Nectar Samples Research Articles

Occurrence of caffeine, saccharin, benzoic acid and sorbic acid in soft drinks and nectars in Portugal and subsequent exposure assessment

A reliable method for the determination of benzoic and sorbic acids, caffeine and saccharin in soft drink and nectars using high performance liquid chromatography and UV detection was validated. The chromatographic separation was achieved with a C18 column (250 × 4.6 mm) and one buffered mobile phase, KH 2PO 4 0.02 M/ACN (90:10)/phosphoric acid at pH 4.2. The effluent was monitored at 220 nm. Benzoic acid was detected in 19 soft drinks, being 11 traditional soft drinks and 8 based on mineral water, with mean concentrations of 158 and 148 mg/L, respectively. Fifteen samples, 7 traditional and 8 based on mineral water, contained sorbic acid, with mean concentrations of 172 and 188 mg/L, respectively. Saccharin and caffeine were not detected in soft drinks based on mineral waters. In contrast, 6 samples of traditional drinks contained both additives, with mean levels of 75 and 97 mg/L, respectively. The four additives were not detected in nectar samples. According to European Union and Portuguese legislation, the maximum permitted level (MPL) for benzoic acid was exceeded in 10 soft drinks, and the MPL for sorbic acid overlapped in 3 samples of the referred samples. Two samples exceeded the MPL for the sum of both preservatives, and in 1 sample the MPL for saccharin was overlapped. The estimated daily intakes (EDI) of benzoic, sorbic acid, and saccharin for the average consumer were below the acceptable daily intakes (ADIs). For benzoic acid, the EDIs were 0.25 and 0.32 mg/kg b.w./day, representing 4.9%, and 6.4% of the ADI, respectively for traditional soft drinks and soft drinks based on mineral water. A similar situation was observed for sorbic acid. In this way, the EDIs were 0.17 and 0.41 mg/kg b.w./day, representing only 0.68% and 1.6% of the ADI for the same kind of drinks. For saccharin, the EDI represents 1.28% of the ADI. The EDI for caffeine was 0.08 mg/kg b.w./day.

Yeasts in floral nectar of some South African plants: Quantification and associations with pollinator type and sugar concentration

There is increasing evidence that nectarivorous yeasts are an important third player in plant–pollinator mutualisms, but their distribution and ecological effects remain poorly known. Here we provide a survey of the frequency and abundance of yeasts in floral nectar from 40 taxonomically diverse South African plant species, test whether they affect nectar properties, and investigate associations between yeast incidence and pollinator type. Microscopical observations of nectar samples revealed that yeasts are widespread in floral nectar of South African species, as revealed by the high percentage of plants (51.3%) and flowers (43.2%) containing those microbes, and that when present, they can reach high densities (up to 3.6 × 10 6 yeast cells/mm 3 in Moraea graminicola). Further, a significant negative correlation was found between yeast density and sugar content ( R s = − 0.463, P = 0.039) and yeast density and nectar concentration ( R s = − 0.470, P = 0.037) in a Watsonia species. Interestingly, variation in yeast incidence among plant species was related to differences in pollinator type, in such a way that the plant species pollinated by birds showed the highest proportion of plants and flowers with yeasts, while those visited only by Hymenoptera showed the lowest values. Our study confirms the ubiquity of nectarivorous yeasts in plant communities and identifies novel ways of approaching the study of nectar characteristics and exciting new perspectives on the role of yeasts in plant–pollinator relationships.

Ultrastructure and post-floral secretion of the pericarpial nectaries of Erythrina speciosa (Fabaceae).

