High Levels Of Sucrose Research Articles

Effect of sucrose concentration on sclerotia production and subsequent apothecial formation by Sclerotinia sclerotiorum

The number, range of individual and total fresh weight of sclerotia produced by an isolate of Sclerotinia sclerotiorum increased linearly with sucrose concentration. Mean weight of sclerotia had a log-normal distribution with respect to sucrose concentration and increased to a maximum at 3 and 5% w/v sucrose. Without any pretreatment, carpogenic germination of sclerotia began between 2–7 wk on moist filter paper under the same environmental conditions used for sclerotium production. Apothecial production increased with time, maximal production taking place after 6–10 wk from sclerotia from low sucrose concentrations. Formation was slower from sclerotia from higher sucrose levels and none were formed on sclerotia produced at 3 and 5% sucrose. Carpogenic germination was restricted mainly to sclerotia less than 10 mg. Production of a single apothecium per sclerotium was more frequent than multiple apothecia production.

Embryo Rescue through in Ovulo Culture in Helianthus

In vitro rescuing of interspecific embryos between sunflower (Helianthus annuus L.) and other Helianthus species has been limited by the inability to culture embryos less developed than the vascular stage. The objective of this research was to develop a technique for rescuing ✕ Helianthus embryos at an earlier growth stage. This objective was achieved by culturing the embryos for 1 wk in ovulo on artificial agar media. During that culture period, 51 to 84% of the embryos from five sunflower genotypes developed to the vascular stage like in vivo sib‐embryos of the same age left as checks on greenhouse plants. Survival and development of sunflower embryos grown in ovulo were not affected by the salt composition of the four media tested (B5, B5S, MS and NN), or benefited by high sucrose levels (90 or 120g L−1). The technique of in ovulo culture resulted in rescuing 52% of H. annuus ✕ H. maximiliani Schrad. hybrid embryos. This indicates that sunflower ovules cultured on standard media fulfilled the requirements of Helianthus hybrid embryos at an early stage of development. After excision from the ovule and subsequent culturing for 2 wk on fresh media with the same composition, 40 to 60% of H. annuus embryos and 25% of H. annuus ✕ H. maximiliani hybrid embryos germinated into plantlets. Six H. annuus ✕ H. maximiliani plantlets survived transfer to the greenhouse and grew into flowering plants that exhibited traits from both parents. These are the first reported hybrid plants between H. annuus and H. maximiliani using sunflower as the female parent.

In vitro tuberization in transgenic potatoes harboring ß-glucoronidase linked to a patatin promoter: effects of sucrose levels and photoperiods

Sections of axenic potato shoots containing one leaf were found to synchronically produce a microtuber in their single leaf axil 7 days after transfer to inductive medium containing 8% sucrose, kinetin and ancymidol (a gibberellin-biosynthesis inhibitor). Shoots of transgenic Solanum tuberosum harboring a chimeric gene containing a patatin promoter sequence followed by the gene coding for ß-glucuronidase as a reporter protein, were utilized. Microtubers were initiated in inductive medium under either long-day (LD) or short-day (SD) photoperiods. The minimal duration of culture in 8% (w/v) sucrose (followed by culture in 2% (w/v) sucrose) is 1 or 3 days, when the shoots were subsequently maintained (for 6 or 4 days) in LD or SD, respectively. Changes in patatin transcription were evaluated by following ß-glucuronidase activity. Strong increase in ß-glucuronidase activity was observed in tuber initials 5 days after transfer to tuber-induction medium. This increase paralleled the accumulation of radioactivity in the tuber initials of shoots cultured in radioactive sucrose. ß-Glucuronidase activity analyses at various periods after induction and in different tissues of the in vitro cultured shoot-sections as well as the elimination of one of the obligatory induction conditions, suggested that the requirement for high sucrose levels does not represent an energy demand but rather an induction signal. Day-length has apparently a decisive role, after exposure to high-levels of sugar, in maintaining the tuberization signal.

