Pollen Preservation Research Articles

Botanical remains of the last 1800 years from Tarawa, Republic of Kiribati, reveal ancient aroid (Cyrtosperma merkusii and Colocasia esculenta) pit cultivation and other cultigens

Recent advances in the study of the antiquity and development of ancient Pacific Island agriculture have been made at sites across much of the region by the application of a range of microfossil techniques, namely analysis of pollen, phytoliths, and starch. Unlike in Melanesia and Polynesia, the application of these techniques in Micronesia is limited. Here we report on microfossil analysis of Micronesian archaeological pit deposits from Tarawa atoll, in the Gilbert Islands (western Kiribati), covering the last 1,800 years. Results show local pit cultivation of Cyrtosperma merkusii and Colocasia esculenta. Together with microfossils of other subsistence taxa, namely Cocos nucifera, Morinda citrifolia, and Pandanus tectorius, and 14C dated macrofossil charcoal of Artocarpus altilis, the evidence is consistent with the atoll subsistence tradition of Remote Oceania. Because plants have differential production and preservation of pollen, phytoliths, and starch, the study shows the value of using combined analyses of these microparts.

Monsoon driven ecosystem and landscape change in the 'Top End' of Australia during the past 35 kyr

The Indo-Australian Summer Monsoon (IASM) is the dominant climate feature of northern Australia, affecting rainfall/runoff patterns over a large portion of the continent and exerting a major control on the ecosystems of Australia's Top End, including the viability of wetland ecosystems and the structure of the woody savanna. We examined the behaviour the IASM from 35 kyr using proxy data preserved in the sediments of Table Top Swamp, a small seasonal swamp in northern Australia. Elemental data, stable C and N isotopes, pollen and sedimentary data were combined to develop a picture of monsoon activity and landscape and ecosystem response. Results demonstrated that between 35 and 25 ka conditions were drier and more stable than present, with a more grass dominated savanna and limited wetland development, implying reduced IASM activity. After ~25 ka, there is evidence of increased moisture at the study site, but also increased IASM variability. However, despite evidence of at least periodic increases in moisture, including periods of wetland establishment, the IASM displayed a subdued response to peak precession insolation forcing by comparison to the other global monsoon systems. Instead, the greatest change occurred from ~10 ka when the continental shelf flooded, increasing moisture advection to the study site and resulting in establishment of a quasi-permeant wetland. Whereas the early Holocene was marked by both the onset of pollen preservation and a wetter vegetation mosaic, indicative of a consistently active IASM, the mid-late Holocene was marked by drier vegetation, increased fire, but also increased C 3 vegetation and runoff, implying increased IASM variability. Holocene changes in ecosystem dynamics occur coincident with an expansion in human population, which likely also influenced vegetation and landscape response at the study site. • Wetlands were likely limited across the Top End and northern Australia before 25 ka with savanna more grass dominated. • The IASM became more effective from 9 ka, with ecosystem developing their current configuration after this time. • There is evidence of human resource use impacting vegetation assemblages in the Top End from the early to mid-Holocene. • There is evidence of both increasing moisture and aridity in the mid- to late-Holocene in the Top End. • Sea level appears to be the major control of IASM strength in the Top End over the past 35 kyr.

Effect of Pollen Genotype, Temperature and Period of Storage on In Vitro Germinability and In Vivo Seed Set in Chrysanthemum—Preliminary Study

