Stigmas Of Flowers Research Articles

Do Larger Pollinators Have Higher Pollination Efficiency for the Generalized Pollination Plant Hibiscus mutabilis?

To understand the reproductive strategies of the typically introduced plant Hibiscus mutabilis and to compare the pollination efficiency of its different pollinators, we observed, measured, and recorded the flowering dynamics, floral traits, and visiting insects of H. mutabilis. Furthermore, we compared the body size, visitation rate, and pollination efficiency of the pollination insects of H. mutabilis. The results indicated that, despite exhibiting specialized moth pollination characteristics based on similarities in flower features to other moth-pollinated species, H. mutabilis actually presented a generalized pollination system. The nectar of H. mutabilis attracted a variety of insects to provide pollination services, a total of five flower visitors, one moth species (Macroglossum pyrrhosticta), and four bee species (Xylocopa appendiculata, Xylocopa dissimilis, Bombus breviceps, and Apis mellifera), were found to provide pollination services for H. mutabilis. The pollination efficiency of these pollinators was related to the parts of their body in contact with the stamens and stigmas of flowers. Although M. pyrrhosticta was larger in size and its visitation frequency in our field observations was higher, its pollination efficiency was lower. This was due to the small part of its body (proboscis) contacting the two sexual organs of H. mutabilis while visiting flowers, resulting in a low amount of pollen being transferred and deposited. In contrast, the bee pollinators’ proboscis was significantly shorter than that of M. pyrrhosticta, and it must enter the flower to suck the nectar that is hidden deeply inside the base of the flower. Therefore, the body parts of bee pollinators in contact with the two sexual organs of H. mutabilis were larger than M. pyrrhosticta in the process of visiting flowers, and the pollination efficiencies were significantly higher than those of M. pyrrhosticta. In addition, larger bee pollinators have higher pollination efficiency. As a result, H. mutabilis suffered from pollen limitation due to the pollination efficiencies of the moth pollinators in the introduced habitats, but it compensated by attracting more species of bee pollinators.

Saliciylic Acid is also Effective Along with Abscisic Acid and Gibberellic Acid in the Orchid Post-Pollination Process

The aim of this study is to determine the endogenous hormone activities of abscisic acid (ABA), Jasmonic acid (JA) and Salicylic acid (SA) in compatible (Intraspecific = ISP) and incompatible pollination (Intergeneric = IGP) in stigmatic ovaries during orchid post-pollination process. It was designed to be Himantoglossum robertianum in ISP experiments and Himantoglossum robertianum and Orchis italica in IGP experiments. Polynariums taken from O. italica have been applied with needles to the flower stigmas of H. robertianum. Ovaries with stigma from both pollination types were taken separately for each day for a total of 10 days and quantitative endogenous hormone analyzes have been performed by LC-MS/MS. After all, SA hormone has been detected for the first time in both ISP and IGP, but only ISP values were significant. The statistical analysis revealed that while SA is significant in only ISP, ABA values were found to be highly significant in both ISP and IGP. ISP9 also showed high significance. Additionally, ABA values were generally higher than SA values, especially in IGP experiments. The results also emphasized the importance of ovarian endogenous hormone activities for the first time. JA was not detected in the analysis.

Biological characteristics of flowers and examination of pollen viability at different developmental stages of Epimedium sagittatum (Sieb. et Zucc.) Maxim

To gain a deeper understanding of the flowering pattern and reproductive characteristics of Epimedium sagittatum, to enrich the research on the flower development of E. sagittatum and its reproductive regulation, and to screen the methods suitable for the rapid detection of pollen viability of E. sagittatum and to promote its cross-breeding. The characteristics of its flower parts were observed, recorded and measured, and the pollen viability of E. sagittatumwas determined by five methods, including TTC staining, I2-KI staining, red ink staining, peroxidase method and in vitro germination method. The flowering process of E. sagittatum can be divided into five stages: calyx dehiscence, bract spathe, petal outgrowth, pollen dispersal, and pollination and withering. The results of I2-KI staining and peroxidase method were significantly higher than those of other methods; the in vitro germination method was intuitive and accurate, but the operation was complicated and time-consuming; the red ink staining method was easy to operate and had obvious staining effect, and the results were the closest to those of the in vitro germination method; and it was found that the pollen of E. sagittatum was not as effective as the in vitro germination method at the bud stamen stage, the flower stigma and the flower bud. It was also found that the pollen viability and germination rate of E. sagittatum pollen were higher in the three periods of bud spitting, petal adductor and pollen dispersal. Comparing the five methods, the red ink staining method was found to be a better method for the rapid detection of pollen viability; the best pollination periods of E. sagittatum were the bud stamen stage, petal adductor stage, and pollen dispersal stage of flowers at the peak of bloom. This study on the flowering and fruiting pattern of E. sagittatum, and the related mechanism of sexual reproduction, can be used as a reference for the next step of research on the breeding of E. sagittatum.

