Individual Flowers Research Articles

Cypripedium lichiangense (Orchidaceae) mimics a humus-rich oviposition site to attract its female pollinator, Ferdinandea cuprea (Syrphidae).

Most species in the genus Cypripedium (Cypripedioideae) produce trap flowers, making it a model lineage to study deceptive pollination. Floral attractants in most species studied appear to target bee species of different sizes. However, more recent publications report fly pollination in some subalpine species, suggesting novel suites of adaptive floral traits. Cypripedium lichiangense (section Trigonopedia) is an endangered subalpine species endemic to the Hengduan Mountains, China. We observed and analysed its floral traits, pollinators and breeding systems over 2 years insitu and in the lab. Cypripedium lichiangense was visited by females of Ferdinandea cuprea (Syrphidae). The pollinia were carried dorsally on the fly thoraces. The eggs of this fly were frequently found in the saccate labellum and on other floral organs, suggesting brood-site mimesis. The orchid is self-compatible, but cross-pollination produces more viable embryos. We propose a new mode of floral mimesis, humus-rich oviposition site mimicry, for C. lichiangense. Compared with the mimesis of aphid colonies attracting syrphid pollinators (subfamily Syrphinae), whose larvae are entomophagic, as reported in some Paphiopedilum species (Cypripedioideae), pollination by deceit in C. lichiangense represents a distinct and separate mode of exploitation of another saprophagic (or phytophagic) larvae syrphid lineage in the subfamily Eristalinae and appears to indicate diversity of pollination strategies in SectionTrigonopedia of Cypripedium. However, this new brood-site mimesis seems to be less attractive to pollinators. As a possible adaptation to the weak attracted pollination strategy, this plant species has a long flowering period and extended lifespan of individual flowers to ensure reproductive success.

Protective Role of Ice Barriers: How Reproductive Organs of Early Flowering and Mountain Plants Escape Frost Injuries

In the temperate zone of Europe, plants flowering in early spring or at high elevation risk that their reproductive organs are harmed by episodic frosts. Focusing on flowers of two mountain and three early-flowering colline to montane distributed species, vulnerability to ice formation and ice management strategies using infrared video thermography were investigated. Three species had ice susceptible flowers and structural ice barriers, between the vegetative and reproductive organs, that prevent ice entrance from the frozen stems. Structural ice barriers as found in Anemona nemorosa and Muscari sp. have not yet been described for herbaceous species that of Jasminum nudiflorum corroborates findings for woody species. Flowers of Galanthus nivalis and Scilla forbesii were ice tolerant. For all herbs, it became clear that the soil acts as a thermal insulator for frost susceptible below ground organs and as a thermal barrier against the spread of ice between individual flowers and leaves. Both ice barrier types presumably promote that the reproductive organs can remain supercooled, and can at least for a certain time-period escape from effects of ice formation. Both effects of ice barriers appear significant in the habitat of the tested species, where episodic freezing events potentially curtail the reproductive success.

Differential reproductive responses to contrasting host species and localities in Psittacanthus calyculatus (Loranthaceae) mistletoes.

Host trees are immediate environments for multi-host mistletoes, so parasitizing different hosts implies exposure to varying environmental conditions between mistletoe generations. Therefore, to maximize reproductive fitness in heterogeneous environments (host species) mistletoes should adjust its reproductive responses in relation to circumstances. Here, we ask how reproductive traits of Psittacanthus calyculatus mistletoes vary on two host tree species (Crataegus mexicana, Prunus serotina) at three different localities. We followed individual mistletoes on each host species and at three localities through the flowering season to quantify traits related to reproductive effort and success, e.g. total number of buds, flowers and fruits produced. In buds about to open, we measured two anthers and quantified the number of pollen grains and their viability. Individual flowers were marked to obtain flower longevity data and were followed until fruit formation. At which time we measured and weighed the fruits and the seeds. Mistletoes from one locality produced more buds, flowers and fruits, and the flowers lasted longer, had larger anthers and produced more pollen as compared to the other two localities. However, mistletoes on Prunus serotina produced fewer floral buds, but their fruits were heaviest, longest and widest and ripened fastest across localities. The probability of fruit formation, percentage of fruits formed, and pollen viability were similar among the mistletoes, regardless of host species or locality. We propose that the observed differences in reproductive effort and success associated with host species or locality are plastic or adaptive in this mistletoe in response to varying conditions.

