Nutritional content of fresh, bee-collected and stored pollen of Aloe greatheadii var. davyana (Asphodelaceae)

Aloe greatheadii var. davyana is the most important indigenous South African bee plant. Fresh, bee-collected and stored pollen of this aloe was collected and analysed for its nutritional content, including amino acid and fatty acid composition. Highly significant differences were found between the three types of pollen. Collection and storage by the bees resulted in increased water (13-21% wet weight) and carbohydrate content (35-61% dry weight), with a resultant decrease in crude protein (51-28% dry weight) and lipid content (10-8% dry weight). Essential amino acids were present in equal or higher amounts than the required minimum levels for honeybee development, with the exception of tryptophan. Fatty acids comprised a higher proportion of total lipid in fresh pollen than in bee-collected and stored pollen. This study is the first to compare the changes that occur in pollen of a single species after collection by honeybees.     

Metabolism and roles of phosphatidylinositol 3-phosphate in pollen development and pollen tube growth in Arabidopsis

Phosphoinositides play important roles in eukaryotic cells, although they constitute a minor fraction of total cellular lipids. Specific kinases and phosphatases function on the regulation of phosphoinositide levels. Phosphatidylinositol 3-phosphate (PtdIns3P), a molecule of phosphoinositides regulates multiple aspects of plant growth and development. In this article, we introduce and discuss the kinases and phosphatases involved in PtdIns3P metabolism and their roles in pollen development and pollen tube growth in Arabidopsis.     

Effects of pollen dilution on infection of Nosema ceranae in honey bees

Multiple stressors are currently threatening honey bee health, including pests and pathogens. Among honey bee pathogens, Nosema ceranae is a microsporidian found parasitizing the western honey bee (Apis mellifera) relatively recently. Honey bee colonies are fed pollen or protein substitute during pollen dearth to boost colony growth and immunity against pests and pathogens. Here we hypothesize that N. ceranae intensity and prevalence will be low in bees receiving high pollen diets, and that honey bees on high pollen diets will have higher survival and/or increased longevity. To test this hypothesis we examined the effects of different quantities of pollen on (a) the intensity and prevalence of N. ceranae and (b) longevity and nutritional physiology of bees inoculated with N. ceranae. Significantly higher spore intensities were observed in treatments that received higher pollen quantities (1:0 and 1:1 pollen:cellulose) when compared to treatments that received relatively lower pollen quantities. There were no significant differences in N. ceranae prevalence among different pollen diet treatments. Interestingly, the bees in higher pollen quantity treatments also had significantly higher survival despite higher intensities of N. ceranae. Significantly higher hypopharyngeal gland protein was observed in the control (no Nosema infection, and receiving a diet of 1:0 pollen:cellulose), followed by 1:0 pollen:cellulose treatment that was inoculated with N. ceranae. Here we demonstrate that diet with higher pollen quantity increases N. ceranae intensity, but also enhances the survival or longevity of honey bees. The information from this study could potentially help beekeepers formulate appropriate protein feeding regimens for their colonies to mitigate N. ceranae problems.     

不同人工代花粉对蜂群群势和生产性能的影响

早春将群势、蜂王年龄和质量基本一致的25群意大利蜜蜂Apis melliferaL.,随机分为5个处理,分别饲喂纯花粉和4种不同的人工代用花粉,观测它们对蜂群群势和生产性能的影响。结果表明,含有添加剂的各代用花粉组与纯花粉组的蜂群的蜂子数量差异均不显著,但均显著高于纯豆粕组(P<0.01);各组产蜜量随着纯花粉所占比例的减少而呈现递减的趋势,但饲喂含有60%花粉+40%豆粕+添加剂1组与纯花粉组没有明显的差异;含有添加剂的各代用花粉组的王台接受率均显著高于纯花粉组(P<0.01);饲喂含有添加剂的各代用花粉组与饲喂纯花粉组相比,王浆产量及蜂王浆中的10-HDA、水分、蛋白质的含量及酸度均没有差异。     

Six years of observation of airborne and deposited pollen in central European Russia: first results

