Changes in carbohydrate contents in shoot tips,leaves and roots of strawberry (Fragaria × ananassa Duch.) during flower-bud differentiation

Flowering is an important step in crop production. Under flower-inducing conditions, biochemical or physiological changes can be recognized. Changes in carbohydrates have an important role in flower development in plants; however, carbohydrate changes during flower bud differentiation in strawberry have not been thoroughly investigated. In this study, runner plants potted in 18 cm diameter pots and grown under non-inducing conditions (28 ± 3/22 ± 3 °C day/night; 16 h day length). When the plants were established, half of the plants then were put under inducing conditions (23 ± 3/13 ± 3 °C day/night; 8 h day length). After the induction period of 21 short-day cycles, plants were brought to non-inductive conditions again. In order to evaluate the carbohydrate changes during flower differentiation, shoot tips, leaves and roots were sampled from four replicated plants collected weekly for the period of 7 weeks. Sucrose, glucose and fructose contents were determined by HPLC, and starch by the anthrone method. The results obtained indicated that the most abundant soluble sugar in all organs tested was sucrose. Sucrose in the shoot tips of induced plants at 42, 56 and 70 days after the start of the short-day treatment were significantly higher than corresponding time in non-induced plants. However, the glucose, fructose and starch contents in shoot tips, leaves and roots of non-induced plants in most sampling dates were greater than those of induced plants. In other words, the shoot tips (bud) of induced plants acted as strong ‘utilizing sink’ and preferentially metabolized carbohydrates rather than storing them. It seems that non-structural carbohydrate contents in shoot tips, leaves and roots of strawberry may have an important role in flower-bud differentiation.     

Cryopreservation of in vitro almond shoot tips by vitrification

Summary

Shoot tips of two almond scion cultivars, ‘Ne Plus Ultra’ and ‘Nonpareil 15-1’, and one almond/peach hybrid rootstock were successfully cryopreserved using a one-step vitrification technique. Three week old in vitro cultures were cold-hardened at 4°C on the multiplication medium (Murashige and Skoog for ‘Ne Plus Ultra’ and the hybrid rootstock; Almehdi and Parfitt for ‘Nonpareil 15-1’) for three weeks. Shoot tips, 2–2.5 mm long, were excised and precultured for 1 d at 4°C on the same basal medium, without plant growth regulators, supplemented with 0.7 M sucrose. After the preculture, the shoot tips were incubated in vitrification solution at 25°C for 45 min for the almond scion cultivars and 60 min for the hybrid rootstock, and then stored under liquid nitrogen (LN) for at least 3 d. After rapid thawing at 30°C, the shoot tips were washed with the appropriate liquid basal medium containing 1.0 M sucrose and then cultured on the same basal medium, solidified with agar, but excluding NH₄NO₃ or (NH₄)₂SO₄. Shoot regeneration was usually observed within 2–3 weeks. Survival after LN, recorded as the percentage of shoot tips that produced at least one new shoot four weeks after thawing, was 87.5, 60.0 and 72.5% for ‘Ne Plus Ultra’, ‘Nonpareil 15–1’ and the hybrid rootstock respectively. The one-step vitrification method is a promising simple technique for cryopreserving almond scion and rootstock shoot tips from in vitro cultures.     

Nutritional and cultural factors affecting rooting of papaya (Carica papaya L.) in vitro

Summary

Experiments were conducted to optimize nutritional and cultural requirements for initiation and growth of roots on papaya in vitro. Axillary shoots were obtained from plants which had been sub-cultured monthly for two years. Root initiation was enhanced when 1 to 2 mm of stem base was removed and shoots were growing actively before transfer to the rooting medium. Decreasing daylength during incubation from 24 h to 12 h promoted root initiation. Within the day temperature range of 22 to 29°C, optimum rooting occurred at 27°C and higher temperatures produced higher mean root weights per shoot. High concentrations of growth factors and the absence of sucrose in the medium both reduced root initiation, however, varying the concentration of sucrose and removing growth factors affected mean root weight per shoot. All media contained a modified de Fossard et al. (1974) basal medium plus 10 μM IBA.     

