Assessment of pollen reward and pollen availability in Solanum stramoniifolium and Solanum paniculatum for buzz‐pollinating carpenter bees

The two widespread tropical Solanum species S. paniculatum and S. stramoniifolium are highly dependent on the visits of large bees that pollinate the flowers while buzzing them. Both Solanum species do not offer nectar reward; the rewarding of bees is thus solely dependent on the availability of pollen. Flower visitors are unable to visually assess the amount of pollen, because the pollen is hidden in poricidal anthers. In this study we ask whether and how the amount of pollen determines the attractiveness of flowers for bees. The number of pollen grains in anthers of S. stramoniifolium was seven times higher than in S. paniculatum. By contrast, the handling time per five flowers for carpenter bees visiting S. paniculatum was 3.5 times shorter than of those visiting S. stramoniifolium. As a result foraging carpenter bees collected a similar number of pollen grains per unit time on flowers of both species. Experimental manipulation of pollen availability by gluing the anther pores showed that the carpenter bees were unable to detect the availability of pollen by means of chemical cues before landing and without buzzing. Our study shows that the efficiency of pollen collecting on S. paniculatum is based on large inflorescences with short between‐flower search times and short handling time of individual flowers, whereas that of S. stramoniifolium relies on a large amount of pollen per flower. Interestingly, large carpenter bees are able to adjust their foraging behaviour to drastically different strategies of pollen reward in otherwise very similar plant species.     

中国柽柳科植物花粉形态特征聚类分析

在观察了中国柽柳科(Tamaricaceae)4属27种植物花粉形态的基础上,对其进行了聚类分析。观察结果表明:该科植物花粉为三沟类型,无三拟孔沟类型,形态及外壁雕纹属间差异明显。花粉特征聚类分析结果表明,中国柽柳科植物花粉大致划分为明显的三组,所包含的种(某些种除外)分别隶属于柽柳科的4属:琵琶柴属(ReaumuriaLinn.)、水柏枝属(MyricariaDesv.)、山柽柳属(MyrtamaOvcz&Kinz.)和柽柳属(TamarixLinn.),而有争议的山柽柳属虽同柽柳属聚在一起,但也较早地分出成为独立的一支,结合种子形态及分子生物学证据,支持将秀丽山柽柳从水柏枝属中分出而另立新属,为传统分类学将该科划分为4属提供了依据。聚类分析进一步将水柏枝属植物花粉和柽柳属植物花粉分别分为2种类型,而琵琶柴属植物花粉类除个别种体积存在差异外,其纹饰类型较为单一,仅划分为1种类型。柽柳属植物花粉聚类分析结果与该属植物花盘类型的划分结果基本一致,融生花盘类型植物的花粉则在两组中均有出现,可能是间生花盘和假顶生花盘类型间的过渡类型。     

Morphological and molecular characterisation and differentiation of <Emphasis Type="Italic">Sargassum baccularia</Emphasis> and <Emphasis Type="Italic">S. polycystum</Emphasis> (Phaeophyta)

Two Sargassum species (S. baccularia and S. polycystum) collected from Teluk Kemang and Cape Rachado, Port Dickson, Negeri Sembilan, Malaysia, which are alike in morphology except for the rhizoidal system and vesicles, were characterised using random amplified polymorphism DNA (RAPD). The genomic DNA of both species was isolated from the leaves using a modified CTAB method. Four random primers, that is, OPA2, OPA3, OPA4 and OPA13, successfully amplified the DNA. The polymorphisms generated by these four primers were analysed using the Dice Coefficient of Similarity and cluster analysis was carried out using GelCompar II Version 2.0 (Applied Maths, Kortrijk, Belgium) based on UPGMA. DNA analysis showed that three primers were able to differentiate the two species. Morphological analysis using Principal Components Analysis (PCA) and discriminant function analysis supported the molecular data. Both species are characterised by heavily muricate main branches, oblong-lanceolate leaves with dentate margins and discoid holdfasts and spherical vesicles; both are dioecious. The only difference is that S. polycystum has secondary holdfasts transformed into stolons. This last characteristic is therefore a very important criterion and may contribute to the difference shown by DNA analysis.     