The aim of the study was to compare the pollen spectra recorded in rural and urban environments in order to examine whether pollen data obtained in the urban environment could also represent the situation in surrounding rural areas and how urban planting affects the regional pollen spectrum. Daily airborne pollen observations were performed with a volumetric Hirst type trap in Moscow (Russia). Modified Tauber traps were located in the Moscow region. The Tauber traps were installed and treated according to Pollen Monitoring Programme (PMP) guidelines. Spearman correlation coefficients were determined between the percentage of total pollen recorded in the Tauber and Hirst type samplers. The data showed that the Tauber spectra are characterised by higher taxonomic variability, mainly due to the greater occurrence of local herbaceous plants. Pollen types registered by Hirst type samplers were predominantly represented by anemophilous arboreal species, used in urban planting. A significant correlation for annual sums was only observed for Betula pollen, the most abundant component in both sampler types. Data obtained in big cities for dominant taxa can be extrapolated to the surrounding rural territories. The simultaneous use of volumetric and gravimetric samplers can be very useful for palaeo-ecological studies to evaluate the presence of local and transported pollen.     

Dynamic aspects of apical zonation in the angiosperm pollen tube

Summary In the apical 10–20 m of actively extending pollen tubes of Epilobium angustifolium, in a zone where the polysaccharide-containing wall precursor bodies (P-particles) dominate and where their movements on superficial observation seem to be random, there is in fact a concerted flux, acropetal movement taking place along the flanks of the tip zone, with a basipetal return flow along the centre. Detailed tracking of individuals shows that lipid globuli (diameters up to 1.5 m) and amyloplasts (dimensions up to 5.5 × 2.5 m) follow similar patterns of movement, but are sorted out in the sub-apical region, the smaller bodies penetrating further towards the apex. The findings are interpreted as indicating that the well-documented apical zonation of the pollen tube is maintained in the fluid circumstances of the growing tube by the filtering of cytoplasmic inclusions through the actin cytoskeleton, which, in conformity with recent fine-structural and other observations, is envisaged as consisting of a network of cross-linked microfilaments and microfilament aggregates at the tube tip giving place progressively to a system of more ordered, longitudinally oriented fibrils in the older parts of the tube. The implications for the operation of the actomyosin motility system and the tip growth mechanism are discussed.     

蜜蜂花粉采集器官和采集飞行的线性比例分析

本研究从采粉工蜂飞行中能量消耗相关的几个方面入手,分析了蜜蜂属(Apis) 8个物种的花粉采集器官。结果表明,花粉筐表面积、翅膀表面积、体重及胸部动力容量与蜂种个体的体长呈极显著相关,并且它们随蜂种个体的增大而呈对数线性比例增加。除意大利蜜蜂(A·mellifera ligustica)以外,花粉团重量与花粉筐和基跗节表面积成线性比例。工蜂负重前后重量的变化与花粉筐和翅膀的表面积不成比例[动物学报51 (5) :947 -951 , 2005]。     

Nutritional indices in the gypsy moth (Lymantria dispar (L.)) under field conditions and host switching situations

A large proportion of gypsy moths (Lymantria dispar (L.)) are likely to experience multiple species diets in the field due to natural wandering and host switching which occurs with these insects. Nutritional indices in fourth and fifth instar gypsy moth larvae were studied in the field for insects that were switched to a second host species when they were fourth instars. The tree species used as hosts were northern pin oak (Quercus ellipsoidalis E. J. Hill), white oak (Q. alba L.), big-tooth aspen (Populus grandidentata Michx.), and trembling aspen (P. tremuloides Michx.). Conclusions of this study include: 1) Insects which fed before the host switch on northern pin oak performed better after the host switch than did insects with other types of early dietary experience. While the northern pin oak-started insects had very low relative food consumption rates on their second host species immediately after the switch, one instar later they had the highest ranked consumption rates. During both instars they had the second highest efficiencies of converting ingested and digested food to body mass. High food consumption rates and relatively high efficiency of food conversion helped these insects to obtain the highest ranked mean relative growth rates in the fifth instar compared to the relative growth rates obtained by insects from any of the other first host species. 2) Among the four host species examined, a second host of trembling aspen was most advantageous for the insects. Feeding on this species after the switch led to higher larval weights and higher relative growth rates for insects than did any of the other second host species. The insects on trembling aspen attained excellent growth despite only mediocre to low food conversion efficiencies. The low efficiencies were offset by high relative food consumption rates. 3) Low food consumption rates often tend to be paired with high efficiency of conversion and vice versa. 4) There is no discernable tendency for the first plant species eaten to cause long-term inductions which affect the ability of gypsy moths to utilize subsequent host plants. Insects did not tend to consume more, grow faster, or be more efficient if their second host plant was either the same as their rearing plant or congeneric to it. Methods are delineated which allow values of nutritional indices to be obtained for insects on intact host plants under field conditions. These methods are useful for the purpose of answering questions about the relative effects that different diet treatments have on insect response.     

