Carbon isotopic composition of Ambrosia and Artemisia pollen: assessment of a C(3) -plant paleophysiological indicator

? There is limited evidence on how shifts in plant physiological performance influence vegetation variations in the paleorecord. ? To evaluate δ(13) C of pollen from C(3) plants as an indicator of community-level physiology, small quantities (10-30 grains) of untreated pollen and sporopollenin from herbarium specimens of Ambrosia (A.?tomentosa and A.?psilostachya) and Artemisia (A.?frigida, A.?ludoviciana and A.?dracunculus), genera abundant in grassland pollen profiles, were isolated by micromanipulation. Their δ(13) C values were measured using a spooling-wire microcombustion device interfaced with an isotope-ratio mass spectrometer. Leaf δ(13) C was also measured. Carbon isotope discrimination (Δ) for untreated pollen, sporopollenin and leaves was compared with historic records of seasonal precipitation amount, vapor pressure deficit and the Palmer Drought Severity Index (PDSI). ? Each species showed positive correlations between Δ of untreated pollen and sporopollenin. Sporopollenin Δ was most strongly correlated with PDSI. Correlations among leaf Δ and moisture indicators were stronger for Ambrosia than Artemisia. ? These results suggest that sporopollenin Δ indicates the level of moisture stress in C(3) plants. Therefore, δ(13) C analysis of pollen promises to help address important paleoecological questions, such as how community-level physiology contributes to shifts in vegetation composition.     

Stable isotopes data (delta13C, delta15N) from the cave bear (Ursus spelaeus): a new approach to its palaeoenvironment and dormancy

Palaeoclimatic data that can be extracted from the isotopic signatures of delta13C and delta15N, which are found in fossil bone collagen, should be analysed according to the specific metabolism of each species. Although Ursus spelaeus is an extinct species, its metabolism is assimilated to current, closely related species of bear. In this study, bone collagen isotopic signatures (delta13C and delta15N) of cave bears from Late Pleistocene Alpine sites were compared to those that have already been documented. The delta13C signature did not seem to follow a systematic trend according to climatic conditions, probably as a consequence of the high variability present in the values of C3 plants, which were the basis of feeding. On the contrary, the delta15N signature displayed higher values in sites corresponding to colder periods in which the delta15N signature appeared to be dominated by the physiology of dormancy. Then, due to the reuse of urea in synthesizing amino acids, the delta15N signature systematically increased along with dormancy duration. This was related to the length of winter and, in turn, depended on climate.     

The Occurrence of <Emphasis Type="Italic">p</Emphasis>-coumaric Acid and Ferulic Acid in Fossil Plant Materials and their Use as UV-proxy

The applicability of p-coumaric acid and ferulic acid concentrations or ratios in (sub)fossil plant remnant as UV-B proxies relies on various aspects, which are discussed in this paper and will be illustrated with some experimental data. A newly developed THM-micropyrolysis–gas chromatography–mass spectrometry method was tested on various spores, pollen and other plant remains, which were analysed for the presence of the UV-absorbing compounds p-coumaric acid and ferulic acid. This revealed that these supposed building-blocks of sporopollenin appear to be present in pollen of many plant species but also in moss spores. The development of this micropyrolysis method paved the way for the quantitative analysis of UV-absorbing compounds in case only a small amount of analyte is available, for example for fossil pollen and spores but also other small palynomorphs and plant fossils. The use of this technique will provide a better insight in the plant responses to UV-radiation, the chemistry of pollen and spores, their fossil counterparts and furthermore the means for a further development of a proxy for the reconstruction of past UV-B radiation.     

The isotopic ecology of African mole rats informs hypotheses on the evolution of human diet

The diets of Australopithecus africanus and Paranthropus robustus are hypothesized to have included C4 plants, such as tropical grasses and sedges, or the tissues of animals which themselves consumed C4 plants. Yet inferences based on the craniodental morphology of A. africanus and P. robustus indicate a seasonal diet governed by hard, brittle foods. Such mechanical characteristics are incompatible with a diet of grasses or uncooked meat, which are too tough for efficient mastication by flat, low-cusped molars. This discrepancy, termed the C4 conundrum, has led to the speculation that C4 plant underground storage organs (USOs) were a source of nutrition for hominin species. We test this hypothesis by examining the isotopic ecology of African mole rats, which consume USOs extensively. We measured delta18O and delta13C of enamel and bone apatite from fossil and modern species distributed across a range of habitats. We show that delta18O values vary little and that delta13C values vary along the C3 to C4/CAM-vegetative axis. Relatively high delta13C values exist in modern Cryptomys hottentotus natalensis and Cryptomys spp. recovered from hominin-bearing deposits. These values overlap those reported for A. africanus and P. robustus and we conclude that the USO hypothesis for hominin diets retains certain plausibility.     

