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.     

An analysis of the growth of forced tulips. 1. Changes in plant fresh and dry weights during growth at two temperatures

Changes in the fresh and dry weights of the component parts of plants of tulip cv. ‘Apeldoorn’ were followed in bulbs kept at low and high temperatures (9 and 18°C respectively) from the time of completion of flower differentiation until anthesis.There were marked differences between shoot dry weights at the two temperatures. At 9°C the stem, leaves and flower grew exponentially throughout the whole period, but at 18°C the specific growth rate of the stem and leaves declined throughout the period of the experiment. At 9°C the proportion of total dry weight in shoots and daughter bulbs was higher than at 18°C, and the proportion in the mother bulb was correspondingly smaller.At both temperatures the $\text{fresh weight}\text{dry weight}$ ratios of the mother bulb, shoot and daughter bulbs declined during dry storage, the decline being greater at 9°C. After planting, the ratio for all plant parts increased at 9°C, but scarcely changed at 18°C.These results are discussed in relation to dormancy, to the low-temperature requirement for successful and rapid flowering and to flower quality.     

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.     

Post-Harvest Studies on Autumn-Drilled Bulb Onions. The Effect of Harvest Date,Conditioning Treatments and Field Drying on Skin Quality and on Storage Performance

Overwintered onion cvs Express Yellow and Senshyu Semi-globe Yellow were harvested at 80% foliar fall-over (early June) and two and four weeks later, in 1975 and 1976. Plants were conditioned for one (1975) or two weeks (1976) at 20°C, 70% RH or 30°C,60% RH or field dried, and then stored at ambient temperature. Measurements of fresh weight loss during the first six weeks after harvest in 1976 indicated that drying was slow and was incomplete after 14 days conditioning at 30°C. Skin staining and splitting generally increased with delay in harvest date. Skin colour improved with delay in harvest date and with conditioning at 20°C. Wastage due to both rotting and sprouting during storage was generally lower when plants from the first two harvest dates were conditioned at 30°C. These bulbs are likely to be useful for long-term storage as total wastage levels of only 20% were reached in both cultivars after 3-5 months storage. Good field drying of the bulbs could not be consistently obtained and consequently storage performance was more variable than for bulbs conditioned at 20 °C and 30 °C before storage.     

Factors affecting the response of tulips to gibberellin

Gibberellic acid (GA₃) treatment of forced tulip crops has potential for producing faster growth to anthesis in the glasshouse, for reducing losses due to floral bud blasting, and for reducing the duration of cold storage needed to obtain satisfactory flowers. Using partly and fully cooled direct-forced tulips, cultivar ‘Apeldoorn’, several factors (relevant to the definition of GA₃ treatments) were studied. Experiments confirmed the previously recorded effects of gibberellins in tulips: GA₃ injections reduced the duration of the glasshouse period, enhanced flower survival and flower length, and reduced stem length at flowering.Following bulb storage at temperatures from ?2 to 20°C, GA₃ reduced the glasshouse period by 15–25% and increased flower length, compared to controls, irrespective of storage temperature. Stem length was also reduced by GA₃, this effect being greater following a storage temperature of 5°C or lower. When GA₃ was applied during the period of 17°C-storage which precedes cool storage, or during or after storage at 5°C, it was found that treatments during or at the end of cool storage were more effective in producing the characteristic effects of GA₃ than were pre-cooling applications. In partly cooled bulbs (but not fully cooled ones), the GA₃-induced earliness of flowering was about doubled when GA₃ injections were given repeatedly at 2-week intervals throughout storage. The responses to GA₃ injections were found to be unmodified by early-lifting and heat-treatment (for earlier forcing), by delaying the start of 5°C storage (for later forcing), by glasshouse temperature (16 and 18°C), and by shading treatments; there was little effect of bulb size.     

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.     

Promotion of floral initiation in ‘Fuerte’ avocado by low temperature and short daylength

Potted avocado (Persea americana Mill., cv. ‘Fuerte’) plants were maintained in growth cabinets for up to 32 weeks and new growth observed for flower formation. Flowers were formed if temperatures were 20°C or below, but with 25° or 30°, even if only for 1 hour per day, flower formation was inhibited. Time to flowering was accelerated, but number of flowers reduced, if daylength was shortened from 15 h to 9 h. With low temperature and short days, full bloom was about 4 months after starting experiments. Spring flowering of cv. ‘Fuerte’ in the field could follow flower induction about 4 months previously with the onset of winter temperatures and daylengths.     

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.     