Factors influencing the transplantation success of micropropagated narcissus bulbils

SummaryThe transplantation phase of narcissus micropropagation was studied using bulbils from bulbing shoots sub-cultured to hormone-free bulbing medium. Transplantation success was enhanced by the incorporation of activated charcoal in the medium, culturing the shoots at a constant 20°C and subjecting bulbils to a period of cold storage at 5°C to overcome dormancy prior to planting out. These measures gave overall figures for transplantation success in a large-scale evaluation experiment of 47.8-81.2% depending on cultivar. Greatest success was achieved using bulbils weighing more than 0.2 g. However, the overall proportion of such bulbils was only 0.19 to 0.20. Early leaf senescence, which limits bulbil growth in culture, appeared to be linked with initial bulbing shoot weight. The beneficial effects on transplantation of using full-strength mineral salts over halfstrength salts and of using one particular clone of cv. St. Keverne, were probably mediated via effects on final bulbil weight. Elevated concentrations of sucrose in the bulbing medium gave no benefit even though final bulbil weight was increased. High sucrose levels gave earlier shoot senescence and increased dormancy. Culture of bulbils in darkness did not effect final bulbil weight but was extremely detrimental to transplantation success. Most unsuccessfully transplanted bulbils showed a foliar growth phase suggesting a premature re-entry into dormancy. With few exceptions, bulbils judged to have been successfully transplanted grew on without problem in their second year.

Respiratory Enzyme Activity in Low Temperature Sweetening of Susceptible and Resistant Potatoes

ABSTRACTDuring storage at 4°C and 12°C, a potato cultivar susceptible to chill‐sweetening (Norchip) accumulated significantly (P≤0.05) higher levels of sucrose, fructose and glucose than a potato selection resistant to chill‐sweetening (ND 860‐2). ND 860‐2 tubers exhibited a significantly (P≤0.05) higher respiration rate throughout storage, reflected in higher activities of phosphofructokinase (PFK), glucose‐6‐phos‐phate dehydrogenase (G6PDH) and 6‐phosphogluconate dehydrogenase (6PGDH). Storage significantly (P≤0.05) reduced respiration rate for both cultivars. G6PDH showed no significant (P>0.05) difference in specific activity or Vmax between 4°C and 12°C for either cultivar. However, Km decreased at 4°C for both cultivars, possibly due to build up of substrate.

Production of isolated somatic embryos from sunflower thin cell layers

We describe here a two step procedure which allows the easy isolation of somatic embryos from Sunflower (Helianthus annuus L.) hypocotyl tissues. Thin cell layers composed of the epidermis plus 3 to 6 parenchyma cell layers were incubated for 5 days in a basal Murashige and Skoog medium using an auxin to cytokinin weight ratio of 1/1. The epidermis layers were then transferred to a Gamborg medium containing a high level of sucrose. After one week of incubation in this medium, many somatic embryos started to be released from the parental epidermal tissue. Even though the germination of these embryos is difficult, we have been able to induce secondary embryos and regenerate fertile plants.

Isolated microspore culture of maize: effects of isolation technique, reduced temperature, and sucrose level

Improvements in ab initio microspore culture of maize are presented using a modified isolation technique, reduced temperature during early stages of culture, and an elevated sucrose level in the culture medium. Blending-isolation, using excised anthers, was less stressful on microspores than pressing anthers against a stainless steel sieve and resulted in a 3-fold increase in the yield of embryo-like structures (ELS). Exposure to reduced temperature (15°C) during the first 4 days of culture improved microspore viability and increased by 2-fold the number of ELS produced. Higher levels of sucrose (8.0-9.5%) also resulted in improved response. Maximum yield in the present study was 92 ELS per 100 anther equivalents, exceeding previously reported values of 15 ELS per 100 anther equivalents for ab initio microspore culture of maize. The increase in the total number ELS produced had no observable effect on their quality as evidenced by the frequency of formation of callus capable of regenerating plants.

Effect of low temperature and sucrose on bulb development and on the carbohydrate status of bulbing shoots of tulipin vitro

Shoots produced from tulip floral stem explants in vitro and incubated at 20°C for 12 to 16 weeks are capable of initiating a bulb primordium at their base. Development of this pri- mordium was enhanced when cultures were subcultured onto medium containing 6% sucrose before incubation at 4°C for 12 weeks followed by final incubation at 20 or 25°C for 20 weeks. Sucrose appeared to be an important type of carbohydrate involved in bulb development. Low-temperature incubation of shoot cultures enhanced bulb development and was associated with a high level of sucrose in the shoots before they were transferred to the final incubation at 20 or 25°C.

Mutagenesis and Triazine Herbicide Effects in Strawberry Shoot Cultures

The effects of simazine on shoot culture of two varieties of strawberry were investigated with a view to establishing a system for in vitro selection of resistant mutants. In single shoots some chlorophyll loss occurred at herbicide levels producing little growth inhibition, but efficient bleaching was associated with severe suppression of growth. Varying simazine and sucrose levels, in both single and multiple shoot cultures did not reveal any conditions where chlorophyll destruction and growth inhibition could be separated. A protective effect, against bleaching, of high sucrose levels was not linked to suppression of photosynthesis, as assessed by CO2-fixation measurements. Mutagenesis with nitrosomethyl urea resulted in chlorophyll deficiencies in about 10% of shoots arising from axillary buds, but no resistant sectors emerged from 8000 and 400 mutagenized explants placed on medium containing inhibitory levels of simazine and streptomycin sulphate, respectively.