Evolutionary stasis of sporopollenin biochemistry revealed by unaltered Pennsylvanian spores

The biopolymer sporopollenin present in the spore/pollen walls of all land plants is regarded as one of the most recalcitrant biomacromolecules (biopolymers), providing protection against a range of abiotic stresses. This long-term stability is demonstrated by the near-ubiquitous presence of pollen and spores in the fossil record with spores providing the first evidence for the colonization of the land. Here, we report for the first time chemical analyses of geologically unaltered sporopollenin from Pennsylvanian (c. 310?million yr before present (MyBP)) cave deposits. Our data show that Pennsylvanian Lycophyta megaspore sporopollenin has a strong chemical resemblance to extant relatives and indicates that a co-polymer model of sporopollenin formation is the most likely configuration. Broader comparison indicates that extant sporopollenin structure is similar across widely spaced phylogenetic groups and suggests land plant sporopollenin structure has remained stable since embryophytes invaded land.     

Studies of Fossil and Modern Spore Wall Biomacromolecules using13C Solid State NMR

A range of Carboniferous lycophyte megaspore exines have beeninvestigated using¹³C magic-angle spinning nuclear magneticresonance (MAS NMR) spectroscopy. Their composition differsconsiderably from sporopollenin obtained from an extant lycophyte.The differences observed result in part from varying degreesof diagenesis. Fossil fern spores, gymnosperm megaspore-membranes and pollenhave also been examined. These show a similar composition tothe fossil lycophyte megaspores. The constituent material ofall of these exines differs considerably from the sporopolleninobtained from comparable extant samples. Despite the changesin composition observed on fossilisation, differences in compositionbetween the major groups of plants may be preserved to someextent in the fossil material. Walls of the fossil prasinophyceanalgal cystTasmanites have been examined and these show a greatersimilarity to fossil cuticle and algaenans than to sporopollenins. The effect of oxidative maceration on fossil and modern sporopolleninshas also been investigated. The main influence of oxidativemaceration is the removal of unsaturated carbon environmentssuch as aromatics; this causes fossil spores to be more susceptibleto oxidative maceration than the modern exines. Heating of modernexine material models the alteration of exines by diagenesis.The changes that occur on heating an extant sample to 150–225°Cgive a chemical composition that is similar to those of thefossil sporopollenins. ¹³C solid state NMR; spores; pollen; fossil; Carboniferous lycopsids; ferns; pteridosperm; gymnosperm; oxidative maceration; heating; thermal maturation     

Pollen morphology of selected crop plants from southern China and testing pollen morphological data in an archaeobotanical study

Identification of pollen grains of cultivated plants is essential in archaeobotanical studies. In this study, we investigated the pollen morphology of 30 species which are representatives of most of the crop plants in southern China, using a light microscope. Our results show that the pollen grains of these species or genera can generally be identified by their size, aperture(s) and exine sculpture. We found that: (1) some cultivated cereals can be distinguished from wild species of Poaceae according to their size frequency combined with their morphological features; (2) the lengths of the equatorial diameter (E), polar axis (P) and the greatest dimension of the lumina (the size of the network sculpturing) of the exine reticulum may be diagnostic features to distinguish some brassicaceous vegetables. There are significant differences between the E and P values among Brassica campestris (B. rapa, oilseed rape, Chinese cabbage), B. alboglabra (B. oleracea var. alboglabra, gai lan, Chinese kale), B. parachinensis (B. rapa var. parachinensis, choy sum, Chinese flowering cabbage) and B. chinensis (B. rapa ssp. chinensis, pak choi), but moderate differences in the longer axis length of the reticulum lumina, which provide potential for identifying species on the basis of pollen grains. We compared the P values and the longer axis length of the lumina of modern specimens of Brassicaceae pollen grains with those of fossil pollen extracted from the Ming-Qing cultural layer in the Fuqikou site at Chongqing, China, and found that the fossil pollen grains of Brassicaceae probably represent vegetable plants related to B. parachinensis. Moreover, we measured the diameters of rice pollen grains from modern paddy fields to assess the pollen size frequency and found that the size range from ~?34 to 38 µm is closely associated with rice pollen in southern China, which can be used to detect pollen signals of human activities in archaeobotanical investigations.     