The occurrence of nectaries in fruits is restricted to a minority of plant families and consistent reports of their occurrence are not found associated with Fabaceae, mainly showing cellular details. The present study aims to describe the anatomical organization and ultrastructure of the pericarpial nectaries (PNs) in Erythrina speciosa, a bird-pollinated species, discussing functional aspects of these unusual structures. Samples of floral buds, ovaries of flowers at anthesis and fruits at several developmental stages were fixed and processed by the usual methods for studies using light, and scanning and transmission electron microscopy. Nectar samples collected by filter paper wicks were subjected to chemical analysis using thin-layer chromatography. The PNs are distributed in isolation on the exocarp. Each PN is represented by a single hyaline trichome that consists of a basal cell at epidermal level, stalk cell(s) and a small secretory multicellular head. The apical stalk cell shows inner periclinal and anticlinal walls impregnated by lipids and lignin and has dense cytoplasm with a prevalence of mitochondria and endoplasmic reticulum. The secretory cells show voluminous nuclei and dense cytoplasm, which predominantly has dictyosomes, rough endoplasmic reticulum, plastids, mitochondria and free ribosomes. At the secretory stage the periplasmic space is prominent and contains secretion residues. Tests for sugar indicate the presence of non-reducing sugars in the secretory cells. Nectar samples from PNs contained sucrose, glucose and fructose. The secretory stage of these PNs extends until fruit maturation and evidence suggests that the energetic source of nectar production is based on pericarp photosynthesis. Patrolling ants were seen foraging on fruits during all stages of fruit development, which suggests that the PNs mediate a symbiotic relationship between ants and plant, similar to the common role of many extrafloral nectaries.

Pollination biology of a night-flowering Galápagos endemic,Ipomoea habeliana(Convolvulaceae)

Ipomoea habeliana is an endemic, night-flowering member of the Galápagos flora. Pollination experiments, flower-visitor observations, nectar sampling, pollen transfer, and pollen to ovule ratio and pollen size studies were included in this project. The large, white flowers of this species set fruit via open pollination (55%), autonomous autogamy (51%), facilitated autogamy (91%), cross-pollination (80%), diurnal open pollination (60%) and nocturnal open pollination (60%). Fruit set is pollen-limited. Ants, beetles, crickets and hawk moths regularly visit the flowers. Ants are the most frequent visitors, but hawk moths are the only effective pollinators. Nectar is available throughout the night, but is most abundant early in the evening when hawk moth visits are most frequent. Experiments with fluorescent dust demonstrate intra- and inter-plant pollen movement by hawk moths. Although this species is adapted for hawk moth pollination, it readily sets fruit via autonomous autogamy when no visits are made. Thus, it is concluded that it is facultatively xenogamous. Additional support for this conclusion is provided by the pollen to ovule ratio of 1407 and by the fact that the plants grow in a region that has few or no faithful pollinators. Conservation efforts for I. habeliana should include hand pollinations, which could significantly increase seed set.

Quantitative Determination of Allergenic 5-Alk(en)ylresorcinols in Mango (Mangifera indica L.) Peel, Pulp, and Fruit Products by High-Performance Liquid Chromatography

Despite a number of serious case reports of mango dermatitis, no attempts at the identification and quantification of allergenic 5-alk(en)ylresorcinols in mango fruits have so far been made. Therefore, total alk(en)ylresorcinol content and relative homologue composition in 13 mango peel samples and 7 samples of mango pulp were determined by HPLC and LC-MS/MS analyses. Furthermore, mango puree and nectar prepared on pilot plant scale were also analyzed and compared with commercially available thermally preserved products. Depending on cultivar, alk(en)ylresorcinol contents ranged from 79.3 to 1850.5 mg/kg of dry matter (DM) in mango peels and from 4.9 to 187.3 mg/kg of DM in samples of mango pulp. The profile of alk(en)ylresorcinols was found to be highly characteristic, with an average homologue composition of C15:0 (6.1%), C15:1 (1.7%), C17:0 (1.1%), C17:1 (52.5%), C17:2 (33.4%), C17:3 (2.4%), C19:1 (2.1%), and C19:2 (0.8%). Mango puree samples prepared from peeled and unpeeled fruits revealed contents of 3.8 and 12.3 mg/kg of fresh weight, respectively. Content and homologue composition were not significantly affected during puree processing and thermal preservation. In nectar samples prepared from peeled and unpeeled fruits, contents of 1.4 and 4.6 mg/L, respectively, were found.

Methyl Syringate: A Chemical Marker of Asphodel (Asphodelus microcarpus Salzm. et Viv.) Monofloral Honey

