Pollen Yield Research Articles

Comparison of nectar and pollen resources in various Tilia species. A case study from southern Poland

Management of food resources is considered fundamental for supporting insect pollinators, whose abundance shows a downward trend on the global scale. Here, the nectar and pollen production (per flower, per 1 m2 of tree crown), the composition of nectar carbohydrates and the levels of pollen proteins was evaluated in eight Tilia species (Malvaceae) growing in SE Poland. In the warm-summer continental climate, Tilia species can improve nectar and pollen resources mainly in June/July. Although the flowering period of each species is short (8.0–14.7 days), appropriate selection of species can extend the availability of food for more than a month. However, the considerable variations in the flowering onset (11.2–20.1 days) may cause significant inter-seasonal shifts in food accessibility.The nectar with its highly changeable sugar concentration (29.5–77.4%) was composed of sucrose, glucose, and fructose; protein content in pollen was 7.2–16.8%. The mean sugar yield was in the range of 0.95–19.1 g per 1 m2 (T. amuriensis – T. platyphyllos, respectively), whereas the mean pollen yield was 1.37–4.1 g per 1 m2 of tree crown (T. amuriensis – T. × euchlora, respectively). Significant year-to-year fluctuations of sugar and pollen yield in linden trees have to be taken into account in conservation schemes, and the introduction of other flowering plants with more stable sugar and pollen production should be considered in an area with a high density of linden trees. Linden flowers mainly support honey bees; nevertheless, wild pollinators (bumble bees, solitary bees, and dipterans) can also benefit from linden floral resources.

High temperature treatment induced production of unreduced 2n pollen in Camellia oleifera

Unreduced gametes through chromosome doubling play a major role in the process of plant polyploidization. Our previous work confirmed that Camellia oleifera can produce natural 2n pollen, and it is possible to induce the 2n pollen formation by high temperature treatment. This study focused on the optimization of the 2n pollen induction technique and the mechanisms of high temperature-induced 2n pollen formation in C. oleifera. We found that the optimal protocol for inducing 2n pollen via high temperature was to perform 45 °C with 4 h at the prophase I stage of the pollen mother cells (PMCs). Meanwhile, high temperature significantly decreased the yield and fertility of 2n pollen. Through the observation of meiosis, abnormal chromosome and cytological behaviour was discovered under high-temperature treatment, and we confirmed that the formation of 2n pollen is caused by abnormal cell plate. Based on weighted gene co-expression network analysis, fifteen hub genes related to cell cycle control were identified. After male flower buds were exposed to heat shock, polygalacturonase gene (CoPGX3) was significantly upregulated. We inferred that high temperature causes the CoPGX3 gene to be overexpressed and that CoPGX3 is redistributed into the cytosol where it degrades cytoplasmic pectin, which leads to an abnormal cell plate. Furthermore, abnormal cytokinesis resulted in the formation of dyads and triads, and PMCs divided to produce 2n pollen. Our findings provide new insights into the mechanism of 2n pollen induced by high temperature in a woody plant and lay a foundation for further ploidy breeding of C. oleifera.

Herbaceous Bee Forage Adaptation Trail in Lowlands of Borana Zone Southern Oromia

To mitigate the shortage of bee forage and help increase honey production, the use of cultivated perennial and annual nectar and pollen sources is highly important in beekeeping development. The study was conducted with the objective of evaluating and identifying adaptable honey bee forage species for beekeeping development. The planting materials were Aschynomene uniflorum, Miloletus alba, Fagopyrum esculentum, Sinaps alba, and Vicia sativa. The species were evaluated based on germination date, time to set flower, days to 50% flowering, number of flower heads per plant (at 50% flowering of the plant), flowering length (blooming duration), maturity date, and plant height at the flowering stage. Among the five evaluated herbaceous bee forage species, three of them, Aschynomene uniflorum, Fagopyrum esculentum, and Sinaps alba, are adapted and perform well in the most important agronomic parameters. Therefore, the selected bee forage species can be promoted, and beekeepers in the study areas and other areas with similar agroecology can utilise the forage species for beekeeping development. Moreover, evaluation of other agronomic parameters such as seeding rate, fertiliser rate, nectar and/or pollen yield, foraging intensity, and others over different locations of the Borana zone is recommended

Floral Calendar of Honeybee Plants in Kellem and West Wollega Zone, Western Ethiopia