Synthesis of aspartic acid and tyrosine by the fire blight pathogen Erwinia amylovora is not required for proliferation on apple flower stigmas or virulence in fruitlets.

The Gram-negative bacterium Erwinia amylovora (Ea) is the causal agent of fire blight, a devastating disease of apples and pears. In the fire blight disease cycle, Ea grows in different plant tissues, each presenting a distinct nutrient environment. Here, we investigate the ability of aspartate and tyrosine double auxotroph Ea lines to proliferate on apple flower stigma surfaces representing the epiphytic growth stage of Ea and in developing fruitlets representing one endophytic growth stage of Ea. Heterologous complementation studies in an Escherichia coli aspartate and tyrosine auxotroph verify that Ea aspartate aminotransferase (AspC) and tyrosine aminotransferase (TyrB) act as aspartate and tyrosine amino transferases. Growth analysis reveals that Ea aspC tyrB mutants multiply to near-wild-type levels on apple flower stigmas and immature fruitlets. Ea AspC and TyrB are reciprocally complementing for aspartate and tyrosine synthesis in Ec and in Ea. Ea aspC and tyrB mutants obtain sufficient aspartate and tyrosine to support multiplication on stigma surfaces and virulence in immature fruitlets.

Managed honeybee hives negatively affect the reproduction of native plants in a dryland nature reserve

Abstract The honeybee, Apis mellifera, stands out for its positive image due to its contribution to crop pollination and honey production, which facilitated its widespread distribution. However, large apiaries resulting in high honeybee densities could increase pollination frequency while increasing competition for floral resources, ultimately affecting native plant fitness. We studied the impact of managed honeybee hives on pollination and reproductive success of native plants in Villavicencio Nature Reserve, Mendoza, Argentina. During the flowering peak, we studied pollination and reproduction of three native plant species (Larrea divaricata, L. cuneifolia and Zuccagnia punctata) near and far from the hives. We estimated pollen deposition on flower stigmas, pollen tubes developed in flower pistils, fruit set, seed set and seed viability. We found that the honeybee hives had a positive effect on the reproduction of the self‐compatible species, L. divaricata. For the self‐incompatible species, results differed among species: Hives had positive effects on the pollination and negative effects on the reproduction of L. cuneifolia, while they had negative effects on the reproduction of Z. punctata. Synthesis and applications. Beekeeping is increasingly turning to natural areas in search of better quality honey; however, increased honeybee abundance in the field could influence the reproduction of native plants. Our results show that the introduction of managed hives negatively affected the reproduction of self‐incompatible native plants. This result allows us to make several recommendations for conservation and management actions concerning beekeeping in natural areas, regarding the among‐year rotation of the location of hives, the number of hives per site, and the need to monitor the reproduction of self‐incompatible species.

Asymmetrical disassortative pollination mediated by long-/short-tongued pollinators in a distylous Limonium myrianthum (Plumbaginaceae) with a short corolla tubular small flower.