Paleobotanical evidences of the Tertiary history and origin of the Mediterranean sclerophyll dendroflora

The evolution of important woody plant groups, ancestral to the modern Mediterranean dendroflora, is surveyed. Altogether, the history and phytogeography of 86 fossil species or species-groups is considered. The major part of the Paleomediterranean woody plants appears in Miocene mixed mesophyllous and mesoxerophyllous, evergreen and deciduous forests. The initial formation of basic Mediterranean sclerophyllous woody vegetation types is referred to periods from the Late Sarmatian to the Late Pontian, in geographic areas between 37° and 45° N latitude.     

Paleobotanical remains from the Paleocene–lower Eocene Vagadkhol Formation, western India and their paleoclimatic and phytogeographic implications

A small assemblage of macro- and micro floral remains comprising fossil leaf impressions, silicified wood, spores, and pollen grains is reported from the Paleocene–lower Eocene Vagadkhol Formation (=Olpad Formation) exposed around Vagadkhol village in the Bharuch District of Gujarat, western India. The fossil leaves are represented by five genera and six species, namely, Polyalthia palaeosimiarum (Annonaceae), Acronychia siwalica (Rutaceae), Terminalia palaeocatapa and T. panandhroensis (Combretaceae), Lagerstroemia patelii (Lythraceae), and a new species, Gardenia vagadkholia (Rubiaceae). The lone fossil wood has been attributed to a new species, Schleicheroxylon bharuchense (Sapindaceae). The palynological assemblage, consisting of pollen grains and spores, comprises eleven taxa with more or less equal representation of pteridophytes, gymnosperms, and angiosperms. Angiospermous pollen grains include a new species Palmidites magnus. Spores are mostly pteridophytic but some fungal spores were also recovered. All the fossil species have been identified in the extant genera. The present day distribution of modern taxa comparable to the fossil assemblage recorded from the Vagadkhol area mostly indicate terrestrial lowland environment. Low frequency of pollen of two highland temperate taxa (Pinaceae) in the assemblage suggests that they may have been transported from a distant source. The wood and leaf taxa in the fossil assemblage are suggestive of tropical moist or wet forest with some deciduousness during the Paleocene–early Eocene. The presence of many fungal taxa further suggests the prevalence of enough humidity at the time of sedimentation.     

δ15N values of tropical savanna and monsoon forest species reflect root specialisations and soil nitrogen status

A large number of herbaceous and woody plants from tropical woodland, savanna, and monsoon forest were analysed to determine the impact of environmental factors (nutrient and water availability, fire) and biological factors (microbial associations, systematics) on plant delta(15)N values. Foliar delta(15)N values of herbaceous and woody species were not related to growth form or phenology, but a strong relationship existed between mycorrhizal status and plant delta(15)N. In woodland and savanna, woody species with ectomycorrhizal (ECM) associations and putative N(2)-fixing species with ECM/arbuscular (AM) associations had lowest foliar delta(15)N values (1.0-0.6 per thousand ), AM species had mostly intermediate delta(15)N values (average +0.6 per thousand ), while non-mycorrhizal Proteaceae had highest delta(15)N values (+2.9 to +4.1 per thousand ). Similar differences in foliar delta(15)N were observed between AM (average 0.1 and 0.2 per thousand ) and non-mycorrhizal (average +0.8 and +0.3 per thousand ) herbaceous species in woodland and savanna. Leguminous savanna species had significantly higher leaf N contents (1.8-2.5% N) than non-fixing species (0.9-1.2% N) indicating substantial N acquisition via N(2) fixation. Monsoon forest species had similar leaf N contents (average 2.4% N) and positive delta(15)N values (+0.9 to +2.4 per thousand ). Soil nitrification and plant NO(3)(-) use was substantially higher in monsoon forest than in woodland or savanna. In the studied communities, higher soil N content and nitrification rates were associated with more positive soil delta(15)N and plant delta(15)N. In support of this notion, Ficus, a high NO(3)(-) using taxa associated with NO(3)(-) rich sites in the savanna, had the highest delta(15)N values of all AM species in the savanna. delta(15)N of xylem sap was examined as a tool for studying plant delta(15)N relations. delta(15)N of xylem sap varied seasonally and between differently aged Acacia and other savanna species. Plants from annually burnt savanna had significantly higher delta(15)N values compared to plants from less frequently burnt savanna, suggesting that foliar (15)N natural abundance could be used as marker for assessing historic fire regimes. Australian woodland and savanna species had low leaf delta(15)N and N content compared to species from equivalent African communities indicating that Australian biota are the more N depauperate. The largest differences in leaf delta(15)N occurred between the dominant ECM Australian and African savanna (miombo) species, which were depleted and enriched in (15)N, respectively. While the depleted delta(15)N of Australian ECM species are similar to those of previous reports on ECM species in natural plant communities, the (15)N-enriched delta(15)N of African ECM species represent an anomaly.     

