Floral visitors of sesame (Sesamum indicum L.): Elucidating their nectar-robbing behaviour and impacts on the plant reproduction.

Nectar robbing is common in angiosperms, especially in long tubular flowers or flowers with spurs that keep nectar out of reach of visitors. However, the robbing behaviour of bees is less understood. Here, we studied the sesame visitors, their robbing behaviour, and the impacts of robbing on plant reproductive fitness. Diverse insect species (primarily members of Hymenoptera) visited sesame flowers. The most effective pollinators were Amegilla zonata, Apis cerana, Apis dorsata, Apis florea, Ceratina binghami, Halictus acrocephalus and Xylocopa amethystina. Almost all visitors with variable percentages revealed the nectar-robbing phenomenon. Robbing activity depended on a complex of multiple attributes, including the visitor's body size, the corolla tube length, the availability and accessibility of nectar, and the resource-collecting task allocation of bees. Robbing activity varied according to flower-visiting species, flowering period and daytime. Robbing was comparatively higher in the late flowering period at 10.00-14.00 h. In the case of robbing visits, flower handling time was lower, and the visitation rate remained higher than non-robbing visits. Robbing visits did not significantly affect fruit and seed sets of sesame. Therefore, we can interpret the nectar-robbing interactions on sesame as commensal, with pollinators benefitting without altering the plant's reproductive fitness.

Spatial and Temporal Variations in Richness, Diversity and Abundance of Floral Visitors of Curry Plants (Bergera koenigii L.): Insights on Plant-Pollinator Interactions.

The reproductive success of flowering plants relates to flower-visitor communities and plant-pollinator interactions. These traits are species- and region-specific and vary across regions, pollinator groups, and plant species. However, little literature exists on the spatiotemporal variation in visitor activity, especially in India. Here, we aimed to depict the spatial and temporal variation in visitor activity on the curry plants (Bergera koenigii). Data were collected at different daytime slots from three vegetation zones (confirmed by field surveys and normalized difference vegetation index values in remote sensing)-dense, medium-density, and low-density vegetation in West Bengal, India. The visitors' richness, diversity, and abundance were higher in the area with dense vegetation. Considering daytime patterns, higher values for these parameters were obtained during 10.00-14.00 h. For most visitors, the flower handling time was shorter, and the visitation rate was higher in dense vegetation areas (at 10.00-14.00 h) than in medium- and low-density vegetation areas. The proportions of different foraging categories varied over time. Vital pollinators were Apis cerana, Apis dorsata, Appias libythea, Halictus acrocephalus, Nomia iridescens, and Tetragonula iridipennis. However, the effectiveness of pollinators remained region-specific. Therefore, it can be concluded that floral visitors' richness, diversity, abundance, and plant-visitor interactions varied spatially with their surrounding vegetation types and also changed daytime-wise.

Intercropping with Pigeonpea (Cajanus cajan L. Millsp.): An Assessment of Its Influence on the Assemblage of Pollinators and Yield of Neighbouring Non-Leguminous Crops.

Intercropping is practiced in modern intensive agriculture considering many benefits, including additive crop yield. However, it may have competitive or facilitative interactions between pollinator-dependant crops. Here, we investigated the reproductive aspects of pigeonpea (Cajanus cajan). We assessed the influence of blooming pigeonpea on pollinator's assemblage and the yield of neighbouring non-leguminous crops (e.g., coriander, mustard). For these, we recorded floral visitors and the yield of the targeted crops from two types of fields-closely situated and distantly situated concerning pigeonpea plantation. Pigeonpea is autogamous, but pollinator's visits enhance fruit and seed sets. Bright, nectariferous flowers emitted several volatile organic compounds and were visited by numerous insect species. The prime pollinators of pigeonpea are carpenter bees and leafcutter bees. In contrast, halictidae, honeybees and stingless bees mainly pollinate the co-blooming non-leguminous crops (coriander and mustard). The richness and abundance of pollinators on these co-blooming crops remain similar in closely situated and distantly situated fields. As a result, the yield of the neighbouring crops is not significantly influenced by the blooming pigeonpea. Therefore, it can be concluded that planting pigeonpea in ridges of agricultural fields will be an additional agricultural output without affecting the assemblage of pollinators and yields of neighbouring co-blooming crops.

Specialized metabolites contributing to colour and scent volatiles in Uvaria hamiltonii flowers.

The present study focuses on the emitted and endogenous scent profiles of Uvaria hamiltonii flowers. Among the 34 compounds identified, sesquiterpenoids were found to dominate the floral volatiles composition. Profiles from endogenous scent volatiles showed higher number of compounds than the emitted ones. The anthocyanin pigment responsible for the flower colour was also explored. It was found that a single anthocyanin compound, cyanidin-3-O-glucoside, was principally responsible for petal colour. Total phenolic content was evaluated and antioxidant capacities were studied with the help of DPPH, FRAP and ABTS assays. The total phenolic content and the antioxidant capacity were higher in methanolic extract as compared to aqueous, petroleum ether and ethyl acetate extracts of U. hamiltonii flowers.