Flowering phenology and reproduction of a forest understorey plant species in response to the local environment

Temperate forest understorey plants are subjected to a strong seasonality in their optimal growing conditions. In winter and early spring, low temperatures are suboptimal for plant growth while light becomes limited later in spring season. We can thus expect that differences in plant phenology in relation to spatiotemporal environmental variation will lead to differences in reproductive output, and hence selection. We specifically studied whether early flowering, a paradoxical pattern that is observed in many plant species, is an adaptive strategy, and whether selection for early flowering was confounded with selection for flower duration or was attributable to environmental variables. We used Geum urbanum as a study species to investigate the effect of relevant environmental factors on the species’ flowering phenology and the consequences for plant reproductive output. We monitored the phenology of four to six plants in each of ten locations in a temperate deciduous forest (Belgium). We first quantified variation in flowering time within individuals and related this temporal variation to individual flower reproductive output. Then, we studied inter-individual variation here-in and linked this to reproduction at the plant level, hence studying the selection differential. We found that flowering within individual plants of Geum urbanum was spread over a long period from June to October. Reproductive output of individual flowers, measured as total seed mass per flower, declined during the season. We found no indication for selection for early flowering but rather for longer flower duration. Larger plants had an earlier flowering onset and a higher seed mass, which suggests that these factors covary and are condition dependent. None of the studied environmental variables could explain plant size, although soil pH and to a lesser extent light availability had a positive direct effect on seed mass per plant. Finally, we suggest that the high intra-individual variation in flowering time, which might be a risk spreading strategy of the plant in the presence of seed predation, limits the potential for selection on flowering phenology.

Intraspecific morphological variation of Bellidiastrum michelii (Asteraceae) along a 1,155 m elevation gradient in the Tatra Mountains.

Plant species that inhabit large elevation gradients in mountain regions are exposed to different environmental conditions. These different conditions may influence plant morphology via plastic responses and/or via genetic adaptation to the local environment. In this study, morphological variation was examined for Bellidiastrum michelii Cass. (Asteraceae) plants growing along a 1,155 m elevation gradient in the Tatra Mountains in Central Europe. The aim was to contribute to gaining a better understanding of within-species morphological variation in a mountain species across elevation gradients. Twelve morphological traits, which were measured for 340 plants collected from 34 sites, were plotted against elevation using Generalised Additive Models. Significant variation in B. michelii morphology was found across the elevation gradient. Plant size, in the form of plant height, total aboveground mass and total leaf mass, decreased significantly with increasing elevation. Similarly, floral traits, such as flower head mass, total flower mass, individual flower mass, flower head diameter and ligulate and tubular flower length, also decreased significantly with increasing elevation. However, the changes in these floral traits were not as large as those observed for plant size traits. Interestingly, the number of flowers produced by the plant, both ligulate and tubular, did not change across the studied elevation gradient. In this study, elevation was found to be an important gradient across which significant intraspecific morphological variation occurred in a mountain plant. These morphological changes may have occurred in response to various abiotic and biotic factors that change along elevation gradients.

Floral scent and pollinator visitation in relation to floral colour morph in the mixed‐mating annual herb Collinsia heterophylla

Even though floral scent is of major importance for pollinator attraction, it is less investigated than other floral traits. Previous studies suggest the importance of joint exploration of olfactory and visual floral cues to understand plant–pollinator interactions. We investigated flower scents in Collinsia heterophylla, a bee‐pollinated, annual herb a with mixed‐mating system combining self‐ and outcross‐pollination. In Collinsia, floral size and development variation is related to mating system, ranging from large‐flowered mixed‐mating species to small‐flowered self‐pollinated species. However, to our knowledge, flower scent has not been described in any species in the genus. We also studied whether flower‐emitted volatiles were coupled to presence versus absence of a coloured band on the upper lip within a population in C. heterophylla, and if these colour morphs affected pollinator visitation. We performed headspace collections of volatiles in the greenhouse from potted flowering plants, and compared these to controls in the bud stage. Flower‐specific volatiles were highly dominated by terpenoid compounds typical of bee‐pollinated plants, such as β‐myrcene, (Z)‐ and (E)‐ocimene and sesquiterpenes (E)‐α‐bergamotene and β‐sesquiphellandrene. The aliphatic ester methyl hexanoate was also prominent, together with additional esters, whereas methyl cinnamate constituted the only aromatic compound. Floral colour morphs showed no qualitative difference in volatiles, but the coloured morph produced significantly higher quantities for seven of the 26 individual flower compounds. A field experiment performed within a natural population, using behavioural observations and florescent dyes dusted on the flowers, could not detect any differences in pollinator visitation between colour morphs. We conclude that C. heterophylla flowers emit volatile compounds commonly associated with attraction of their most important pollinators. It would be highly interesting to explore the function of floral scent for pollinator attraction and relate floral scent to mating system variation across Collinsia for a better understanding of pollinator influence on floral evolution.

