Pollen Research Articles

Viability fertility and SEM studies on cryopreserved pollen of cashew (Anacardium occidentale L.)

Abstract Cryopreservation can be utilized as an efficient and reliable tool for long-term conservation of cashew genetic diversity. This study aims at pollen germination in vitro, SEM studies, pollen cryopreservation and fruit set with cryostored pollen of cashew. Brewbaker’s and Kwack (1963) medium enriched with 30% sucrose and15% PEG elicited significant pollen germination in vitro. Madakkathara-2 recorded high viability profiles both with respect to fresh (90.32%) and cryopreserved (85.53%) pollen when compared to other genotypes and species. Anacardium othonianum recorded lower viability in fresh (40.97%) as well as cryopreserved (25.43%). The pollen grains were cryopreserved for six months and post viability assessment was carried out at regular intervals. Field pollination was carried and in vivo fertility was assessed using four month cryostored pollen. A fruit set range of13.17 to 30.67% and a seed germinability range from 37.75 to 63.64% was recorded. Both in vitro and in vivo results show the reliability of pollen cryopreservation, which can be effectively used in breeding and conservation of the cashew gene pool.

Unravelling 6000 years of interplay among environmental changes, anthropogenic activities, and Vesuvius eruptions in the upper Sarno Plain (Campania, Italy)

Abstract Pollen analysis was carried out on the infilling succession of the Fossa San Vito sinkhole, at the NE foothills of the Sarno Plain (Italy). Four 14C dates and six tephra layers constrain the pollen sequence between ca. 6000 and 500 cal yr BP. A forested environment, with a few signs of human activities, characterizes the pre-protohistoric period (ca. 6000–2750 yr BP). Stability of the arboreal pollen grains to non-arboreal pollen grains (AP/NAP) curve is due to climate-related opposite oscillations of deciduous and evergreen forest. In this period, the pyroclastic products from Neapolitan volcanoes that reached the upper Sarno Plain seem to have affected neither vegetation nor human activities. In the archaic and classic periods (ca. 2750–1500 yr BP), intensive deforestation and increase in anthropogenic indicators indicate the occurrence of grazing and crop activities managed by the main urban centers located in the plain: Pompeii, Stabiae, and Nuceria. After the Pompeii eruption in CE 79, a rapid re-afforestation and decline in all anthropogenic indicators testify to the temporary abandonment of the area, linked to the disastrous demise of the main economic centers. The upper plain was repopulated and exploited in the Late Ancient and Middle Ages (ca. 1700–500 yr BP), as indicated by the increase in all crop and grazing indicators.

Tracking the Spread of Pollen on Social Media Using Pollen-Related Messages From Twitter: Retrospective Analysis.

Allergy disorders caused by biological particles, such as the proteins in some airborne pollen grains, are currently considered one of the most common chronic diseases, and European Academy of Allergy and Clinical Immunology forecasts indicate that within 15 years 50% of Europeans will have some kind of allergy as a consequence of urbanization, industrialization, pollution, and climate change. The aim of this study was to monitor and analyze the dissemination of information about pollen symptoms from December 2006 to January 2022. By conducting a comprehensive evaluation of public comments and trends on Twitter, the research sought to provide valuable insights into the impact of pollen on sensitive individuals, ultimately enhancing our understanding of how pollen-related information spreads and its implications for public health awareness. Using a blend of large language models, dimensionality reduction, unsupervised clustering, and term frequency-inverse document frequency, alongside visual representations such as word clouds and semantic interaction graphs, our study analyzed Twitter data to uncover insights on respiratory allergies. This concise methodology enabled the extraction of significant themes and patterns, offering a deep dive into public knowledge and discussions surrounding respiratory allergies on Twitter. The months between March and August had the highest volume of messages. The percentage of patient tweets appeared to increase notably during the later years, and there was also a potential increase in the prevalence of symptoms, mainly in the morning hours, indicating a potential rise in pollen allergies and related discussions on social media. While pollen allergy is a global issue, specific sociocultural, political, and economic contexts mean that patients experience symptomatology at a localized level, needing appropriate localized responses. The interpretation of tweet information represents a valuable tool to take preventive measures to mitigate the impact of pollen allergy on sensitive patients to achieve equity in living conditions and enhance access to health information and services.