The systematic value of pollen morphology in Smilacaceae

Smilacaceae are a small family of dioecious, mostly climbing, net-veined monocotyledons with a cosmopolitan distribution. Relatively little is known about the variation of pollen morphology within the family. For this reason, and to investigate the systematic value of palynology in Smilacaceae, pollen from 125 species of Smilax, Heterosmilax, and Ripogonum was examined using light and scanning electron microscopy. Ten of these were examined further by transmission electron microscopy. Four distinct pollen types grouped into two major pollen classes were distinguished: Class 1, represented by the pollen of all Smilax and Heterosmilax species, is mostly spheroidal, inaperturate, and spinulate or microspinulate, with a thin, fragile exine of varied sculpturing; three pollen types are represented within this class. Class 2 is found only in Ripogonum and contains a single pollen type with prolate, monosulcate, reticulately-sculptured pollen. The unique pollen morphology of Ripogonum supports its removal from Smilacaceae. In contrast, the characteristics of Heterosmilax pollen intergrade with those seen in Smilax, suggesting that the former might be better reduced to synonymy with the latter. A key to the identification of these pollen types is presented along with a discussion of geographic and possible evolutionary trends among them.     

Lectins of the <Emphasis Type="Italic">Nicotiana tabacum</Emphasis> pollen grain walls stimulating in vitro pollen germination

Proteins diffusing from tobacco pollen grains into external medium, being inactivated by low temperature (0°C), were shown to stimulate pollen germination in vitro. Fractionation of these proteins by affinity chromatography using α-D-methylmannopyranoside (MMP) immobilized on agarose resulted in the isolation of lectins stimulating germination. The mol wts of these lectins were estimated by SDS-PAGE as 58, 69, and 74 kD. A stimulatory effect of these lectins was determined by their specific interaction with carbohydrate determinants because a competitive sugar (0.3 M MMP) suppressed completely lectin effect on germination. Polyvalent lectins capable of erythrocyte agglutination were also found among diffused proteins. These lectins are glycoproteins with Glu/Man carbohydrate determinants. MMP did not affect their capability of agglutination. This finding permits a conclusion that pollen grain wall contains lectins differing in their carbohydrate specificity.     

Modern surface pollen assemblages from the Middle and High Atlas,Morocco: insights into pollen representation and transport

Thirty-three modern surface samples were collected in the environmentally and climatologically contrasting regions of the Middle and High Atlas Mountains, Morocco. Samples representing forest and steppe montane environments (1935–2760 m above sea level) are clustered around study sites at Lake Tislit (High Atlas, semi-arid oro-Mediterranean bioclime) and Lake Sidi Ali and Michliffen (Middle Atlas, sub-humid montane Mediterranean bioclime). Good discrimination between regional pollen spectra is evident, with Middle Atlas samples reflecting higher arboreal cover (Cedrus and evergreen Quercus) and High Atlas samples with high abundances of non-arboreal taxa, including Artemisia and Fabaceae. These four taxa (Cedrus, evergreen Quercus, Artemisia and Fabaceae) are furthermore shown to be reliable indicators of local source vegetation within a 100 m² quadrat, taking into account threshold abundances of 7%, 20%, 4% and 10%, respectively. Deciduous Quercus, Olea and Phillyrea show long-distance pollen dispersal across both regions, contributing to non-trivial arboreal pollen (AP) values of up to 35% (typically 20–30%) in the High Atlas spectra. In the Middle Atlas, AP values of 40 to 50% occur in open sampling locations and > 60% under forest canopy cover. These insights should be taken into account when interpreting ancient pollen spectra from regional lakes and bogs for palaeoenvironmental reconstruction.     