In heterostylous plants, short-tongued pollinators are often ineffective/inefficient owing to the limitations imposed by a long corolla tube. However, it is unclear how disassortative pollen transfer is achieved in small flowers. We investigated the pollination pattern and floral morph variation by analyzing heterostylous syndrome, pollinator groups, and pollen deposition after a single visitation in two Limonium myrianthum populations with short-corolla-tubular small flowers. The predominant pollinators in the Hutubi population were pollen-seeking short-tongued syrphids, which can only transfer pollen between high-level sexual organs. In the Xishan population, nectar-seeking short-tongued insects were efficient pollinators with symmetrical disassortative pollen transfer between high- and low-level sexual organs, whereas long-tongued pollinators had a low efficiency between high-level sexual organs due to the low contact probability with the stigma of long-styled flowers (L-morph), which no longer offered the same advantage observed in tubular flowers. Asymmetrical disassortative pollination may cause the female fitness of short-styled (S-morph) individuals in the Hutubi and L-morph individuals in the Xishan population to suffer greater selection pressure and exhibit a higher degree of floral morph variation. Limonium myrianthum exhibits an unusual pollination pattern in which the small flowers with short corolla tubes make it possible for short-tongued insects to become effective pollinators. However, factors such as the position of stigma-anther within the flower, pollinator species and their preference further caused asymmetrical disassortative pollen transfer. Therefore, more factors should be considered when evaluating the effectiveness of short- and long-tongued insects in pollination service.

Describing heterostyly, pollen, and sexual organ reciprocity in Rourea chrysomalla (Connaraceae), a rare and threatened species from the Brazilian Cerrado

Rourea chrysomalla is a rare and endemic plant species from the Brazilian Cerrado, presumably threatened and lacking records within conservation units. In this study, we recorded and characterized, for the first time, the floral and pollen dimorphism, as well as the reciprocity of sexual organs among different morphs of R. chrysomalla. For this purpose, fertile individuals were observed over three years in two natural populations and supplemented by herbarium data. This species is distylous and distinctly exhibits two types of flowers, each characterized by stamens arranged in two whorls of unequal lengths: L-styled and S-styled morphs, both occuring in similar proportions in the two populations. Cross-pollination among anthers of any stamen whorl in L-styled flowers and stigmas in S-styled flowers is more precise in the two morphs, while anthers in S-styled flowers are less reciprocal with the stigmas in L-styled flowers. S-styled flowers exhibit larger pollen grains compared to L-styled flowers, with no differences between the two whorls of stamens. The balanced proportion of floral morphs provides equal opportunities for pollen donation and reception, and reciprocity between morphs is essential for the conservation of R. chrysomalla due to its limited distribution and low population density in the central Brazilian savanna.

Cell wall invertase 3 plays critical roles in providing sugars during pollination and fertilization in cucumber.

In plants, pollen-pistil interactions during pollination and fertilization mediate pollen hydration and germination, pollen tube growth, and seed set and development. Cell wall invertases (CWINs) help provide the carbohydrates for pollen development; however, their roles in pollination and fertilization have not been well established. In cucumber (Cucumis sativus), CsCWIN3 showed the highest expression in flowers, and we further examined CsCWIN3 for functions during pollination to seed set. Both CsCWIN3 transcript and CsCWIN3 protein exhibited similar expression patterns in the sepals, petals, stamen filaments, anther tapetum, and pollen of male flowers, as well as in the stigma, style, transmitting tract, and ovule funiculus of female flowers. Notably, repression of CsCWIN3 in cucumber did not affect the formation of parthenocarpic fruit but resulted in an arrested growth of stigma integuments in female flowers and a partially delayed dehiscence of anthers with decreased pollen viability in male flowers. Consequently, the pollen tube grew poorly in the gynoecia after pollination. In addition, CsCWIN3-RNA interference plants also showed affected seed development. Considering that sugar transporters could function in cucumber fecundity, we highlight the role of CsCWIN3 and a potential close collaboration between CWIN and sugar transporters in these processes. Overall, we used molecular and physiological analyses to determine the CsCWIN3-mediated metabolism during pollen formation, pollen tube growth, and plant fecundity. CsCWIN3 has essential roles from pollination and fertilization to seed set but not parthenocarpic fruit development in cucumber.

Inter-species interactions between two bacterial flower commensals and a floral pathogen reduce disease incidence and alter pathogen activity.