Label-free quantitative phase imaging and analysis of airborne pollen

Abstract Pollen morphology, involving the physical characteristics of pollen grains from seed plants during reproduction, plays an important role in plant biology, ecology, and evolution. High pollen concentrations in the air can degrade air quality and exacerbate respiratory conditions such as asthma. Understanding pollen morphology and its implications for air quality is significant for mitigating respiratory health risks. Conventionally, fluorescence microscopy is used for pollen imaging, but photobleaching, quenching, and phototoxicity affect the surface morphology and do not provide quantitative data on the pollen grains. For this study, we used bright field (BF) imaging and quantitative phase imaging (QPI), a label-free interferometric microscopy method, to look at differences in the shape of pollen. BF imaging provides information about the shape and size of the different pollens but has a limitation of low contrast. To obtain high-contrast images and quantitative data on the pollen grains without any exogenous agents, we employed QPI and BF imaging in the present study. QPI enables the extraction of detailed information regarding the cell wall, aperture, and thickness of pollen while also maintaining their natural state without the need for chemical treatments. In the present work, we sampled the ambient air from May 2023 to January 2024 on the IIT Delhi campus. Subsequently, QPI and BF imaging have been done for pollen identification and phase analysis of arboreal and non-arboreal pollen. Further, by utilizing the information obtained from BF microscopy and QPI, different species of pollen have been identified, and a pollen calendar has been prepared for exhibiting pollen season throughout the year. To the best of the authors’ knowledge, they have conducted the QPI of airborne pollen grains for the first time; this technique holds great potential for characterizing airborne pollens without the need for staining or sample preparation.

A high-throughput protocol for testing heat-stress tolerance in pollen

AbstractViable pollen is crucial for fertilization, but pollen is generally highly susceptible to heat stress. A quick, reliable method for testing the heat-stress tolerance of pollen is needed to improve the heat-stress tolerance in plants, but current methods require considerable space and labor. In addition, many such methods only test tolerance to a single constant temperature, making it time-consuming to screen heat tolerance over a wide temperature range and to examine the dynamics of pollen viability at different temperatures. To address this issue, we aimed to: (1) develop an easy, reliable method for measuring pollen viability at different temperatures; and (2) identify the best temperature range for screening pollen with high heat-stress tolerance. We harvested mature pollen from wheat (Triticum aestivum) plants and transferred it to a 96-well plate filled with liquid medium containing sucrose. We placed the plate in a PCR machine operating under a gradient PCR program to simultaneously test a range of temperatures. After incubating the pollen for 4 h, at temperatures ranging from 21.9 to 47 °C, we examined the pollen grains under a light microscope and employed a specific image analysis pipeline to assess the effects of temperature on pollen morphology, germination, and tube growth. This method facilitated the high-throughput screening of many pollen samples, enabling rapid, reliable, and precise analysis of pollen viability in response to temperature. Our approach should be applicable to other plant species and could be used to identify quantitative trait loci or genes influencing heat stress tolerance in pollen for breeding programs.