Effects of air and soil temperatures on flower development and morphology of satsuma mandarin

Three experiments were conducted in growth chambers to observe effects of air and soil temperatures in early and mid-winter on flower development and morphology of satsuma mandarin (Citrus unshiu Marc. cv. Okitsu Wase) budded on trifoliate orange. Four year old trees were used in Experiments I and III, and one year old ones in Experiment II. In Experiments I and II, air and soil temperature treatments of 15/15, 15/30, 30/15 and 30/ 30°C were started on 16 December, 1988. The trees sprouted flowers within seven days at 30/30°C, 11 days at 30/15°C, 21 days at 15/30°C, and 33 days at 15/15°C, respectively. There were few flowers at 30/30°C, extremely few at 30/15°C and many at both 15/15°C and 15/30°C. The days required to flowering and the flowering period were longer at the low air temperature. The number of flowers per tree, the number of flowers per node and the sprouting rate were greater at the low air temperature. A combination temperature of 30/15°C greatly decreased sprouting rate, the number of flowers per node and the number of flowers per tree. It seems likely that the chilling requirement might not be satisfied by mid-December. The trees might continue to accumulate chilling temperature at 15°C in the growth chamber. The trees at the high air temperature developed smaller flowers and ovaries. At an air temperature of 15°C, higher soil temperature resulted in bigger flowers and ovaries. In Experiment III, temperature treatments of 25/15,25/25 and 25/30°C were imposed on 6 January, 1989. The trees at 25/15°C required longer days to sprout and to blossom than at 25/25 and 25/30°C. The last two treatments did not differ in their effects. Soil temperature treatments did not result in significant effects on flower morphology, when they were applied after the chilling requirement was satisfied.     

The Effect of Cold Storage and Treatment with Gibberellic Acid on Flowering and Bulb Yields of Dutch Iris

Iris bulbs of the varieties Wedgewood and Prof. Blaauvv were injected with 50 or 500 μg. gibberellic acid (GA) before or after cold storage (10° C.) of 18 or 35 days. GA injection accelerated flowering by up to 19 days ; it had little or no effect on length of leaves or flower stem. It was most effective when applied at an early stage after flower initiation.

GA injection reduced bulb yield of Wedgiwood plants, and had no effect on, nor increased bulb yield of, Prof. Blaauw plants.

GA spraying (seven times at 10^-2M of GA) accelerated flowering and increased foliage growth in both varieties. It increased flower stem elongation and reduced bulb yield in Wedgfcwood plants.     

Factors Affecting the Control by Hot Water Treatment of Stem Nematode Ditylenchus Dipsaci (Kühn) Filipjev in Narcissus Bulbs

Hot water treatment (H.W.T.) of narcissus bulbs for three hours at temperatures from 111 °F (43.9 °C) to 114 °F (45.6 °C) failed to give a complete kill of stem nematode. Storage of bulbs at 86–94 °F (30.0–34.4 °C) for some days before H.W.T. resulted in less efficient killing of the pest, but in the following season the bulbs grew more vigorously and produced more flowers. Soaking bulbs for three hours at 65 °F (18.3 °C) before H.W.T. did not improve either the efficiency of nematode kill or the subsequent growth or flowering of heavily infested bulbs, but it improved nematode kill when bulbs were lightly infested. Water temperatures above 114 °F, up to and including 118 °F (47.8 °C), improved the kill of nematode but caused progressively increasing damage to the bulbs.     

Temperature effects on corm dormancy and growth of Zephyra elegans D.Don

Experiments were performed with the Chilean geophyte Zephyra elegans, a potential cut flower, to evaluate the effect of corm weight and storage temperature on corm dormancy, and to determine the effect of day and night growing temperatures on its growth and flowering. Z. elegans has a deciduous and synanthous growth habit and the corm is replaced annually. Dormant corms were stored at different constant temperatures or temperature combinations from 20 to 40 °C. Corms released from their dormancy were grown at 15/10, 20/15, or 25/20 °C day/night temperatures. Corms of various weights were planted at the same date after being stored dry at 25 °C for 22 weeks. They all emerged 19–38 days after planting, showing that dormancy release was not affected by corm weight. A 20-week corm storage treatment at a constant 25 °C resulted in the most rapid corm sprouting. Sprouting percentage was reduced at higher or lower storage temperatures. Temperature also affected plant growth. When plants were grown at 15/10 or 20/15 °C they emerged and flowered more rapidly than when they were grown at 25/20 °C. The latter growing temperature also resulted in poor flower quality.     

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.     

Cardinal temperatures and thermal requirements for germination of cineraria seed

Summary

Effects of temperature on the rate of germination, measured as the reciprocal of the time taken for half the population to germinate, were studied in cineraria cvs Cindy Blue and Cindy Dark Red. The base, optimum and maximum temperatures for germination were derived respectively as 1.6, 24.8 and 37.8°C in cv. Cindy Blue, close to T_b = 1.9, T_o = 24.5 and T_m = 38.4°C in cv. Cindy Dark Red. All seeds of each cultivar had a common base temperature but needed different thermal times to germinate. Seed of cv. Cindy Dark Red began to germinate after ca. 30°Cd compared with 35°Cd required by cv. Cindy Blue. A thermal time of ca. 50°Cd was required for half the population to germinate in each cultivar and the thermal requirement for germination fraction >0.5 was similar in both cultivars. The base and maximum temperatures for germination were similar to those determined previously for leaf initiation and flower development.     

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.     