The relationship between airborne pollen distribution and the frequency of specific pollen sensitization at two climatically different locations in Switzerland

Pollen data reported from the two monitoring stations of Locarno-Monti, on the southern slopes of the Alps, and Zurich on the northern slopes of the Alps, for the years 1989–1993 were compared with meteorological data from the corresponding locations and with the prevalence of pollinosis and frequency of specific pollen sensitization in patients with pollinosis. It was so discovered that the recorded quantity of allergenic pollen types (Alnus, Corylus, Betula, Fraxinus, Poaceae, Castaneae,Olea andArtemisia) south of the Alps is higher by a factor of 2.9 than that north of the Alps. These differences are due to the distinctly milder climate in the canton of Ticino (south of the Alps) showing higher annual mean temperatures, more sunshine duration and less precipitation days with higher amounts of precipitation. The allergological data show additionally that the summer pollinosis, caused byCastanea andOlea, is probably responsible for the differing prevalence of pollinosis at the two sites. Finally, we can summarize that in Switzerland pollen from Poaceae, Betulaceae and Oleacea are the most important for pollinosis.     

Effects of pollen quality and quantity on pollen limitation in Crataegus monogyna (Rosaceae) in NW Spain

Pollen limitation occurs when plants produce less fruits and/or seeds than they would with adequate pollen receipt. If the addition of cross-pollen to stigmas increases fruit/seed production, it is interpreted as an evidence of pollen limitation. Much of the limitation may be associated with the quality rather than quantity of pollen; however, most studies do not discriminate between the two, which may lead to misinterpretation of the results. We studied the effects of quality and quantity of pollen on the reproduction of a northern Spanish population of Crataegus monogyna. The treatments included self- and cross-pollination, and supplementation to open and bagged flowers. The response variables considered were number of pollen grains per stigma, pollen tubes per style, and initial and final fruit set. In the Cantabrian range, C. monogyna requires insect pollinators to set fruit and is partially self-incompatible. We found that the number of pollen tubes did not differ between cross- and self-pollination treatments; however, self-pollinated flowers set less fruits than flowers that received pure cross-pollen or were supplemented with both cross- and self-pollen. The experimental design allowed us to infer qualitative rather than quantitative pollen limitation. Comparison of the number of pollen grains and tubes, and initial and final fruit set among pollination treatments suggested post-zygotic embryo selection against selfed progeny.     

Immunocytochemical evidence of calreticulin-like protein in pollen tubes and styles of Petunia hybrida Hort.

With a polyclonal antibody raised against calreticulin (CRT) the locations where the protein occurs in unpollinated and pollinated styles of Petunia hybrida were localized. The epitopes binding the CRT antibody were immunolocalized preferentially in pollen tubes. In transmitting tract cells, both before and after pollination, the level of CRT was low. The protein was mainly localized in the cytosol and around dictyosomes of transmitting-tract cells. In pollen tubes, a high level of CRT was found at their tips rich in endoplasmatic reticulum, cisternae piles of reticular and/or dictyosomal origin, and vesicles. Binding sites of the CRT antibody were also found in the internal callosic cell wall of the pollen tube. These results indicate a role of CRT in cells directly participating in pollen-pistil interaction.     

Effects of high humidity and temperature stress on pollen membrane integrity and pollen vigour in Nicotiana tabacum

Summary The prolonged exposure of pollen Nicotiana tabacum to high humidity at both room temperature and 38° C did not affect membrane integrity as revealed by the fluorochromatic reaction (FCR) test, but did affect pollen vigour. At room temperature germination was not affected, although tube growth was reduced; at 38° C, there was both a reduction in tube growth and delayed germination. When the pollen was subjected to 1 h hydration followed by 1 h desiccation (up to a maximum of four cycles) at room temperature, a reduction in the FCR, germination and tube length after each desiccation treatment was observed. Subsequent hydration fully restored the FCR, but only partially restored germination and tube growth. At 38° C, however, FCR, germination, and tube growth were drastically reduced. The implications of these results on the relationship between FCR and germinability, the responses of pollen exposed to humidity and temperature stress in the field, and on pollen storage are discussed.     