Among many challenges in chrysanthemum cross-breeding, the access to viable pollen for hybridization of cultivars distant in location and different in flowering time is required. Low pollen viability along with incompatibility are mainly responsible for low seed set in modern chrysanthemum cultivars. The aim of the study was to test various temperatures and periods of pollen storage of Chrysanthemum × morifolium in order to elaborate the method of chrysanthemum pollen preservation for cross-breeding purposes. In the first experiment, in vitro pollen germination of four cultivars was investigated following storage at 20 °C, 4 °C, −20 °C, and −80 °C, for one, four, and eight weeks. The second experiment focused on in vivo seed set after one week pollen treatment with 20 °C, 4 °C, −20 °C, and −80 °C (three pollen donor cultivars tested). Pollen in vitro germinability, as well as seed set efficiency, was generally low and cultivar dependent. Independent of the period of storage, stored pollen germinability was lower (5.30–6.63%) than fresh pollen (8.15%). Incubation of pollen in −80 °C significantly increased pollen germinability (9.80%), as well as seed set efficiency in comparison to control (19.28% and 10.21%, respectively) provided the cultivars are compatible. Among cultivars, the highest germinability of pollen was found in ‘Brda’ and ‘Donna’ (8.2% and 8.23%, respectively), while ‘Bydgoszczanka’ showed the lowest germinability (2.97%). There were also pollen genotype dependent effects in in vivo seed set efficiency, which was highest in ’Brda’ (17.57%) and much lower in ‘Jutrzenka’ and ‘Polka’ (1.34% and 0.39%, respectively), which contributed to the incompatibility of crossed cultivars rather than pollen viability.

Preservation methods of honey bee-collected pollen are not a source of bias in ITS2 metabarcoding.

Pollen metabarcoding is emerging as a powerful tool for ecological research and offers unprecedented scale in citizen science projects for environmental monitoring via honey bees. Biases in metabarcoding can be introduced at any stage of sample processing and preservation is at the forefront of the pipeline. While in metabarcoding studies pollen has been preserved at - 20°C (FRZ), this is not the best method for citizen scientists. Herein, we compared this method with ethanol (EtOH), silica gel (SG) and room temperature (RT) for preservation of pollen collected from hives in Austria and Denmark. After ~ 4months of storage, DNAs were extracted with a food kit, and their quality and concentration measured. Most DNA extracts exhibited 260/280 absorbance ratios close to the optimal 1.8, with RT samples from Austria performing slightly worse than FRZ and SG samples (P < 0.027). Statistical differences were also detected for DNA concentration, with EtOH samples producing lower yields than RT and FRZ samples in both countries and SG in Austria (P < 0.042). Yet, qualitative and quantitative assessments of floral composition obtained using high-throughput sequencing with the ITS2 barcode gave non-significant effects of preservation methods on richness, relative abundance and Shannon diversity, in both countries. While freezing and ethanol are commonly employed for archiving tissue for molecular applications, desiccation is cheaper and easier to use regarding both storage and transportation. Since SG is less dependent on ambient humidity and less prone to contamination than RT, we recommend SG for preserving pollen for metabarcoding. SG is straightforward for laymen to use and hence robust for widespread application in citizen science studies.

Is bat guano a potential pollen trap? A comparative assessment from conventional soil and moss substrates from Eraaning Cave of Meghalaya, India

This study examines the pattern of preservation of pollen and non-pollen palynomorphs on bat guano samples in Eraaning Cave in relation to the current vegetation of the surrounding Garo hills of Meghalaya. It is observed that, the recorded pollen data does reflect the tropical mixed deciduous forest with an admixture of riparian and evergreen plant taxa from the local and regional vegetation. The presence of evergreen and riparian taxa namely, Mesua, Schima, Duabanga, and Syzygium in the pollen assemblage is strongly indicative of the high rainfall in the region. The recovery of fern and fungal spores in the pollen assemblage also reflects the warm and humid climatic condition in this region. The forestland and open-land samples from the vicinity of the cave were also studied to understand the nature of pollen preservation in relation to the bat guano samples. The presence of cereal, Areca, Psidium, and Citrus along with Melastoma pollen in both bat guano and open-land samples is indicative of the anthropogenic activities in and around the study area. Multivariate principal component analysis (PCA) and box plot were applied to the quantified data obtained from pollen frequency analyses which clearly revealed a significant variation and similarity in vegetation types among the surface samples collected in and around Eraaning Cave. The generated pollen data from the bat guano, forestland, and open-land samples reveals that, bat guano in cave sediments provides a reliable substrate to understand the modern pollen and vegetation relationship and can fruitfully be utilized as a baseline for the reconstruction of the palaeoecology in the Garo hills of Meghalaya. The study also suggested that the bat species utilized the mixed vegetation composition and different landforms as their preferred habitats as demonstrated by the pollen data from the bat guano samples.