During the liquid chromatographic study of the phenolic fraction of monofloral honeys was detected in the asphodel honey ( Asphodelus microcarpus Salzm. et Viv.) chromatogram a distinctive peak not detected in other monofloral honeys such as Arbutus unedo L., Hedysarum coronarium , Eucalyptus spp., and Galactites tomentosa . After thin layer chromatography (TLC) purification and characterization by NMR and LC-MS/MS, the compound was identified as methyl syringate (MSYR) and confirmed against an original standard. Levels of MSYR were measured in honeys of 2005, 2006, and 2007 by HPLC-DAD analysis. Level determination of MSYR was repeated in 2008 for 2006 and 2007 honeys to evaluate chemical stability of this phenolic compound. Levels of MSYR measured 1 year after the sampling did not show significant statistical differences (p < 0.05). The stability of MSYR was also confirmed by 12 asphodel honey samples collected in 2005 that showed amounts of methyl syringate comparable with those found in fresh honey. For the evaluation of MSYR origin, samples of nectars were collected from flowers and the content of MSYR was measured. Levels of MSYR in honeys are originated from the nectar with an average contribution of the nectar to the honey of 80%. Melissopalinological analysis did not allow the attribution of the honey monofloral origin because levels of asphodel pollen were <6% for all analyzed samples. Previously reported levels of MSYR for robinia, rape, chestnut, clover, linden blossom, dandelion, sunflower, thyme, manuka, and fir honeys were <5 mg/kg. For this reason, a minimum level of 122.6 mg/kg for MSYR in asphodel honeys can be considered as a chemical marker and, unlike the melissopalynological analysis, can be used for the origin attribution and to evaluate the percent of asphodel nectar in the honey.

Yeasts in floral nectar: a quantitative survey

One peculiarity of floral nectar that remains relatively unexplored from an ecological perspective is its role as a natural habitat for micro-organisms. This study assesses the frequency of occurrence and abundance of yeast cells in floral nectar of insect-pollinated plants from three contrasting plant communities on two continents. Possible correlations between interspecific differences in yeast incidence and pollinator composition are also explored. The study was conducted at three widely separated areas, two in the Iberian Peninsula (Spain) and one in the Yucatán Peninsula (Mexico). Floral nectar samples from 130 species (37-63 species per region) in 44 families were examined microscopically for the presence of yeast cells. For one of the Spanish sites, the relationship across species between incidence of yeasts in nectar and the proportion of flowers visited by each of five major pollinator categories was also investigated. Yeasts occurred regularly in the floral nectar of many species, where they sometimes reached extraordinary densities (up to 4 x 10(5) cells mm(-3)). Depending on the region, between 32 and 44 % of all nectar samples contained yeasts. Yeast cell densities in the order of 10(4) cells mm(-3) were commonplace, and densities >10(5) cells mm(-3) were not rare. About one-fifth of species at each site had mean yeast cell densities >10(4) cells mm(-3). Across species, yeast frequency and abundance were directly correlated with the proportion of floral visits by bumble-bees, and inversely with the proportion of visits by solitary bees. Incorporating nectar yeasts into the scenario of plant-pollinator interactions opens up a number of intriguing avenues for research. In addition, with yeasts being as ubiquitous and abundant in floral nectars as revealed by this study, and given their astounding metabolic versatility, studies focusing on nectar chemical features should carefully control for the presence of yeasts in nectar samples.

Information costs of reduced-effort habitat monitoring in a butterfly recovery program

Habitat monitoring typically requires a large amount of effort and resources. Project managers are likely to consider cost-cutting options but they may not critically review the information costs of implementing those options. An effort recently began in New York State to monitor critical habitat and restoration progress aimed at recovering the federally endangered Karner blue butterfly (Lycaeides melissa samuelis). Specific strategies were proposed to increase efficiency of fieldwork: (1) estimate larval host plant (wild blue lupine, Lupinus perennis) abundance from cover data, (2) area-based standardization of sample size for nectar sampling, (3) use a minimum cover threshold to trigger nectar species counts, (4) use multiple observers. I quantitatively reviewed these time savers for effects on raw data quality, and for potential effects on interpreting habitat quality as part of recovery criteria. Cover-based models of lupine abundance differed between metapopulation recovery areas, area-based sampling was sufficient to detect over 80% of priority nectar species in most sites, nectar information loss was high due to the minimum cover threshold, and overall results from different observers were similar with one exception. Direct lupine stem counting is recommended over cover estimation, statistical interpolation (rarefaction) and extrapolation (asymptotic estimators) is recommended over area-based nectar sampling, use of minimum cover criteria is strongly discouraged, and field crews need botanical expertise and careful instructions. This example highlights why strategies to save time and money with monitoring fieldwork should be ‘put to the test’.