Fire blight, caused by Erwinia amylovora, is one of the most important plant diseases of pome fruits. Previous work largely suggested plant microbiota commensals suppressed disease by antagonizing pathogen growth. However, inter-species interactions of multiple flower commensals and their influence on pathogen activity and behavior have not been well studied. Here, we show that co-inoculating two bacterial strains that naturally colonize the apple flowers reduces disease incidence. We further demonstrate that the interactions between these two microbiota commensals and the floral pathogen led to the emergence of new gene expression patterns and a strong alteration of the external pH, factors that may modify the pathogen's behavior. Our findings emphasize the critical role of emergent properties mediated by inter-species interactions between plant microbiota and plant pathogens and their impact on plant health.

Influence of naphthalene acetic acid on aborted okra growth, bioactive compound and minerals

The study was conducted to evaluate the effect of different concentrations of NAA (naphthalene acetic acid) on seedless okra production, vitamin C, carotenoids, flavonoids, antioxidants (DPPH), phenolic, and mineral content. The micro-syringe injection in flower stigma was an innovative method of application and was used in this experiment rather than spray as a common and traditional method. The flower stigma injection method was applied on the flower stigma after the anthesis of the flower of the okra plant using NAA at different concentrations. The lowest concentration (25 mg/l) of NAA greatly increased the pod setting compared to the higher concentrations and control. NAA application at 25 and 50 mg/l concentrations induced higher values of pod length, diameter, size, weight, ascorbic acid (vitamin C), and soluble solid content over the control. The chlorophyll content in leaves was affected significantly by different concentrations of NAA. It was found that 25 and 50 mg/l concentrations of NAA significantly increased chlorophyll content, fiber, moisture, flavonoid, carotenoid, antioxidant (DPPH), minerals and phenolic content compared to the other concentrations and control. In addition to that control and 25 mg/l concentrations of NAA, had increased the production of healthy seeds compared to the 50 and 100 mg/l. Moreover, 50 and 100mg/l of concentrations showed higher aborted seed (seedless) than the other concentration and control. Therefore, it seems that 25 mg/l is the best concentration for pod growth and development as well as 100mg/l is the best for seedless okra production.

Non-flying mammal pollination in Massonia grandiflora

Pollination by small non-flying mammals occurs in Africa, Australia, Asia and the Neotropics. One hotspot is in the winter rainfall zone of the Cape Floral Region of South Africa. This phenomenon is known for a handful of plant lineages, of which one comprises geoflorous monocots including the tribe Hyacintheae of the Asparagaceae. Small mammal pollination has been documented for four members of the Hyacintheae. A further representative of this taxon, Massonia grandiflora, is hypothesized to be pollinated by small mammals as it shares floral characters with other plants adapted to small mammal pollinators. The study aims at the identification of the pollinators and the characterisation of the floral features of M. grandiflora as well as to experimentally test whether the plants’ nectar scent is an attractant to the flower visitors. With direct observations and video monitoring, we demonstrate the fitting between the head of elephant-shrews and rodents and the bowl-shaped flowers with protruding stigmas and styles as well as pollen transfer from the plants’ anthers on the animals’ body parts that made contact with the stigma. We experimentally show the transfer of pollen surrogates by elephant-shrews and rodents from the anthers via the animals’ fur onto the stigmas of conspecific flowers. Pollen loads on the animals’ snout and in their faeces represent indirect evidence for flower visits. Insects and birds were not observed as nectar consumers. Choice tests revealed that mice and elephant-shrews are attracted by nectar scent. We conclude that the fragrant nectar attracts mice and elephant-shrews as pollinators, whereas its bitterness and viscosity as well as the flowers’ visual crypsis might filter out insects (and birds) as less effective pollinators.

Heteromorphism of normal and abnormal flowers of date palm cv. “Barhee” and comparison of green and red Ghanami pollens as dominant pollen