Monitoring of Airborne Pollen: A Patent Review

Air pollution is recognized by the World Health Organization as the major environmental threat; therefore, air quality is constantly being monitored by monitoring stations. However, the most common atmospheric pollutants being monitored do not include pollen. Among the reasons for the lack of pollen control is that there are different types and sizes of pollen. The largest particles commonly being monitored by air monitoring stations have a maximum aerodynamic diameter of 10 microns, while the aerodynamic diameter of most pollen grains is known to range from 10 to 100 microns. For this reason, most pollen is not being detected by air monitoring stations. For the patents found in a literature review, monitoring pollen concentration in the air requires the discrimination of pollen grains from particulate matter of a similar size, as well as the identification of the type of pollen grains detected, since different pollen types may produce different effects, such as allergic reactions, asthma, and lung cancer, in exposed people. In this work, 15 patent documents regarding pollen monitoring were identified and reviewed using three search engines: Google Patents, WIPO’s PatentScope, and the United States Patent and Trademark Office (USPTO) database. The extracted data from the patents included whether they differentiate pollen type, pollen size, and sensor type and whether they provide real-time data. The results show that 93.33% of the patents identify pollen type, while 80% of the patents identify pollen size. Most of the patents use light-scattering and image sensors and use image processing techniques to analyze particles. Furthermore, 40% of the patents were found to implement artificial intelligence. Further, it was found that only nine patents provide real-time data, which is an important feature of an air monitoring system.

Pollen biology and metaxenic studies on early maturing grape (Vitis vinifera) genotypes

The present experiment was conducted during 2020–21 and 2021–22 at ICAR-Indian Agricultural Research Institute, New Delhi to study the impact of open-, self-, and cross-pollination on metaxenic traits (berries) and the incidence of cleistogamy in grapes (Vitis vinifera L.). Seven different cross-combinations were used on the grape variety Pusa Navrang, which were planted at 3 m × 3 m spacing and trained on the Y-trellis training system. The experiment was laid out in a randomized block design (RBD) with four replications. The incidence of cleistogamy, berry set, retention percentage, and the metaxenia effect of pollen grains in different grapevine varieties, namely, Pusa Navrang (PN), Black Muscat (BM), Pusa Swarnika (PS), Beauty Seedless (BS), Perlette (PER), Male Hybrid (MH), were studied. Also, pollen quantity and viability were determined for the different grapevine varieties under study. Depending on the genotypes and whether the fruit set is obtained inside the covered flowers, cleistogamy was confirmed. A significantly higher berry set (40–85%) and retention (32–77%) were recorded in open- and self-pollinated flowers. The total number of pollens/anther in six grape genotypes ranged from 7916.62–23832.02, whereas the maximum active pollen rates were noted in the Male Hybrid (70.01%) and Black Muscat (66.80%). The pollens from the Beauty Seedless genotype exhibited significant enhancement of metaxenic traits such as berry set, retention, and size in Pusa Navrang. Therefore, utilizing Beauty Seedless as a pollen parent in grape breeding programmes holds promise for enhancing berry set and overall berry quality, thus enhancing the hybridization efficiency.

Effects of Pine Pollen Polysaccharides and Sulfated Polysaccharides on Ulcerative Colitis in Mice by Regulating Th17/Treg.

This study was to investigate the effects of the polysaccharides (PPM60-III) and sulfated polysaccharides (SPPM60-III) of pine pollen on the Th17/Treg balance, inflammatory cytokines, intestinal microbiota, and metabolite distribution in 3% DSS drinking water-induced UC mice. First of all, the physiological results showed that PPM60-III and SPPM60-III could alleviate UC, which was shown by the reduction in liver Treg cells, the rebalance of Th17/Treg, and the modulation of inflammatory cytokines. In addition, the 16S rRNA results showed that PPM60-III and SPPM60-III could decrease Beijerinck and Bifidobacterium, and increase Akkermansia, Escherichia coli, and Fidobacteria. Finally, the metabonomics results showed that PPM60-III and SPPM60-III also restored purine and glycerolipid metabolism, up-regulated nicotinate and nicotinamide metabolism and caffeine metabolism to inhibit inflammation. In conclusion, PPM60-III and SPPM60-III could inhibit UC by regulating gut bacteria composition and metabolite distribution; SPPM60-III showed better anti-colitis activity.

Does long-term radiation exposure in Chornobyl impact the reproductive structures of Nuphar lutea (Linné) Smith?

