Search Results (23)

Pollen–stigma interactions have been studied extensively because they play an important role in sexual reproduction and crop yield. The vast majority of studies have focused on dry stigmas, which are typical of many model and agricultural plants; however, the data obtained are difficult to apply to plants with wet stigmas, such as tomato and tobacco. Pollen germination in this case occurs in a liquid, an exudate, which has a complex, species-specific composition. UPLC-ESI-MS-based hormone screening was carried out for six plant genera belonging to Solanaceae, Bromeliaceae, and Gesneriaceae families and revealed jasmonic acid (JA), abscisic acid (ABA) and/or jasmonoyl-L-isoleucine (IleJA) in stigma exudates of tobacco, tomato, and Streptocarpus sp. To assess the physiological significance of plant hormones in stigma exudate we tested their effect in vitro, finding that JA, IleJA, and MeJa significantly stimulated germination of tobacco pollen, with JA being most effective in accordance with its predominance in the stigma exudate; furthermore, ABA stimulated pollen germination in all tested species including bromeliads despite the lack of this hormone in their exudates. Both JA and ABA had an anti-oxidant effect on germinating pollen. Possible functions of hormones and ROS in exudate as well as ways of implementing the anti-oxidant effect of phytohormones are discussed. Full article

This study investigates geochemical indicators (TOC, TN, C/N, δ¹³Corg, δ¹⁵N, and pollen indicators) from sediment samples of Zigetang Co Lake on the Tibetan Plateau (TP) to explore past climate changes in the lake basin. The findings aim to provide essential data for developing sustainable strategies for the TP region. From 14.0 to 10.8 cal. ka BP, the δ¹⁵N, TOC, TN, and δ¹³Corg value of the lake sediments was relatively low; this indicated a low organic matter input into the lake, reflecting a probably cold and arid environment. In addition, the pollen was primarily composed of Artemisia and Gramineae, which are adapted to cold environments, further confirming that the climate during this period was likely cold and dry. From 10.8 to 8.2 cal. ka BP, the changes in the main plant composition were likely due to increased solar radiation, the onset of the monsoon, and higher temperatures and precipitation, which created more favorable conditions for the growth of Cyperaceae. From 8.2 to 4.2 cal. ka BP, when the solar radiation weakened and the monsoon diminished, the basin maintained relatively high water levels, with regional precipitation being likely influenced by westerly winds. From 4.2 to 0.01 cal. ka BP, δ¹³Corg and δ¹⁵N initially decreased and then increased, which was likely a transition from a cold–wet climate to warm–dry conditions during the late Holocene, and the Pollen sum also showed significant changes. Understanding climate evolution and vegetation changes is crucial for formulating timely policies to ensure regional sustainable development. Full article

Pollination in angiosperms depends on complex communication between pollen grains and stigmas, classified as wet or dry, depending on the presence or absence of secretions at the stigma surface, respectively. In species with wet stigma, the cuticle is disrupted and the presence of exudates is indicative of their receptivity. Most stigma studies are focused on a few species and families, many of them with self-incompatibility systems. However, there is scarce knowledge about the stigma composition in Fabaceae, the third angiosperm family, whose stigmas have been classified as semidry. Here we report the first transcriptome profiling and DEGs of Vicia faba L. styles and stigmas from autofertile (flowers able to self-fertilize in the absence of manipulation, whose exudate is released spontaneously) and autosterile (flowers that need to be manipulated to break the cuticle and release the exudates to be receptive) inbred lines. From the 76,269 contigs obtained from the de novo assembly, only 45.1% of the sequences were annotated with at least one GO term. A total of 115,920, 75,489, and 70,801 annotations were assigned to Biological Process (BP), Cellular Component (CC), and Molecular Function (MF) categories, respectively, and 5918 differentially expressed genes (DEGs) were identified between the autofertile and the autosterile lines. Among the most enriched metabolic pathways in the DEGs subset were those related with amino acid biosynthesis, terpenoid metabolism, or signal transduction. Some DEGs have been related with previous QTLs identified for autofertility traits, and their putative functions are discussed. The results derived from this work provide an important transcriptomic reference for style-stigma processes to aid our understanding of the molecular mechanisms involved in faba bean fertilization. Full article