A major limitation to the use of tissue culture techniques for propagating date palms cv. "Barhee" is the production of plants with abnormal phenotypes (low fruit set and multi-carple fruits) as a result of somaclonal diversity. In addition, pollination with specific of male date palm pollen results in better fruit set and thus higher fruit production. So, this study was conducted to compare the anatomical and morphological characteristics, investigate the possible abnormalities of off-shoot and tissue culture-derived trees, and compare the pollen grain characteristics of Green Ghanami and Red Ghanami male date palm cultivars as the dominant Pollinator of "Barhee" during the growing season of 2019–2020 at Date palm and Tropical Research Center and Shahid Chamran Univeristy of Ahvaz, Iran. This experiment was laid out as a randomized complete blocks design with nine replications. The results revealed that the pollen grain of Green Ghanami had higher polar and equatorial axis than those of Red Ghanami, while the P/E ratio index and inter-edge distance of pollen grains of Red Ghanami were significantly higher than those of Green Ghanami. On the other hand, off-shoot-derived trees of cv. "Barhee" had larger flowers with lower flower density per strand than the tissue culture-derived trees. The stigma characteristics of the upper and lower flowers strands of the offshoot-derived trees were similar to each other and had three completely intact stigmas capable of receiving pollen grains. In tissue culture-derived trees, the lower flowers of the strand had wrinkled and dried stigmas, whereas the three stigmas of the upper flowers were completely undamaged. In addition, the flower of the tissue culture-derived trees had three carpels, one of which had an ovary with an aborted egg. In contrast, in the flower of off shoot-derived trees, only one carpel had a healthy ovary and the other two carpels were without ovaries and degenerated.Generally, it can be concluded that heteromorphic self-incompatibility and abnormality of the atypical flower stigma of tissue culture-derived trees cause the pollen grain not to germinate and grow inside the style.

Discovery of microRNAs in Pyrus stigma exudates opens new research avenues in Horticulture.

In many plant species, flower stigma secretions are important in early stages of sexual reproduction. Previous chemical analysis and proteomic characterization of these exudates provided insights into their biological function. Nevertheless, the presence of nucleic acids in the stigma exudates has not been previously reported. Here, we studied the stigma exudates of Pyrus communis, Pyrus pyrifolia, and Pyrus syriaca and showed them to harbor extracellular RNAs of various sizes. RNA sequencing revealed, for the first time, the presence of known Rosaceae mature microRNAs (miRs), also abundant in the stigma source tissue. Predicted targets of the exudate miRs in the Arabidopsis thaliana genome include genes involved in various biological processes. Several of these genes are pollen transcribed, suggesting possible involvement of exudate miRs in transcriptional regulation of the pollen. Moreover, extracellular miRs can potentially act across kingdoms and target genes of stigma interacting organisms/microorganisms, thus opening novel applicative avenues in Horticulture.

Stigmas of holoparasitic Phelipanche arenaria (Orobanchaceae) – a suitable ephemeric flower habitat for development unique microbiome

BackgroundMicrobial communities have occasionally been observed in part of the ephemeric reproductive structure of floral stigmas, but their prevalence, phylogenetic diversity and ecological roles are understudied. This report describes the first study of bacterial and fungal communities in immature and mature stigma tissue of the endangered holoparasitic plant Phelipanche arenaria. Culture-dependent methods coupled with next-generation sequencing indicated that a small surface of the flower stigma was an unexpectedly rich and diverse microhabitat for colonization of microbial. We also compared the enzymatic activity of the bacterial communities between immature and mature stigmas samples.ResultsUsing high-throughput sequencing methods, we identified and classified 39 to over 51 OTUs per sample for bacterial OTUs represented by Pantoea agglomerans and P. ananatis, comprising 50.6%, followed by Pseudomonas, Luteibacter spp., Sphingomonas spp. with 17% of total frequency. The bacterial profile of immature stigmas of P. arenaria contained unique microorganisms (21 of the most numerous OTUs) that were not confirmed in mature stigmas. However, the enzymatic activity of bacteria in mature stigmas of P. arenaria showed more activity than observed in immature stigmas. In the fungal profile, we recorded even 80 OTUs in mature stigmas, consisting of Capnodiales 45.03% of the total abundance with 28.27% of frequency was created by Alternaria eichhorniae (10.55%), Mycosphaerella tassiana (9.69%), and Aureobasidium pullulans (8.03%). Additionally, numerous putative plant growth-promoting bacteria, fungal pathogens and pathogen-antagonistic yeasts were also detected.ConclusionsOur study uncovered that P. arenaria stigmas host diverse bacterial and fungal communities. These microorganisms are well known and have been described as beneficial for biotechnological and environmental applications (e.g., production of different enzymes and antimicrobial compounds). This research provided valuable insight into the parasitic plant–microbe interactions.