Beekeeping has significantly contributed to environmental conservation and the preservation of natural resources. Although the quality and quantity of flora available play a major role in the success of the sector, the botanical makeup of natural vegetation varies greatly. This study was conducted targeting the identification and documentation of major honeybee floras and their flowering calendar. Midland and lowland agroecologies were purposively selected. Continuous field plant registration was performed. Melissopalynological analysis from bee pollen and honey were used to identify floral origin. Field observations identified 59 and 63 plants in the midland and lowlands, respectively. Season 1 had the highest pollen yields, ranging from 11051.8 ± 56.4 g (midlands) to 878.3 ± 18.3 g (lowlands), while season 4 ranged from 16.8 ± 6.3 g (midlands) to 15.6 ± 7.4 g (lowlands) and had the lowest pollen yield. In both regions, February, March, July, and August are the months when pollen is not brought into the hive and could be used as starvation periods. A total of 1430.8 ± 75.4 and 1291.8 ± 71.4 g of bee pollen/hive were collected throughout the year in midland and lowland, respectively, and Asteraceae was the richest family accounting around 90% of pollen weight. In both agroecologies, honey is harvested three times a year. In the midland, monofloral honey, namely, Guizotia spp (64.42%) and Croton macrostychus (47.42%), was harvested in November and May, respectively, while honey harvested in February was multifloral type. Similarly, in the lowlands, monofloral honey of Guizotia spp (51.85%), Coffee arabica (55.22%), and Croton macrostychus (50.42%) was harvested in December, March, and June, respectively. Based on the results, Bidens prestinaria, Bidens pilosa, Guizotia spp, C. macrostachyus, Eucalyptus spp, Lepidium sativum, Zea mays, Hypostes trifolia, Vernonia spp, Trifolium spp, Helianthus annuus, C. arabica, Brassica abyssinica, Andropogon abyssinicus, Sorghum bicolor, Cordia africana, Syzygium guineense, and Terminalia spp are major bee plants. It is found that the study area is rich in bee plant diversity and hence has a potential for honey production.

Ресурсный потенциал медоносных растений степного Придонья

Melliferous lands comprise the categories of forest fund lands, where melliferous plants and plants that provide high pollen yield grow. Bees pollinating entomophilous plants are 6–10 times more beneficial to forest lands compared to the favours from productive honey flows. The research objectives included identifying the features of the ecological and biological characteristics of melliferous plants of the Fabacea family, specifying the onset, duration and intensity of flowering, determining the sugar content in the nectar of one flower and honey productivity in the steppe Don region. Registration plots were laid out by the route method for the assessment of melliferous resources and determination of the resource potential of forest lands. Necessary observations, registration work, mathematical and statistical data processing were carried out according to the generally accepted methods. The territory of the steppe Don region, where the forest fund lands of the Rostov region are located, has favorable weather conditions and a rich forage base for bees. Тhe honey potential of the studied resources is a dynamic indicator and is of interest both for forest beekeeping and for scientific research. We used the sums of effective temperatures to determine the flowering sequence and characteristics of melliferous plants. The dwarf Russian almond blossoms first among arboreal melliferous plants of the legume family, while the Japanese pagoda tree blossoms last in the middle of the summer honey flow period. Black locust forest stands (497 kg/ha), lands dominated by Japanese pagoda tree (484 kg/ha) and honey locust (245 kg/ha) have the highest honey productivity. The research results showed that the black locust plantations with a bioresource potential of 7111.29 ton in the eastern and central areas of the region are significant for honey flow on the forest fund lands. Forest lands with predominance of spring melliferous plants of boxthorn and dwarf Russian almond on non-forest lands of the forest fund provide a supporting honey flow with a bioresource potential of 2749.168 ton. The studies that were carried out are of practical importance and will allow determining the resource potential of forest lands for honey flow more accurately in the future. In case of a high level of forestry and beekeeping practices, even under adverse weather conditions during nectar harvesting, it will be possible to obtain a productive honey flow, while ensuring timely and effective pollination of forest plants.