Pollen heteromorphism in Schleichera Lour. (Sapindaceae), observed in surface soil samples from central India

Angiosperms display striking variation of pollen morphological features within and between populations of the same species, as well as within individual plants. We describe and illustrate variation of pollen aperture number, which is called pollen heteromorphism, in Schleichera Lour. (Sapindaceae) from surface soil samples collected from central India, based on combined observations from light microscopy (LM) and confocal laser scanning microscopy (CLSM). Tri-zono-parasyncolporoidate pollen grains are, in general, known to occur in Schleichera Lour., but occasional tetra-zono-parasyncolporoidate pollen is also recorded, for the first time, from Chhattisgarh State, central India. Changes in ploidy level (diploidy/polyploidy), chromosome number, the C-value of DNA, completion of meiosis, as well as environmental factors and/or pollination ecology could be driving the occurrence of pollen heteromorphism. The present study could provide insights into the phylogeny and systematics, and has implications for pollen preservation as well.

Assessing the use of mangrove pollen as a quantitative sea‐level indicator on Mahé, Seychelles

AbstractWe investigated the potential of mangrove pollen from Mahé, Seychelles, to improve existing metre‐scale Late Holocene sediment‐based sea‐level reconstructions. Mangrove species at two mangrove sites are broadly zoned according to elevation within the tidal frame. Modern pollen rain from traps deployed for 1 year generally have a poor relationship with modern vegetation, and relatively low pollen production rates. Pollen from mangrove species that live in narrow elevation zones (e.g. Avicennia marina) are poorly represented in modern pollen rain, while pollen from mangrove species that live across a larger elevational range (e.g. Rhizophora mucronata) are relatively well represented. Pollen was found in extremely low concentrations in mangrove surface and core sediments, which inhibited further study into pollen transport and preservation. The results from this modern study demonstrate that utilizing mangrove pollen would not decrease existing metre‐scale vertical uncertainties in Late Holocene sea‐level reconstructions in the Seychelles. We suggest that this approach may still be successful in other locations if mangrove vegetation is (i) zoned at a more extensive lateral scale and (ii) is closely associated with modern pollen rain and surface sediments, and (iii) sedimentological conditions promote the preservation of pollen in fossil sequences.

Modern pollen and vegetation relationships in a mangrove tidal creek, South Andaman, Andaman & Nicobar Islands, India and their palaeoecological implications

This paper presents the first modern pollen, non-pollen palynomorphs and grain size data from a pristine mangrove tidal creek on the South Andaman Island, Andaman and Nicobar Islands, India. The surface sediment samples were collected from different mangrove environments of the Wright Myo Creek, South Andaman to study the relationship between the pollen-spore data and present vegetation cover. Results show that pollen from local vegetation more abundant, whereas regional vegetation surrounding the depositional site is poorly represented. Heritiera littoralis, Ceriops tagal, Excoecaria agallocha and Bruguiera gymnorrhiza are markedly abundant in the landward zone. The transitional and seaward pollen assemblages are characterized by Rhizophora mucronata, Avicennia marina and Bruguiera gymnorrhiza pollen types. Pollen from mangroves are locally restricted and reflect the distributions of the source plants and mangrove types. However, the greatest concentrations of allochthonous taxa of evergreen, deciduous and montane components are derived from the surrounding lands. This area receives high rainfall during monsoon favouring long distribution of palynomorphs i.e. allochthonous species from hinterland to the depositional site through connecting drainage system. Abundance of non-pollen palynomorphs suggest not only humid as well as wet conditions, but also the particular salinity and pH characteristics of mangrove types in the area. Such relationships were evident in the Redundancy Analysis (RDA), which revealed that the first two axes of the RDA with self-values of 0.63 and 0.06 respectively explained 68.4% of data variation and 95.2% of the correlation between pollen and the environment. Additionally, the RDA analysis between Non-Pollen Palynomorph (NPP) data and the environmental variables showed that the first and second axes with self-values of 0.60 and 0.04 respectively, explained 68.4% and 96.1% of NPP data variance, respectively. The granulometric analysis clearly indicates that sand fraction is maximum towards sea, whereas suspended sediments (silt and clay) are significantly higher towards transitional and landward zones. This is well corroborated with pollen preservation in this area. At the mouth of the creek, strong hydrodynamic flow and low pollen percentages is observed, while abundant pollen are noticed in the suspended sediments probably due to weak hydrodynamic forces towards land. Therefore, the effects on pollen assemblages from sediment dynamic conditions must be taken into consideration during the reconstruction of palaeovegetation and palaeoclimate. The presented dataset provides new information on modern pollen assemblages and their relationship to the vegetation types and environmental conditions, which can also be effectively applied to other mangrove ecosystems of South and South East Asian regions to reconstruct palaeovegetation and palaeoclimatic changes.