基于蜂蜜孢粉学鉴定秦岭中华蜜蜂的蜜源木本植物

蜜源木本植物的鉴定能为中华蜜蜂Apis cerana cerana保护和利用提供依据.本研究从在秦岭地区收集的4份中华蜜蜂蜂蜜中分离出植物花粉,然后在扫描电镜下观察花粉形态,根据花粉大小、赤道面观、极面观、表面纹饰对花粉所属植物的种类进行鉴定.共鉴定出中华蜜蜂利用的蜜源木本植物13科,19属,20种.其中以壳斗科Fagaceae、忍冬科Caprifoliaceae最多,卫矛科Celastraceae、桦木科Betulaceae、蔷薇科Rosaceae次之.这些蜜源木本植物中有13种是药用植物.秦岭地区丰富的蜜源木本植物为中华蜜蜂的生存提供了食物资源;同时中华蜜蜂作为传粉昆虫,对维持秦岭地区蜜源植物的生存和生态系统稳定起着重要的作用.     

Sources of organic carbon and depositional environment in the Bengal delta plain sediments during the Holocene period

This study investigated the sources of organic matter and sediment depositional environment within fluviatile sediments of the Ganges–Meghna (GM) delta plains. The very low contents of trace metals e.g., chromium (Cr), cobalt (Co), scandium (Sc), and vanadium (V), organic carbon content, and cerium (Ce)-anomaly data of sediments indicate the redox conditions that fall within the boundary of oxic–anoxic condition, with dominantly oxic conditions in the sediment deposition environment. The higher atomic carbon nitrogen (C/N)a ratios and depleted stable carbon isotope ratio (δ¹³C) values for sediments from three study areas indicated the terrestrial sources of organic matter derived from C₃ plant materials, whereas the contribution of organic materials from C₄ vegetation and riverine productivity is low. Some silty sand samples exhibited lower (C/N)a ratios and enriched δ¹³C values in Sonargaon and Faridpur areas that are attributed to the adsorption of ammonium ions on clay minerals and the contribution of organic matter from C₄ plants. Total sulfur over total organic carbon (TS/TOC) ratios in sediments of the Ganges delta reflect the nonmarine environments of sediment deposition. The lower ratios of syringyl to vanillyl phenols (S/V), cinnamyl to vanillyl phenols (C/V), and acid to aldehyde in vanillyl phenols (Ad/Al)v observed in Daudkandi indicate that the lignin in sediments derived from dominant woody gymnosperm sources and is very highly degraded. By contrast, the S/V ratio, C/V ratios, and [Ad/Al]v ratios in Faridpur suggest that the lignin in sediments derived from a mixture of woody and nonwoody angiosperm plant tissue contribution that underwent high degradation as well.     

