low pressure for more than 5 days.     

Effect of precooling at 5 or −1°C on shoot growth,flowering and carbohydrate metabolism in tulip bulbs

Precooling of dry tulip bulbs at ?1°C may be advantageous, compared with precooling at 5°C. Increasing the duration of precooling enhanced the growth of the shoots after planting, improved flower quality, and reduced the number of days to flower. The positive benefit of a stepwise precooling (5°C for 3 weeks, then ?1°C) was evident.Shoot elongation was promoted, and number of days to flower was reduced when the bulbs were precooled at ?1°C for less than 12 weeks. Extension of precooling beyond 12 weeks, however, was more effective with 5°C precooling. With few exceptions, sufficient precooling at either 5 or ?1°C gave a high percentage of flowering plants with first-quality flowers. Short durations (6–8 weeks) of precooling sometimes promoted flower blasting.Precooling at 5 or ?1°C had a similar effect upon the carbohydrate interconversion in scales and shoots of the bulbs, which as a rule is more pronounced at the lower temperature. The shoots accumulated sucrose, and to some extent fructosyl sucroses, during the 15 weeks precooling. Starch was also accumulated, the highest concentration being obtained at 5°C. The amount of starch was reduced in the scales during precooling, while the concentration of sucrose and fructosyl sucroses increased to a maximum value and then slowly diminished after about 9 weeks of precooling. The monosaccharides, glucose and fructose showed very small variations.     

Substitution of the cold requirement of tulip CV. ‘apeldoorn’ by GA3

To investigate whether GA₃ can substitute for the requirement, 1 mg GA₃ was injected in dry stored bulbs before, during or after the following treatments: (a) 12 weeks at 21°C, (b) 12 weeks at 5°C, (c) 6 weeks at 21°C followed by 6 weeks at 5°C, and (d) 6 weeks at 5°C followed by 6 weeks at 21°C. The bulbs were then planted in light at 15°C. Plants from bulbs previously subjected to (d) flowered earlier than bulbs from treatments (a) and (c) but later than those subjected to (b). Both the GA₃ and the 5°C treatments shortened the time from planting until flowering; however, GA₃ produced shorter plants and induced the formation of parthenocarpic fruits. Reduction of scape length by GA₃ was less when it was given at a later time during treatments (a) and (c) whereas the scape lengths of bulbs subjected to treatments (b) and (d) were hardly affected by the time chosen for GA₃ application.