The effect of light onin vitro microtuberization of potato cultivars

The effect of an 8 h light/day or total darkness photoperiod on thein vitro microtuberization of cultivars “Red Pontiac”, “Shepody”, “Kennebec” and “Yukon Gold” was investigated using a medium consisting of Murashige and Skoog salts, vitamins, high sucrose and high benzylamino purine levels and cultured at 16°C for 12 weeks. Percent tuberization of the singlenode leaf cuttings averaged over all 4 cultivars was initially lower, with the 8 h photoperiod at 4 weeks, but later was similar to the total darkness photoperiod at 8 and 12 weeks. Microtubers from all cultivars had a higher mean fresh weight when treated with an 8 h photoperiod as compared with total darkness, though the difference was not significant with “Yukon Gold.” ldRed Pontiac” and “Shepody” produced microtubers that were well over twice the fresh weight of those produced in the total darkness treatment. Delayed leaf senescence, microtuber greening, and nodal rooting were evident with the 8 h light treatment.

Carbohydrate Partitioning and Nodule Function in Common Bean after Heat Stress

Previous work has shown that daily temperature maxima of 38 °C eliminate N2‐fixing activity in common bean (Phaseolus vulgaris L.) in less than 3 d. The purpose of this work was to (i) determine if this response is related to diminished supply of C to nodules and (ii) investigate the recovery of nodule function following short‐term heat stress. ‘Jutiapa’ was grown in sand culture at 26/22 °C (day/night) until 16 d after planting, then transferred to 38/22 °C for 6 d. Acetylene reduction activity (ARA) was eliminated at 38 °C, but nodule concentrations of sucrose and glucose at that temperature were equal or higher than at 26 °C throughout the 6‐d period. Stressed nodules and controls had 127 ± 12 and 90 ± 10 mg of starch per g of dry weight, respectively, after 3 d of treatment, which was the largest difference observed. Treated plants tended to have higher levels of sucrose, glucose, and starch in shoots, particularly in stems, than did controls. In a similar experiment, cells of stressed nodules showed loss of cytoplasm and rupture of peribacteroid membranes after 6 d of heat. Recovery of ARA started 1 wk after the removal of the stress; at that point, treated plants and controls had shoot N contents of 30 and 118 mg plant−1, respectively. This N deficiency caused long‐lasting alterations of plant growth and development. The inhibition of nodule function by high temperature was not related to availability of carbohydrate, but to the breakdown of the bacteria‐infected cells.

Dry weight accumulation and starch‐synthesis enzymes in grain of cultured ears of three winter wheat varieties

Detached ears of three winter wheat (Triticum aestivum L.) varieties were cultured in solution for 12 days with sucrose levels varying from 36.5 to 292 mM. The dry weight and starch content of grains increased asymptotically with the sucrose level in the solution. At 4 days of culture, glucose phosphate isomerase (EC 5.3.1.9) activity grain−1 was lower with 36.5 mM than with higher sucrose levels in the medium; at 8 days, adenosinc diphosphoglucose pyrophosphorylase (EC 2.7.7.27) and (soluble plus bound) starch synthase (EC 2.4.1.21) activities grain−1 were higher with 146 and 292 mM sucrose than with 36.5 and 73 mM sucrose. The multiple regression of starch content over these enzyme activities showed that starch synthase was relatively more important as an independent variable. The dry weight and starch content of grains were higher in the variety Maris Huntsman than in Splendeur and Hobbit. The water content of grains was lower in Splendeur than in the other two varieties. At 4 days the glucose phosphate isomerase, adenosine diphosphoglucose pyrophosphorylase and starch synthase activities grain−1 were smaller in Splendeur than in Hobbit and Maris Huntsman and al 8 days they were higher in Maris Huntsman than in Hobbit and Splendeur. The varietal differences in starch content of grains were related to the activities of glucose phosphate isomerase and especially of starch synthase.