The effect of grafting on pollen fertility and seed production of diploid interspecific hybrid and tetraploid eggplant genotypes

Solanum melongena is susceptible to diverse diseases and parasites, in particular the wilts (bacterial, Fusarium and Verticillium), nematodes, and some insects. Solanum torvum is robust to Verticillium and some bacterial wilts and root-knot nematode. It was reported that interspecific hybrid plants originated out of the hybridization of these species were sterile. In our previous studies that have been carried out to overcome this interspecific hybridization barrier, only from Faselis F1 that was used as the female parent, many interspecific hybrid seeds were obtained and 9.07% of the seeds grew into plants in vitro. The percentage of pollen viability and germination of tetraploid interspecific hybrid (amphidiploid) genotypes that have been produced by in vitro colchicine treatment, were 6.8 and 3.4 fold of its source diploid genotype, respectively. However, the increment was not high enough to overcome the interspecific hybridization barrier between S. torvum and S. melongena. In this study, the changes in pollen fertility of diploid interspecific hybrids and tetraploid plants, which have grafted on Pala or Faselis F1 , were investigated. Pollen viability and germination percentage in diploid genotypes were not affected by grafting, although they increased significantly (51.54% and 119.73%, respectively) in tetraploid genotypes by grafting. It was determined that the fertile diploid rootstock used for the tetraploid genotypes that produced by chromosome doubling from cultured eggplants could increase the number of seeds per fruit. It was concluded that some fertile diploid varieties can be used as rootstocks in order to increase pollen viability, germination rate and seed yield of tetraploid genotypes with low pollen yield obtained from cultivated eggplant by chromosome doubling.

Plants enhancing urban pollinators: Nectar rather than pollen attracts pollinators of Cotoneaster species

Urban green areas can play a crucial role in establishing spaces that are valuable for pollinators. However, to help ‘pollinator-friendly’ management of urban areas, complete information on the quantity and quality of available floral reward is needed. In this paper, the nectar and pollen of six Cotoneaster species (Rosaceae) were investigated in a two-year experiment established in Lublin city, SE Poland. In temperate climate, Cotoneaster species can ensure nectar and pollen in the full spring period (May/early June) or in early summer (June). A single species can support pollinators on average for 22.9 days. Flowers of Cotoneaster species produce high quantities of nectar (2.27–9.48 mg per flower) and low amounts of pollen (0.11–0.33 mg per flower). On average, the total sugar yield in Cotoneaster species was 11.5 g/m2 (2.3–22.2 g/m2), whereas the total pollen yield was 1.3 g/m2 (0.8–2.8 g/m2). Due to the high potential for total sugar yield, C. macrophyllus, C. lucidus, and C. horizontalis should be recommended to optimize the management of food resources in urban areas. Honeybee was the main insect visitor (70.1 % of the total number of visitors); therefore, Cotoneaster species can be considered valuable for urban beekeepers. However, conservation schemes for bumblebees (21.3 % of the total number of visitors) might also benefit from arrangements with these shrubs. Nevertheless, considering Cotoneaster species in conservation protocols, good-yielding pollen plants should be introduced to compensate for insufficient nutrient intake from pollen in spring.

Bacterial Species Associated with Highly Allergenic Plant Pollen Yield a High Level of Endotoxins and Induce Chemokine and Cytokine Release from Human A549 Cells

Sensitization to pollen allergens has been increasing in Europe every year. Most studies in this field are related to climate change, phenology, allergens associated with different pollens, and allergic disorders. As a plant microhabitat, pollen is colonized by diverse microorganisms, including endotoxin-producing bacteria which may contribute to pollen allergy (pollinosis). Therefore, bacteria isolated from high allergenic and low allergenic plant pollen, as well as the pollen itself with all microbial inhabitants, were used to assess the effect of the pollen by measuring the endotoxins lipopolysaccharides (LPS) and lipoteichoic acid (LTA) concentrations and their effect on chemokine and cytokine release from transwell cultured epithelial A549 cells as a model of epithelial lung barrier. High allergenic pollen showed a significantly higher level of bacterial endotoxins; interestingly, the endotoxin level found in the bacterial isolates from high allergenic pollen was significantly higher compared to that of bacteria from low allergenic pollen. Moreover, bacterial LPS concentrations across different pollen species positively correlated with the LPS concentration across their corresponding bacterial isolates. Selected bacterial isolates from hazel pollen (HA5, HA13, and HA7) co-cultured with A549 cells induced a potent concentration-dependent release of the chemokine interleukin-8 and monocyte chemotactic protein-1 as well as the cytokine TNF-alpha and interleukin-2 to both apical and basal compartments of the transwell model. This study clearly shows the role of bacteria and bacterial endotoxins in the pollen allergy as well as seasonal allergic rhinitis.