野慈姑(Sagittaria trifolia)人工授粉的有效性:授粉工具与花粉保存

人工授粉作为一项关键性技术在生态研究与农业生产领域广泛应用，但是授粉过程中的工具有效性以及花粉保存尚未受到研究者的关注。以植物野慈姑为试验材料，研究了人工授粉方式和花粉保存条件对繁殖的影响。两年的结果表明，相较于直接接触式授粉，借助毛刷工具授粉显著降低了野慈姑的座果概率和种子数。花粉经过半小时野外高温保存后，其授粉的座果概率显著高于对照组，但单果种子数和种子大小保持稳定。综上，在野慈姑的人工授粉中应避免使用毛刷等工具，离体花粉可置于野外环境适当保存。在相关应用中，研究人员应当警惕工具授粉造成的负面影响，注意比较工具与其他授粉方式的等效性，保证实验的科学性。;Artificial pollination is a key technology with a wide range of applications in the fields of ecological research and agricultural practice. However, the effectiveness of pollination tools and pollen preservation has not received much attention. In this study, we investigated the effects of different artificial pollination methods and pollen storage conditions on the reproductive performance of Sagittaria trifolia. Results of two years showed that compared with direct contact pollination, pollination with brush tools significantly reduced fruiting probability and seed number in S. trifolia. The conditions of pollen handling also had significant effect on fruiting probability, in which half-hour field temperature storage had an advantage over control, whereas seed number per fruit and seed size remained stable. In summary, to aid artificial pollination in S. trifolia, pollination tools such as brushes should be avoided due to their negative effects on seed reproduction, and pollen in vitro can be preserved under field condition for an appropriate time. In related applications, researchers should be cautious of pollination tools and pay attention to the equivalence of different pollination methods prior to comparative experiments, in order to ensure scientific validity.

Lipids Oxidized Volatile Compounds Profuced in Pine Pollen as affected by Electron-beam Sterilization and Ultra-high Temperature Sterilization

ABSTRACT Pine pollen is rich in unsaturated fatty acids. However, unsaturated fatty acids are oxidized during processing. The oxidation of lipids may affect the odor of pine pollen. Different sterilization methods have different effects on lipid oxidation. In this study, we found that electron-beam sterilization is superior to ultra-high temperature sterilization in odor preservation. Using gas chromatography–mass spectrometry, volatile components were identified in electron-beam sterilization and ultra-high temperature sterilization processed pine pollen. Furthermore, the loss of vitamin C and polyphenols in the processing aggravated lipid oxidation, which made the odor of pine pollen worse. Moreover, lipid oxidase can accelerate lipid oxidation, thus affecting the odor of pine pollen, which was not conducive to the preservation of pine pollen. The results suggested that the components of unpleasant odor were identified as volatile aldehydes and volatile acids, and the odor was mainly produced by the oxidation of linoleic acid.