Comparison between Solanum torvum Sw. and S. melongena L. after Ralstonia solanacearum inoculation

Bacterial wilt, caused by Ralstonia solanacearum, is one of the most devastating plant diseases, affecting some economically important Solanaceae crops. In contrast, Solanum torvum, also known as wild eggplant, does not wilt when infested with R. solanacearum. In order to describe the mechanism underlying the response of S. torvum, it was compared with the cultivated eggplant, S. melongena, when both were infected with the same R. solanacearum strain. No wilting occurred in S. torvum, although the bacteria colonised roots and stems in both species within the first 24 h. There were marked differences beyond 24 h, consisting of high bacterial mortality in S. torvum. Using the calli model, our investigations revealed an increase in cell wall monoamine oxidase activity in S. torvum after R. solanacearum inoculation, which did not occur in S. melongena.     

Resource limitation and pollen source (self and outcross) affecting seed production in two louseworts, Pedicularis siphonantha and P. longiflora (Orobanchaceae)

Two animal-pollinated hermaphrodite plants, Pedicularis siphonantha and P. longiflora , have been used to investigate factors limiting seed production in natural populations. To evaluate the potential seed abortion due to resources limitation, seed development has been observed and seed count conducted twice. Seed production per capsule has been compared when flowers have been removed and in a control group. Open pollination has been investigated and pollen supplementation undertaken to estimate the possibility of pollen limitation. Results show that seed abortion is frequent. Stigmatic pollen load is significantly higher than ovule number per ovary under open pollination for both species. Additional self and outcross pollen did not affect seed production. Flower removal significantly increases seed production per capsule, which indicates that seed production of the studied species is limited by available resources. To detect differences in seed production between flowers pollinated by self and outcross pollen, hand pollination of bagged flowers has also been conducted in natural populations of the two Pedicularis species. Compared with open pollination, hand-pollinating self-pollen decreases, while outcross pollen increases seed production per capsule. Such results suggest that inbreeding depression in the two self-compatible species may also result in partial seed abortion under open pollination if mixed pollen is deposited on the stigma. Our results also suggest that pollen interference plays an important role in low female fertility in the two Pedicularis species.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 83–89.     

A 250 year comparison of historical, macrofossil and pollen records of aquatic plants in a shallow lake

1. Sedimentary remains of aquatic plants, both vegetative (turions, leaves, spines) and reproductive (fruits, seeds, pollen), may provide a record of temporal changes in the submerged vegetation of lakes. An independent assessment of the degree to which these remains reflect past floristic change is, however, rarely possible. 2. By exploiting an extensive series of historical plant records for a small shallow lake we compare plant macrofossil (three cores) and pollen (one core) profiles with the documented sequence of submerged vegetation change since c. 1750 AD. The data set is based on 146 site visits with 658 observations including 42 taxa classified as aquatic, spanning 250 years. 3. Approximately 40% of the historically recorded aquatic taxa were represented by macro‐remains. In general macrofossils underestimated past species diversity, with pondweeds (three of eight historically recorded Potamogeton species were found) particularly poorly represented. Nonetheless, several taxa not reported from historical surveys (e.g. Myriophyllum alterniflorum and Characeae) were present in the sediment record. 4. The pollen record revealed taxa which left no macro‐remains (e.g. Littorella uniflora), and the macrofossil record provided improved taxonomic resolution for some taxa (e.g. Potamogeton) and a more reliable record of persistence, appearance and loss of others (e.g. Myriophyllum spp. and Nymphaeaceae). 5. Detrended correspondence analysis indicated that changes in the community composition evidenced by the palaeolimnological and historical records were synchronous and of a similar magnitude. Both records pointed to a major change at around 1800, with the historical record suggesting a more abrupt change than the sedimentary data. There was good agreement on a subsequent change c. 1930. 6. The palaeolimnological data did not provide a complete inventory of historically recorded species. Nevertheless, these results suggest that combined macrofossil and pollen records provide a reliable indication of temporal change in the dominant components of the submerged and floating‐leaved aquatic vegetation of shallow lakes. As such palaeolimnology may provide a useful tool for establishing community dynamics and successions of plants over decadal to centennial timescales.     