Rose Pollen Management Methods to Improve Productivity

Roses are one of the most highly produced and purchased ornamental plants worldwide. Procurement and preservation of pollen is essential for the production of diverse rose varieties. In this study, we analyzed pollen management conditions, such as the pollen collection stage, drying time, and storage temperature, to determine optimal conditions for rose pollen management. Pollens were stored under different conditions and the pollen vitality and germination rate were investigated through an optical microscope. The vitality of pollen was an essential factor for rose breeding and depended on the storage conditions. Collecting pollen in the seventh flowering stage resulted in a relatively higher pollen yield. Drying the flower for 5 h after the anther opened improved pollen germination. The germination rate of freshly collected pollen was similar to that of pollen stored at temperatures between −20 °C and −72 °C for up to 30 days, indicating the efficacy of pollen storage at sub-zero temperatures. Since the rate of fruiting increases when pollination is performed three times, considering the time and cost of breeding, it is appropriate to pollinate three times to increase the number of seeds. This study provides an efficient pollen management method to collect and store pollen for breeding.

Fossilized pollen malformations as indicators of past environmental stress and meiotic disruption: insights from modern conifers

AbstractPollen malformations have been proposed as a paleoenvironmental stress proxy. However, the frequency and variability of pollen malformations under near-optimal conditions and environmental stress, as well as their developmental origins, remain unclear. To bridge these gaps, we compared pollen malformation frequencies and assemblages of 14 extant conifer genera of Pinaceae and Podocarpaceae producing saccate (winged) grains grown under near-optimal conditions. These baseline pollen yields were compared with those produced by Pinus mugo ‘Columnaris’ cultured under an abiotic stress—three experimentally heightened ultraviolet-B radiation (UV-B) regimes proposed for the end-Permian crisis. We additionally reviewed previous cytological literature of abnormal microsporogenesis in conifers. Under near-optimal conditions, malformations comprise <3% of pollen yields in 12 out of 13 bisaccate genera and >10% of yields in the naturally trisaccate Dacrycarpus dacrydioides. We detected no phylogenetic pattern in malformation assemblages of the baseline comparisons. UV-B–irradiated P. mugo produced significantly higher malformation frequencies and different assemblage compositions when compared with baseline bisaccate lineages. We propose that pollen malformations originate during the meiotic and tetrad stages of microsporogenesis and present a framework for the ontogeny of different malformation types seen in the fossil record. Malformations comprising >3% of bisaccate pollen yields can be used as a paleoenvironmental stress proxy, but rare, naturally trisaccate lineages are not suitable for such assessments. Furthermore, heightened UV-B not only increases pollen malformation production, but also alters the types of abnormalities trees produce. Different environmental stresses may therefore leave behind distinct fingerprints in the fossil record.

Urban Bees Benefit from a Native Forest Species Grown in a City Environment–A Case Study of Geranium Phaeum L.

Abstract This two-year study tested whether urban bees benefit from the forest perennial Geranium phaeum L. replanted from natural stands to an urban environment. The flowering abundance and phenology, spectrum of insect visitors, nectar and pollen production, and the energetic value of nectar were investigated in Lublin, SE Poland. The apiarian value of G. phaeum was studied for the first time. The species bloomed abundantly from late April to early June and can be regarded as a valuable spring food resource for urban bees, mainly bumblebees, which accounted for >50% of all visits in both years of study. Bees collected mainly nectar. The highest daily pollen and nectar sugar amount offered by a plant reached 73.7 mg and 36.5 mg, respectively, with the caloric value of nectar of 146 cal. The estimated mean sugar yield, caloric value of nectar and pollen yield · m−2 were 1.7 mg, 6.9 kcal, and 3.4 mg, respectively. The current study confirms the advantage of using native plants in urban landscaping and proves their positive role in strengthening both wild and managed bee populations in cities. The finding that wild plants translocated from the natural habitat can develop a self-sustaining population in the urban environment and establish beneficial relationships with urban bees is of interest in terms of the conservation of both native plants and pollinators.

Colchicine induction of 'Old Blush' 2n pollen for the hybridization and breeding of tetraploid rose.

Obtaining 2n pollen from the diploid Chinese old rose ‘Old Blush’ through artificial induction is one important means of hybridizing and breeding modern tetraploid roses. We used colchicine-induced 2n pollen to assess normal viability during hybridization and fructification. The results showed that the pollen mother cell had lagging chromosomes and parallel spindles at meiosis I stage, following which the 2n pollen was produced from dyads and triads with doubled chromosomes. We obtained 4.30% viable 2n pollen, which was significantly higher than the yield of the spontaneous 2n pollen (1.00%) using an optimal treatment combination of induction for 24 h with 0.50% colchicine. There was no significant difference between the external morphology of the induced 2n pollen and the spontaneous 2n pollen, whereas both types of 2n pollen possessed finer furrows, and fewer and smaller pores than the 1n pollen, and the external morphology of 2n pollen was more evolved. In terms of in vitro germination rate and pollen tube length, the induced 2n pollen did not differ significantly from the spontaneous 2n pollen. The survival rate of the floral buds was significantly decreased with increased colchicine concentration and treatment time.