Pollen characteristics of Zelyony Mys yedoma and ground squirrel' burrows

The pollen characteristics of the Zelyony Mys yedoma record cyclical changes in vegetation cover, both on a local and regional scale. There are three local pollen zones such as: Varia +Artemisia, Varia + Selaginella sibirica, and Pinus + Betula sect. Nanae. Pollen spectra reflect open landscapes of mosaic hypo-arctic tundra. Some local pollen zones in the ice wedges correspond to the local pollen zones of yedoma: Varia + Selaginella sibirica dates from 41.9-33.8 CalBP, Pinus + Betula sect. Nanae (P+B) is approximately dated to 33.5-30 CalBP. Reconstruction of the annual thawing index showed several fluctuations: two short-term periods of significant deterioration of vegetation conditions (annual thawing index was about 200-300 deg. &amp;times; days, about 46, 34-33 CalBP), and two periods of improvement of vegetation conditions 45-43 and 32 CalBP (annual thawing index was about 600-750 deg. x days). Regional pollen in burrows is the same in synchronous horizons of yedoma. Noticeable amount of larch pollen (10%) in the fossil burrows in the Zelyony Mys yedoma showed that favorable conditions are created in the burrows for the preservation of larch pollen. The seeds found in minks reflect animal dietary preferences and only partlially local vegetation around minks. Reconstruction of positive temperature sums indicates the palinospectra reflect three-fold fluctuations of vegetation conditions: two short periods of substantial deterioration of vegetation conditions (the sum of positive temperatures is about 200-300 degrees x days), about 46, 34-33 thousand&amp;nbsp;years (and two periods of improvement of vegetation conditions 45-43 thousand years (sum of positive temperatures about 600 degrees x days) and 32 thousand years (sum of positive temperatures about 750&amp;nbsp;degrees x days).

Pollen viability and the preliminary study of pollen preservation method of Amorphophallus koratensis Gagnep. (Araceae), the potential exotic ornamental plant

ISHS I International Symposium on Botanical Gardens and Landscapes Pollen viability and the preliminary study of pollen preservation method of Amorphophallus koratensis Gagnep. (Araceae), the potential exotic ornamental plant

Optimization of in vitro germination and cryopreservation conditions for preserving date palm pollen in the USDA National Plant Germplasm System

Date palm (Phoenix dactylifera L.) is a staple crop across arid and semi-arid regions around the world. Both genebanks and date palm breeders benefit by having clearly defined methods for the long-term preservation of pollen. Methods were developed to cryopreserve pollen from date palm trees in the USDA-ARS National Plant Germplasm System. First, in vitro pollen germination conditions were optimized using five cultivars. Then, date palm pollen equilibrated over saturated salt solutions of Ca(NO3)2 or MgCl2 at 23 °C (46% and 33% RH, respectively) or in a room set at 23% RH and 5 °C. Pollen was kept at these conditions for one to 56 days and then placed into liquid nitrogen vapor (LNV). Viability was assessed for fresh, moisture-equilibrated (non-LNV and LNV-exposed), and pollen stored in LNV for 9 months. The highest level of in vitro pollen germination was observed for date palm cultivar Thoory BC3 (60 ± 2%) when it was rehydrated for 2 h and then incubated at 23 °C on Marquard medium with 15% sucrose. Viability remained stable for pollen that was stored in LNV for 9 months. In addition, pollen also remained viable if it was cooled to and warmed from LNV for up to 60 cycles. These data suggest that date palm pollen can be successfully placed in genebank cryostorage. Using optimized in vitro germination conditions, date palm pollen can survive at least 9 months in LNV and can be cooled to and warmed from LNV at least 60 times.

Southern Patagonian archaeologicalsites (47°-49 S; 72° W, Argentina)as pollen Records: Pollen Preservation Analysis Considerations for Accurate Palaeoenvironmental Reconstructions

Southern Patagonian archaeologicalsites (47°-49 S; 72° W, Argentina)as pollen Records: Pollen Preservation Analysis Considerations for Accurate Palaeoenvironmental Reconstructions

Comparing pollen data from moss cushions and a volumetric sampler: the study in the city of Florence (Italy)

