Individual Pollen Research Articles

ОПРЕДЕЛЕНИЕ СКОРОСТЕЙ ОСЕДАНИЯ ПЫЛЬЦЕВЫХ КЛАСТЕРОВ АНЕМОФИЛЬНЫХ РАСТЕНИЙ, ПРОИЗРАСТАЮЩИХ В ЦСБС СО РАН

A study is made on the sedimentation of pollen particles of the anemophilous plants of six species (Salix caprea L., Salix pentandra L., Betula davurica Pall., Plantago media L., Chenopodium album L.,Artemisia sieversiana Willd.), growing in the CSBG SB RAS. These species are widely represented in the biocenosis of the Russian Federation and are the producers of substantial amounts of allergenic pollen which can be carried by winds over great territories. It is shown that there is a considerable number of clusters that contain two and more pollen grains. Sedimentation rates are determined of both the individual pollen grains of these plants and their clusters with 2-6 pollen grains. It has been established that the sedimentation rate of clusters depends on the number of the pollen grains contained.

Elevational transects of modern pollen samples: Site-specific temperatures as a tool for palaeoclimate reconstructions in the Alps

The potential of quantitatively reconstructing climate from modern pollen assemblages from high mountain environments has been widely debated but seldom tested. We analysed the pollen deposition in 53 surface samples (mosses) in relation to July temperature in two elevational transects in the European Alps. Each surface-sample site was assigned climate data derived from the local-scale climate. We compared our results with a larger calibration set extracted from the European Modern Pollen Database (EMPD) and centred on the European Alps. This also was assigned local climate data. The main calibration set (234 pollen samples) had Alnus harmonized at genus level; in contrast, a second set was selected (174) that retained the taxonomic resolution of Alnus viridis, which is one of the main climate indicators in the timberline ecotone. The overall and individual pollen responses to July temperature were inferred by canonical correspondence analysis (CCA), generalized linear regression (eHOF) and weighted averaging (WA). Quantitative climate reconstructions for each sample site of the two elevational transects were obtained using transfer functions, that is, WA and WA partial least squares (WA-PLS) regressions. In each calibration set, around 30% of the pollen taxa show a relationship with July temperature through monotonic or unimodal functions. The best transfer function obtained has a good statistical performance, with a determination coefficient ( r2) of 0.74. We propose new calibration procedures formulated to include the full climate space of the modelled taxa, as well as to account for uphill pollen transport in the high mountains and for human activity.

Measuring the growth force of invasive plant cells using Flexure integrated Lab-on-a-Chip (FiLoC)

The pollen tube is a tip growing cell that is able to invade plant tissues in order to accomplish its function — the delivery of sperm cells to the ovule. The pistillar tissues through which the tube has to elongate represent a formidable mechanical obstacle, but it is unknown how much force the growing tube is able to exert, or how mechanical impedance affects its growth behavior. We quantified the invasive force of individual pollen tubes using a microfluidic lab-on-a-chip device featuring a microscopic cantilever. Using finite element method the maximum invasive growth force of the growing pollen tube was determined to be in the microNewton range. Real time monitoring revealed that contact with the mechanical obstacle caused a shift in the peak frequency characterizing the oscillatory behavior of the pollen tube growth rate. This suggests the presence of a feedback-based control mechanism with a mechanical regulatory component.

Multivariate Analysis of MALDI Imaging Mass Spectrometry Data of Mixtures of Single Pollen Grains.

Mixtures of pollen grains of three different species (Corylus avellana, Alnus cordata, and Pinus sylvestris) were investigated by matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF imaging MS). The amount of pollen grains was reduced stepwise from > 10 to single pollen grains. For sample pretreatment, we modified a previously applied approach, where any additional extraction steps were omitted. Our results show that characteristic pollen MALDI mass spectra can be obtained from a single pollen grain, which is the prerequisite for a reliable pollen classification in practical applications. MALDI imaging of laterally resolved pollen grains provides additional information by reducing the complexity of the MS spectra of mixtures, where frequently peak discrimination is observed. Combined with multivariate statistical analyses, such as principal component analysis (PCA), our approach offers the chance for a fast and reliable identification of individual pollen grains by mass spectrometry. Graphical Abstract ᅟ.