This paper presents the first continuous (gap-free) Late Glacial-Early Holocene (LGEH) pollen record for the Iberian Pyrenees resolved at centennial resolution. The main aims are (i) to provide a standard chronostratigraphic correlation framework, (ii) to unravel the relationships between vegetation shifts, climatic changes and fire, and (iii) to obtain a regional picture of LGEH vegetation for the Pyrenees and the surrounding lowlands. Seven pollen assemblage zones were obtained and correlated with the stadial/interstadial phases of the Greenland ice cores that serve as a global reference. Several well-dated datums were also derived for keystone individual taxa that are useful for correlation purposes. Four vegetation types were identified, two of them corresponding to conifer and deciduous forests (Cf, Df) and two representing open vegetation types (O1, O2) with no modern analogs, dominated by Artemisia-Poaceae and Saxifraga-Cichorioideae, respectively. Forests dominated during interstadial phases (Bølling/Allerød and Early Holocene), whereas O1 dominated during stadials (Oldest Dryas and Younger Dryas), with O2 being important only in the first half of the Younger Dryas. The use of pollen-independent proxies for temperature and moisture allowed the reconstruction of paleoclimatic trends and the responses of the four vegetation types defined. The most relevant observation in this sense was the finding of wet climates during the Younger Dryas, which challenges the traditional view of arid conditions for this phase on the basis of former pollen records. Fire incidence was low until the Early Holocene, when regional fires were exacerbated, probably due to the combination of higher temperatures and forest biomass accumulation. These results are compared with the pollen records available for the whole Pyrenean range and the surrounding lowlands within the framework of elevational, climatic and biogeographical gradients. Some potential future developments are suggested on the basis of the obtained results, with an emphasis on the reconsideration of the LGEH spatiotemporal moisture patterns and the comparison of the Pyrenees with other European ranges from different climatic and biogeographical regions. Full article

The parameters for assessing the quality of honey produced by Apis mellifera are standardized worldwide. The physicochemical properties of honey might vary extensively due to factors such as the geographical area where it was produced and the season in which it was harvested. Little information is available on variations in honey quality among different harvest periods in tropical areas, and particularly in neotropical dry forests. This study describes variations in seventeen physicochemical parameters and the pollen diversity of honey harvested from beehives during the dry season in February, March, and April 2021, in the dry arc of Panama. Potassium is the most abundant mineral in honey samples, and its concentration increases during the harvest period from February to April. A PCA analysis showed significant differences among the samples collected during different harvest periods. The pollen diversity also differs among honey samples from February compared with March and April. The results indicate that climatic conditions may play an important role in the quality of honey produced in the dry arc of Panama. Furthermore, these results might be useful for establishing quality-control parameters of bee honey produced in Panama in support of beekeeping activities in seasonal wet–dry areas of the tropics. Full article

Pollen germination in vivo on wet stigmas is assisted by the receptive fluid—stigma exudate. Its exact composition is still unknown because only some components have been studied. For the first time, hormonal screening was carried out, and the fatty acid (FA) composition of lipid-rich (Nicotiana tabacum) and sugar-rich (Lilium longiflorum) exudates was studied. Screening of exudate for the presence of plant hormones using HPLC-MS revealed abscisic acid (ABA) in tobacco stigma exudate at the two stages of development, at pre-maturity and in mature stigmas awaiting pollination, increasing at the fertile stage. To assess physiological significance of ABA on stigma, we tested the effect of this hormone in vitro. ABA concentration found in the exudate strongly stimulated the germination of tobacco pollen, a lower concentration had a weaker effect, increasing the concentration did not increase the effect. GC-MS analysis showed that both types of exudate are characterized by a predominance of saturated FAs. The lipids of tobacco stigma exudate contain significantly more myristic, oleic, and linoleic acids, resulting in a higher unsaturation index relative to lily stigma exudate lipids. The latter, in turn, contain more 14-hexadecenoic and arachidic acids. Both exudates were found to contain significant amounts of squalene. The possible involvement of saturated FAs, ABA, and squalene in various exudate functions, as well as their potential relationship on the stigma, is discussed. Full article

