The mode of action of ethephon in increasing health of gladiolus corms

Gladiolus corms and cormels were treated with various combinations of ethephon and the fungicides methylethyl mercury benzoate, benomyl, thiobendazole and methylmercury dicyandiamide either before or after storage at 10 °C and 30 °C for 6 weeks. The treated corms were examined for germination, splitting and rot symptoms caused by Fusarium oxysporum f. sp. gladioli.

Ethephon increased corm splitting in all treatments; it also increased germination in corms stored at 30 °C, and it increased the proportion of corms showing typical Fusarium rot symptoms by stimulating the growth of latent internal Fusarium. The effectiveness of the fungicides tested against F. oxysporum f. sp. gladioli was enhanced by the addition of ethephon. Permeability of corms to methylethyl mercury benzoate was increased by ethephon, and it is concluded that ethephon improves the efficiency of this fungicide, and probably of other fungicides as well, by increasing their penetration into gladiolus corms.     

Effects of various gaseous compounds and respiratory inhibitors on breaking dormancy of freesia corms

The exposure of freesia corms to an atmosphere containing 1 ml/l C₂H₄ strongly promoted sprouting of the corms when the treatment was applied at a high temperature (28–31°C), but the response was weak at temperatures below 20°C. Repeated treatments with C₂H₄ did not enhance sprouting, i.e. was not more effective than a single treatment. Exposure to an atmosphere containing CO of concentrations over 1 ml/l accelerated sprouting. The maximum effect of CO was obtained with 10 ml/l at 28–31°C.The effect of C₂H₄ combined with CO was similar to that of a single treatment with each separately. Soaking corms in solutions of 10^?1 M potassium cyanide and 30 g/l calcium cyanamide effectively promoted sprouting, but similar treatments with slaked lime and thiourea had no effect.Treatments with C₂H₄, CO, KCN and CaCN₂ did not stimulate C₂H₄-evolution in dormant corms. Respiration of the corms was increased by C₂H₄ and CO, and decreased by KCN and CaCN₂.     

Corm induction and multiplication of Amorphophallus albus in vitro

Summary

Amorphophallus albus, belonging to the family Araceae, has attracted widespread attention due to its considerable economic and medicinal importance. The natural propagation coefficient of A. albus is very low, which limits application of this crop. In vitro corms can be used for propagation of A. albus and have been proved to be superior over in vitro plantlets. To optimise procedures for in vitro corm production and multiplication, the effects of phytohormones, sucrose concentrations and incubation conditions with desirable phytohormone combinations for callus induction, corm formation and corm growth of A. albus were investigated. The results showed that calli were induced at high frequency from petiole segments on Murashige and Skoog medium supplemented with 1.0 mg l^–1 naphthaleneacetic acid (NAA) and 1.0 mg l^–1 6-benzyladenine (BA). Compact nodular calli were desirable for corm formation, and optimum corm formation was obtained in the presence of 0.5 mg l^–1 NAA and 2.0 mg l^–1 BA. With this auxin and cytokinin combination, an increase in sucrose concentration from 2% to 6% (w/v) significantly increased the corm formation rate and favoured corm growth, but negative effects occurred at higher sucrose concentrations. By incubating over a range of temperatures from 19°C – 28°C, 22°C produced the largest numbers of corms and highest mean fresh weight of each corm. Short-day (8 h) or long-day (16 h) photoperiods did not affect corm formation and growth significantly, except that corm weight fell under long-day conditions. The multiplication rate of in vitro corms was enhanced by apical meristem wounding. It was possible to store in vitro produced corms at 4°C for as long as 90 d to overcome apical dormancy and accelerate sprouting after planting into soil. This work has established an efficient protocol for multiplication of A. albus through an in vitro corm system.     