Formation pattern in five types of pollen tetrad in Pseuduvaria trimera (Annonaceae).

In basal angiosperms, there are several types of permanent tetrad but their formation pattern remains elusive. Pseuduvaria trimera has five types of tetrads and is the species with the most abundant tetrad types in Annonaceae. In order to interpret the formation pattern of different tetrad types, pollen development was investigated from the microspore mother cell stage to the bicellular pollen stage and the ultrastructure of pollen wall in the five tetrad types using light microscopy, transmission electron microscopy, and confocal laser scanning microscopy. Both successive and intermediate cytokinesis were observed within the same anther. The nucleus location of the microspores together with cytokinesis determine the number and the spatial arrangement of callose plates, and further have an effect on the tetrad types. The anthers with or without septation and the arrangement of microsporocytes might be also related to the tetrad type. The individual pollen grains within the tetrads are connected with each other by crosswall cohesion and cytoplasmic channels at localized points in the proximal walls. The various types of tetrads, cytokinesis, and cohesion in P. trimera reflect the high diversity in pollen development, which enhances the dramatic variety in pollen morphology in this family. Our observations of the development of tetrads provided some new insights for interpreting the factors influencing the types of tetrads, and reported the existence of a cytoplasmic channel in Annonaceae for the first time.

Effects of tephra falls on vegetation: A Late‐Quaternary record from southern Italy

Abstract Impacts of tephra deposition on vegetation are recorded in a series of 10 high temporal resolution absolute pollen diagrams from Lago Grande di Monticchio, each diagram spanning a single tephra deposition event during the last glacial–interglacial cycle. Sediment accumulation rates determined by counting and measurement of annual laminations (“varves”) provide an accurate and precise chronology, enabling the minimum recovery time after a tephra fall to be determined. In most cases, pollen accumulation rate was reduced after the tephra fall, indicating reduced vegetation productivity. Tephra deposition events also led to changes in vegetation composition, although these varied in magnitude. The magnitude and duration of the impacts upon the vegetation were related to the thickness of the tephra layer deposited, the thickest layers examined (>250 mm) having minimum recovery times of up to a century and thicker layers generally having greater impacts upon pollen productivity and vegetation composition. Tephra chemistry also influenced the persistence of the impact. The nature of the prevailing vegetation prior to the tephra fall influenced the degree and persistence of the impact. Tephra layers <30 mm thick had minimum recovery times of up to 90 years when they fell on wooded steppe vegetation, whereas cold steppe recovered much more quickly, as did forest. The relative sensitivity of wooded steppe was contrary to our expectations. Of individual pollen taxa, Cupressaceae emerged as particularly sensitive to tephra deposition. Synthesis. Applying absolute pollen analytical methods to a sediment record with a well‐supported and precise chronology obtained from a lake in a volcanic region where the vegetation has been subject to numerous tephra deposition events enabled us to explore the impacts of such events. Our results provide evidence of differential impacts upon individual plant taxa and of differential sensitivity of three vegetation types that have prevailed in the region during the last glacial–interglacial cycle. The influences of tephra thickness and chemistry on minimum recovery time were substantial. Our results are relevant to forecasting the potential impacts upon ecosystems of volcanic eruptions.