通过玻璃化超低温处理脱除草莓轻型黄边病毒(SMYEV)研究

以草莓品种明宝为材料,取茎尖做初代培养,继代扩繁5次后,取2mm左右的茎尖,利用玻璃化超低温技术对SMYEV进行脱除,并利用结合内标的多重RT-PCR技术对再生植株进行病毒检测。结果表明,在病毒脱除过程中,预培养蔗糖浓度为0.5mol/L,处理3d;装载处理为25℃,60min;玻璃化处理为0℃,120min;液氮处理60min后,进行40℃水浴2min,草莓茎尖的存活率为76%,而草莓轻型黄边病毒的脱除率为95%。只有通过液氮处理才可以脱除该病毒,液氮处理前的玻璃化处理脱毒率为0。利用超低温脱毒法可以简便有效地脱除SMYEV。     

Some physiological changes in strawberry (Fragaria × ananassa ‘Camarosa’) plants under heat stress

Summary

The effects of heat injury induced by long exposures were evaluated in strawberry (Fragaria × ananassa ‘plants’) Camarosa in this study. Seedlings were grown in 14 × 12 cm pots using perlite for three weeks at 25/10°C day/night temperature, and watered daily by modified 1/3 Hoagland nutrient solution. Half of the plants were transferred to a growth chamber with a constant 25°C, 16/8 h (light/dark) photoperiod regime and 1200 lux light intensity for a week to acclimate the plants. Temperature was increased stepwise (5 K per 48 h) to 30, 35, 40°C and finally to 45°C. In addition to others, plants were transferred from the outside to the growth chamber, at each temperature step to impose a heat shock. Leaf relative water content (RWC, %), loss of turgidity, chlorophyll content (Spad value) and heat-stress tolerance (HTS; LT₅₀) were measured in control and stressed plants. Total soluble proteins and total DNA were extracted from the leaves following the above treatments using standard procedures and total protein contents were determined using a Bradford assay. In general, effects of gradual heat stress (GHS) and shock heat stress (SHS) on the variables studied were mostly significant, except for chlorophyll content, while the effect of temperatures was significant for all the variables. Interaction between the heat stress type and temperature treatments was not significant for leaf RWC, loss of turgidity and chlorophyll content. Data also indicated that total protein and DNA contents were changed significantly by heat stress types (GHS and SHS) and/or temperature treatments. The plants exposed to GHS exhibited a significant increase in HST compared with the plants exposed to SHS (LT₅₀ of 41.5°C and 39°C, respectively). Consequently, gradual heat stress increased HST in strawberry leaves. Increased HST may be associated with the accumulation of several heat-stable proteins in GHS plants.     

Effects of chilling on the formation of secondary growing-centres in flowers of the glasshouse carnation

The incidence of secondary growing-centres within the flowers of carnation was increased when plants were chilled at 5°C for 1–3 weeks during flower development. Application of GA₃ to shoots in the early stages of flower formation also caused an increase in the number of secondary growing-centres formed. Shoot tips excised from plants that had been chilled yielded greater amounts of diffusible gibberellin-like substances than shoot tips excised from plants that had been grown at normal glasshouse temperatures. It is suggested that endogenous gibberellins have a role in controlling the formation of secondary growing-centres within the flower.     

Long-day and nitrogen conditioning of ‘Albion’ strawberry (Fragaria X ananassa Duch.) enhances off-season field production

Experiments conducted over 2 years evaluated photoperiod and nitrogen conditioning of ‘Albion’ strawberry (Fragaria x ananassa Duch.) plants for off-season field production in New Jersey, USA. Plants were conditioned the first year with natural days (ND, natural daylength) or long days (LD, natural daylength supplemented with 24 h incandescent radiation) for one week followed by 100 or 800 ppm N for 4 weeks under ND or LD. The second year, plants were conditioned with ND or LD for 1 week followed by 1 to 6 weeks of 100 or 800 ppm nitrogen (N) under ND or LD. After conditioning, plants were established in plasticulture. Ripe fruit were harvested from August through October both years. LD conditioning enhanced precocity by approximately 9 days in both studies. Productivity was also enhanced by conditioning with LD or elevated N. Plants grown on silver or white mulch were more productive than those grown on black mulch in the first study, but not the second.     