Cultivar and temperature effects on starch in the primary thickening meristem of onion bulbs

Summary

The effect of cultivar and temperature on the temporal pattern of starch occurrence in the primary thickening meristem (PTM) of onion (Allium cepa L. var. cepa) bulbs was studied. Bulbs of four cultivars differing in their sprouting behaviour in dry storage were analysed during bulb development for the concentration of starch in the PTM and inner sprout growth by histochemical analysis and determination of leaf ratio, respectively. Generally, in all cultivars the concentration of starch in the PTM was high during active growth, decreased to a low value during sprout dormancy, and increased before or concomitant with inner sprouting. The duration of the low starch period varied between cultivars. If onions were stored at low (18C), intermediate (158C), or high (308C) temperature, inner sprouting was delayed at low and high temperature compared with the intermediate temperature, whereas starch increased before sprouting at low and intermediate temperature, but became undetectable at high temperature. Moreover, if benzyladenine was injected into onions stored at high temperature, sprouting was readily induced, but starch in the PTM remained undetectable and no root initiation occurred. Since the PTM is not only responsible for the stem thickening but also for root initiation we conclude (i) that low starch in the PTM primarily indicates root dormancy and only indirectly sprout dormancy, and (ii) that high temperature-imposed sprout dormancy is actually based on root dormancy.     

Effect of ethylene on breaking dormancy of freesia corms

Ethylene (C₂H₄) applied before chilling stimulated rooting and sprouting, and increased root number and length per corm. Only when corms experienced high temperature for a certain period before or after C₂H₄ treatment was a promotive effect on sprouting observed. When C₂H₄ was applied at the beginning of the high-temperature storage, the effect was greatest and all treated corms sprouted within 2 weeks of planting. Effects of ethephon on sprouting were slight.Shortening the dormant period with C₂H₄ could be useful for practical freesia forcing, since C₂H₄ has no adverse effects on the development of the root and the shoot.     

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.     

Changes in endogenous cytokinin-like substances and growth inhibitors in freesia corms during high-temperature treatment for breaking dormancy

High summer temperatures are required to break dormancy of freesia corms and cormels. Endogenous cytokinin levels were low in corms at the lifting-date, 25 May, but increased after 3 months storage at 30°C. Cytokinin levels in cormels increased gradually during summer storage at natural room temperature, reaching a maximum on 25 August when cormels had the capacity to sprout, then decreased to low levels on 25 September. Inhibitor levels in cormels decreased gradually during storage. A zeatin riboside-like compound, water-soluble cytokinins and an abscisic acid-like compound were present in freesia corms. Dormant corms, soaked for 18 h in 1000 mg/l benzyladenine solution, showed 100% sprouting. We conclude that high temperatures cause a decrease in inhibitors and an increase in cytokinins, which together result in the breaking of the dormant state of corms and cormels of freesia.     

Effects of Denapon and Ethrel on thinning grapes

The effectiveness of Denapon and Ethrel as a thinning chemical for ‘Muscat of Alexandria’ grape was examined from 1980 to 1982 with various timings and concentrations of application. Ethrel applied at 50 mg l^?1 by cluster-dipping or shoot-spraying at full bloom, or 6 days after full bloom, resulted in over-thinning and chemical injury, and no thinning effect was found when Ethrel was applied at 10 or 5 mg l^?1 on the same dates. The only treatment which exhibited a desirable thinning effect was shoot-spraying at 50 mg l^?1 12 days after full bloom, but this markedly inhibited berry growth. Denapon applied at 1667 mg l^?1 by shoot-spraying at full bloom, or 6 days after full bloom, reduced the number of berries per cluster almost adequately and consistently without any unfavorable side effects. This chemical applied at 834 mg l^?1 was nearly as effective as when applied at 1667 mg l^?1, but the effectiveness of the former was less consistent than that of the latter. From these results, Denapon is thought to be a promising thinning chemical for ‘Muscat of Alexandria’.     

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.     

Effects of duration of exposure to ethylene on dormancy release in freesia corms

The exposure of freesia corms to ethylene (C₂H₄) at ca. 10 μl/l air for only 5 h was sufficient to promote sprouting, either under a closed system in which corms were treated in a sealed space of 3–10 1 or under a flow system in which corms were exposed to a continuous flow of air containing C₂H₄. Under the closed system, little change in corm response to C₂H₄ was found with increasing duration of exposure from 5 to 48 h, and the C0₂ concentration reached nearly 4% after 48 h. On the other hand, under the flow system, in which CO₂ did not accumulate above 0.1%, the promotive effect of C₂H₄ was diminished by extended exposure from 5 to 48 h.Repeated treatment with C₂H₄ for 23 h daily on 4 successive days resulted in the lowering of the promotive effect as compared with a single treatment, but repeated application of C₂H₄ for 5 h daily showed the same effect as a single application and gave a high sprouting rate similar to smoke treatment, independent of ambient temperature ranging from 25 to 35° C.Corms exposed to C₂H₄ for 5 h daily, or to smoke for 4 days, exhibited a better chilling response and advanced flowering.     