Holocene vegetation history of the Jeseníky Mts: Deepening elevational contrast in pollen assemblages since late prehistory

AbstractQuestionsHow did the vegetation of a Central European mountain region with a fragmented alpine zone develop during the Holocene? When did human land use start to alter summit grasslands? Which gradient in pollen assemblages was strongest and was it consistent through time?LocationJeseníky Mountains, Czech Republic.MethodsSixteen pollen records were subjected to DCA in order to explore patterns of compositional similarities in the fossil pollen data. Because only the last 6,000 years were recorded in the study sites from mountain summits, we restricted further analysis to this period. Twelve radiocarbon‐dated pollen records were subjected to DCCA constrained by modelled calibrated age. Responses of individual pollen types to the principal DCCA gradients were tested with GAMs.ResultsIn the DCA, Early Holocene samples were located close to recent ones due to abundant pollen of herbs, Poaceae, Betula, Pinus sylvestris type and rare pollen of climax deciduous trees. In the DCCA for the last 6,000 years, the sorting of sites along the first unconstrained axis correlated with altitude, which is a complex factor corresponding to temperature and geomorphology (flat summits vs alluvia of mountain rivulets). This elevational differentiation became more pronounced after 2,250 cal BP when summit peatlands started to contain more Vaccinium, Calluna vulgaris, Amaranthaceae, Plantago lanceolata and Rumex acetosa type pollen. In contrast, mid‐elevation pollen spectra started to contain more meadow herbs (Caltha, Potentilla type, Cirsium/Carduus). Picea pollen was surprisingly more associated with mid‐elevation than high‐elevation sites, unlike Fagus.ConclusionIncreasing contrast between summits and middle elevation alluvia seems to be a major feature of vegetation development over the last 6,000 years. While alluvial areas were encroached by Alnus–Picea forests, and later locally transformed into wet grasslands, grazing and forest burning at summits gradually increased abundance of acidophytic dwarf shrubs and peatlands, especially since the Iron Age. Human impact might facilitate beech expansion at high elevations, with Picea‐dominated forests being restricted to alluvia and around mid‐elevation basin peatlands prior to establishment of modern Picea plantations.

Temperature variations in the southern Great Lakes during the last deglaciation: Comparison between pollen and GDGT proxies

Our understanding of deglacial climate history in the southern Great Lakes region of the United States is primarily based upon fossil pollen data, with few independent and multi-proxy climate reconstructions. Here we introduce a new, well-dated fossil pollen record from Stotzel-Leis, OH, and a new deglacial temperature record based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) at Silver Lake, OH. We compare these new data to previously published records and to a regional stack of pollen-based temperature reconstructions from Stotzel-Leis, Silver Lake, and three other well-dated sites. The new and previously published pollen records at Stotzel-Leis are similar, but our new age model brings vegetation events into closer alignment with known climatic events such as the Younger Dryas (YD). brGDGT-inferred temperatures correlate strongly with pollen-based regional temperature reconstructions, with the strongest correlation obtained for a global soil-based brGDGT calibration (r2 = 0.88), lending confidence to the deglacial reconstructions and the use of brGDGT and regional pollen stacks as paleotemperature proxies in eastern North America. However, individual pollen records show large differences in timing, rates, and amplitudes of inferred temperature change, indicating caution with paleoclimatic inferences based on single-site pollen records. From 16.0 to 10.0ka, both proxies indicate that regional temperatures rose by ∼10 °C, roughly double the ∼5 °C estimates for the Northern Hemisphere reported in prior syntheses. Change-point analysis of the pollen stack shows accelerated warming at 14.0 ± 1.2ka, cooling at 12.6 ± 0.4ka, and warming from 11.6 ± 0.5ka into the Holocene. The timing of Bølling-Allerød (B-A) warming and YD onset in our records lag by ∼300–500 years those reported in syntheses of temperature records from the northern mid-latitudes. This discrepancy is too large to be attributed to uncertainties in radiocarbon dating, and correlation between pollen and brGDGT temperature reconstructions rules out vegetation lags as a cause. However, the YD termination appears synchronous among the brGDGT record, regional pollen stack, and Northern Hemisphere stack. The cause of the larger and lagged temperature changes in the southern Great Lakes relative to Northern Hemisphere averages remains unclear, but may be due to the effects of continentality and ice sheet extent on regional climate evolution.

Individual pollen limitation, phylogeny and selection.

This article is a Commentary on Trunschke et al., 214: 1381–1389.