Pollen development in orchids 4. Cytoskeleton and ultrastructure of the unequal pollen mitosis inPhalaenopsis

Summary The unequal first mitosis in pollen ofPhalaenopsis results in a small generative cell cut off at the distal surface of the microspore and a large vegetative cell. No preprophase band of microtubules is present, but polarization of the microspore prior to this critical division is well marked. A generative pole microtubule system (GPMS) marks the path of nuclear migration to the distal surface, and the organelles become unequally distributed. Mitochondria, plastids and dictyosomes are concentrated around the vegetative pole in the center of the microspore and are almost totally excluded from the generative pole. The prophase spindle is multipolar with a dominant convergence center at the GPMS site. The metaphase spindle is disc-shaped with numerous minipoles terminating in broad polar regions. In anaphase, the spindle becomes cone-shaped as the spindle elongates and the vegetative pole narrows. These changes in spindle architecture are reflected in the initial shaping of the telophase chromosome groups. F-actin is coaligned with microtubules in the spindle and is also seen as a network in the cytoplasm. An outstanding feature of orchid pollen mitosis is the abundance of endoplasmic reticulum (ER) associated with the spindle. ER extends along the kinetochore fibers, and the numerous foci of spindle fibers at the broad poles terminate in a complex of ER.Abbreviations CLSM confocal laser scanning microscope/microscopy - DMSO dimethyl sulfoxide - ER endoplasmic reticulum - FITC fluorescein isothiocyanate - GPMS generative pole microtubule system - MBS m-maleimidobenzoic acidN-hydroxysuccinimide ester - PPB preprophase band of microtubules - RhPh rhodamine palloidin - TEM transmission electron microscope/microscopy     

Variation of pollen limitation in the early flowering Mediterranean geophyte Narcissus assoanus (Amaryllidaceae)

A recent literature review indicates that pollen limitation of female fertility is a common feature of flowering plants. Despite the ecological and evolutionary significance of pollen limitation, most studies have only examined fertility in a single population at one time. Here we investigate pollen limitation of fruit and seed set in five populations of Narcissus assoanus, a self- sterile, insect-pollinated geophyte, over 2–3 years in southern France. In common with many early spring flowering plants, pollinator visitation to N. assoanus is often infrequent. Supplemental hand-pollination of flowers with outcross pollen significantly increased overall fruit and seed set by 11% and 19%, respectively. Four of the five populations experienced some pollen limitation during the study. For a given year, there was significant variation in pollen limitation among populations. Two of the populations were pollen limited in one year but not in other years in which they were studied. Seed:ovule ratios for open- and hand-pollinated flowers averaged 0.29 and 0.33, respectively. While hand pollination significantly increased the seed:ovule ratio, the low value obtained indicates that the majority of ovules in flowers do not mature seeds despite hand pollination. The role of genetic and environmental factors governing low seed:ovule ratios in N. assoanus is discussed. Received: 28 December 1999 / Accepted: 6 April 2000     

Mitochondrial development and activity of binucleate and trinucleate pollen during germination in vitro