The influence of fruiting on the bud sprouting and flower induction responses to chilling in Citrus

Summary

The effect of chilling temperatures on bud sprouting and flower formation was compared on fruiting and non-fruiting ‘Owari’ satsuma mandarin (Citrus unshiu Marc) trees. On non-fruiting trees, bud dormancy was weak, and a significant proportion of buds were able to sprout at high temperatures without being chilled. Separate effects of low temperatures on bud sprouting and flower induction were demonstrated. On fruiting trees these two effects of low temperatures were also demonstrated on summer-flush buds, but not on older (spring-flush) buds. The spring-flush buds from fruiting trees scarcely sprouted without being chilled. These buds required a longer chilling period for dormancy release than for flower induction, and it was not possible to separate the effect of low temperature on flower induction from the effect on dormancy release. The presence of fruit reduced flower formation by reducing bud sprouting. Furthermore, fruit had a direct inhibitive effect on vernalization which resulted in increased formation of vegetative shoots. The effect of fruit and low temperature on flowering was unrelated to carbohydrate accumulation in the leaves or the roots.     

Effect of low temperatures on pulp browning and endogenous abscisic acid and ethylene concentrations in peach (Prunus persica L.) fruit during post-harvest storage

Summary

Changes in the severity of pulp browning, endogenous abscisic acid (ABA) and ethylene concentrations, and related gene expression in peach (Prunus persica L. ‘Bayuecui’) fruit stored at the biological freezing-point temperature (BFT; 1ºC), at 4ºC, or at room temperature (20ºC; as a control) were investigated.The results showed that fruit stored at room temperature showed climacteric changes in ethylene and ABA concentrations and in levels of expression of the corresponding ethylene synthetase genes (PpACS1, PpACO1) and the gene for a key enzyme of ABA synthesis (PpNCED), concomitant with a significant decrease in fruit firmness and an increase in juice yield. Meanwhile, two sucrose synthase genes (PpSUS1 and PpSUS2) were expressed at relatively low levels. However, fruit firmness decreased slightly and chilling injury (CI) increased significantly 40 d after storage (DAS) at 4ºC, with a significant accumulation of proline [from 8.33 µg g^–1 (at t = 0 d) to 9.125 µg g^–1 (at t = 40 d)]. In contrast, fruit firmness decreased slowly and pulp browning increased slightly 80 DAS at the BFT ( 1ºC), with a lower accumulation of proline than in fruit stored at 4ºC. The concentrations of soluble sugars and titratable acidity decreased during storage at 1ºC, 4ºC, or 20ºC, but there was a peak of soluble sugars at a late stage of storage at the BFT ( 1ºC). The fruit browning index was significantly and positively correlated (R ² = 0.967) with ABA concentration. The decrease in ABA concentration in cold-stored fruit (at both 1ºC and 4ºC) inhibited ethylene production. Moreover, there was no significant correlation between CI in fruit and ethylene production. In conclusion, the decrease in ABA concentration reduced ethylene concentrations and inhibited the development of pulp browning, which resulted in an improved taste, but crisper fruit, when fruit were stored at the BFT (–1ºC).     

Response of potted tulips to new and established growth-retarding chemicals

A range of growth-retarding chemicals was evaluated for their potential in the production of compact pot-grown tulips: ancymidol, piproctanyl bromide (Alden), dikegulac-sodium (Atrinal), a phenyl tetrazole compound (coded PP528), 2,3-dihydro-5,6-diphenyl-1,4-oxathiin (coded UBI-P293), chlorphonium chloride (Phosfon), 2-chloroethylphosphonic acid (Ethrel), and 5 morphactins. All chemicals were applied as single soil drenches 1–2 days after transferring plants to the glasshouse. Mid- and late-season forced bulbs of cultivars ‘Apeldoorn’, ‘Paul Richter’ and ‘Rose Copland’ were used.Piproctanyl bromide and chlorphonium chloride were ineffective, the former causing some stimulation of top internode extension. Ethrel at high concentrations gave a slight reduction in first internode length only, associated with a degree of flower-bud blasting. Dikegulac-sodium gave some reduction in stem and petal length, depending on cultivar. PP528 induced flower-bud blasting, adverse changes in flower colour and reduced petal length at concentrations which effectively shortened stems. Morphactins were toxic or caused flower-bud blasting and other floral abnormalities at high concentrations; at lower doses most morphactins reduced first internode length, while some increased length of the upper internodes, inducing nastic curvature and occasionally altering flower shape. Most effective height control was achieved with ancymidol and UBI-P293, the latter being the more active (at the concentrations tested); flower quality was good. In one experiment only, ancymidol slightly delayed flowering. High concentrations of UBI-P293 gave rise to some flower-bud blasting, especially in ‘Rose Copland’ which showed other adverse side-effects such as decreased length and longevity of the flowers, not only with UBI-P293 but also with higher doses of some other retardants.     