草莓果实蔗糖和己糖的代谢特性及其与糖积累的关系(英文)

以设施栽培的枥乙女草莓为试材,研究蔗糖代谢和己糖代谢关键酶在草莓果实糖积累进程中的作用。采集花后1～8周的果实,分别测定果实中葡萄糖、果糖、蔗糖的含量和蔗糖磷酸合酶(SPS)、蔗糖合酶(SS)、可溶性酸性转化酶(AI)、中性转化酶(NI)、己糖激酶(HXK)及果糖激酶(FRK)等蔗糖和己糖代谢酶的活性。结果表明,草莓果实的总糖含量随果实发育持续积累,但蔗糖的快速积累对果实后期糖的积累贡献最大。在果实发育前期,草莓AI活性随果实发育而下降,但在果实发育后期,AI活力随果实成熟而急剧上升,这使果实最终以积累己糖为主。果实蔗糖快速积累期,合成蔗糖的酶SPS和SS(合成方向)的活性下降到较低水平,表明这2种酶对草莓后期果实蔗糖的快速积累贡献较少。果实发育后期较低的HXK和FRK活力有利于果实糖的快速积累。     

Long-day control of flowering in everbearing strawberries

Summary

Photoperiod and temperature control of flowering in a number of perpetual-flowering or everbearing strawberry cultivars of widely varying pedigree has been studied in controlled environments. Flower bud initiation in the cultivars ‘Flamenco’, ‘Ridder’, ‘Rita’ and ‘Rondo’ was significantly advanced by long-day (LD) conditions at temperatures of 15°C and 21ºC; while, at 27ºC, flowering took place under LD conditions only. Some plants of the seed-propagated F₁-hybrid ‘Elan’, raised at 21°C, also flowered under short-day (SD) conditions at 27°C, but reverted to the vegetative state after a few weeks when maintained under these conditions. When vegetative plants growing in SD at 27°C were transferred to LD conditions at the same temperature, they consistently initiated flower buds and started flowering after about 4 weeks. At such a high temperature, flowering could thus be turned on and off by switching between SD and LD conditions. This applied to all the cultivars studied. Also the cultivar ‘Everest’, which was tested only at 21°C, produced similar results. Night interruption for 2 h was effective in bringing about the LD response. At 9°C, flowering was substantially delayed, especially in ‘Flamenco’ and, at this temperature, flowering was unaffected by photoperiod. Runner formation was generally promoted by high temperature and SD conditions, but the photoperiodic effect varied between experiments. We conclude that everbearing strawberry cultivars, in general, whether of the older European-type or the modern Californian-type originating from crosses with selections of Fragaria virginiana ssp. glauca, are qualitative (obligatory) LD plants at high temperature (27°C), and quantitative LD plants at intermediate temperatures. Only at temperatures below 10°C are these cultivars day-neutral.     

Effects of temperature and daylength on growth and flowering of roselle, Hibiscus sabdariffa L.

Hibiscus sabdariffa L. was found to show an ambiphotoperiodic reaction, flowering both in short days and in extremely long days, but remaining vegetative (at least at 21–25° C) in a 16 h day. Flowering had a dual effect on growth. When floral induction was strong, lateral buds developed into flowers and the number of branches was proportionally reduced. The first stage of floral induction, however, was accompanied by a decrease of apical dominance. Plants shifted to long days after only a short stay at an inductive daylength, and plants moved to short days after a prolonged stay in long days, formed many more branches and a much greater vegetative mass than plants grown in continuous short days or long days.Plants were already sensitive to daylength in the cotyledon stage. Floral induction was not carried over from short days into long days. After marginal induction, floral buds reverted to vegetative shoots, or aborted and were replaced by a shoot from the axil of a bract.In short days, seedlings form shallowly three-lobed leaves until the generative stage, when only entire leaves are formed. In long days, the leaves are deeply five-lobed, also when the plant flowers.     