Nowadays, wild grapevine populations are quite limited and sporadic mainly due to habitat destruction, land-use change, and the spread of pathogens that have reduced their distribution range. Palaeoecological, archaeobotanical, and genetic studies indicate that modern cultivars of Vitis vinifera are the results of the domestication of the dioecious, and sometimes hermaphrodite, wild species standing in riparian zones and wet environments. Wild grapevine populations have declined as a consequence of various forms of anthropogenic disturbance and were assigned by the IUCN Red List of Threatened Species to the Least Concern category. The River Crati Natural Reserve (Riserva Naturale Foce del Crati), located in southern Italy, hosts a population of Vitis vinifera subsp. sylvestris in a rewilding wet forest close to the Ionian Sea. These protected areas are of high scientific, biogeographic, and conservation interest in terms of Mediterranean biodiversity. Dendroecological and pollen morpho-biometric analyses of the wild grapevine are presented in this study. Palaeoecological perspectives for a landscape management strategy aimed at conserving and restoring the relic grapevine population are discussed. Full article

Citrus species have a “wet”-type stigma with abundant exudate, and their style contains numerous canals. For successful seed formation, the process includes pollen grain germination on the stigma, pollen tube development and growth through the stigma and style and, ultimately, successful ovule fertilization. However, preventing the fertilization process can be useful for many agronomic and plant-breeding purposes, such as seedless fruits or for developing new varieties. Several studies have recently shown the inhibition effect of sulfur on pollen tube development inside the Nadorcott mandarin stigma and its effective application to obtain seedless mandarins. However, when applied to the stigma, how can sulfur inhibit pollen tube growth? Moreover, does sulfur have the same effect on other species? The main objective of the present study is to clarify the mode of action of sulfur on the ultrastructure of the Nadorcott mandarin stigma and style. To fulfill this goal, untreated flowers and flowers treated with sulfur were pollinated 24 h later. The treated and untreated stigmas were analyzed and compared with several microscopy techniques. The main results showed that sulfur specifically caused an alteration to the outer layer of stigma papillary cells. This marked alteration resulted in papillary cells losing their functionality due to the deterioration and degradation of their cellular structure. Basal papillae, the stigmatic tissue and stylar canals also underwent major alteration. Sulfur also modified the quantity and uniformity distribution of the stigmatic exudate. All these alterations collectively prevented pollen tube development inside the stigma. These effects have been observed in several Citrus species and varieties, and in some other horticultural species, which suggests a generic (non species-specific) action. Full article

The upland lakes (ULs) in Carajás, southeastern Amazonia, have been extensively studied with respect to their high-resolution structural geology, geomorphology, stratigraphy, multielement and isotope geochemistry, palynology and limnology. These studies have generated large multiproxy datasets, which were integrated in this review to explain the formation and evolution of the ULs. These ULs evolved during the Pliocene–Pleistocene periods through several episodes of a subsidence of the lateritic crust (canga) promoted by fault reactivation. The resulting ULs were filled under wet/dry and warm/cool paleoclimatic conditions during the Pleistocene period. The multielement geochemical signature indicates that the detrital sediments of these ULs were predominantly derived from weathered canga and ferruginous soils, while the sedimentary organic matter came from autochthonous (siliceous sponge spicules, algae, macrophytes) and allochthonous (C3/C4 canga and forest plants and freshwater dissolved organic carbon) sources. Modern pollen rain suggests that even small ULs can record both the influence of canga vegetation and forest signals; thus, they can serve as reliable sites to provide a record of vegetation history. The integrated data from the sedimentary cores indicate that the active ULs have never dried up during the last 50 ka cal BP. However, subaerial exposure occurred in filled ULs, such as the Tarzan mountain range during the Last Glacial Maximum (LGM) and the Bocaína and S11 mountain ranges in the mid-Holocene period, due to the drier conditions. Considering the organic proxies, the expansion of C4 plants has been observed in the S11 and Tarzan ULs during dry events. Extensive precipitation of siderite in UL deposits during the LGM indicated drier paleoenvironmental conditions, interrupting the predominantly wet conditions. However, there is no evidence of widespread forest replacement by savanna in the Carajás plateau of southeastern Amazonia during the late Pleistocene and Holocene. Full article