Soil Humus, Iron, Sulphate and Magnesium Content Affect Nectar Traits of Wild Garlic (Allium ursinum L.).

Recent studies revealed that from various ecological factors influencing nectar yield and quality of a plant, soil properties can be as important as microclimatic features. To date, few studies have investigated the relationship of soil characters to nectar traits of bee pollinated plants growing in natural associations. Our study intended to reveal which soil properties had the most powerful impact on nectar variables of wild garlic (Allium ursinum L.). Specimens were collected from fourteen habitats in two different years, and were potted in their original soil under the same climatic conditions. Nectar volumes and sugar concentrations were measured and soil samples were analysed for fourteen parameters. Statistical analyses revealed that the number of nectar producing Allium flowers, as well as the nectar volume and sugar content of nectar in individual flowers were influenced by both year and habitat. The humus, iron and sulphate content of soil showed negative correlation with the number of flowers producing nectar; total nectar volumes were negatively correlated with humus and iron content, but positively affected by magnesium content of the soil. Our results suggest that in addition to the effect of microclimatic factors, certain soil properties can have significant impact on nectar traits.

Criteria to select vegetal species for restoration of plant-pollinator interactions in agricultural landscapes of the Pampa grassland (Argentina)

Ecological functions, including pollination services, can be successfully restored in degraded ecosystems. In this study we propose a procedure for selection of target species to be employed in the restoration of plant-pollinator interactions in agricultural landscapes, which is illustrated by a case study located in the Tandilia System, in the Southern Pampa grasslands of Argentina. Based on information from a large pollination network dataset of 12 hills, composed of 172 pollinators and 96 plants (metaweb), we identified the plant species playing a major role in the maintenance of pollination mutualisms. We obtained a ranking of interaction frequency for each of the 96 plant species of the metaweb, and selected native plants that received more than 100 individual flower visitors. The targeted species were evaluated using ten criteria related to ecological, technical and cultural characteristics, and then ranked according to their suitability for use in restoration projects (species rank, SR). From the total number of plant species (96) registered for all sampled hills, we identified a total of 24 plant species that represented 90% of the total interactions and 25% of the plant species recorded in the metaweb. Six of the 24 selected species were excluded since they were non-native, leaving 18 targeted native plant species. The SR value ranged between 2.68 and 8, with a mean of 4.63 ± 1.40. Two genera presented the highest SR values (Eryngium sp. and Baccharis sp.), and are recognized as potential candidates for restoration of other ecosystems. A rank that evaluates plant species capable of rehabilitating plant-pollinator interactions will form a solid basis for planning restoration projects, which are crucial for biodiversity rehabilitation and conservation.

Mechanisms of Male-Male Interference during Dispersal of Orchid Pollen

AbstractSiring success of flowering plants depends on the fates of male gametophytes, which compete for access to stigmas, stylar resources, and ovules. Although rarely considered, pollen may often compete during dispersal, affecting the processes required for export to stigmas: pollen pickup, transport, and deposition. We quantified dispersal interference by tracking bee-mediated dispersal of stained Anacamptis morio (Orchidaceae) pollen from individual donor flowers and inferred the affected dispersal mechanisms on the basis of the fit of a process-based model. During individual trials, all recipient flowers were either emasculated, precluding interference with donor pollen, or intact, adding potentially interfering pollen to the pollinator. The presence of competing pollinaria on bees reduced pickup of additional pollinaria, doubled the overall proportion of lost donor pollen, and reduced total pollen export by 27%. Interference specifically increased loss of donor pollen between successive flower visits and variation in deposition among trials, and it likely also reduced pollen contact with stigmas and pollen deposition when contact occurred. Thus, by altering pollen removal, transport, and deposition, male-male interference during pollen dispersal can significantly-and perhaps commonly-limit plant-siring success.