Both developmental and metabolic signals activate the promoter of a class I patatin gene

Patatin is one of the major soluble proteins in potato tubers and is encoded by a multigene family. Based on structural considerations two classes of patatin genes are distinguished. The 5'-upstream regulatory region of a class I gene contained within a 1.5 kb sequence is essential and sufficient to direct a high level of tuber-specific gene activity which was on average 100- to 1000-fold higher in tubers as compared to leaf, stem and roots in greenhouse grown transgenic potato plants when fused to the beta-glucuronidase reporter gene. Histochemical analysis revealed this activity to be present in parenchymatic tissue but not in the peripheral phellem cells of transgenic tubers. Furthermore the promoter fragment can be activated in leaves under conditions that simulate the need for the accumulation of starch in storage organs, i.e. high levels of sucrose. The expression is restricted to both mesophyll and epidermal cells in contrast to vascular tissue or hair cells.

Adaptation of the Euryhaline CharophyteLamprothamnium papulosumto Brackish and Freshwater: Turgor Pressure and Vacuolar Solute Concentrations During Steady-State Culture and After Hypo-osmotic Treatment

The euryhaline charophyte Lamprothamnium papulosum (Wallr.) J. Gr. was adapted to media with decreasing salinities ranging from 550 to ∼0 mosmol kg−1. Vegetative plants grown in media with osmotic pressures (φ0) in the range of 550 to 130 mosmol kg−1 maintained a constant turgor pressure (Δφ) at 309 + 7 mosmol kg−1. The ions K+, Na+ and Cl−, were the predominant solutes in the vacuole. Changes in their concentrations account for the variation in internal osmotic pressure (φ1) with, φ0. The divalent ions Mg2+, Ca2+ and SO42- were also present in significant amounts, but their concentrations did not alter with changes in, φ0. In cells subjected to hypo-osmotic shock the regulation of Δφ was incomplete. The turgor pressure increased from 302 to 383 mosmol kg−1. The first rapid response to the sudden decrease in φ0 was a loss of K+ and Cl−. In contrast to the decrease in ionic concentrations an accumulation of sucrose occurred which could account for the increase of Δφ. The increase in sucrose concentration started 24 to 48 h after the downshock and reached its highest value after 3 to 4 weeks. The sucrose concentration in the vacuole was up to 320 mol m−3. During this time the ionic content continued to decrease but did not counterbalance the sucrose concentration sufficiently to regain the original Δφ. High sucrose levels accompanied by an enhanced Δφ were also observed during the period of fructification (sexual reproduction: formation of antheridia and oogonia) in Lamprothamnium kept under conditions of constant salinity. It is concluded that high sucrose content and elevated Δφ are characteristic of sexual reproduction in this charophyte. Lamprothamnium is able to tolerate different Δφ during various developmental stages (e.g. vegetative and reproductive phases).

The effects of different levels of dietary sucrose on root caries subsequent to gingivectomy in conventional rats infected with Actinomyces viscosus M-100.

Three groups of weanling, Sprague-Dawley-derived rats were inoculated with Actinomyces viscosus M-100 and fed powdered diet containing either 67%, 5%, or 0% confectioner's sugar. Two further groups were fed diet containing 5% confectioner's sugar and inoculated with Streptococcus sobrinus 6715 or S. sobrinus 6715 plus A. viscosus M-100. The most coronal 1 mm of gingiva was removed from maxillary and mandibular right molar quadrants (gingivectomy), and the animals re-inoculated following gingivectomy. The animals were killed 64 days following gingivectomy, and the lingual surface of mandibular first molar roots was measured for exposed root-surface area and root caries. In the groups of rats infected with A. viscosus M-100, root caries area was significantly greater in the group fed diet containing 67% confectioner's sugar. Sucrose level did not significantly affect the amount of exposed lingual first molar root area regardless of whether the tooth had been subjected to a gingivectomy. In the groups of rats receiving diet containing 5% confectioner's sugar, there were no significant differences in root caries area or exposed root-surface area, regardless of the infection status of the animals. In the rat model presented here, a high level of dietary sucrose was a necessary condition for the initiation of root caries in the absence of other readily fermentable carbohydrates.

Postharvest Characteristics of Geraldton Wax Flowers

Abstract Abscission of flowers of Geraldton wax (Chamelaucium uncinatum Schau., Myrtaceae) exposed to ethylene was prevented by pulsing with silver thiosulfate. Both a short pulse (15 min, 4.0 mm Ag+) at 25°C and an overnight pulse (0.5 mm Ag+) at 2° were effective treatments. Silver thiosulfate did not improve the vase-life of flowers held in air. Gamma irradiation (60Co source), an insect control measure, resulted in a reduction in vase-life; even at doses as low as 0.05 kGy. Vase-life of Geraldton wax flowers was not affected by prior storage for up to 2 weeks at 0° to 2°. Iprodione pretreatment (1 g·liter−1, 30-sec dip) for Botrytis cinerea Pers. control improved the vase-life of flowers stored for 2 weeks. A preservative solution containing sucrose (1% to 3% w/v) and 8-hydroxyquinoline sulfate (200 mg·liter−1) increased the vase-life of Geraldton wax flowers. Higher sucrose levels (>5% w/v) may cause desiccation of foliage and excessive nectar secretion from floral nectaries. Chemical name used: 3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1-imidazolidinecarboxamide (iprodione).