Detection of botanical adulterants in saffron powder

Saffron is a unique spice obtained by drying stigmas of saffron flowers (Crocus sativus L.). Due to its high price, economically motivated adulteration occurs relatively often. The presented study aimed to develop an effective strategy for the detection of the following potential botanical adulterants used for a saffron substitution or dilution: safflower (Carthamus tinctorius L.), calendula (Calendula officinalis L.), turmeric (Curcuma longa L.), achiote (Bixa orellana L.), red pepper (Capsicum spp.), mountain arnica (Arnica montana L.), beet (Beta vulgaris L.), and pomegranate (Punica granatum L.). A non-target screening strategy based on ultra-high performance reverse-phase liquid chromatography coupled to tandem high-resolution mass spectrometry (UHPLC-HRMS/MS) was employed for the analysis of an aqueous ethanol plant extract. By using multivariate statistical methods, principal components analysis (PCA), and partial least squares discriminant analysis (PLS-DA), for processing the generated “chemical fingerprints,” metabolites unique to the investigated plants could be identified. To enable routine saffron authenticity control by target screening, an internal spectral database was developed; currently, it involves 82 unique markers. In this way, the detection addition as low as 1% (w/w) of all analyzed botanical adulterants in admixture with saffron was possible. The developed method was used to control 7 saffron powder samples from the Czech market, and none of the monitored adulterants were confirmed.

Adaptive function of duodichogamy: Why do chestnut trees have two pollen emission phases?

Intersexual mating facilitation in flowering plants has been largely underexplored. Duodichogamy is a rare flowering system in which individual plants flower in the sequence male-female-male. We studied the adaptive advantages of this flowering system using chestnuts (Castanea spp., Fagaceae) as models. These insect-pollinated trees produce many unisexual male catkins responsible for a first staminate phase and a few bisexual catkins responsible for a second staminate phase. We hypothesized that duodichogamy increases female mating success by facilitating pollen deposition on stigmas of the rewardless female flowers through their proximity with attractive male flowers responsible for the minor staminate phase. We monitored insect visits to 11 chestnut trees during the entire flowering period and explored reproductive traits of all known duodichogamous species using published evidence. In chestnuts, insects visited trees more frequently during the first staminate phase but visited female flowers more frequently during the second staminate phase. All 21 animal-pollinated duodichogamous species identified are mass-flowering woody plants at high risk of self-pollination. In 20 of 21 cases, gynoecia (female flower parts) are located close to androecia (male flower parts), typically those responsible for the second minor staminate phase, whereas androecia are often distant from gynoecia. Our results suggest that duodichogamy increases female mating success by facilitating pollen deposition on stigmas by means of the attractiveness of the associated male flowers while effectively limiting self-pollination.

Divergent responses of generalist and specialist pollinators to experimental drought: Outcomes for plant reproduction.

Drought is an increasingly important consequence of climate change. Drought often causes plants to alter patterns of resource allocation, which in turn can affect how plants interact with other species. How these altered interactions subsequently influence plant reproductive success remains incompletely understood and may depend on the degree of specialization exhibited by antagonists and mutualists. Specialist pollinators, for example, are dependent on floral resources from their obligate hosts and under drought conditions may thus indiscriminately visit these hosts (at least in certain circumstances). Generalist pollinators, in contrast, may only forage on host plants in good condition, given that they can forage on other plant species. We tested this hypothesis and its consequences for plant reproduction in squash (Cucurbita pepo) grown along an experimental moisture gradient ranging from dry (growth and flowering compromised) to wet conditions. Floral visitation increased with plant soil moisture for generalist honey bees but was independent of plant soil moisture for specialist squash bees. Pollen production increased with plant soil moisture, and fluorescent pigments placed on flowers revealed that pollinators primarily moved pollen from male flowers on well-watered plants to the stigmas of female flowers on well-watered plants. Seed set increased with increasing plant soil moisture but, notably, was higher in bee-pollinated plants compared to plants pollinated by hand with an even mix of pollen from plants grown at either end of the experimental moisture gradient. These results suggest that superior pollen rewards, perhaps combined with selective foraging by generalists, enhanced reproductive success in C. pepo when plant soil moisture was high and more generally illustrate that pollinator behavior may contribute to how drought conditions affect plant reproduction.