Crown branching and cropping potential in strawberry (Fragaria ananassa Duch.) can be enhanced by daylength treatments

Summary

When strawberries (Fragaria ananassa Duch.) are produced in a greenhouse, usually two crops a year are obtained; in the fall and in the spring. To increase productivity, new cultivation techniques are needed. The aim of this study was to examine the effect of daylength treatments on the performance of strawberry plants to improve plant production protocols. The possibility of obtaining two successive crops during forcing was explored by exposing plants of cultivar Korona to two successive short day (SD) treatments followed by cold storage. The following daylength treatments were studied: 3 wk SD + 2 wk long day (LD) + 3 wk SD (3SD2LD3SD), 3 wk SD + 4 wk LD + 3 wk SD (3SD4LD3SD), and 10 wk SD (10SD). In addition, crown branching was studied in plants subjected to SD treatments. Two successive SD treatments enabled two successive flowering and cropping periods during greenhouse forcing after eight weeks of cold storage.The first SD treatment caused crown branching and induced flowering in the apical meristem of the main-crown and in the oldest axillary meristem(s), whereas younger axillary meristems were induced during the second SD treatment. Marketable yield and the number of inflorescences were comparable in 3SD4LD3SD and 10SD, but considerably lower in 3SD2LD3SD. However, this study demonstrated the high cropping potential of artificially SD treated plants, which makes them a potential alternative for greenhouse strawberry cultivation. Multi-crowned plants of ‘Korona’ can be produced by subjecting young plants to a three week SD treatment, and crown branches can be induced to flowering by a new SD treatment resulting in a very high cropping potential. Induced plants can be stored at –1°C for later forcing.     

Conditioning is not needed for late summer and early fall production of June-planted ‘Albion’ strawberry (Fragaria X ananassa Duch.) in the plasticulture system

Two plant types [direct planted, cold-stored dormant crowns (crowns) or dormant crowns grown in a greenhouse for 3 weeks prior to field planting (plugs)] of ‘Albion’ strawberry (Fragaria x ananassa Duch.) were evaluated in off-season field production under LD (long day: natural daylength supplemented with 24 h incandescent radiation) or ND (natural daylength) in New Jersey, USA. After 1 week under LD or ND plants received either 100 or 800 ppm N for 4 weeks. Inflorescence, runner, and branch crown production were monitored and fruit harvested from July through September. Field conditioning was ineffective for enhancing total yield of June-planted ‘Albion’ in off-season production. If early summer planting is anticipated, conditioning is not needed. Growing plugs in the greenhouse before transplanting to the production field is not beneficial and reduces productivity with the early summer plantings. Extending the daylength with continuous incandescent lighting to mimic LD during production is not recommended for early summer planting as productivity and fruit size are reduced under continuous low level lighting.     

草莓果实发育过程中糖代谢相关基因的表达分析

 为了分析草莓（Fragaria × ananassa Duch.）果实发育过程中可溶性糖积累与相关基因表达量的关系,以‘杜克拉’草莓7个发育时期的果实为试材,利用实时荧光定量RT-PCR的方法,分析果实发育中蔗糖转运蛋白及糖代谢关键酶（酸性转化酶、蔗糖合成酶和蔗糖磷酸合成酶）4个基因的表达量以及可溶性糖含量的变化趋势。结果表明,蔗糖、葡萄糖和果糖含量随着果实发育都呈逐渐增加的趋势,尤其蔗糖积累与果实成熟的关系较密切。随着果实发育,蔗糖磷酸合成酶基因表达量呈逐渐增加的趋势,尤其在果实发育的后期增加较快;蔗糖合成酶和酸性转化酶基因表达量除了白熟期和转色期外,呈逐渐降低的趋势;蔗糖转运蛋白基因表达量呈先升后降,降后又升的变化趋势,尤其在白熟期前急剧增加。结合可溶性糖和基因变化趋势分析表明,蔗糖转运蛋白和蔗糖磷酸合成酶在草莓果实发育过程中发挥着重要的作用。     