Effect of temperature on growth,dry matter production and starch accumulation in ten mango (Mangifera indica L.) cultivars

Summary

Ten mango cultivars of tropical and subtropical origin (Carabao, Kensington, Nam Dok Mai, Alphonso, Dashehari, Florigon, Glenn, Irwin, Haden and Sensation) were grafted onto cv. Kensington seedling rootstock and held at four day/night temperatures for 20 weeks (15/10°C, 20/15°C, 25/20°C and 30/25°C). Vegetative growth increased with increasing temperatures. All grew vegetatively at 25/20°C and 30/25°C. Cultivars which did not grow at 20/15°C were Carabao, Kensington and Dashehari. Cultivars Kensington, Nam Dok Mai, Alphonso, Florigon, Glenn, Irwin, Haden and Sensation produced flower panicles at 15/10°C. The rise in temperature increased the average number of growth flushes (in responsive cultivars) from 0.48 at 15/10°C to 3.21 at 30/25°C, and the number of leaves per growth flush (1.22 at 15/10°C to 13.63 at 30/25°C). Distribution of dry matter from new growth was mostly to the roots at the lowest temperature (95% at 15/10°C) and to the leaves (58%) at 30/25°C. The mean daily temperature for zero vegetative growth was calculated to be 15°C. Temperature and related growth activity also affected the concentration of starch in the woody tissue of rootstock trunks at the end of 20 weeks (15.9% starch at 15/10°C v. 4.8% starch at 30/25°C). ‘Irwin’ had the highest starch concentration at the two higher temperatures (twice that of any other cultivar at 30/25°C) while ‘Kensington’ the lowest starch level at 25/20°C, ca. 50% of most other cultivars.     

Effects of Temperature on the Growth of Corchorus Olitorius

Controlled environment experiments were conducted using base-line growth study conditions to evaluate the responses of cvs Angbadu and Yaya of Corchorus olitorius, a tropical leafy vegetable, to day/night temperatures of 25°/20°, 30°/25° and 35°/30°C. Some of the parameters studied were greatest at 35°/30°C and least at 25°/20°C for both cultivars. Dry weights of both cultivars increased with rising temperatures during the first 21 days after emergence, and the greatest leaf area was at 30°/25°C for both. The nearest to the optimum temperature regime for this species was 30°/25°C. Based on leaf area at any temperature, cv Yaya would be preferred, but its superiority over cv Angbadu as indicated by dry weight is due to some extent to its greater stem length which is not composed of nutritionally important tissue.     

Comparison of Climate Change Effects on Pome And Stone Fruit Phenology Between Balkan Countries and Bonn/Germany

The objective of the joint project between the two universities of Bonn and Sarajevo was to study the effects of climate change associated with warmer winter and spring temperatures on fruit tree phenology. Changes in flowering date of apple and cherry were correlated with local weather data obtained concomitantly on-site at four locations in the Balkan countries Slovenia, Serbia, B & H and at Bonn, Germany.Phenological data of flower opening (F1; BBCH 61) of apple cv. ‘Golden Delicious’ originated from 55 years at Cacak (44?°N, Serbia) and at Klein-Altendorf, University of Bonn (50?°N), cv. ‘Bobovec’ from the University of Ljubljana (46?°N, Slovenia) and cherry cv. ‘Burlat’ (35 years at Klein-Altendorf, 50?°N) and 20–30 years at Tuzla (44?°N, B & H) and Mostar (43?°N, Bosnia & Herzegovina; B & H).The annual precipitation showed a negligible change in the last 55 years of ±5% in the Balkan countries (e.?g. Cacak, 699?mm), but only ±1.8% at Klein-Altendorf (605?mm) with a slight shift to more winter rainfall.Regression analysis showed an increase in mean temperature of 1.7?°C (annual) and 1.45?°C for the vegetation period at Klein-Altendorf (last 55 years), Germany. In the evaluated Balkan stations, the greatest increase in annual air temperature between two climate phases (until 1987 versus from 1988 until now) was at Ljubljana (1.4?°C) and Cacak (1.2?°C) in contrast to the least increase (0.3?°C) at Tuzla (annual average 10?°C) and an intermediate value (0.9?°C) in the warmer Mostar (annual average 14.5?°C).This recent temperature increase advanced flower opening by 10–14 days for apple such as cv. ‘Golden Delicious’ at Cacak and 7–10 days (last 55 years) at Bonn and 4–5 days (last 35 years) for the early cherry cv. ‘Burlat’ at Klein-Altendorf/Bonn; at Mostar and Tuzla, the effect of climate change was greater with the early cherry cv. ‘Burlat’ (26 days) compared with the difference of the late cherry cultivar (16 days). Before recent climate change (1973–1987), cherry flower was advanced by 10 days in the warmer med climate at Mostar but delayed by 16 days in the cooler Tuzla. The results, i.?e. the flower advancement in the Continental climate but flower delay in the med climate, are discussed with respect to the risk of late frost and countermeasures to combat climate change effects.     

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.