Use of Osmotic Inhibition in Studies of Shoot Formation in Tobacco Callus Cultures

Tobacco (Nicotiana tabacum) callus was transferred from permissive shoot-forming (SF) to inhibitory conditions and vice versa at different days in culture. Inhibition occurred when high levels (10%, 12%, 15%, w/v) of sucrose were added to the medium. Reciprocal tissue transfers were made at key histological stages of the SF process, and known biochemical and biophysical correlates of the process were examined after the transfers. The earlier in culture the cells were exposed to the permissive SF conditions, the greater was the number of shoots formed. High sucrose levels inhibited all stages of the SF process. Transfer of the SF tissue to the inhibitory conditions caused a reduction of the preferential cell division zones, the disorganization of meristemoids into parenchymatous tissue, and the accumulation of starch. Osmotic adjustment took place in the reciprocal transfers occurring rapidly in the early stages of culture and more slowly in older tissue. The changes in the rate of respiration could not be correlated with the above events. This approach to the study of in vitro organogenesis appears to be useful for examining the mechanism of tissue and organ differentiation.

Sink Metabolism in Tomato Fruit

Carbohydrate composition and key enzymes involved in carbohydrate metabolism were assayed throughout development of Lycopersicon esculentum and L. chmielewskii fruit. Translocation and assimilation of asymmetric sucrose and total soluble solids content was also determined in both species. The data showed that L. chmielewskii accumulated less starch than L. esculentum, and this was related to a lower level of ADPglucose pyrophosphorylase and a higher level of phosphorylase in L. chmielewskii. L. chmielewskii accumulated sucrose throughout fruit development rather than glucose and fructose which were accumulated by L. esculentum. A low level of invertase and nondetectable levels of sucrose synthase were associated with the high level of sucrose in L. chmielewskii. Translocation and assimilation of asymmetrically labeled sucrose indicated that sucrose accumulated in L. chmielewskii fruit was imported and stored directly in the fruit without intervening metabolism along the translocation path. In contrast, the relatively low level of radioactive sucrose found in L. esculentum fruit appeared to arise from hydrolysis and resynthesis of sucrose. The possible relationship between the level of soluble solids and differences in carbohydrate metabolism in sink tissue of the two species is discussed.

Characterization of phloem exudation from castor-bean cotyledons

Exudate was collected fromRicinus communis L. cotyledons after cutting the hypocotyl. It contained high levels of sucrose and potassium, a low level of calcium, and a pH of approx. 7.5. After application of [(14)C] sucrose to the cotyledons, radioactivity could be recovered from the exudate, indicating that the exudate was derived from the phloem. Using data from a number of individual seedlings, correlations between loading rates of sucrose, translocation rates, and sucrose and potassium contents were analyzed. A positive correlation was found between the rate of sucrose loading and the rate of sucrose exudation, whereas a negative correlation existed between the contents of sucrose and potassium in the phloem.

Effects of carbohydrate source on voluntary activity and myocardial metabolism in chicks

In an effort to study the effects of different carbohydrate sources on voluntary activity and on myocardial constituents and enzyme activities in chicks, restricted feeding was applied with equal amounts of carbohydrate in the form of glucose (GC), sucrose (SC) or fructose (FC) to induce voluntary activity measured by Wahmann activity wheels. The performance was measured as average daily wheel turns during 12 days on diet and was almost the same for the SC and FC groups but 14–18% higher in the GC group. Heart weights, and the myocardial contents of protein, RNA and DNA as well as the citrate synthase activity were similar with all three diets, but the activities of lactate dehydrogenase and cytochrome c oxidase were lower in the FC as compared to the SC and GC groups. The FC chicks had increased myocardial activity of beta-glucuronidase that was correlated to the increase in the heart per body weight ratio. Within each dietary group the protein content correlated to the content of RNA. This study shows that high levels of fructose and sucrose compared to glucose as energy source in chicks resulted in decreased capacity to perform exercise but this lower performance as not correlated to a decreased oxidative metabolic capacity of the myocardium.