Apis mellifera pollen loads to understand the pollen foraging pattern used for apicultural practice in a potentially agricultural belt in Bengal, India / Cargas polínicas de Apis mellifera para entender los patrones de forrajeo de polen usados en apicultura en una franja potencialmente agrícola en Bengala, India

Abstract For accurate determination of polleniferous taxa vis-a-vis floral fidelity of Apis mellifera L. in North 24 Pargana, West Bengal, we carried out pollen analyses of individual corbicular pollen loads collected from four apiaries during 2015-2016. Among the 2 434 analyzed loads, 72.97 % were unifloral type, 19.0 % bifloral and 8.10 % were multifloral in pollen composition. We identified 43 different types of palynomorphs belonged to 28 botanical families. Major polleniferous plant species include: Alangium salviifolium, Borassus flabellifer, Brassica nigra, Coriandrum sativum, Croton bonplandianum, Cyanotis axillaris, Luffa cylindrica, Neolamarckia cadamba, Phoenix sylvestris, Poa gangetica, Sesamum indicum and Trema orientalis. Among them, T. orientalis is newly reported from West Bengal especially during June to August (monsoon season). The plant family provided maximum number of loads was Arecaceae (20.91 %), followed by Brassicaceae (16.2 %), Poaceae (6.70 %), Pedaliaceae (6.38 %), Apiaceae (6.16 %) and Fabaceae (5.38 %). Month wise highest number of pollen diversity were obtained during March (13 pollen types) and a minimum of 6 types in November. The present investigation will help the beekeepers to maintain their hives in the region for sustainable apicultural practices.(AU)

Resumen Para una determinación precisa de taxa polinífero y fidelidad floral de Apis mellifera en Pargana Norte 24, Bengala Occidental, realizamos análisis de cargas individuales de polen corbicular, recolectados en cuatro apiarios durante 2015-2016. De las 2 434 cargas analizadas, 72.97 % fueron de tipo unifloral, 19.0 % bifloral y 8.10 % multifloral, en la composición del polen. Identificamos 43 tipos diferentes de palinomorfos pertenecientes a 28 familias botánicas. Las especies principales de plantas poliníferas incluyen: Alangium salviifolium, Borassus flabellifer, Brassica nigra, Coriandrum sativum, Croton bonplandianum, Cyanotis axillaris, Luffa cylindrica, Neolamarckia cadamba, Phoenix sylvestris, Poa gangetica, Sesamum indicum y Trema orientalis. Entre estas, T. orientalis ha sido reportada recientemente en Bengala Occidental, especialmente de junio a agosto (temporada de monsones). La familia de plantas que presentó máxima cantidad de cargas fue: Arecaceae (20.91 %), seguida por Brassicaceae (16.2 %), Poaceae (6.70 %), Pedaliaceae (6.38 %), Apiaceae (6.16 %) y Fabaceae (5.38 %). De acuerdo al mes, el número mayor de diversidad de polen se obtuvo durante marzo (13 tipos de polen) y un mínimo de seis tipos en noviembre. La presente investigación ayudará a los apicultores a mantener sus colmenas en la región para prácticas apícolas sostenibles.(AU)

Expression dynamics of miRNAs and their targets in seed germination conditions reveals miRNA-ta-siRNA crosstalk as regulator of seed germination.

Seed germination paves the way for the dormant embryo to establish itself as a new plant marking the first critical step in postembryonic plant growth and development. Germination starts with the uptake of water (imbibition), followed by induction of transcription, translation, energy metabolism, and cell division processes. Although small RNAs have been implicated in many developmental processes, their role during seed germination stages and conditions remained elusive. Here we show that seed germination conditions, like imbibition and temperature, dynamically regulate the expression of many developmentally important miRNAs and their targets. We have identified 58 miRNAs belonging to 30 different families at different seed germination conditions. Amongst these, 15 miRNAs and their targets were significantly differentially expressed in Arabidopsis seeds in dry and 12 h, 24 h and 48 h of imbibition. Interestingly, differential expression of miR390, which targets trans-acting siRNA locus (TAS3) derived transcripts, resulted in alteration of tasiR-ARF mediated regulation of expression of target AUXIN RESPONSE FACTORs (ARF2/3/4). Our results suggest that the dynamic expression of several miRNAs, their targets, and a crosstalk between miRNA and ta-siRNA pathways contribute to the regulation of seed germination in Arabidopsis thaliana.

Small RNA mediated regulation of seed germination.

Mature seeds of most of the higher plants harbor dormant embryos and go through the complex process of germination under favorable environmental conditions. The germination process involves dynamic physiological, cellular and metabolic events that are controlled by the interplay of several gene products and different phytohormones. The small non-coding RNAs comprise key regulatory modules in the process of seed dormancy and germination. Recent studies have implicated the small RNAs in plant growth in correlation with various plant physiological processes including hormone signaling and stress response. In this review we provide a brief overview of the regulation of seed germination or dormancy while emphasizing on the current understanding of the role of small RNAs in this regard. We have also highlighted specific examples of stress responsive small RNAs in seed germination and discussed their future potential.