Морфометрическая изменчивость видов рода Cypripedium в коллекции Центрального сибирского ботанического сада СО РАН

The article is devoted to the study of the genus Cypripedium L., three of the studied species of this genus are included in the Red Book of the Russian Federation. Biological material was taken from natural phytocenoses of the Novosibirsk region and the Altai Republic and introduced on the collection site of the Central Siberian Botanical Garden. The adaptive response of individuals was studied at the morphological level depending on environmental changes in ex situ conditions. The presence of all main stages in the phenological cycle in the adapting representatives of the three species (except for fruiting in Cypripedium × ventricosum) is an indicator of optimal ecological conditions for ex situ. A comparative analysis of morphometric characters in generative individuals was carried out and significant differences between in situ and ex situ were revealed. The adaptive changes associated with the response to natural abiotic ecological conditions were also identified. The revealed differences in morphometric data for the three species allow us to note the presence of a significant adaptive reaction in C. calceolus and C. macranthon and relative adaptive inertia in C. × ventricosum. The ecological optimum in abiotic factors for the three studied species from the genus Cypripedium is the indicators for 2018.The factors for 2018 became optimal for the developmentt of generative buds, which led to 100 % flowering of individuals in C. macranthon in 2019. We also performed a dental analysis of the lower surface of the bracts in three species and studied the morphology of the stomatal apparatus. We have noted significant differences between the species, under the same eco-conditions, in the size of stomata and their number per 1 cm2.

A Nonparametric Model for Analysis of Flowering Patterns of Herbaceous Multi-flowered Monocarpic Shoots.

One of the approaches to plant development description involves phenological curves, which represent the time variations of certain traits. Most models applied to various plant taxa and life forms describe their phenology, including flowering, at the population level, and insufficient attention is paid to the modeling at the individual one. Individual modeling is more complicated than populational one owing to the multilevel structure of a phenotype. And as a result, it is accompanied by a significant increase in the number of model parameters, many of which are both interdependent and non-transferable between species. Here, we present a simple structural-dynamic data-driven model to describe the flowering patterns of individual monocarpic shoots of herbaceous plants with multi-flowered inflorescences. This model is nonparametric, thus being convenient and applicable to various plant species. Our results showed the operability of the proposed model and its potential in the detection of hidden trends in the input data. This is illustrated by the example of the herbaceous polycarpic Campanula sarmatica, Campanulaceae family, whose inflorescences demonstrate a wide variability in the structure and dynamics of flowering. For example, using our model, we found that the shape of the flowering curve of C. sarmatica shoots as a whole is determined by only two factors, the ratio of the number of flowers on the main and lateral axes, and the time of the flowering shift from the main axis to the lateral axes. The proposed model accurately mimics the individual flowering pattern with due natural variability. It can be used to simulate the flowering of a group of individuals in cenopopulational studies or practical tasks, e.g., in landscape design. Flowering patterns that characterize inflorescence development at the individual level can serve as informative phenotypic traits in anthoecological and developmental studies, and in inflorescence diagnostics.

Temporal and spatial dynamics in the apple flower microbiome in the presence of the phytopathogen Erwinia amylovora.

Plant microbiomes have important roles in plant health and productivity. However, despite flowers being directly linked to reproductive outcomes, little is known about the microbiomes of flowers and their potential interaction with pathogen infection. Here, we investigated the temporal spatial dynamics of the apple stigma microbiome when challenged with a phytopathogen Erwinia amylovora, the causal agent of fire blight disease. We profiled the microbiome from the stigmas of individual flowers, greatly increasing the resolution at which we can characterize shifts in the composition of the microbiome. Individual flowers harbored unique microbiomes at the operational taxonomic unit level. However, taxonomic analysis of community succession showed a population gradually dominated by bacteria within the families Enterobacteriaceae and Pseudomonadaceae. Flowers inoculated with E. amylovora established large populations of the phytopathogen, with pathogen-specific gene counts of >3.0 × 107 in 90% of the flowers. Yet, only 42% of inoculated flowers later developed fire blight symptoms. This reveals that pathogen abundance on the stigma is not sufficient to predict disease outcome. Our data demonstrate that apple flowers represent an excellent model in which to characterize how plant microbiomes establish, develop, and correlate with biological processes such as disease progression in an experimentally tractable plant organ.