The 1986 Chornobyl Nuclear Power Plant accident caused radioactive contamination of water bodies within the Pripyat River floodplain, resulting in the accumulation of radionuclides by macrophytes, which are fundamental species in water ecosystems. Yellow water lily Nuphar lutea (L.) Smith., a macrophyte playing a significant role in the formation of vegetation cover in aquatic ecosystems, is commonly considered as a bioindicator of water pollution. In this study, we investigate the potential of N. lutea as an indicator of radionuclide contamination in water bodies, particularly through changes in its reproductive structures, such as pollen viability, morphology of pollen grains, seeds, and fruits. Our findings reveal that pollen viability remains stable at total absorbed dose rates below 14.4 μGy/h, with only 1–4% of sterile grains. However, beyond this threshold the percentage of sterile grains increases nearly fivefold, pointing to high internal plant exposure to 90Sr. A similar trend was observed in the allometry and size of pollen grains, where small and flattened grains are formed in the reservoir with the highest external radiation dose rate (≥14.4 μGy/h). On the other hand, while morphometric parameters of fruits are influenced by radiation, their variation appears to be the result of a combination of physicochemical factors and the trophic status of a water body. Our research highlights the adverse impact of long-term radiation exposure on the male reproductive system of N. lutea and shows the potential of using the pollen grains sterility as an indicators of heavily radionuclide-contaminated water bodies. Additionally, we observed gradual changes in a pollen allometric length-to-width coefficient as the radiation dose level increases.

Classostrobus doylei, a new cheirolepidiaceous cone with in situ pollen from the Figueira da Foz Formation (lower Aptian – upper Albian), western Portugal

The genus Classostrobus was established to accommodate unattached Classopollis-containing cones. It is noteworthy that Classopollis as a whole shows significant variation in morphological structure, and male cones bearing Classopollis pollen grains are rarer than vegetative organs of cheirolepidiaceous conifers. A new cheirolepidiaceous microsporangiate cone, Classostrobus doylei, containing Classopollis triangulus pollen grains is described for the first time based on a single specimen from sedimentary rocks exposed in the Carregueira open-cast clay pit complex close to the small village of Juncal, in the Estremadura region, (Lusitanian Basin, western Portugal). The plant-bearing horizon from Carregueira is included in the basal part of the Famalicão Member of the Figueira da Foz Formation, considered to be of late Aptian – early Albian age. The new microsporangiate cone is small, about 2.0 mm long and 1.5 mm wide, ovoid in shape and of typically coniferous structure, probably belonging to Pseudofrenelopsis zlatkoi. The male cone consists of about 16 peltate, imbricated microsporophylls of deltoid shape. Each sporophyll is composed of a stalk and deltoid head showing abaxially 4-5 ovoid pollen sacs. The marginal parts of the sporophylls display long and unicellular trichomes. The observed in situ pollen grains are triangular to subcircular in outline, 16-28 μm in diameter, with an equatorial girdle, subequatorial rimula, proximal trilete scar and a distal cryptopore. The pollen ultrastructure is typical for Classopollis, except for the destroyed condition of the exine. The in situ pollen grains under study are consistent with the data on known dispersed Classopollis triangulus.

Nectar and pollen source of natural honey produced by Apis cerana skorikovi Engel (= himalaya): Palynological analysis from tropical to sub-tropical forests of eastern Himalaya

This study deals with the palynological analysis of natural “Himalayan cerana” honey collected from the tropical to sub-tropical forests of the eastern Himalaya (West Sikkim, Ziro valley of Arunachal Pradesh and sub-Himalayan region of West Bengal). A total of 12 honey samples were analysed. Among the six samples from Sikkim, one is found unifloral and remaining five samples are found to be multifloral. Similarly, the Kolakham (West Bengal) sample is found multifloral, whereas both the honey samples of Alipurduar (West Bengal) are found to be unifloral. All the three Arunachal Pradesh samples are found multifloral. Absolute pollen count (APC) reveals that the unifloral winter honeys are poor in APC compared to the multifloral ones. Significant occurrence of anemophilous pollen grains in honey samples points towards there entrapment either during long distance flight of the bees or on the sticky hive surfaces. The nectar calendars show that winter season is the honey dearth period in the study areas of the eastern Himalaya. Finally, the diversity and richness of the pollen grains in the honey samples also reflect the bee plant diversity of the surroundings. The study may further be useful to assess the potential for establishing a moderate to large-scale bee-keeping industry which may provide an alternate source of livelihood to improve the socio-economic set up of the local economically backward ethnic communities.