Field methods for sampling and storing nectar from flowers with low nectar volumes

Although several methods of sampling and storing floral nectar are available, little information exists on sampling and storing nectar from flowers with low nectar volumes. Methods for sampling and storing nectar from the flowers of species with low floral nectar volumes (<1 microL) were investigated using the flowers of Eucalyptus species. Sampling with microcapillary tubes, blotting up with filter paper, washing and rinsing were compared to determine masses of sugars recovered and differences in sugar ratios. Storage methods included room temperature, refrigeration and freezing treatments; the addition of antimicrobial agents benzyl alcohol or methanol to some of these treatments was also evaluated. Nectar samples were analysed using high-performance liquid chromatography and the masses of sucrose, glucose and fructose in each sample were determined. Masses of sugars varied significantly among sampling treatments, but the highest yielding methods, rinsing and washing, were not significantly different. A washing time of 1 min was as effective as one of 20 min. Storage trials showed that the sugar concentration measurements of nectar solutions changed rapidly, with the best results achieved for refrigeration with no additive (sucrose and fructose were stable for at least 2 weeks). Sugar ratios, however, remained relatively stable in most treatments and did not change significantly across 4 weeks for the methanol plus refrigerator and freezing treatments, and 2 weeks for the refrigeration treatment with no additive. Washing is recommended for nectar collection from flowers with low nectar volumes in the field (with the understanding that one wash underestimates the amounts of sugars present in a flower), as is immediate analysis of sugar mass. In view of the great variation in results depending on nectar collection and storage methods, caution should be exercised in their choice, and their accuracy should be evaluated. The use of pulsed amperometric detection, more specific than refractive index detection, may improve the accuracy of nectar sugar analysis.

DESCRIPTIVE PROFILE OF PEACH NECTAR SWEETENED WITH SUCROSE AND DIFFERENT SWEETENERS

ABSTRACT Consumers are looking even more for food with pleasant characteristics in terms of flavor, appearance, aroma and texture. Thanks to technological advances, it is possible to find low‐calorie products with these characteristics, with competitive prices when compared with similar products containing sucrose. In this study, peach nectar samples containing sucrose and the sweeteners aspartame, cyclamate/saccharin 2:1 blend, stevia, sucralose and acesulfame‐K, were evaluated by Descriptive Quantitative Analysis. This methodology is the most complete and sophisticated technique for the sensory characterization of a product, because it allows a complete description of all the attributes existent in such product. Eleven consumers were selected by their discriminative capacity, repeatability of judgment and agreement with the sensory team. Sucrose sample were at ideal sweetness and the sweeteners samples were at equi‐sweet concentrations. The descriptive terms were yellow color (YCL), cloudy aspect (CLD), brightness (BRI), visual viscosity (VIS), peach aroma (PAR), sweet aroma (SAR), herb aroma (HAR), peach flavor (PFL), sweetness (SWE), bitterness (BIT), herb flavor (HFL), sourness (SOU), residual bitterness (RBT), residual sweetness (RSW), astringency (AST) and body (BOD). The results were evaluated by analysis of variance, Tukey's test and Principal Component Analysis. The results show that the samples did not have statistical difference (P ≤ 0.05) in the attributes YCL, CLD and BRI. The sample sweetened with sucrose presented higher grades in the attributes VIS, PAR, PFL, SWE and BOD, differing statistically (P ≤ 0.05) from the other samples. Samples containing Stevia received high grades in unpleasant attributes, such as HAR, HFL, BIT, RBT and RSW, which would certainly influence its acceptance in consumers' tests. Acesulfame‐K also presented high grades in the attributes BIT and RBT.PRACTICAL APPLICATIONSQuantitative Descriptive Analysis is one of the most sophisticated methods to characterize sensory attributes of products, providing a complete description of important sensory properties. With this technique, it is possible to study qualitative and quantitative aspects of the products.This methodology is used when launching a new product; in quality control applications; to track sensory changes in a product over time; to correlate instrumental, chemical or physical with sensory measurements, among others.In this research, several lexicons were generated to describe the peach nectar sweetened with different sweeteners, highlighting some characteristics of sweeteners such as bitterness and residual tastes. It also presents a comparison among the nectar sweetened with sucrose and sweeteners and shows which sweetener has a descriptive profile more similar to sucrose.With this information, people suffering from diabetes or obesity, major problems in the whole world, could find a sugar substitute with similar properties of sucrose.