马铃薯茎尖小滴玻璃化法超低温保存及其再生植株的遗传稳定性

以马铃薯试管苗为试材,对其茎尖小滴玻璃化法超低温保存的影响因素进行了研究,并对再生植株进行了遗传稳定性检测。结果表明,马铃薯茎尖依次在含有0.3 mol · L-1和0.5 mol · L-1蔗糖的液体MS培养基中预培养各1 d后,在0 ℃下PVS2处理30 min,转到铝箔条上PVS2小滴上（约15 μL）,将粘有茎尖的铝箔条在液氮里蘸一下,然后直接装入盛满液氮的冷冻管中,投入液氮至少保持1 h。室温下用含有1.2 mol · L-1蔗糖的MS液体培养基解冻并洗涤30 min后,接种到MS + 0.5 mg · L-1 Zeatin + 0.1 mg · L-1 NAA＋1.0 mg · L-1 GA3恢复培养基上,存活率和再生率最高达79.91%和62.52%。通过SSR分子标记检测,再生植株的遗传稳定性没有发生改变。     

Responses of Alstroemeria ‘Regina’ to temperature treatments prior to flower-inducing temperatures

Days to flower (DTF) were inversely related to the number of weeks (0–8) that Alstroemeria ‘Regina’ plants remained at 5°C, a vernalizing temperature, before being moved to 13°C, a vernalizing as well as a forcing temperature. However, when the number of weeks at 5°C was added to the DTF, no difference in the total time to flower was observed between plants treated at 5°C or those grown continuously at 13°C, as they both induced flowering. One-year-old plants maintained at 21°C, a non-inductive temperature, and not divided prior to the 5°C treatments, showed an increase in total shoot production, and delayed DTF, compared to plants which were divided. When divided plants were maintained for 16 weeks at 21°C prior to 5°C treatments, total shoot production was reduced but flowering was accelerated compared to plants maintained for 8 weeks at 21°C after dividing. Total shoot and flowering-shoot production was not affected by increasing the durations of time at 5°C when plants were grown at 21°C and divided prior to this treatment. Thus, the pre-treatment of dividing or maintaining plants at 21°C prior to a 5°C treatment affected subsequent shoot production and DTF.     

Encapsulation of shoot tips of guava (Psidium guajava L.) for short-term storage and germplasm exchange

Shoot tips obtained from in vitro grown plantlets of guava (Psidium guajava L.) were encapsulated in calcium alginate beads for short-term storage and germplasm exchange. A gelling matrix of 3% sodium alginate and 100 mM calcium chloride was found most suitable for formation of ideal calcium alginate beads. Maximum percent response for conversion of encapsulated shoot tips into plantlets was obtained on growth regulator free full strength liquid MS medium. The regrowth ability of encapsulated shoot tips was affected by medium strength and sucrose concentrations in the medium. Encapsulated shoot tips could be stored at low temperature (4 °C) up to 30 days with a survival frequency of 25%. After 60 days of storage under minimal growth conditions (sucrose lacking medium), about 75% encapsulated shoot tips were converted into plantlets when subcultured on 3% sucrose containing medium. Plantlets regenerated from encapsulated shoot tips were acclimatized successfully.     

Low night-temperatures affect the metabolism of raffinose-family oligosaccharides in melon (Cucumis melo L.) leaves during fruit expansion

Summary

This study served to reveal the effects and mechanism of low night-temperatures on the metabolism of raffinose-family oligosaccharides in melon (Cucumis melo L.) leaves. We investigated the carbohydrate contents and sugar-metabolising enzyme activities in leaves under normal (15°C; control) and two low night-temperature (12°C or 9°C) conditions during fruit expansion. The results showed that the greatest difference in carbohydrate metabolism occurred between 9°C at night and the 15°C control. Compared to the normal night temperature, total carbohydrate accumulation, in particular raffinose, increased and the ratio of raffinose to total carbohydrates exhibited the greatest increase in melon leaves treated at 9°C at night, while the ratio of sucrose to total carbohydrates declined at the end of the same treatment. These data suggested that 9°C at night played an important role in partitioning carbon from sucrose to raffinose-family oligosaccharides (RFO), and that raffinose may serve dual purposes in stress protection and carbon storage. Meanwhile, the activities of sugar-metabolising enzymes were notably affected by 9°C at night. Sucrose synthase (SS), sucrose phosphate synthase (SPS) and, in particular, galactinol and stachyose synthase activities decreased markedly, while acid invertase (AI) and neutral invertase (NI) activities increased sharply, which restricted sucrose and RFO synthesis. Overall, these data suggest that the decline in stachyose and galactinol synthase activities were the main limiting factor for RFO synthesis in melon leaves at 9°C at night. They also indicated that the reduction in stachyose metabolism may be an important factor during the development of unmarketable fruit.     