Inflorescence Development and Floral Organogenesis in Taraxacum kok-saghyz.

Rubber dandelion (Taraxacum kok-saghyz Rodin; TK) has received attention for its natural rubber content as a strategic biomaterial, and a promising, sustainable, and renewable alternative to synthetic rubber from fossil carbon sources. Extensive research on the domestication and rubber content of TK has demonstrated TK’s potential in industrial applications as a relevant natural rubber and latex-producing alternative crop. However, many aspects of its biology have been neglected in published studies. For example, floral development is still poorly characterized. TK inflorescences were studied by scanning electron microscopy. Nine stages of early inflorescence development are proposed, and floral micromorphology is detailed. Individual flower primordia development starts at the periphery and proceeds centripetally in the newly-formed inflorescence meristem. Floral organogenesis begins in the outermost flowers of the capitulum, with corolla ring and androecium formation. Following, pappus primordium—forming a ring around the base of the corolla tube—and gynoecium are observed. The transition from vegetative to inflorescence meristem was observed 21 days after germination. This description of inflorescence and flower development in TK sheds light on the complex process of flowering, pollination, and reproduction. This study will be useful for genetics, breeding, systematics, and development of agronomical practices for this new rubber-producing crop.

Automated grapevine flower detection and quantification method based on computer vision and deep learning from on-the-go imaging using a mobile sensing platform under field conditions

Grape yield forecasting is a valuable economic and quality issue for the grape and wine industry. The number of flowers at bloom could be used as an early indicator towards crop forecast in viticulture. The purpose of this work was to develop a non-invasive method for grapevine flower counting by on-the-go image acquisition, using a combination of deep learning and computer vision technology. A mobile sensing platform was used at 5 km/h to automatically capture Red Green Blue (RGB) images of vineyard canopy at night using artificial illumination under field conditions. For the image data set, 96 vines from six grapevine varieties were selected. For ground-truthing, the number of flowers per inflorescence was counted on a set of clusters before flowering, while yield per vine was weighted at harvest. The developed algorithm comprised two general steps: inflorescences’ segmentation, and individual flower detection. In both steps, the best results were obtained using the deep fully convolutional neural network SegNet architecture with a VGG19 network as the encoder, with F1 score values of 0.93 and 0.73 in the inflorescences segmentation and the individual flower detection steps, respectively. These values showed the high accuracy of the network. A determination coefficient (R2) of 0.91 between the detected number of flowers and the actual number of flowers per vine was obtained. In addition, a linear regression model was trained to estimate the actual number of flowers from the number of detected flowers. A root mean squared error (RMSE) of 590 flowers per vine and a normalized root mean squared error (NRMSE) of 23.7% was obtained. An R2 above 0.70 was achieved between the estimated number of actual flowers and the final yield, per vine. These results show that the number of flowers per vine can be estimated using machine vision and deep learning. The developed imaging platform can be used by the wine industry in commercial vineyards for a satisfactory early crop yield forecasting.

Effect of macronutrients, microbial consortium and biostimulants on growth and yield of African marigold (Tagetes serecta L.)

The present study was undertaken to bring out the best combination of microbial consortium on effect of biostimulant for the growth and yield of African marigold (Tagetes erecta L.) hybrid L3. The experiment was conducted in open field condition in a randomized block design with 10 treatments combinations and replicated thrice at ICAR-KVK, Bagalkot during the year 2017. Application of bio-control agents viz., Trichoderma harzianum, Pseudomonas fluorescens, Bacillus subtilis were applied in different combinations through soil application (SA), seedling treatment (ST), and foliar spray/application (FA) and were evaluated for growth promotion and disease management in marigold. The bio-stimulant, vermiwash was applied as foliar spray at four intervals at 30, 45, 60 and 75 days after transplanting. Observations were recorded on marigold growth, flowering and yield parameters. The growth parameters viz., plant height, number of primary branches per plant, plant spread, number of leaves per plant were recorded highest in treatment T8 compared to other treatments. Days taken for first flowering, days taken for 50% flowering, flower diameter, individual flower weight, flowering duration, number of flowers per plant, flower yield per plant and flower yield per hectare were also recorded highest in treatment T8 which received combined soil application of 50% recommended dose of fertilizers (63:30:30 Kg NPK ha-1) + soil application of bioagents @ 3kg/acre followed by seedling dip and foliar spray of Trichoderma harzianum (10ml/litre) +Pseudomonas fluorescens (10ml/litre)+ Bacillus subtilis (10ml/litre) and vermiwash (0.5%) compared to control. The disease incidence (PDI) of leaf spot and flower blight was observed less in T8 whereas, leaf spot and flower blight was high in control. Hence, treatment T8 was best for growth, development and disease management through organic way in marigold.