Peatlands play an important role in the global carbon cycle but have been exploited over many centuries, which reduces their carbon storage capacity. To investigate peatland development during the late Holocene and their restoration after peat extraction, we applied a multi-proxy paleoecological (pollen, plant macrofossils, testate amoebae, loss on ignition, peat humification, etc.) approach to undisturbed and floating vegetation mat deposits of the Gorenki peatland (Meshchera Lowlands, East European Plain). Peatland development started around 2550 before the common era (BCE) as a waterlogged eutrophic birch forest (terrestrial paludification) surrounded by a broadleaf forest. Around 2400 BCE, the peatland turned into an open mire with Sphagnum mosses, sedges, and willows. During 900–800 BCE, the mire transformed into a wet mesotrophic peatland surrounded by a spruce forest. The first human settlements and deforestation around 300–400 CE coincided with oligotrophization of the mire. The growth of the Slavic population in the region in 14th century CE caused transformation of indigenous spruce–broadleaf forests into croplands, and the mire became drier and forested. Since peat extraction was abandoned in the beginning of 20th century CE, the mire has undergone self-restoration starting with the formation of a Sphagnum cuspidatum/obtusum quagmire on the floating peat remains. The Sphagnum mat stabilized during 1960–2000 CE. During the last twenty years, agricultural activity decreased and pine forests were restored in the adjacent area; the floating mat became drier and more oligotrophic, which can lead to the formation of a bog in the absence of considerable anthropogenic impact. Full article

The aim of this study was to reconstruct the vegetation changes, fire history and local landscape dynamics of central Croatia (the western part of south-eastern Europe) from 9800 cal yr BP to the beginning of the Common Era. Pollen, non-pollen palynomorphs and charcoal were analysed for the first time in the aforementioned area by modern palynological methods. Three different assemblage (sub)zones were identified: “Pinus-Fagus-Quercetum mixtum” (Preboreal), “Fagus-Corylus” (Boreal) and “Alnus-Fagus” (Atlantic, Subboreal and older Subatlantic). Additionally, the oldest observation (~9800 cal yr BP) of beech pollen for continental Croatia was confirmed by radiocarbon dating. Our results indicated a possibly milder climate with less extreme temperatures and higher precipitation during the Preboreal chronozone, alongside intensive flooding, a transition from a mosaic of wetland/wet grassland communities to alder carr during the Boreal, and an unusually long multi-thousand-year period, the annual presence of alder on the mire itself. An increase in the number of secondary anthropogenic indicators can be tracked from the 6th century BC to the beginning of the Common Era. Although regional vegetation changes are insufficiently clear, our results fill a gap in the interpretation of vegetation/palaeoenvironmental changes before the Common Era in in this part of Europe. Full article

There is little information on the use of pollen in molecular research, despite the increased interest in genome editing by pollen-mediated transformation. This paper presents an essential toolbox of technical procedures and observations for molecular studies on onion (Allium cepa L.) pollen. PCR is a useful tool as an express method to evaluate editing results before pollination. A direct PCR protocol for pollen suspension has been adapted without needing DNA pre-extraction. We showed that the outer layer of lipids known as pollenkitt is a limiting factor for successful PCR on pollen. A simple pre-washing step of pollen suspension was able to eliminate the pollenkitt and enormously affect the PCR results. Additionally, our pollenkitt study helped us develop a simple and effective pollination method using wetted onion pollen grains. Classical manual pollination usually is conducted by intact pollen without wetting. Most existing methods of the editing system delivery into pollen are carried out in a wet medium with consequent drying before pollination, which adversely affects the viability of pollen. The optimal medium for wet pollination was 12% sucrose water solution. Our method of using wetted pollen grains for pollination might be very beneficial for pollen genetic manipulation. Full article