Estimated intake of the sweeteners, acesulfame-K and aspartame, from soft drinks, soft drinks based on mineral waters and nectars for a group of Portuguese teenage students

In a survey of levels of acesulfame-K and aspartame in soft drinks and in light nectars, the intake of these intense sweeteners was estimated for a group of teenage students. Acesulfame-K was detected in 72% of the soft drinks, with a mean concentration of 72 mg l−1 and aspartame was found in 92% of the samples with a mean concentration of 89 mg l−1. When data on the content of these sweeteners in soft drinks were analysed according to flavour, cola drinks had the highest mean levels for both sweeteners with 98 and 103 mg l−1 for acesulfame-K and aspartame, respectively. For soft drinks based on mineral water, aspartame was found in 62% of the samples, with a mean concentration of 82 mg l−1 and acesulfame-K was found in 77%, with a mean level of 48 mg l−1. All samples of nectars contained acesulfame-K, with a mean concentration of 128 mg l−1 and aspartame was detected in 80% of the samples with a mean concentration of 73 mg l−1. A frequency questionnaire, designed to identify adolescents having high consumption of these drinks, was completed by a randomly selected sample of teenagers (n = 65) living in the city of Coimbra, in 2007. The estimated daily intakes (EDI) of acesulfame-K and aspartame for the average consumer were below the acceptable daily intakes (ADIs). For acesulfame-K, the EDI was 0.7 mg kg−1 bw day−1 for soft drinks, 0.2 mg kg−1 bw day−1 for soft drinks based on mineral waters, and 0.5 mg kg−1 bw day−1 for nectars, representing 8.0%, 2.2%, and 5.8% of the ADI, respectively. A similar situation was observed for aspartame. In this way, the EDI for soft drinks was 1.1 mg kg−1 day−1, representing only 2.9% of the ADI. In respect of nectars, the EDI was 0.2 mg kg−1 bw day−1, representing 0.5% of the ADI. Soft drinks based on mineral waters showed the lowest EDI values of 0.3 mg kg−1 bw day−1, accounting for 0.7% of the ADI.

Test method for detecting adulterated apple juice using piezoelectric resonators

The adsorption of a mixture of volatile components comprising the aroma of apple juice was studied using piezoelectric quartz microweighing. Conventional gas-chromatographic adsorbents and specific films of different natures were used to modify the electrodes of a piezoelectric sensor. The conditions of the juice analysis were optimized using a piezoelectric sensor array in the batch mode. Different samples of apple juice and nectar were analyzed under the same conditions using the piezoelectric sensor array. The quality of the samples was estimated by comparing kinetic mass aromagrams. A method was developed for the rapid estimation and assortment identification or the detection of the adulteration of natural and reconstituted apple juice.

Variação da concentração de vitamina C, ºBrix e acidez em néctar de laranja em embalagens cartonadas

. Modification of vitamin C concentration, Brix and acidity in orange nectar in aseptic packaging. Samples of orange nectar in aseptic packaging were stored in controlled room temperature (25°C) and in a refrigerator (4°C). For eight weeks, analyses of vitamin C, Brix and acidity were conducted as the packages were opened, and their residual products were further analyzed during a period of four days stored in a refrigerator. By using statistical models from the results found, it was concluded that storage temperature influences the quantity of vitamin C in orange nectar. There was a significant decrease in vitamin C concentration in nectar, but storage temperature does not influence acidity or Brix. Storage time does influence vitamin C, Brix and acidity. It was concluded that after eight weeks of storage and four days of opening the package, the amount of vitamin C in a 200 mL glass of orange nectar is enough to supply the average needed daily intake (60 mg) of vitamin C for an adult.

Dynamics of pesticide residues in nectar and pollen of mustard (Brassica juncea (L.) Czern.) grown in Himachal Pradesh (India)