Pollen–pollen interactions in Betula pendula in vitro

Direct pollen interactions, as well as interactions mediated by a recipient, can have a remarkable influence on pollen fertilization ability. Under conditions of pollen competition it could be advantageous if pollen grains interfered with the germination of other pollen. The aim of this study was to find out if there are direct negative or positive pollen–pollen interactions between pollen grains from genetically slightly different donors. The in vitro germinability of the pollen from several Betula pendula Roth clones was investigated. The pollen interactions between the clones were examined pairwise by using equal pollen mixtures. In three of the eight cases the germination percentage of the pollen mixture was significantly higher than the average germination percentage of the separate clones that formed the mixture, which indicates some type of interaction between the pollen populations. We found only positive interactions between the pollen of clones. This study also documented density-dependent germination of pollen grains in vitro (=pollen population effect). Adding an aqueous pollen extract to the incubation medium increased the germination percentages of poorly germinating pollen and small pollen populations. Germination-stimulating effects were found to exist both with fresh and dead pollen. Such direct pollen–pollen interactions could be explained by specific water-soluble substances diffusing from pollen grains.     

Karyotype differentiation between Koelreuteria bipinnata and K. elegans ssp. formosana (Sapindaceae) based on chromosome banding patterns

Koelreuteria Laxm., a genus in the tribe Koelreuterieae (Sapindaceae), includes three tree species that are widely recognized as having horticultural merit. The two more closely related species, K. bipinnata Franch. and K. elegans (Seem.) A. C. Sm., are easily distinguished from K. paniculata Laxm. by their bipinnate leaves. In this study, both species were investigated cytogenetically and their karyotypes and heterochromatic patterns were compared. Koelreuteria bipinnata and K. elegans ssp. formosana (Hayata) F. G. Mey. both have 2 n  = 32 but their karyotypes present slight morphological differences when observed using conventional staining. Chromosome banding patterns are reported for the first time for this genus. Both species exhibit terminal heterochromatic blocks, as revealed by C-Giemsa and C-CMA₃, but the band size varies between the species. Koelreuteria bipinnata has larger heterochromatic blocks and more GC-rich segments, while in K. elegans ssp. formosana these bands are smaller. The relationship between the karyotype features in these closely related species is discussed.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 451–455.     

Unilateral and bilateral hybridization barriers in inter-series crosses of 4x 2EBN Solanum stoloniferum, S. pinnatisectum, S. cardiophyllum, and 2x 2EBN S. tuberosum haploids and haploid-species hybrids

Wild Mexican potato species are an important untapped source of useful variation for potato improvement. Introgression methods such as 2n gametes, chromosome doubling, and crossing with disomic 4x 2 endosperm balance number (EBN) bridge species have been used to overcome post-zygotic endosperm failure according to the EBN hypothesis. Stylar barriers can prevent zygote formation, bilaterally when zygote formation is blocked in both directions of the cross or unilaterally when zygote formation is blocked in self incompatible (SI) × self compatible (SC) crosses. In several Solanaceae species, the S-locus for SI has been implicated in interspecific incompatibility. The objectives of this research were to determine if: (1) disomic 4x 2EBN Solanum stoloniferum can be used as a bridge species for introgression of the Mexican 2x 1EBN species Solanum cardiophyllum and Solanum pinnatisectum, (2) pre- and/or post-zygotic barriers limit hybridization among EBN compatible Solanum inter-series crosses, and (3) reproductive barriers act unilaterally or bilaterally. Fruit formation and seed set was recorded for inter-pollinations of S. stoloniferum, 4x 2EBN chromosome doubled S. cardiophyllum and S. pinnatisectum, and 2x 2EBN S. tuberosum haploids (HAP) or haploid-species hybrids (H-S). In vivo pollen tube growth was analyzed for each cross combination with fluorescence microscopy. Attempts to create bridge hybrids between S. stoloniferum, and S. cardiophyllum or S. pinnatisectum were not successful. Pre- and post-zygotic barriers prevented seed formation in crosses involving S. cardiophyllum and S. pinnatisectum. Self compatibility in S. stoloniferum and S. pinnatisectum suggests that the S-locus does not contribute to the stylar barriers observed with these species. Alternatively, the presence of functional and nonfunctional (SC) S-alleles may explain interspecific incompatibility in intra- and inter-ploidy crosses. A non-stylar unilateral incongruity was discovered in H-S/HAP × S. stoloniferum crosses, indicating either a post-zygotic barrier, or a pre-zygotic barrier acting at or within the ovary. Furthermore, lack of S. stoloniferum pollen rejection may occur through absence of S. stoloniferum pollen-active genes needed to initiate pollen rejection, or through competitive interaction in S-locus heterozygous S. stoloniferum pollen. Introgression strategies using these species would benefit potato breeding by introducing genetic diversity for several traits simultaneously through co-current introgression.     