The Effects of Nitrogen,Potassium and Sub-Irrigation on the Yield,Quality and Composition of Single-Truss Tomatoes

The effects of nitrogen and potassium on the growth of single-truss tomatoes and on the yield and quality of the fruit have been examined. Two successive crops of cv. Minicraigella were grown with sub-irrigation in a tiered-trough system, the troughs containing a 7:3:2 mixture of loam, peat and grit. Four concentrations of nitrogen in solution (100, 150, 200 and 250 ppm N) were tested in factorial combination with three concentrations of potassium (200, 300 and 400 ppm K), the treatments being replicated four times.

Plant height and leaf length increased markedly with N concentration, as also did the numbers of flowers and marketable fruits per plant, the mean weight per fruit and the total yield. Low N levels delayed harvesting. The proportion of unevenly ripened fruit decreased with increasing concentrations both of N and K. The percentage of hollow fruits was decreased by high K but increased with N concentration.

The titratable acidity of the expressed fruit juices increased significantly with N concentration (P<0.001) but was little affected by K treatment. The N concentration of the nutrient solution also largely controlled the percentage of K in the leaves and the total uptake of this nutrient. These unexpected results were attributed to stimulation of growth by N, leading to increased water requirement and hence to increased application of both N and K by the automatic sub-irrigation system.

The highest yields and best quality fruit were obtained with 250 ppm N and 400 ppm K in the solution, although lower concentrations of K might be preferable after continued cropping in the same compost.     

小苍兰连续6个月供花栽培技术研究

利用促成栽培、常规栽培和延迟栽培相结合的方法,使小苍兰在上海地区达到１２月至次年５月连续６个月供花。促成栽培为种球经乙烯利处理提前打破休眠,再结合低温加赤霉素处理,于１２月至次年２月供花;在高温期间采取降温措施和低温期间采取加温措施,于２月底～３月供花。常规栽培于３月底～４月底供花。延迟栽培为１２月１日～１２月２０日种植常温贮藏的小球茎,于５月份供花。     

The Influence of Controlled Atmospheres on the Respiration Rates and Storage Behaviour of Strawberry Fruits

The output of CO₂ from strawberries, cv. Cambridge Favourite, held at 4.5 °C in air, I, 2 or 5% 0₂ fell to a minimum after 5 days. Thereafter the rate increased, more rapidly in air (in which rotting was more prevalent) than in 1 or 2% O₂.

Strawberry fruits stored at 3 °C in air, 5, 10, 15 and 20% CO₂ remained in good condition for 10 days, and all concentrations of CO₂ reduced rotting due to Botrytis. The alcohol content of the fruit increased with the length of storage and with higher concentrations of CO₂; 20% CO₂ caused severe injury after 30 days.

It is suggested that long-term storage in O₂ concentrations of 1% or lower may lead to off-flavours, and that the use of higher CO₂ concentrations may be restricted to storage for up to 7 days where adequate refrigeration is unavailable. Loss of flavour which occurred under all conditions after 15–20 days appears to be the main factor limiting the long-term storage of United Kingdom strawberries.     

In vitro corm production in Gloriosa superba L., an Ayurvedic medicinal plant

Summary

In vitro production of corms from Gloriosa superba L. using three kinds of explants: dormant, non-dormant corm buds and 30 d old in vitro derived multiple shoots is reported. Excellent responses was obtained in terms of corm production using MS medium supplemented with B₅ vitamins, 6% sucrose, 2iP, ADS and ANL for corm formation from dormant corm buds, using Kin, ADS and ANL for corm formation from non-dormant corm buds and using BAP, ADS and ANL for callus derived multiple shoot corm formation. Well developed corms were obtained from the tissue cultured plants with no dormancy breaking requirement.     