Pollen effect (xenia) for evaluating breeding materials in maize

Pollen effect (xenia) plays an important role in modifying biochemical constituents of maize (Zea mays L.) kernels. The objectives of this study were to i) evaluate the effect of filial generations on certain genetic estimations; ii) compare general (GCA) and specific combining ability (SCA) effects obtained from Griffing?s diallel analyses between parental (F0) and F1 generations; iii) determine the relationships between pollen effect and genetic estimations; and iv) examine the possible utility of pollen effect for improving kernel-quality traits (protein and oil contents). We conducted two experiments (F0 in 2011 and F1 in 2013) and examined kernel protein and oil contents. Individual pollen effects (IPE) and specific individual pollen effects (SIPE) were computed. The results showed that entries (E) and filial generations (G) and E ? G interaction variances were significant for both protein and oil contents, whereas changes in genetic estimates between generations were highly variable. The signs and magnitudes of GCA effects were similar and highly correlated (r > 0.80) between F0 and F1 generations for all four diallel methods. In addition, GCA effects were highly correlated with IPE estimates for all four diallel methods. Specific combining ability (SCA) estimates between F0 and F1 generations were moderately correlated (r = 0.50) in Method IV for oil and highly negatively correlated (r = -1.00) in Method III for protein content. Heterosis analyses showed that hybrids could not be evaluated on the basis of the F0 generation to predict their F1 performances. Individual pollen effects between generations showed higher correlation for protein content (r = 1.00) than for oil content (r = 0.40). Specific individual pollen effects of parents were also slightly higher for protein content (r = 0.74) than for oil content (r = 0.62). We concluded that the direct or indirect utilization of pollen effect (xenia) was possible for parental evaluation but not suitable for hybrid evaluation for kernel oil and protein contents.

Pollen food allergy syndrome in Turkey: Clinical characteristics and evaluation of its association with skin test reactivity to pollens.

There is limited data regarding pollen food allergy syndrome (PFAS) in Turkey. To investigate the clinical characteristics and possible risk factors of PFAS in Turkey, and to evaluate if there was an association between skin test reactivity to pollens and presence of PFAS. A total of 254 consecutive adult patients with pollen sensitivity were prospectively recruited. Patients were interviewed with a questionnaire including a list of pollen-associated foods. Patients were classified as having PFAS if they reported clear allergic symptoms compatible with PFAS. All participants underwent skin prick tests (SPT) to a panel of common aeroallergens, prick-to-prick tests with culprit fresh foods were performed in patients who gave consent. Self-reported PFAS was observed in 49 patients (19.3%). The most common culprit foods were kiwi, peach, tomato, melon and watermelon. Multiple logistic regression analysis showed that potential risk factors for PFAS were having asthma (OR=2.392, P=0.044) and tree pollen sensitization (OR=2.904, P=0.004). There were no significant differences in the SPT wheal sizes to individual pollen extracts between patients with and without PFAS with a positive SPT result for that pollen extract (P>0.05). PFAS is frequent in pollen sensitized adults in Turkey. The most commonly implicated foods are kiwi, peach,tomato, melon and watermelon, in our geographical region. SPT wheal sizes to pollen extracts seems to be similar in patients with and without PFAS.

Correlation of pollen counts and number of hospital visits of asthmatic and allergic rhinitis patients.

Aims and Objectives:Environmental pollens are known to cause exacerbation of symptoms of patients with allergic rhinitis (AR) and asthma. During pollen months, number of patients visiting hospital has been shown to increase in some studies. However, in India, such studies are lacking. Therefore, we aimed to study pollen counts and to find its correlation with number of new patients attending Asthma Bhawan for 2 years.Materials and Methods:Aerobiological sampling was done using Burkard 24 h spore trap system. The site selected for the entrapment of the air spore was the building of Asthma Bhawan situated at Vidhyadhar Nagar, Jaipur. New patients coming with problems of respiratory allergy such as AR or asthma were recruited in the study. Skin prick tests (SPTs) were carried out after obtaining consent in these patients. Monthly pollen counts of trees, weeds and grasses were correlated with the number of new patients. Pollen calendar was prepared for 2 years.Results:Average annual pollen count during 2011 and 2012 were 14,460.5. In the analysis, 37 types of species or families were identified. Pollen count showed two seasonal peaks during March–April and from August to October. January and June showed the lowest pollen counts in 2 years. Average monthly count of grass pollens showed significant correlation with number of new patients (r = 0.59). However, monthly pollen count of trees and weeds did not correlate. The correlation of the pollen count of individual pollen with the SPT positivity to that pollen showed significant correlation with Chenopodium album only.Conclusions:It can be concluded that there were two peaks of pollen count in a year during March–April and August–October. Average monthly pollen counts of grass were significantly correlated with the number of hospital visits of new patients.