Why are there so many bee-orchid species? Adaptive radiation by intra-specific competition for mnesic pollinators.

Adaptive radiations occur mostly in response to environmental variation through the evolution of key innovations that allow emerging species to occupy new ecological niches. Such biological innovations may play a major role in niche divergence when emerging species are engaged in reciprocal ecological interactions. To demonstrate coevolution is a difficult task; only a few studies have confirmed coevolution as driver of speciation and diversification. Herein we review current knowledge about bee orchid (Ophrys spp.) reproductive biology. We propose that the adaptive radiation of the Mediterranean orchid genus Ophrys, comprising several hundred species, is due to coevolutionary dynamics between these plants and their pollinators. We suggest that pollination by sexual swindling used by Ophrys orchids is the main driver of this coevolution. Flowers of each Ophrys species mimic a sexually receptive female of one particular insect species, mainly bees. Male bees are first attracted by pseudo-pheromones emitted by Ophrys flowers that are similar to the sexual pheromones of their females. Males then are lured by the flower shape, colour and hairiness, and attempt to copulate with the flower, which glues pollen onto their bodies. Pollen is later transferred to the stigma of another flower of the same Ophrys species during similar copulation attempts. In contrast to rewarding pollination strategies, Ophrys pollinators appear to be parasitized. Here we propose that this apparent parasitism is in fact a coevolutionary relationship between Ophrys and their pollinators. For plants, pollination by sexual swindling could ensure pollination efficiency and specificity, and gene flow among populations. For pollinators, pollination by sexual swindling could allow habitat matching and inbreeding avoidance. Pollinators might use the pseudo-pheromones emitted by Ophrys to locate suitable habitats from a distance within complex landscapes. In small populations, male pollinators would disperse once they have memorized the local diversity of sexual pseudo-pheromone bouquets or if all Ophrys flowers are fertilized and thus repel pollinators via production of repulsive pheromones that mimic those produced by fertilized female bees. We propose the following evolutionary scenario: Ophrys radiation is driven by strong intra-specific competition among Ophrys individuals for the attraction of species-specific pollinators, which is a consequence of the high cognitive abilities of pollinators. Male bees record the pheromone signatures of kin or of previously courted partners to avoid further copulation attempts, thereby inducing strong selection on Ophrys for variation in odour bouquets emitted by individual flowers. The resulting odour bouquets could by chance correspond to pseudo-pheromones of the females of another bee species, and thus attract a new pollinator. If such pollinator shifts occur simultaneously in several indivuals, pollen exchanges might occur and initiate speciation. To reinforce the attraction of the new pollinator and secure prezygotic isolation, the following step is directional selection on flower phenotypes (shape, colour and hairiness) towards a better match with the body of the pollinator's female. Pollinator shift and the resulting prezygotic isolation is adaptive for new Ophrys species because they may benefit from competitor-free space for limited pollinators. We end our review by proritizing several critical research avenues.

Studies on Response of African Marigold (Tagetes erecta) to NPK, Humic Acid and Zinc Sulphate in Red and Lateritic Soils of Jhargarm District of West Bengal

A field experiment was carried out at Kapgari village of Jhargram district of West Bengal, to study the effects of NPK, humic acid and zinc sulphate on the growth and yield of African marigold (Tagetes erecta L.), during the year 2018 and 2019. The experiment included three treatments with ten replications were designed in Randomized Block Design. First treatment (T1) was with the recommended doses of NPK (120: 120: 100 kg/ha). Second treatment (T2) was to apply fertigation of 75% of the recommended doses in three splits whereas the third treatment (T3) was to apply fertigation of 75% of the recommended doses in five splits along with foliar application (30 and 45 days after planting) of humic acid (0.2%) and Zinc Sulphate (0.2%). Results revealed that the plants treated with T3 found to have maximum plant height (67.6 cm), plant spread (45.2 cm2) and number of branches per plant (27.2) as well as the number of flowers plant-1 (21.7), flower diameter (5.4 cm), individual flower weight (6.6 g) and yield of flower (230.6 q/ha) were also found highest by applying the same.