Paleontology of Pennsylvanian transgressive deposits in northwestern Precordillera, San Juan province, Argentina

In central-western Argentina, sedimentological and paleontological studies have identified changes in sea levels during the Pennsylvanian period. After the late Serpukhovian-early Bashkirian postglacial transgression, two main flooding events occurred. Among these, Pennsylvanian transgressions 1 and 2 are considered the most significant. New palynological samples recovered from the T1 transgression in Puesto Volcán, western Precordillera (San Juan province) reveal the presence of the Raistrickia densa-Convolutispora muriornata (DM) Biozone. The palynofloras are characterized by the recognition of Ahrensisporites cristatus, Lundbladispora spp., Raistrickia densa, Spelaeotriletes ybertii, and monosaccate pollen grains. The composition of the assemblages includes some taeniate pollen grains suggesting their assignment to the Subzone B. A new orthoconic cephalopod was also identified in the same stratigraphic interval, which adds to the invertebrate faunal record and confirms the marine environment. Imprints of foliage of Fedekurtzia argentina complete the paleofloristic assemblage. A late Bashkirian-earliest Moscovian age is suggested according to the well constrained radiometric control of the palynostratigraphy in the region.

Disruption of Energy Metabolism and Reactive Oxygen Species Homeostasis in Honglian Type-Cytoplasmic Male Sterility (HL-CMS) Rice Pollen

Honglian type-cytoplasmic male sterility (HL-CMS) is caused by the inter-communication between the nucleus and mitochondria. However, the mechanisms by which sterility genes regulate metabolic alterations and changes in mitochondrial morphology in the pollen of HL-CMS remains unclear. In this study, we compared the morphological differences between the pollen of the male sterile line YA and the near-isogenic line NIL-Rf6 using hematoxylin and eosin staining as well as 4ʹ,6-diamidino- 2-phenylindole (DAPI) staining. HL-CMS is characterized by gametophytic sterility, where the aborted pollen grains are empty and the tapetal layer remains intact. Transmission electron microscopy was employed to observe mitochondrial morphological changes at the microspore stage, revealing that significant mitochondrial alternations, characterized by the formation of 'large spherical mitochondria', occurred at the binucleate stage in the YA line. Additionally, metabolomics analysis revealed decreased levels of metabolites associated with the carbohydrate and flavonoid pathways. Notably, the decrease in flavonoids was found to contribute to an elevation in reactive oxygen species (ROS) levels. Therefore, we propose a model in which rice fertility is modulated by the levels of pollen carbohydrates and flavonoid metabolites, with impaired mitochondrial energy production and reduced flavonoid biosynthesis being the main causes of ROS accumulation and pollen abortion in rice.

Imaging pollen using a Raspberry Pi and LED with deep learning

The production of low-cost, small footprint imaging sensor would be invaluable for airborne global monitoring of pollen, which could allow for mitigation of hay fever symptoms. We demonstrate the use of a white light LED (light emitting diode) to illuminate pollen grains and capture their scattering pattern using a Raspberry Pi camera. The scattering patterns are transformed into 20× microscope magnification equivalent images using deep learning. We show the ability to produce images of pollen from plant species previously unseen by the neural network in training. Such a technique could be applied to imaging airborne particulates that contribute to air pollution, and could be used in the field of environmental science, health science and agriculture.