Stable carbon isotope analyses of nanogram quantities of particulate organic carbon (pollen) with laser ablation nano combustion gas chromatography/isotope ratio mass spectrometry.

RationaleAnalyses of stable carbon isotope ratios (δ 13C values) of organic and inorganic matter remains have been instrumental for much of our understanding of present and past environmental and biological processes. Until recently, the analytical window of such analyses has been limited to samples containing at least several μg of carbon.MethodsHere we present a setup combining laser ablation, nano combustion gas chromatography and isotope ratio mass spectrometry (LA/nC/GC/IRMS). A deep UV (193 nm) laser is used for optimal fragmentation of organic matter with minimum fractionation effects and an exceptionally small ablation chamber and combustion oven are used to reduce the minimum sample mass requirement compared with previous studies.ResultsAnalyses of the international IAEA CH‐7 polyethylene standard show optimal accuracy, and precision better than 0.5‰, when measuring at least 42 ng C. Application to untreated modern Eucalyptus globulus (C3 plant) and Zea mays (C4 plant) pollen grains shows a ~ 16‰ offset between these species. Within each single Z. mays pollen grain, replicate analyses show almost identical δ 13C values.ConclusionsIsotopic offsets between individual pollen grains exceed analytical uncertainties, therefore probably reflecting interspecimen variability of ~0.5–0.9‰. These promising results set the stage for investigating both δ 13C values and natural carbon isotopic variability between single specimens of a single population of all kinds of organic particles yielding tens of nanograms of carbon. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd.

Central and Eastern European Spring Pollen Allergens and Their Expression Analysis—State of the Art

Spring pollinosis has become a part of life for many people throughout the world. A wide range of knowledge about the allergenic potential of individual pollen allergen types is documented well, but the starting point of the pollen allergens expression regulation in plants itself is still not fully answered. Expression analysis of pollen allergens does not yet have any specific protocols or methods developed, despite a very good sequence background available in public bioinformatics databases. However, research in this area of interest has a great application potential for breeding and biotechnology of allergenic plants that may benefit from the knowledge of the expression of allergen coding genes in individual varieties or genotypes. Here, a brief review of up-to-date knowledge about the coding sequences of central and eastern European spring pollen allergens is introduced together with real-time based analysis of the expression of two of the main pollen allergens–PR protein type and profilin type of birch and hazelnut.

Rapid Molecular Identification and Quantification of Allergenic Pollen By Real-Time PCR

Identifying and quantifying airborne pollen is important for causal assessment of allergic symptoms, for determining which pollens should be tested and for interpreting the results of allergy tests. Present pollen counting methods are time-consuming, require specific expertise and training, and are prone to subjective variability. Our goal is to devise a sensitive, high throughput method of quantifying pollen load in environmental samples. 9 different pure pollen samples, including grass (Paspalum notatum), trees (Morella cerifera, Morus alba, Juniperus ashei, Pinus strobus, Quercus virginiana, Taxodium distichum, Ulmus americana), and ragweed (Ambrosia artemisifolia) were used for analysis (courtesy of Tom Greer PhD, Greer Laboratories). Genomic DNA (gDNA) was extracted from pure pollens using a modification of the DNAzol ES procedure. Primers specific for the 5.8S rRNA genes of the different pollens were designed for quantitative real-time PCR (qPCR) using a SYBRGreen-based PCR assay. Individual gDNA from the pollens was detectable to sub nanogram levels. Individual pollen gDNA was detected in samples consisting of a mixture of all 9 pollen gDNAs. Specific pollens were detected in gDNA extracted from randomly admixed samples of the various pollen samples. The selected primers provided accurate identification in mixed samples with variable efficiency. qPCR detection of the pollen gDNA is sensitive and specific. The current assay can be expanded to include additional species and/or modified to detect pollens native to distinct geographical regions. Actual environmental sample quantification is necessary to prove applicability.