Weather and nodule mediated variations in delta 13C and delta 15N values in field-grown soybean (Glycine max L.) with special interest in the analyses of xylem fluids

The nodulating soybean (Enrei) and its non-nodulating mutant (EN 1282) were grown in outdoor plots for 2 years (1994: extraordinary dry, high temperature, 1995: ordinary year). Carbon and nitrogen accumulation, delta 13C and delta 15N values in plant parts and xylem fluids and delta 15N values in the water-extractable soil N were analysed throughout the growing period. Plant growth in 1994 was rapid during the early growth stages, but no pods were produced. In 1995, plant growth was normal and pods were formed. The delta 13C values of the leaves were less negative in 1994 than in 1995 and the nodulated plants showed less negative delta 13C values than non-nodulated plants in both years. The delta 13C values of the leaves during the vegetative phase were positively correlated to the leaf N concentrations. Leaf N concentrations in their turn were influenced by nodulation and weather conditions and/or soil available N. The delta 15N values in the plants and xylem fluids were lower in the nodulated soybean than in non-nodulated soybean in both years, and estimates of the contribution of N2 fixation in nodulated plants based on plant top delta 15N values were 7-14% in 1994 and 37-63% in 1995. The delta 13C values of xylem fluids did not differ between nodulated and non-nodulated plants. Thus, the expected contribution by phosphopenolpyruvate carboxylase-mediated CO2 fixation in the root nodules to plant C-incorporation could not have been significant.     

THE ULTRASTRUCTURE OF PHYCOPELTIS (CHROOLEPIDACEAE: CHLOROPHYTA). I. SPOROPOLLENIN IN THE CELL WALLS

Electron microscope observations on Phycopeltis epiphyton, a subaerial green alga found growing on the leaves of vascular plants and bryophytes, revealed the presence of a densely staining material within the inner and outer zones of the cell walls. This material resists acetolysis, is degraded by chromic acid, is unaffected by ethanolamine and exhibits secondary fluorescence when stained with the fluorochrome Primuline. These characteristics, together with infrared absorption spectra indicate that, on the basis of currently accepted criteria, the densely staining material is a sporopollenin and that it is a major component of the cell wall. Tests for cellulose, chitin, and lignin were negative, and little if any silica is present. It is suggested that negative results in tests for cellulose may be due to a masking effect by the sporopollenin. Comparison of the fine structure of the cell walls of P. epiphyton, pollen grains, and algal cells (known to contain sporopollenin) supports the suggestion that sporopollenin deposition on “unit membranes” is universal. Morphological similarity among sporopollenin lamellae in P. epiphyton, pollen grains, spores of land plants, and the trilaminar sporopollenin sheath in Chlorella, Scenedesmus, and Pediastrum indicates that the structures may be analogous. As in pollen grains, sporopollenin may provide protection against desiccation and parasitism. It may also be involved in the adhesion of Phycopeltis to host plants and in the adhesion between adjacent filaments of the thallus.     

浙江丽水木本植物区系的研究

丽水市位于浙江西南部,是浙江木本植物最丰富的地区之一,共有木本植物95科338属1128种。通过对科、属、种的统计分析,该地区木本植物区系基本特征为：（1）植物种类丰富;（2）起源古老、单型属和寡种属较多;（3）各类地理成分复杂,与世界各地有着不同程度的联系,以温带成分为主;（4）区系过渡性明显。     

Gelechiidae moths are capable of chemically dissolving the pollen of their host plants: first documented sporopollenin breakdown by an animal

Background

Many insects feed on pollen surface lipids and contents accessible through the germination pores. Pollen walls, however, are not broken down because they consist of sporopollenin and are highly resistant to physical and enzymatic damage. Here we report that certain Microlepidoptera chemically dissolve pollen grains with exudates from their mouthparts.

Methodology/Principal Findings

Field observations and experiments in tropical China revealed that two species of Deltophora (Gelechioidea) are the exclusive pollinators of two species of Phyllanthus (Phyllanthaceae) on which their larvae develop and from which the adults take pollen and nectar. DNA sequences placed the moths and plants phylogenetically and confirmed that larvae were those of the pollinating moths; molecular clock dating suggests that the moth clade is younger than the plant clade. Captive moths with pollen on their mouthparts after 2-3 days of starvation no longer carried intact grains, and SEM photographs showed exine fragments on their proboscises. GC-MS revealed cis-β-ocimene as the dominant volatile in leaves and flowers, but GC-MS analyses of proboscis extracts failed to reveal an obvious sporopollenin-dissolving compound. A candidate is ethanolamine, which occurs in insect hemolymphs and is used to dissolve sporopollenin by palynologists.

Conclusions/Significance

This is the first report of any insect and indeed any animal chemically dissolving pollen.     