Early Floral Resources for Urban Bees From Ornamental Shrubs Ribes Aureum, Ribes Sanguineum and Staphylea Pinnata

Abstract This research aims to assess ornamental shrubs Ribes aureum, R. sanguineum and Staphylea pinnata as an early food source for urban bees. In a two-year study, the abundance and flowering pattern, nectar and pollen production, and spectrum of urban insect visitors were investigated in Lublin, SE Poland. The apiarian value of S. pinnata was studied for the first time. The studied species exhibited abundant and extended flowering, skewed inflorescence flowering pattern, and persistent flowers and inflorescences. They bloomed from late March to late May and could be considered as valuable early foraging resources for urban bees, despite the substantial differences between the species. The highest mean sugar yield and pollen yield · plant−1 (92.9 g and 44.0 g, respectively) was estimated for S. pinnata whereas the lowest ones were found in R. sanguineum (4.3 g and 1.8 g, respectively). Hymenopterans were the principal flower visitors in the studied species accounting for more than 79% of all visits.

Comparing methods for controlled capture and quantification of pollen in Cannabis sativa.

PremisePrecise pollen collection methods are necessary for crop breeding, but anemophilous pollen is notoriously difficult to capture and control. Here we compared a variety of methods for the controlled capture of cannabis pollen, intended to ease the process of cross‐fertilization for breeding this wind‐pollinated plant, and measured the utility of light spectroscopy for quantifying relative pollen yield.Methods and ResultsIn two independent trials, we compared a control method of pollen collection (hand collection) to either vacuum‐, water‐, or bag‐collection methods. We used visible light spectroscopy to quantify relative pollen yield, and validated this approach using microscopic pollen counts. We determined that pollen yield was highest when using hand collection or vacuum collection, but efficiency did not differ significantly among methods.ConclusionsTo maximize yield, pollen should be collected by hand or vacuum, but all collection methods were equally efficient in a relative sense because yield increased with collection time. We also found that light spectroscopy is an accurate and rapid method of quantifying pollen abundance (R 2 = 0.86) in a liquid suspension.

Flowering, Forage Value, and Insect Pollination in Borage (Borago Officinalis L.) Cultivated in Se Poland

Abstract The three-year study on borage was conducted in Lublin, SE Poland. The aims were to investigate the flowering pattern and abundance, and the attractiveness (in terms of nectar and pollen production) for flower-visiting insects, mainly bees. Insect visitation and the effect of pollinators on fruit set and seed set were assessed as well. Flowering of borage started in the latter half of June and lasted eight weeks. The mean number of flowers · m−2 of the crop was 4570 per season. A borage flower produced on average 4.0 mg of nectar with a mean sugar concentration of 31.5%. The mean total sugar amount secreted in nectar was 1.2 mg. The pollen amount · flower−1 was 1.1 mg. A borage plant can supply insects with 1.1 g of nectar sugars and 1.1 g of pollen. The estimated nectar sugar yield and pollen yield per 1 m2 of the crop were similar, i.e. 5.2 g. Bees accounted for 73.0% of all insect visits to the borage flowers. The presence of insect pollinators increased the fruit set by 43.3% and seed set by 26.8%.

Evaluation of the honey and pollen yield of Melipona interrupta bee colonies in the Amazon region

The objective of this research was to evaluate the productivity of honey and pollen of Melipona interrupta (Jandaíra) colonies during a one-year period. This study was conducted in meliponiculture production colonies located in community of Coroca in the City of Santarém, Pará, from October 2016 to December 2017. All collections of meliponiculture material were conducted during the first week of each month. Characteristics such as the total number of food pots, height, diameter, and volume of honey and pollen pots, the mass of the colony, production of pollen and honey, and the productivity of the bee colony as a whole were constantly monitored. Each month, biometric measurements of fifteen colonies of native bees of the specie were conducted and analyzed in the Statistical Analysis System. The greatest honey production by these colonies was strongly correlated with the less-rainy period that occurs in the region, and this production was most pronounced during October through December.