Effect of temperature on dormancy in strawberry

Early in autumn, at the end of September or at the beginning of October, strawberry plants of the cultivars ‘Glasa’ and ‘Tioga’ were transferred from outdoors to separate phytotron glasshouses at constant temperatures of 10° and 14°C. In November a number of these plants were chilled at 3°C for 0 to 4 weeks and subsequently forced; the rest remained at 10° and 14°C until June.The plants kept at 10°C and subsequently chilled and forced, grew faster and more vigorously than those pretreated at 14°C. The 14° plants showed more pronounced growth differences resulting from the length of the chilling treatments than did the 10° plants. Those remaining continuously at 10° developed vigorously from March onwards, while those at 14°C retained their flat appearance into June. These results showed that a continuous temperature as high as 10°C was still able to break dormancy in the strawberry plants, while 14°C was ineffective.     

香蕉茎尖的玻璃化法超低温保存及其植株再生

 以香蕉(Musa spp. ) 为试材, 对其离体培养茎尖玻璃化法超低温保存影响因素进行研究。结果表明, 不定芽在MS + 3.0～5.0 mg/L 6-BA + 0.1 mg/L NAA的培养基上分化较好。香蕉茎尖超低温保存较佳体系是: 2.0～3.0 cm的茎尖在含0.4 mol/L蔗糖培养基上预培养2 d, 剥取带1～2个叶原基的茎尖(长1.0～1.5 mm) , 室温(25℃) 下装载液(MS + 2 mol/L甘油+ 0.4 mol/L蔗糖) 装载20～30 min, 然后用玻璃化溶液( PVS2 ) 于0℃下处理40 min, 换1次PVS2后迅速投入液氮。保存至少1 h后, 在40℃水浴中化冻90 s, 用1.2 mol/L蔗糖培养液洗涤2次, 每次10 min, 然后转入含0.3 mol /L蔗糖的MS培养基上,暗培养10～15 h后转移到含0.5 mg/L 62BA的MS培养基中, 暗培养1周后转移到正常光下, 3个香蕉品种(巴西蕉、广东香蕉2 号、广东粉蕉1 号) 的成活率分别为75.9%、40.0%和69.6% , 再生率分别为63.4%、35.0%和63.4%。再生植株生长和分化正常, 生根后可移栽成活。     

Conditioning alleviates reduced yield of smaller plugs of ‘Albion’ strawberry (Fragaria X ananassa Duch.) in off-season plasticulture production

The influences of plug size, planting density, and mulch colour on responses to photoperiod and nitrogen conditioning of ‘Albion’ strawberry (Fragaria x ananassa Duch.) plants were evaluated in off-season field production in New Jersey, USA. Three different sized plug plants (7.6 cm square pots, 24-cell plug trays, or 50-cell plug trays) were conditioned with natural days (ND, natural daylength) or long days (LD, natural daylength supplemented with 24 h incandescent radiation) for one week followed by ND plus 100 ppm nitrogen (N) for 4 weeks or LD plus 800 ppm N for 4 weeks. Plants were then established in plasticulture on black, white, or silver mulch. In a second experiment, plug plants (439 cm³) were conditioned with LD and nitrogen then established in plasticulture on black, white, or silver mulch at 3 planting densities (0.46, 0.23, and 0.16 m²?plant^?1 (2, 4, and 6 plants?m^?2)). Fruit were harvested from August through October in both experiments. Conditioning enhanced off-season fall production. White plastic enhanced survival, productivity, and fruit size and larger plugs were more productive than smaller ones. If smaller plugs are desired, conditioning prevents the reduction in yield observed with non-conditioned smaller plugs.