Cunninghamia beardii sp. nov. (Cupressaceae: Cunninghamioideae), Anatomically Preserved Pollen Cones from the Eocene of Vancouver Island, British Columbia, Canada

Premise of research. A large pollen cone cluster attached to a cunninghamioid twig and surrounded by leaves has been identified from Eocene calcium carbonate marine concretions from the Appian Way locality on Vancouver Island, British Columbia, Canada. The cluster preserves 18 cones but probably bore at least 24 pollen cones based on cone placement in the cluster.Methodology. Specimens were studied using the cellulose acetate peel technique, and reconstructions were made with ImageJ visualization software. Pollen was examined using SEM.Pivotal results. Cones are helically arranged around the tip of an ultimate leafy branch that terminates in scale leaves, each showing a central resin canal. Vegetative leaves on the twig are amphistomatic, showing typical cunninghamioid anatomy, with a large central resin canal abaxial to the vascular bundle, an elongate zone of transfusion tissue, a nonplicate mesophyll, and a hypodermis three to four cells thick. Each pollen cone is produced in the axil of a bract and has three scale leaves surrounding the base of the cone axis. Individual pollen cones have helically arranged microsporophylls, each with three elongate abaxial pollen sacs. While the cones are immature, pollen sacs with pollen are present in several cones. The exine is scabrate, with numerous orbicules, and no papilla is evident.Conclusions. This cluster provides the first detailed anatomically preserved fossil evidence for the pollen cones of Cunninghamia. It shows a large number of similarities to the pollen cone clusters of extant Cunninghamia lanceolata and Cunninghamia konishii and the Late Cretaceous Cunninghamia taylorii, strengthening hypotheses for a basal position of cunninghamioids within the Cupressaceae and further demonstrating that some characters of Cunninghamia have remained relatively unchanged since at least the mid-Cretaceous.

Variation in pollen-donor composition among pollinators in an entomophilous tree species, Castanea crenata, revealed by single-pollen genotyping.

BackgroundIn plants, reproductive success is largely determined by the composition of pollen (i.e., self-pollen and outcross-pollen from near and distant pollen-donors) transported as a result of pollinator foraging behavior (e.g., pollen carryover). However, little evidence is available on how and to what extent the pollen carryover affects the pollen-donor composition and on which insect taxa are effective outcross-pollen transporters under field conditions. In this study, we explored roles of foraging behavior of insect pollinators on pollen-donor composition and subsequent reproductive success in a woody plant.MethodsWe performed paternity analyses based on microsatellite genotyping of individual pollen grains found on diurnal pollinators (i.e., bumblebee, small bee, fly, small beetle, and honeybee) visiting Castanea crenata trees.ResultsThe outcross-pollen rate was highest in bumblebees (66%), followed by small bees (35%), flies (31%), and small beetles (18%). The effective number of pollen donors, representing pollen carryover, was greater in bumblebees (9.71) than in flies (3.40), small bees (3.32), and small beetles (3.06). The high percentages of pollen from outside the plot on bumblebees (65.4%) and flies (71.2%) compared to small bees (35.3%) and small beetles (13.5%) demonstrated their longer pollen dispersal distances.ConclusionsAll of the diurnal insects carried outcross-pollen grains for long distances via pollen carryover. This fact suggests that a wide range of insect taxa are potential outcross-pollen transporters for the self-incompatible C. crenata.