Bi-and trinucleate pollen generally differ in the extent of their mitochondrial development at anther dehiscence and in the rate of their attainment of maximum-phosphorylative capacity during germination in vitro, as judged from experiments with representatives of both groups.The typically trinucleate pollen of Aster tripolium L. immediately respired at a high rate, maintaining a high energy charge. Mitochondria attained maximum electron-transducing capacity within 2 min of incubation, while tube growth started within 3 min. In contrast, the binucleate pollen of Typha latifolia L. only gradually reached a relatively low rate of respiration, concomitant with a temporary decrease in energy charge, upon immersion in the germination medium. Development of the mitochondrial, electrontransducing system occurred in about 75 min, after which the first pollen tubes emerged. Starting from a poor differentiation, mitochondria became increasingly normal in appearance as germination proceeded.The binucleate pollen of Nicotiana alata Link et Otto and Tradescantia paludosa Anders. et Woods. showed intermediate characteristics: Nicotiana resembled Typha but mitochondria developed at a higher rate; Tradescantia germinated more rapidly and resembled the trinucleate pollen of Aster.Inhibitors of mitochondrial or cytoplasmic protein synthesis failed to affect the development of the mitochondrial, respiratory capacities during pollen germination. It is concluded that the duration of the lag period is determined by the level and rate of mitochondrial development and not by the division of the generative cell.Abbreviations BSA bovine serum albumine - CAP D(-) threo chloramphenicol - CHI cycloheximide - DNP 2-4 dinitrophenol - EBr ethidium bromide - EC energy charge - EGTA ethyleneglycol-bis (2-aminoethyl ether) N, N-tetra-acetic acid - EM electron microscope - ETC electron transfer chain - HEPES N-2-hydroxyethyl piperazine N-2-ethane sulfonic acid - LSD least significant difference - PVP polyvinyl pyrrolidone - RCR respiratory control ratio - RH relative humidity - TCA tricarboxylic acid - TES N-tris (hydroxymethyl) methyl-2-aminoethane sulfonic acid - URCI uncoupler respiratory control index (Hunter et al. 1976)     

In vitro pollen embryogenesis in Nicotiana tabacum L. and its relation to pollen sterility,sex balance,and floral induction of the pollen donor plants

Pollen sterility, sex balance, and floral induction of the pollen donor plants were tested for a possible relation to embryogenesis from in vitro cultured tobacco pollen (Nicotiana tabacum L. var. Badischer Burley). The pollen grains destined to become embryos in culture (P-grains) were sterile for the donor plants as judged by their staining reaction with acetocarmine and fluorescin-diacetate, and by an in vitro germination test. They were produced in high frequency in flowers which exhibited a shift in sex balance towards femaleness. Sex balance could be measured by the relative length of pistil to stamens. High P-grain frequency, high pollen sterility, and a shift in sex balance towards femaleness could be induced by raising the donor plants under short days and/or low temperature (18–15° C) as compared to long days at 24° C. Short days and/or low temperature also reinforced floral induction, revealing that the tobacco variety Badischer Burley is a quantitative short day and low temperature plant and that the variety follows the rule that conditions of strong floral induction shift sex balance towards femaleness. At 12° C and short days, contabescent flowers were formed with completely sterile anthers containing a few and mostly collapsed P-grains. Based on these results, it is now possible to predict conditions by which haploids via pollen embryogenesis might be produced in high frequency from low-yielding and recalcitrant species.Abbreviations DPF dead pollen grain frequency - LD24 long days at 24° C - PD pollen dimorphism - P:S ratio of pistil to stamen length - SD15 short days at 15° C     

The significance of pollen signal in present-day marine terrigenous sediments: The example of the Gulf of Lions (western Mediterranean Sea)

Terrigenous marine and continental sediments constitute pollen reservoirs able to fulfil the lack of Pleistocene data extracted from autochtonous lacustrine sediments for palaeovegetation reconstructions. Nevertheless, it is essential to constrain the signification of the pollen signal in such still under-exploited sediments. This article introduces a study carried out on the shelf of the Gulf of Lions. It aims at (1) highlighting the transport of pollen grains and the signification of the record in that area as well as at (2) discussing the pollen transport in various sedimentary contexts. The present study was carried out on surface water of the Rhone River, sea water and surface sediments of the shelf of the Gulf of Lions. The pollen content of the Rhone River and of its plume is in agreement with the season of sampling. On the contrary, the other samples of sea water did not contain any pollen grain. The samples from the surface sediments of the shelf are very rich in pollen grains and evidence the absence of sorting by currents except for Pinus. Indeed, its relative abundance increases when the fluvial impact decreases. The pollen signal (except Pinus) records the phytogeographic changes linked to the different drainage basins. The riparian woodland is over-represented at the Rhone River mouth. In front of the Pyreneo-languedocian rivers, Mediterranean xerophytes pollen grains are more abundant. From these results and from others taken in the literature, a model of pollen transport is built: all thin terrigenous sediments contain pollen grains essentially transported by rivers while autochthonous sediments (i.e., found in closed lakes or marine pelagic sediments) contain pollen grains brought by wind. Small closed lakes (or peat bogs) pollen spectra document local floras while those from pelagic marine sediments document floras from several hundred square kilometres.