Environmental and species‐specific controls on δ13C and δ15N in dominant woody plants from central‐western Argentinian drylands

Spatial variation in mean annual precipitation is the principal driver of plant water and nitrogen status in drylands. The natural abundance of carbon stable isotopes (δ¹³C) in photosynthetic tissues of C3 plants is an indicator of time‐integrated behaviour of stomatal conductance; while that of nitrogen stable isotopes (δ¹⁵N) is an indicator of the main source of plant N (soil N vs. atmospheric N₂). Previous studies in drylands have documented that plant δ¹³C and δ¹⁵N values increase with decreasing mean annual precipitation due to reductions in stomatal conductance, and soil enriched in ¹⁵N, respectively. However, evidence for this comes from studies focused on stable isotopes measurements integrated at the plant community level or on dominant plants at the site level, but little effort has been made to study C and N isotope variations within a species growing along rainfall gradients. We analysed plant δ¹³C, δ¹⁵N and C/N values of three woody species having different phenological leaf traits (deciduous, perennial and aphyllous) along a regional mean annual precipitation gradient from the central‐western Argentinian drylands. Noticeably, plant δ¹³C and δ¹⁵N values in the three woody species did not increase towards sites with low precipitation or at the start of the growing season (drier period), as we expected. These results suggest that environmental factors other than mean annual precipitation may be affecting plant δ¹³C and δ¹⁵N. The short‐term environmental conditions may interact with species‐specific plant traits related to water and nitrogen use strategies and override the predictive influence of the mean annual precipitation on plant δ¹³C and δ¹⁵N widely reported in drylands.     

Compound-specific deltaD-delta13C analyses of n-alkanes extracted from terrestrial and aquatic plants

Stable hydrogen and carbon isotopic compositions of individual n-alkanes were determined for various terrestrial plants (33 samples including 27 species) and aquatic plants (six species) in natural environments from Japan and Thailand. In C3 plants, n-alkanes extracted from angiosperms have a deltaD value of -152+/-26 per thousand (relative to Standard Mean Ocean Water [SMOW]) and delta13C value of -36.1+/-2.7 per thousand (relative to Peedde Belemnite [PDB]), and those from gymnosperms have a deltaD value of -149+/-16 per thousand and delta13C value of -31.6+/-1.7 per thousand. Angiosperms have n-alkanes depleted in 13C relative to gymnosperms. n-Alkanes from C4 plants have a deltaD value of -171+/-12 per thousand and delta13C value of -20.5+/-2.1 per thousand, being a little depleted in D and much enriched in 13C compared to C3 plants. n-Alkanes of CAM plants are a little depleted in D and vary widely in delta13C relative to those of C3 and C4 plants. In aquatic plants, n-alkanes from freshwater plants have a deltaD value of -187+/-16 per thousand and delta13C value of -25.3+/-1.9 per thousand, and those from seaweeds have a deltaD value of -155+/-34 per thousand and delta13C value of -22.8+/-1.0 per thousand. All n-alkanes from various plant classes are more depleted in D and 13C relative to environmental water and bulk tissue, respectively. In addition, the hydrogen and carbon isotopic fractionations during n-alkane synthesis are distinctive for these various plant classes. While C3 plants have smaller isotopic fractionations in both D and 13C, seaweed has larger isotopic fractionations.     

Grassland development under glacial and interglacial conditions in southern Africa: review of pollen,phytolith and isotope evidence

Pollen evidence suggests that grasslands were well established in southern Africa by the Late Tertiary. Evidence for grassland composition in the region during the Quaternary includes published accounts of isotopes, grass phytoliths and pollen of both grasses and woody plants from a wide range of different environments. Isotope data were derived from speleothems (stalagmites), fossil bones, and fossil tooth enamel and plant material in fossil hyrax dung. The different data types suggest that, with perhaps the exception of the dry southern Kalahari region, temperate grassland consisted of a relatively increased C₃- to C₄-grass ratios during the Last Glacial Maximum (LGM). Cold winter temperature extremes in the southern high latitude and altitude regions and a persistent winter rainfall pattern over the Cape region during the LGM probably limited the distribution of C₄ grasses and canceled out any advantages gained from lowered CO₂ concentrations in the atmosphere. In contrast, in the tropics where marked seasonal temperature fluctuations were lacking, C₄-grass growth was favored.