The climate of Europe during the Holocene: a gridded pollen-based reconstruction and its multi-proxy evaluation

We present a new gridded climate reconstruction for Europe for the last 12,000 years based on pollen data. The reconstruction is an update of Davis et al. (2003) using the same methodology, but with a greatly expanded fossil and surface-sample dataset and more rigorous quality-control. The modern pollen dataset has been increased by more than 80%, and the fossil pollen dataset by more than 50%, representing almost 60,000 individual pollen samples. The climate parameters reconstructed include summer/winter and annual temperatures and precipitation, as well as a measure of moisture balance, and growing degree-days above 5 °C. Confidence limits were established for the reconstruction based on transfer function and interpolation uncertainties. The reconstruction takes account of post-glacial isostatic readjustment which resulted in a potential warming bias of up to +1–2 °C for parts of Fennoscandia in the early Holocene, as well as changes in palaeogeography resulting from decaying ice sheets and rising post-glacial sea-levels. This new dataset has been evaluated against previously published independent quantitative climate reconstructions from a variety of archives on a site-by-site basis across Europe. The results of this comparison are generally very good; only chironomid-based reconstructions showed substantial differences with our values. Our reconstruction is available for download as gridded maps throughout the Holocene on a 1000-year time-step. The gridded format makes our reconstructions suitable for comparison with climate model output and for other applications such as vegetation and land-use modelling. Our new climate reconstruction suggests that warming in Europe during the mid-Holocene was greater in winter than in summer, an apparent paradox that is not consistent with current climate model simulations and traditional interpretations of Milankovitch theory.

Assessing the importance of climate variables for the spatial distribution of modern pollen data in China

To assess the importance of climate variables for the distribution of modern pollen data in China, we present a continental-scale dataset consisting of 1374 samples. Boosted regression trees and constrained ordination techniques are employed to quantify the importance of six climate variables (annual precipitation, PANN; actual/potential evapotranspiration ratio, Alpha; mean annual temperature, TANN; mean temperature of the warmest month, MTWA; mean temperature of the coldest month, MTCO; annual sum of the growing degree days above 5°C, GDD5) for the distribution of individual pollen taxa and modern pollen assemblages. The results show that taxon-specific responses to the climate variables display a wide regional diversity and that the climate variables with low collinearity that best account for the spatial variability of modern pollen assemblages differ regionally. PANN is the most important variable in northwestern and northeastern China and the Tibetan Plateau, while MTWA and MTCO are the dominant variables in east-central and southern China. This suggests that the climate variables that can be optimally reconstructed from fossil pollen data vary in different bioclimatic regions of China. This feature is typical to many continental-scale modern pollen datasets and needs to be considered in pollen-based climate reconstructions.

Development of a new CMS system in pigeonpea utilizing crosses with Cajanus lanceolatus (WV Fitgz) van der Maesen

Cytoplasmic male sterility is an important biological tool which is now available to pigeonpea breeders to exploit heterosis/hybrid vigor. A variety of CMS systems have been developed when wild relatives of pigeonpea from different gene pools were crossed as the female parent with cultivated types as the male parent. This paper reports a second source of CMS developed by using the cultivated pigeonpea as the female parent and one of its wild relative Cajanus lanceolatus (WV Fitgz) van der Maesen as the pollen donor, as such the A5 CMS system derived from C. acutifolius. All the F1 hybrids were evaluated to confirm hybridity using 27 simple sequence repeat (SSR) markers. SSR marker analysis of parents provided 17 polymorphic markers from a total of 27 SSR markers used. Subsequently polymorphic SSRs were used to confirm the hybridity of the F1 plants. F1 hybrid plants were crossed with a range of pigeonpea cultivars to identify maintainers of male sterility. Morphology of the F1 and backcross generations, cytology of the sterile as well as fertile floral buds derived from the crosses between sterile F1 hybrids and unrelated pigeonpea cultivars were studied. An important observation made was that male sterility was a post meiotic process. Microsporogenesis was normal until the tetrad stage, but none of them formed pollen grains. Instead, they grouped together within the pollen mother cell wall and the tetrads did not separate into individual pollen grains.