An Ecofriendly Nature-Inspired Microcarrier for Enhancing Delivery, Stability, and Biocidal Efficacy of Phage-Based Biopesticides.

In pursuit of sustainable agricultural production, the development of environmentally friendly and effective biopesticides is essential to improve food security and environmental sustainability. Bacteriophages, as emerging biocontrol agents, offer an alternative to conventional antibiotics and synthetic chemical pesticides. The primary challenges in applying phage-based biopesticides in agricultural settings are their inherent fragility and low biocidal efficacy, particularly the susceptibility to sunlight exposure. This study addresses the aforementioned challenges by innovatively encapsulating phages in sporopollenin exine capsules (SECs), which are derived from plant pollen grains. The size of the apertures on SECs could be controlled through a non-thermal and rapid process, combining reinflation and vacuum infusion techniques. This unique feature facilitates the high-efficiency encapsulation and controlled release of phages under various conditions. The proposed SECs could encapsulate over 9 log PFU g-1 of phages and significantly enhance the ultraviolet (UV) resistance of phages, thereby ensuring their enhanced survivability and antimicrobial efficacy. The effectiveness of SECs encapsulated phages (T7@SECs) in preventing and treating bacterial contamination on lettuce leaves is further demonstrated, highlighting the practical applicability of this novel biopesticide in field applications. Overall, this study exploits the potential of SECs in the development of phage-based biopesticides, presenting a promising strategy to enhancing agricultural sustainability.

Ultrafast and one-step coating sporopollenin exine capsules with metal-phenolic networks for bio-composite applications

Sporopollenin exine capsules (SECs), extracted from plant pollen grains, are becoming increasingly popular as natural microcapsules for a broad spectrum of bio-composite applications due to their plentiful supply, resilience to chemicals and physical stress, unique species-specific designs, exceptional consistency in structure, and significant internal volume. However, SECs have a relatively bioinert interface hindering their application in biomaterials. Thus, surface modification is an efficient strategy to convert SECs into biocompatible materials better for biological applications. Previous approaches predominantly depend on labor-intensive, multi-stage procedures that are time-consuming. Herein, we report an ultrafast, one-step, and effective modification strategy to render SECs biocompatibility by coating them with ferric ions and tannic acids, which endow them with a better cell adhesion property. In summary, our results show that this ultrafast and one-step biocompatibility strategy enhances the functional characteristics of SECs and holds wide-ranging implications for bio-composite applications..

DNA barcoding, pollen and seed characteristics for documentation of four monocot Mediterranean endemic plant species in Egypt

Endemic taxa are critical constituents in the flora of most parts of the world. Recently, most of these taxa have become exposed to extinction. This study aims to increase understanding of four monocot Mediterranean threatened endemic taxa in Egypt (Allium mareoticum Bornm. & Gauba, Bromus aegyptiacus Tausch, Muscari salah-eidii (Täckh. & Boulos) Hosni, Pancratium arabicum Sickenb.) by description of their pollen and seed and authentication of DNA barcoding using rbcL and matK genes. Twenty field visits were conducted from March 2017 till April 2023 including different localities through Mediterranean area for covering the presence of these species. Characterization of pollen grains and seeds were examined using a light (LM) and scanning electron microscopes (SEM). DNA barcoding was carried out for documentation of the four species. Maturase K (matK) and ribulose-bisphosphate carboxylase (rbcL) were used as primers for PCR amplification and gene sequencing. The two genes were successful in identifying Allium mareoticum, Bromus aegyptiacus, and Muscari salah-eidii at the genus level and Pancratium arabicum at both species and genus levels for rbcL marker, and the genus level for matK marker. This study is considered a leading study for new barcodes of (A) mareoticum, (B) aegyptiacus, and M. salah-eidii which were initially made available to the NCBI.