Does an invader have a bright side? Floral reward in two Solidago species

The knowledge of nectar secretion and pollen production is important for understanding the biology of invasive species. In the present paper, the floral reward in Solidago canadensis and S. gigantea (Asteraceae), two invasive plant species in Europe, were investigated. Flowers of Solidago species are protandrous. The floral nectar was found to be rich in hexose (sucrose/fructose/glucose – 13.8/32.7/53.5% in S. canadensis and 18.3/35.1/46.6% in S. gigantea). The per-flower rewards (sugars/pollen) in the Solidago species were not abundant; however, due to the formation of dense populations and massive floral display, high amounts of resources were produced at the community level. The mean sugar output was 482.3 kg/ha in S. canadensis and 121.6 kg/ha in S. gigantea. The mean pollen yield was 30.7 kg/ha (S. canadensis) and 6.5 kg/ha (S. gigantea). In the landscape with limited floral resources, the nectar and pollen available in Solidago flowers are important and can provide additional (or even exclusive) food resources for pollinators during summer/late summer. In particular, areas invaded by Solidago species may be attractive to beekeepers, as >80.0% of visits were performed by Apis mellifera. However, a broad spectrum of wild insect visitors (including Bombus spp., Vespula spp., Diptera, Lepidoptera, Coleoptera) deserves further studies to assess the impact of mass flowering in Solidago species on the native plant species-insect interactions.

Nectar and pollen production of Helianthus tuberosus L. – an exotic plant with invasiveness potential

Abstract In Central Europe, Helianthus tuberosus L. is a late summer/autumn bloomer (August/November). The disc florets produce both nectar and pollen. Floral reward is available in male-phase flowers (pollen and nectar) and in female-phase flowers (nectar). The floral reward is attractive to a variety of insect visitors (honey bees, wasps, flies and butterflies). The season of blooming as well as the total sugar yield (25.4 – 47.4 kg ha−1) and pollen yield (57.8 – 212.7 kg ha−1) indicate that H. tuberosus is important in the enhancement of food resources for pollinators. The generative reproduction in H. tuberosus is impaired (the species does not set seeds/fruits). However, due to its attractiveness for a variety of pollinators in both rural and urban areas, the spread of H. tuberosus should be monitored. Moreover, its propagation needs to be attended with restrictions.

Floral reward and insect visitors in six ornamental Lonicera species – Plants suitable for urban bee-friendly gardens

Pollinator decline is a global threat with serious consequences to biodiversity. Mosaic structure of urban habitats and greenery areas are regarded beneficial for insects. However, for proper ‘pollinator-friendly’ management of urban areas, detailed information on floral reward offered by particular plant species is required. In this paper floral rewards of six ornamental Lonicera species (Caprifoliaceae), growing in the city of Lublin, SE Poland, were investigated. In this temperate zone, the investigated Lonicera species bloomed during May-June or May-October and could be considered as valuable food resources for pollinating insects. The mean amount of nectar sugars per shrub ranged 8.6–66.3 g (L. caprifolium - L. maackii, respectively). The mean pollen yield was 2.1–110.1 g per shrub (L. xylosteum – L. maackii, respectively). Due to considerable differences in corolla depth, Lonicera species attracted diverse groups of insect visitors, i.e. short-corolla species represented morning pattern of flower opening and attracted mainly honey bees and bumble bees, while long-corolla species opened in the evening and lured Apoidea, butterflies (mainly hawkmoths), and sporadically wasps, syrphid flies and beetles. Two high sugar- and pollen-yielding species, L. maackii and L. tatarica, are however regarded invasive in some geographical areas. Therefore, the spread of the species should be carefully monitored in urban green areas.

A preliminary study of the modern pollen of Tripura, Northeast India

The vegetation distribution in Tripura, Northeast India was studied from the modern pollen assemblages at various sites in the region. Sediment samples and moss cushions were collected along transects from North to South Tripura to assess the modern pollen taxa dominant in the region. A number of taxa showing a modern day distribution of moist deciduous mixed vegetation dominant in Tripura were observed in the modern pollen data. Statistical significance of the modern–pollen data was verified using one–way ANOVA technique. Despite the limited pollen taxa recorded in the surface samples the analysis proved the potential of the pollen data and scope for future palynological studies. The impact of anthropogenic activity is clearly visible through the low sample yield and presence of taxa such as Poaceae, Amaranthaceae, Solanaceae, etc. Other factors such as entomophilous tendency and/or low yield of pollen in tropical plants, excessive rainfall, sediment distribution and jhum cultivation could contribute to the lack of pollen preservation in the region.