In Italy, aerobiological monitoring is usually carried out by the regional agencies for environmental protection (ARPA [Agenzia Regionale per la Protezione Ambientale]) using volumetric samplers. Another widespread method for the study of airborne pollen is the analysis of moss cushions, generally used to relate pollen rain to flora and vegetation. In this study, we compare the data coming from these two pollen monitoring methods: volumetric samplers and moss cushions. The study was carried out in the city of Florence (Italy) and took into consideration two different spans of time. The two pollen monitoring methods show quantitative and qualitative differences. The main discrepancy seems to be the direct consequence of the different preservation time of the grains in the moss cushions depending on the features of the pollen grains. The study also provides an estimate of the period of pollen accumulation and preservation in moss cushions, which turned out to be more than five years. The two sampling methods furnish complementary information; volumetric samplers especially suited for aerobiological studies and moss cushions for environmental and palaeobotanical research.

Palynomorphs in surface sediments of the North-Western Black Sea as indicators of environmental conditions

Most previous Black Sea palynology studies have used pollen-spore assemblages as proxies for climate and landscape changes, and dinocyst assemblages as proxies for surface water salinity. However, there are few data on within-region variations in these assemblages using large sets of surface samples and a full suite of palynomorphs, including terrigenous pollen + spores, freshwater algal spores, and organic remains of marine microplankton, micro- and meiobenthos. Here we fill this knowledge gap, using results from a palynological study of 43 surface samples from water depths of 71–905 mbsl on the Ukrainian Shelf and adjoining continental slope, NW Black Sea. The palynology samples were collected in conjunction with water and sediment chemistry data, grain-size, micropaleontological and meiobenthos data from the EU-FP6 project HERMES “Hotspot Ecosystems Research on the Margins of European Seas”. This dataset uniquely covers shelf and upper slope areas east and west of the Odessa-Sinop Fault Zone (OSFZ) that delimits areas of lower and higher hydrocarbon gas contents, respectively.The new data show that on the wide shelf with a shallow (ca. 80 m) oxycline, pollen assemblages differ from classical models for marine pollen transport. On the Ukrainian Shelf, pollen concentrations are extraordinarily high far offshore and the grains are often pyrite-infilled. These features apparently reflect high pollen preservation potential in low oxygen sediments, probably enhanced by cross-shelf transport of land-derived particulate organic matter. The new data have important consequences for accurate modelling of carbon burial and storage in epicontinental seas, and they provide a baseline for evaluating marine pollen concentrations expected to reflect the early Neolithic farming on the Ukrainian shelf. Furthermore, although large concentrations of dinocysts comprise more than half of the total Non-Pollen Palynomorphs (NPP), the high pollen concentrations skew the P:D index (pollen:dinocyst ratio) commonly used to evaluate changes in paleo-shoreline (proxy sea-level) positions. Despite the discharge of several large rivers to the Ukrainian Shelf, there are negligible traces of freshwater algae in the HERMES samples except at Sta. 15 where Pediastrum is abundant. Overall, palynomorphs of terrestrial origin make up about half (52%) of the acid-resistant organic-walled particles on the outer NW Black Sea Shelf and adjacent slope.The abundances of the major micro- and meiobenthic palynomorph groups show the same trends east and west of the OSFZ as the micropaleontological data reported for the HERMES samples taken at the same sites. The combined microzooplankton and zoobenthos surface assemblage data provide an important new baseline for evaluating historical and past changes in biodiversity and aquatic foodweb structure in the now polluted NW Black Sea. Comparison can also be made with foodweb reconstructions for Permian black shales.

Development and Optimization of a Germination Assay and Long-Term Storage for Cannabis sativa Pollen.

Pollen viability and storage is of great interest to cannabis breeders and researchers to maintain desirable germplasm for future use in breeding or for biotechnological and gene editing applications. Here, we report a simple and efficient cryopreservation method for long-term storage of Cannabis sativa pollen. Additionally, the bicellular nature of cannabis pollen was identified using DAPI (4′,6-diamidino-2-phenylindole) staining. A pollen germination assay was developed to assess cannabis pollen viability and used to demonstrate that pollen collected from different principal growth stages exhibited differential longevity. Finally, a simple and efficient method that employs pollen combined with baked whole wheat flour and subsequent desiccation under vacuum was developed for the long-term cryopreservation of C. sativa pollen. Using this method, pollen viability was maintained in liquid nitrogen after four months, suggesting long-term preservation of cannabis pollen.