Relationships between pollen assemblages and modern vegetation of the southern Gaoligong Mountains region, southwest China

Comprehensive understanding of the modern pollen–vegetation relationship is crucial for utilizing fossil pollen to reconstruct palaeovegetation, especially in mountainous areas of southwestern China. In this study, we present forty-five modern surface samples collected from five different vegetation communities of the southern Gaoligong Mountains region, and the vegetation composition was investigated at each sample site. The modern pollen assemblages were analyzed through multivariate analysis to evaluate the relationships between vegetation types and pollen assemblages, and to investigate the representation of major pollen types in different vegetation types. The results indicate that the surface pollen assemblages of different vegetation types reliably represent the modern vegetation. The median R-values of dominant pollen taxa in the Gaoligong Mountains region can be ordered as follows: Pinus > Alnus > Poaceae > evergreen Quercus. The over-representation of Pinus pollen, attributed to its high productivity and strong dispersal ability, makes it the dominant component of exotic pollen. Conversely, the under-representation of evergreen Quercus suggests that the presence of its pollen within a sample might indicate the growth of the local parent plant in the study area. The human activities in the region have a recognizable effect on the surface pollen spectra and also exert a significant negative impact on pollen diversity. Our study supplements the modern pollen database of the mountain regions in southwestern China, and provides representative modern pollen analogues to interpret fossil pollen records from southwestern China and similar regions.

Foraging Activity and Preference of Pollen Sources by Stingless Bee, Heterotrigona itama in Tropical Lowland Forest of Terengganu

Stingless bees (Hymenoptera: Apidae: Meliponini) are a highly diversified group of eusocial corbiculate bees distributed in tropical and subtropical areas. However, studies on the relation of stingless bee activeness with environmental parameters and pollen source preference are very limited particularly from the lowland forest of East Coast Peninsular Malaysia. Hence, this study aimed to determine the relationship between stingless bee, Heterotrigona itama foraging activity with environmental factors (temperature, humidity, and light intensity) and preference of floral sources in a meliponiary of Marang, Terengganu. The foraging activities of five healthy colonies of H. itama were observed from 0700 to 1700 hours on hot sunny days for eight months of study period (August 2020 – September 2021). The foraging activity was enumerated using camera recording for 10 minutes at one-hour intervals (0700-1700 hours). In this study, the peak time for H. itama to go forage was observed at 0900 until 1100 hours in the early morning and declined rapidly from 1100 until 1700 hours. October 2020 recorded the highest activeness of stingless bees, followed by August 2021 and September 2021. There was a significant difference in the interaction of stingless bee activeness between time and months [F67,424 = 3.498, p<0.05]. However, temperature, humidity and light intensity did not significantly influence the activeness of stingless bees. Acacia mangium was the most frequent pollen grain collected by H. itama, followed by Melastoma malabathricum and other pollen types were considered minor pollen types (<15%). Findings from this study can help beekeepers to understand the foraging behaviour of stingless bee colonies and the preference of the available pollen resources for sustainable meliponiculture management practice.

Bee–plant interactions identified by pollen analysis of honey from the stingless bee Tetragonisca fiebrigi (Schwarz, 1938) in southern Brazil

ABSTRACT Pollen analysis of honey reveals information about bee–plant interactions and networks that, in some cases, are lost through mere observation of bees on flowers. This information on bee–plant interactions is valuable for the protection of bees and vegetal speciesand pollination of crop plants. To provideinsights into bee–plant interactions, palynological evidence was developedfromthe collection of honey. The objective of this study is to determine the plants that the bees (Tetragonisca fiebrigi) visit for honey production in southern Brazil (Rio Grande do Sul). For this, 24 honey samples were collectedfrom five regions of northeastern Rio Grande do Sul, southern Brazil. A total of 64 pollen types were found in the honey samples fromT.fiebrigi in southern Brazil, mainly from trees. The most common pollen types in the samples were from Schinus terebinthifolia, Schizolobium parahyba, Handroanthus sp., Morus nigra, and Rosa cf. grandiflora. The pollen grains show a high diversity of plants, including those with important ecological functions.