Photo-sensitive "flip-flop" characteristics of the developing Narcissus plant (daffodil phototropism).

The developing Narcissus pseudonarcissus plant (daffodil) is shown to face towards a preferential direction (east, south, west, or north, in that order) before flowering. Said directionality is accomplished by stem bending, a phototropic response mechanism, which is sensitive to partial blocking of the available sunlight from the local environmental. Polar distribution diagrams show that with partial environmental shading from the north, east, south, or west, the developing daffodil plant always excludes facing in that direction, to absorb maximum available sunlight. Stem buckling experiments, equivalent to stem bending, are presented measuring the Euler buckling exponent n = - 2.1 for daffodil flower stems, in good agreement with theory, r = 0.99. Individual flower stems are capable of generating 2-3 lbf of vertical force, which explains the plants ability to penetrate frozen ground cover. Results from 193 daffodil flower stems are presented, showing that 61.7% face East [95% CI 54-70%], 17.1% face South, 15.0% face West, and only 6.2% face North [95% CI 2-10%], depending strongly on the partial shading effect of the surrounding environment.

Dominant bee species and floral abundance drive parasite temporal dynamics in plant-pollinator communities.

Pollinator declines can leave communities less diverse and potentially at increased risk to infectious diseases. Species-rich plant and bee communities have high species turnover, making the study of disease dynamics challenging. To address how temporal dynamics shape parasite prevalence in plant and bee communities, we screened >5,000 bees and flowers through an entire growing season for five common bee microparasites (Nosema ceranae, N. bombi, Crithidia bombi, C. expoeki and neogregarines). Over 110 bee species and 89 flower species were screened, revealing 42% of bee species (12.2% individual bees) and 70% of flower species (8.7% individual flowers) had at least one parasite in or on them, respectively. Some common flowers (e.g., Lychnis flos-cuculi) harboured multiple parasite species, whilst others (e.g., Lythrum salicaria) had few. Significant temporal variation of parasite prevalence in bees was linked to bee diversity, bee and flower abundance, and community composition. Specifically, we found that bee communities had the highest prevalence late in the season, when social bees (Bombus spp. and Apis mellifera) were dominant and bee diversity was lowest. Conversely, prevalence on flowers was lowest late in the season when floral abundance was the highest. Thus, turnover in the bee community impacted community-wide prevalence, and turnover in the plant community impacted when parasite transmission was likely to occur at flowers. These results imply that efforts to improve bee health will benefit from promoting high floral numbers to reduce transmission risk, maintaining bee diversity to dilute parasites, and monitoring the abundance of dominant competent hosts.

Seasonal variation in the diversity of flowering orchids at Santa Catarina Lachatao, Oaxaca, Mexico

Background: Orchidaceae represents around 7.1-8.52 % of the angiosperms known in the planet. In Mexico, orchids are the third family more diverse, and Oaxaca is the state with the highest richness in the country. Orchids are widely distributed in tropical environments, but they are also distributed in temperate forests, where they have been scarcely studied.
 Questions: What is the diversity of orchid species at the locality of Santa Catarina Lachatao? Which subfamilies and growth forms are distributed at that locality? Do the community of orchids flowers differentially between seasons?
 Studied species: Species of the Orchidaceae family.
 Study site and dates: Santa Catarina Lachatao, Oaxaca, 2017-2018.
 Methods: Orchids were collected monthly throughout a year. Collected specimens were identified. Richness, abundance and diversity index were estimated for the whole flowering community, and per subfamily and growth form. These parameters were compared between seasons.
 Results: The community of orchids was composed by 4,933 flowering individuals from 74 species from the subfamilies Epidendroideae and Orchidoideae. Orchids with terrestrial, epiphyte, and rupicolous growth forms were collected. Total diversity index and species composition varied between seasons. Seasonal variation in abundance, diversity and species composition per subfamily and per growth form was also detected.
 Conclusions: Orchid diversity at the locality is high (9.68 % of the richness recorded for Oaxaca), and varies between seasons. The high species richness, the endemisms and endangered species found, call to take prompt actions to protect and manage the forest to assure its conservation and the diversity within it.