Residues dynamics of Endosulfan (525.00 g a.i. ha(-1)), Imidacloprid seed treatment (21 g a.i. kg(-1)), Lambdacyhalothrin (75.00 g a.i. ha(-1)) and Spiromesifen (225.00 g a.i. ha(-1)) in nectar and pollen of mustard, Brassica juncea (L.) Czern. grown in Himachal Pradesh (India) were determined through bioassay (using Drosophila melanogaster Meig. as test organism) and GC (Gas chromatographic) and HPLC (High performance liquid chromatographic) methods. In general chromatographic methods were more sensitive for the determination of above given pesticides compared to bioassay method. Average recoveries in nectar samples varied between 82.85 and 88.90% by bioassay and 91.20 and 93.55% by chromatographic techniques. In pollen samples, recoveries varied between 81.44 and 86.44% by bioassay and 88.50 and 91.30% by chromatographic methods. Imidacloprid residues were neither found in nectar nor in pollen samples at the time of sampling i.e. 50% of flowering. The order of average half life of residues was: Lambdacyhalothrin (12.45 h) < Spiromesifen (19.99 h) < Endosulfan (27.49 h) for nectar and Spiromesifen (9.69 h) < Lambdacyhalothrin (12.44 h) < Endosulfan (17.84 h) for pollen samples. It was found that Imidcloprid seed treatment was practically harmless to honey bees, whereas a waiting period of 5 days must be observed on crops sprayed with these chemicals during blooms to avoid any accidental hazards to honey bees.

Analysis of amino acids in nectar from Silene colorata Poiret (Caryophyllaceae)

Nectar samples were collected from Silene colorata Poiret (Caryophyllaceae), in three different populations from south-western Spain: Zahara de la Sierra (Cadiz), Bornos (Cadiz) and Bormujos (Seville). Samples were analysed for amino acids by reverse-phase high-performance liquid chromatography with precolumn phenylisotiocyanate (PITC) derivatization. The method has the advantage of being highly sensitive, capable of detecting nanogram (ng) quantities of amino acids. Eighteen amino acids were identified and quantified. The mean number of amino acids in a nectar sample was 14 (SD = 2.8). Six amino acids (threonine, alanine, arginine, proline, tyrosine and methionine) were detected in all samples, accounting for 83% of the total amino acids content; proline and arginine were the most abundant amino acids, accounting for 40% and 20% of the total amino acids, respectively. The mean amounts of amino acids in nectar samples per population were 824, 782 and 356 µm in Zahara de la Sierra, Bornos and Bormujos, respectively. Environmental variations such as temperature and sunlight are factors influencing the metabolic processes of nectar production. Our results may contradict the theory that the chemical constituents of floral nectar vary according to the kinds of pollinators. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 49–56.

Exposure to Clothianidin Seed-Treated Canola Has No Long-Term Impact on Honey Bees

We conducted a long-term investigation to ascertain effects on honey bee, Apis mellifera L., colonies during and after exposure to flowering canola, Brassica napus variety Hyola 420, grown from clothianidin-treated seed. Colonies were placed in the middle of 1-ha clothianidin seed-treated or control canola fields for 3 wk during bloom, and thereafter they were moved to a fall apiary. There were four treated and four control fields, and four colonies per field, giving 32 colonies total. Bee mortality, worker longevity, and brood development were regularly assessed in each colony for 130 d from initial exposure to canola. Samples of honey, beeswax, pollen, and nectar were regularly collected for 130 d, and the samples were analyzed for clothianidin residues by using high-performance liquid chromatography with tandem mass spectrometry detection. Overall, no differences in bee mortality, worker longevity, or brood development occurred between control and treatment groups throughout the study. Weight gains of and honey yields from colonies in treated fields were not significantly different from those in control fields. Although clothianidin residues were detected in honey, nectar, and pollen from colonies in clothianidin-treated fields, maximum concentrations detected were 8- to 22-fold below the reported no observable adverse effects concentration. Clothianidin residues were not detected in any beeswax sample. Assessment of overwintered colonies in spring found no differences in those originally exposed to treated or control canola. The results show that honey bee colonies will, in the long-term, be unaffected by exposure to clothianidin seed-treated canola.

Intra-plant Variation in Nectar Sugar Composition in Two Aquilegia Species (Ranunculaceae): Contrasting Patterns under Field and Glasshouse Conditions