Ethylene production,EFE activity and ACC concentrations during the growth and development of Liatris spicata cv. Callilepis

SUMMARY

The ethylene production rate, ACC content and EFE activity were studied during growth and development of Liatris spicata cv. Callilepis, to obtain information which might help in directing the physiological response of the plant towards practical cultivation needs. Ethylene production and the other variates were measured in the whole plant and separately in the aerial part and corm. The amount of ethylene emitted depends on the stage of development of the plant, suggesting that the hormone is important in all stages of the life cycle of liatris. In the aerial part the highest EFE activity and ACC concentrations were found between sprouting and the formation of the basal leaf rosette. These values then fell until the first flowers open, when they began to rise again. In the corm, high concentrations of ACC present when the plants are taken out of cold storage fell during the first weeks of cultivation; EFE activity, on the other hand, was minimal and rose sharply with imbibition. A physiological interpretation of the results is offered.     

The influence of photoperiod and plant density on yield of winter-grown gladioli in Queensland

The yields of inflorescences, corms and cormlets, and the inflorescence quality of winter-grown gladioli in south-east Queensland, were studied under 2 daylength regimes, 3 plant densities (150 000, 300 000 and 450 000 corms ha^?1) and 3 plant arrangements (bed, double row and single row). The daylength treatments were the natural daylength (12.3–14.5 hours) and a 24-hour photoperiod treatment in which natural daylengths were extended using incandescent light of an intensity of 150 lux. Two cultivars were used.Extending the photoperiod to 24 hours delayed flowering by approximately 15 days, and increased the number of inflorescences harvested from low, medium and high density treatments by 20, 91 and 169%, respectively, when compared to the inflorescence yield from these density treatments under natural daylengths. The quality of the inflorescences from the high-density treatment receiving the 24-hour photoperiod was similar or superior in all quality characteristics to that of inflorescences grown under the most favourable density treatment under natural daylengths (150 000 corm ha^?1). Plant arrangement had little effect on the number of days to flowering or inflorescence yield but inflorescence quality was improved when plants were grown in a double-row arrangement compared to those from the bed or single-row arrangements. Extension of the photoperiod had no effect on the number of new corms per plot. However, the average weight of new corms and the weight of cormlets per plot and per corm were reduced by approximately 32, 71 and 63%, respectively, when compared to the results obtained from plants grown under natural daylengths. These results suggest that flowers compete for available photosynthates with corms and cormlet development.The economic feasibility of extending photoperiod for the commercial production of winter-grown gladioli in south-east Queensland is discussed.     

Effects of concentration and propagule age on the efficacy of gibberellic acid for breaking dormancy in potato minitubers

Summary

The effects of a post-harvest application of gibberellic acid (GA₃) at various concentrations (0, 10, 25, 50, or 100 mg l^–1) and for different periods of incubation (1, 2, or 3 h) on the breaking of dormancy and on sprouting in potato (Solanum tuberosum L., cv. Marfona) minitubers of two ages (freshly-harvested or 1 week after harvest) were investigated. Compared with untreated, control minitubers, GA₃-treated minitubers showed a significantly shorter period of dormancy (46 d), especially when the minitubers were treated at all concentrations immediately after harvest (41 d). GA₃ treatment had a greater effect on dormancy in freshly-harvested minitubers than in 1 week-old minitubers, probably because of the reduced uptake of GA₃ solution after skin-set. At lower concentrations of GA₃, the period of dormancy tended to decrease the longer the minitubers were immersed in the GA₃ solution. In contrast, at higher concentrations of GA₃, the duration of immersion only had an effect up to 2 h and any longer immersion was ineffective. The average number of sprouts was not affected by GA₃ concentration, or by the time of incubation, but was significantly higher for freshly-harvested minitubers (1.4) than for 1 week-old minitubers (1.2). The lengths of the sprouts increased with an increase in GA₃ concentration, especially in freshly-harvested minitubers. Consequently, immersing freshly-harvested potato minitubers in a low concentration of GA₃ (up to 25 mg l^–1) for up to 3 h effectively shortened the period of dormancy and led to the formation of sprouts of optimum length.