This paper presents new results on a quali-quantitative analysis of the heterocysts of the Rivularia type as a key bioindicator informative on local eutrophic conditions. The Rivularia type is usually reported in palynological analyses due to the thick, multilayered envelope that ensures the preservation of heterocysts in sediments. Samples come from two continuous terrestrial cores (N-S3: 77 samples, C-S1: 20 samples) drilled in the area surrounding the Bronze Age site of the Terramara S. Rosa di Poviglio (Po Plain; N Italy) and spanning at least over the last 15 ka years. Concentrations and percentages of the Rivularia type, combined with pollen curves of wet environments, describe local variability and rapid changes in ecological conditions over the millennia of deposition. Given the abundance and diversity of heterocysts of the Rivularia type in the studied samples, this paper attempts to group these cells based on morphology (ellipsoidal or elongated) and the state of preservation of the sheaths (presence or absence). Actually, it is difficult to confirm a relationship between heterocyst morphologies and the presence of different cyanobacteria species. Increasingly accurate identification of heterocysts from biostratigraphical archives may improve the data available on these bioindicators for achieving more detailed decoding of wetland (and terrestrial) transformations. Since the Bronze Age and at the most recent levels, the Rivularia type may be a good indicator of the local presence of agriculture and livestock, which lead to trophic and water changes in the soil. Full article

This study investigated pollen application methods for artificial pollination in tetraploid kiwifruit cultivars ‘Halla Gold’ and ‘Sweet Gold’ grown in a nonheated plastic-film house in Jeju, Korea. Pollen of the hexaploid cultivar ‘Bohwa’ (A. chinensis var. deliciosa) bred in Korea was used for artificial pollination. We examined the effect of repeated pollination, pretreatment of stigma with wetting materials, application of dry pollen or pollen in suspension on fruit quality, and seed formation. With repeated pollination, pollen tubes in the pistil reached and penetrated the ovule three days after artificial pollination, although the pattern varied depending on the number of dry pollen applications. In both cultivars, the number of pollen tubes was clearly higher following repeated pollination than following single pollination, and fruit weight, dry matter (DM), number of seeds, and 100-seed weight were also higher. When pistillate flowers were pollinated with dry pollen immediately after water sprinkle, both cultivars showed the lowest fruit weight, DM, firmness, number of seeds, and 100-seed weight, whereas there were no significant differences in fruit quality or seed formation for dry pollen application 1 h after water sprinkle, or immediately or 1 h after suspension medium sprinkle. For pollination using a pollen suspension, the fruit weight was lower in both cultivars. There were no significant differences in fruit quality and seed formation following application of dry pollen or a pollen suspension, except for fruit weight in ‘Sweet Gold’. It could be seen from the results of this study that raindrops or dewdrops on the stigma might reduce the efficiency of artificial pollination using dry pollen. Still, the application of repeated pollination enhanced the efficiency of artificial pollination. Full article

A new pollen analysis and major and trace element contents were conducted on a 40 m long gravity core recovered from the Taiwan Shoal (sand ridges), south of the Taiwan Strait, beginning in the Late Pleistocene. The changes in the pollen assemblage and concentration represent the climate change around the Taiwan Shoal and the strength of the Zhe-Min Coastal Current, whereas variations in major and trace element contents can imply the source of the sediments in the Taiwan Shoal, which are correlated with the rise or fall of the sea level with increased marine dinoflagellate cysts. The interval of 40–30 m was characterized by high pollen and spore concentrations, and evergreen Quercus was dominant taxon, which indicates a warm sedimentary environment, and the surrounding area of the Taiwan Shoal were covered by a tropical and subtropical broad-leaved forest. There were no pollen and spores from 30–24 m, which indicates a strong hydrodynamic sedimentary environment, and most of the Taiwan Shoal might have been experience subaerial exposure. The interval of 24–17 m was characterized by the reappearance of pollen and spores, as well as marine dinoflagellate cysts and foraminifera, suggesting the climate was warm and wet in the study area and an apparent marine sedimentary environment with relatively high sea level. Deciduous Quercus dominated the interval of 17–12 m, which indicated that the climate was relatively cool, corresponding to the end of Marine isotope stages3 (MIS3) to the Last Glacial Maximum accompanied by weathering and denudation. Above 12 m, the low pollen concentration with increased marine dinoflagellate cysts and foraminifera abundance suggested a marine sedimentary environment in the Taiwan Shoal. The high concentrations in Pinus corresponds to Holocene high sea level. Full article