Intra-specific variation in nectar chemistry under natural conditions has been only rarely explored, yet it is an essential aspect of our understanding of how pollinator-mediated selection might act on nectar traits. This paper examines intra-specific variation in nectar sugar composition in field and glasshouse plants of the bumblebee-pollinated perennial herbs Aquilegia vulgaris subsp. vulgaris and Aquilegia pyrenaica subsp. cazorlensis (Ranunculaceae). The aims of the study are to assess the generality of extreme intra-plant variation in nectar sugar composition recently reported for other species in the field, and gaining insight on the possible mechanisms involved. The proportions of glucose, fructose and sucrose in single-nectary nectar samples collected from field and glasshouse plants were determined using high performance liquid chromatography. A hierarchical variance partition was used to dissect total variance into components due to variation among plants, flowers within plants, and nectaries within flowers. Nectar of the two species was mostly sucrose-dominated, but composition varied widely in the field, ranging from sucrose-only to fructose-dominated. Most intra-specific variance was due to differences among nectaries of the same flower, and flowers of the same plant. The high intra-plant variation in sugar composition exhibited by field plants vanished in the glasshouse, where nectar composition emerged as a remarkably constant feature across plants, flowers and nectaries. In addition to corroborating the results of previous studies documenting extreme intra-plant variation in nectar sugar composition in the field, this study suggests that such variation may ultimately be caused by biotic factors operating on the nectar in the field but not in the glasshouse. Pollinator visitation and pollinator-borne yeasts are suggested as likely causal agents.

Extreme intraplant variation in nectar sugar composition in an insect‐pollinated perennial herb

Variation in nectar chemistry among plants, flowers, or individual nectaries of a given species has been only rarely explored, yet it is an essential aspect to our understanding of how pollinator-mediated selection might act on nectar traits. This paper describes variation in nectar sugar composition in a population of the perennial herb Helleborus foetidus (Ranunculaceae) and dissects it into components due to variation among plants, flowers of the same plant, and nectaries of the same flower. The proportions of sucrose, glucose, and fructose in single-nectary nectar samples collected at two times in the flowering season were determined using high performance liquid chromatography (HPLC). Sugar composition varied extensively among nectaries, and nearly all combinations of individual sugars were recorded. Population-wide variance was mainly accounted for by variation among flowers of the same plant (56% of total), nectaries of the same flower (30%), and only minimally by differences among plants (14%). In absolute terms, intraplant variation was similar to or greater than that ordinarily reported in interspecific comparisons. Results suggest that the prevailing notion of intraspecific constancy in nectar sugar composition may be unwarranted for some species and that more elaborate nectar sampling designs are required to detect and appropriately account for extensive within-plant variance. Within-plant variation in nectar sugar composition will limit the ability of pollinators to exert selection on nectar chemistry in H. foetidus and may be advantageous to plants by reducing the number of flowers visited per foraging bout by variance-sensitive, risk-averse pollinators.

Prevalence of Antibiotics in Nectar and Honey in South Tamilnadu, India

Abstract Reverse‐Phase High‐performance Liquid Chromatography (RP‐HPLC) based technique is one of the most sensitive techniques to detect the antibiotics present in honey. In the southern part of Tamilnadu, India, majority of the farmlands are occupied by plantations such as coconut, banana and rubber. A variety of antimicrobial compounds and antibiotics, which have been reported in pollen, nectar and other floral parts of the plant, gets accumulated in honey through honeybees (Apis mellifera). We have collected the nectar samples from banana (Musa paridasiaca) and rubber (Ficus elastica) flowers and the honey from honey hives of banana and rubber cultivated areas. The extracted nectar and honey samples are subjected to RP‐HPLC analysis with authentic antibiotic standards. Nectar and honey samples showed 4–17, 11–29 μg/kg of streptomycin, 2–29, 3–44 μg/kg of ampicillin and 17–34, 26–48 μg/kg of kanamycin respectively.

The Brief Piping Signal of the Honey Bee: Begging Call or Stop Signal?

AbstractFor over 40 yr, investigators have recognized that the brief piping signal plays a role in the foraging operation of a honey bee colony. The function of this signal, however, remains uncertain. The main objective of this study was to determine whether, under normal foraging conditions, bees following waggle dancers produce brief piping signals to beg nectar samples from the dancers. We made observations on waggle dancers and their followers in an undisturbed colony whose foragers gathered nectar and pollen from flowers. We found that waggle dancers do often receive brief piping signals, that the bees producing these signals are generally dance followers, and that these signals increase a waggle dancer's tendency to stop dancing. We also found, however, that the brief piping signal is clearly not a begging call; 0 of 41 waggle dancers that received a piping signal from a dance follower gave a nectar sample to the bee that produced the signal. Our results support the hypothesis that the brief piping signal is a stop signal; it serves to shut off waggle dancing. But why some dance followers pipe the dancer they are following, thereby inhibiting her dancing, remains unclear and warrants further investigation.