Histological changes of Berberis mikuna pollen grains in relation to viability and germinability

Berberis mikuna is a spontaneous shrub grown in the Tucuman-Bolivian subtropical jungle area and its fruits were highly prized as food by diaguitas and calchaquies who were local populations. Fruits are rich in phenolic compounds which would be responsible for the beneficial properties for health. Pollen preservation in gene banks should be implemented as standard procedures since pollen is a useful source of diverse alleles within a gene pool. Therefore, the aim of this work was to study the histological and ultrastructural changes of pollen grains after 45 days of conservation at different temperatures. Berberis mikuna pollen grain germination and viability decreased significantly after 45 days of its collection. Germination and viability decreased with increasing storage temperature, although the viability in T45 Ref and T45 Fr was similar. Ultrastructure studies revealed differences in the fibrillar structure of the intine, as well as the decrease in starch reserve in pollen grains stored at 5 °C andat room temperature.

An examination of rockshelter palynology: Carpenter’s Gap 1, northwestern Australia

Carpenter’s Gap 1 is a large rockshelter located within the Kimberley region of northwestern Australia. The site provides valuable archives of late Quaternary palaeoecological information within an area known for a lack of deposits preserving long-term continuous botanical records. Previous studies of the macrobotanic, phytolith and wood charcoal records from Carpenter’s Gap 1 are in general agreement about changes in broad vegetation patterns over time but differ in the time scales used, in the representation of some species, and in the interpretation of changes – particularly on the degree to which the variations in the record represent cultural activities. An examination of palynology (the transport, deposition and preservation of pollen within the rockshelter environment) provides more detail to the vegetation patterns identified in these previous studies. In addition, because the pollen most likely reflects the vegetation of the site’s surrounds over time rather than plants introduced into the shelter by people, interpretation can be more confidently linked to environmental change, and by inference climatic conditions. The pollen data reveal pre-glacial mixed wooded vegetation. From the beginning of the Holocene, tree loss occurred in a transition from monsoonal forest to thicket and eucalypt forest to woodland. Vegetation transition around the mid Holocene suggests a shift in climate, becoming drier and more variable towards and into the late Holocene. The role of fire in the establishment of vegetation communities remains under investigation.

The ROS-associated programmed cell death causes the decline of pollen viability recovered from cryopreservation in Paeonia lactiflora.

After cryopreservation, the occurrence of apoptosis-like programmed cell death events induced by the accumulation of ROS reduces pollen viability. Cryopreservation, as a biotechnological means for long-term preservation of pollen, has been applied to many species. However, after cryopreservation, the viability of pollen significantly decreases via a mechanism that is not completely clear. In this study, the pollen of Paeonia lactiflora 'Zi Feng Chao Yang', which exhibits significantly reduced viability after liquid nitrogen (LN2) storage, was used to study the relationship among pollen viability, programmed cell death (PCD) and reactive oxygen species (ROS). The apoptosis rate was increased significantly in pollen with decreased viability after cryopreservation, and the changes in ROS generation and hydrogen peroxide (H2O2) were consistent with the apoptosis rate. Correlation analysis results showed that the apoptosis rate is positively correlated with ROS generation and H2O2 content. In addition, ascorbic acid (AsA), glutathione (GSH) and ascorbic acid reductase (APX) levels were significantly correlated with ROS and H2O2. After LN2 preservation for 8months, the exogenous antioxidants AsA and GSH at appropriate concentrations significantly decreased H2O2 content, inhibited PCD indicator levels, and increased cryopreserved pollen viability. These observations suggest that PCD occurred in pollen during LN2 preservation for 1-8months and was induced by the accumulation of ROS in pollen after cryopreservation, thus explaining the main reasons for the reduction in pollen viability after cryopreservation in LN2.