gener: a server‐based analysis of pollen pool structure

The server‐based program gener performs the two‐generation analysis of pollen flow for data consisting of mother/offspring arrays using genetic markers. The gener program decomposes the genetic variance sampled by maternal individuals within and among pollen pool components of genetic variance and is accessible from http://dyerlab.bio.vcu.edu . These estimates are used to construct the test statistic, Φ_ft , whose significance is tested via permutation. The Φ_ft statistic can subsequently be used to quantify genetic effective pollen donor population size (N_ep), effective mating area and dispersal distance. Furthermore, the gener program can calculate Φ_ft values for all pairs of substrata within the data set.     

A survey of modern pollen and vegetation along a south–north transect in Mongolia

Aim This modern pollen‐rain study documents the spatial and quantitative relationships between modern pollen and vegetation in Mongolia, and explores the potential for using this relationship in palaeoclimatic reconstructions. Location East‐central Mongolia. Methods We collected 104 pollen surface samples along a south–north transect across five vegetation zones in Mongolia. Discriminant analysis was used to classify the modern pollen spectra into five pollen assemblages corresponding to the five vegetation zones. Hierarchical cluster analysis was used to divide the main pollen taxa into two major groups and seven subgroups representing the dry and moist vegetation types and the main vegetation communities within them. Results Each vegetation zone along the transect can be characterized by a distinctive modern pollen assemblage as follows: (1) desert zone: Chenopodiaceae–Zygophyllaceae–Nitraria–Poaceae pollen assemblage; (2) desert‐steppe zone: Poaceae–Chenopodiaceae pollen assemblage; (3) steppe zone: Artemisia–Aster‐type–Poaceae–Pinus Haploxylon‐type pollen assemblage; (4) forest‐steppe zone: Pinus Haploxylon‐type–Picea–Artemisia–Betula, montane forb/shrub and pteridophyte pollen assemblage; and (5) mountain taiga zone: Pinus Haploxylon‐type–Picea–Poaceae–Cyperaceae, montane forb/shrub and Pteridophyte pollen assemblage. Main conclusions Based on the ratio between the major pollen taxon groups and subgroups, we propose two pollen–climate indices that represent the precipitation and temperature conditions in the study region. When plotted along our south–north transect, the moisture indices (M) and temperature indices (T) mimic the regional gradients of precipitation and temperature across Mongolia very closely. These pollen–climate indices can be used for palaeoclimatic reconstruction based on fossil pollen data.     

芫花的花粉形态观察及生活力和萌发率分析

Pollen morphology of Daphne genkwa Sieb.et Zucc.was observed by scanning electron microscope(SEM),and its viability and germination rate were measured by TTC and sucrose in vitro culture methods.The results show that pollen is stenopalynous type with a diameter of 15.6-21.6 μm.Per pollen has 10-16 apertures which is irregular circular with a diameter of 1.4-2.0 μm.Surface ornamentation of pollen is rough reticulate pattern which is circular polygon(tetragon-heptagon,mostly pentagon-hexagon).Pollen viability is 51% by TTC.Sucrose of different concentrations has a significant effect on pollen germination rate during pollen culture.And pollen germination rate is the highest with a percentage of 27.0% in medium containing 50 g·L-1 sucrose,while pollen could not germinate in medium containing sucrose over 250 g·L-1.Otherwise,there is the phenomenon of "multi-aperture germination" during pollen germinating.