Underutilized Crocus Sativus L. Flowers: A Hidden Source of Sustainable High Value-Added Ingredients

Crocus sativus L. is used as a spice due to its organoleptic characteristics. Only flower stigmas are used for its production, as the rest of the flower is discarded as waste. This fact represents a lack of sustainability, since around 230,000 flowers are necessary to produce 1 kg of saffron. The main aim of this study was to contribute to the valorization of Crocus sativus L. spice and its floral by-products, through the study of their nutritional value and composition, in terms of hydrophilic and lipophilic compounds, as well as their functional properties. The results showed that saffron stigmas and floral bio-residues presented high contents of fiber, and the most abundant macronutrient were the carbohydrates, followed by proteins, and a low content in fats. All samples had high concentrations of glucose, fructose, lactic and malic acids, and minerals, mainly K, Ca and Mg. Furthermore, the polyunsaturated fatty acids were predominant, being linoleic acid (C18:2n6) the most abundant. Therefore, this research provides more in-depth information about the composition of saffron stigmas and floral by-products, to be considered as promising sources for the development of functional ingredients with new applications in the food industry.

Study on pollen viability and stigma receptivity throughout the flowering period in the selected taxa of the Gesneriaceae family

ABSTRACT Plants in the Gesneriaceae family are appreciated for their decorative leaves and flowers, ease of cultivation, and shade tolerance. Sexual hybridisation has long been carried out for producing novel hybrids. However, scientific knowledge is lacking on the correct timing of pollination in this family. This study was conducted to elucidate the optimal timing for pollination by screening pollen viability and stigma receptivity throughout the flowering period in eight gesneriad taxa. Pollen viability was evaluated by the in vitro germination test and stigma receptivity was based on stigma morphology and pistil length. The flowering duration varied from 10 days in Alsobia to 18 days in Streptocarpus. While the pollens of Episcia, Kohleria, Saintpaulia, Sinningia, and Smithiantha had totally lost viability 2–5 days before the flowers withered, a slightly contrasting situation was observed in the cases of Alsobia, Deinostigma, and Streptocarpus, where a small portion of pollen grains remained viable towards the end of the flowering period. The highest pollen germination rate was recorded from 1 day in Alsobia, Episcia, and Kohleria, to 9 days in Deinostigma. The reduction in pollen germination was rapid in Alsobia, Saintpaulia, and Smithiantha, and moderate in the remaining taxa. The greatest pollen tube growth occurred at 1–3 days after flower opening and decreased rapidly in all the taxa tested. The longest pistil of 2.03–3.50 cm was observed at 3–8 days of anthesis depending on the plant tested. The findings in this study suggest that higher pollination success may be achieved using pollen grains of newly opened flowers and stigmas of mature flowers in this family.

Parallel developments in floral adaptations to obligate moth pollination mutualism in tribe Phyllantheae (Phyllanthaceae).

Several groups within tribe Phyllantheae (Phyllanthaceae) formed, independently, an (obligate) pollination mutualism with Epicephala moths, which originally had been parasitic. In this pollination system, female moths actively collect pollen from staminate flowers and deposit it on the stigma of pistillate flowers, after which they place at least one egg in or against the ovary. The high pollination rate makes the system beneficial for the plants, whereas the larvae are provided with food (part of the developing seeds) and some protection against predation. Qualitative comparisons are made between non-moth-pollinated lineages, used as outgroups and various, independently moth-pollinated Phyllantheae clades, used as ingroups, thereby looking for parallel developments. The flowers of both sexes of various groups display similar, convergent morphological adaptations to the pollination system, likely to secure the obligate relationship and to improve efficiency. Sepals in both sexes, free or partly to highly connate, are commonly upright and form a narrow tube. The staminate flowers often have united, vertical stamens with the anthers along the androphore or on top of the androphore. Pistillate flowers generally reduce the stigmatic surface, either by making the stigmas shorter or by uniting them into a cone with a small opening at the top for pollen deposition. Less obvious is the reduction of the stigmatic papillae; these are often present in non-moth-pollinated taxa, but absent in the moth-pollinated species. The most diverging, parallel adaptations to moth pollination are currently found in the Palaeotropics, whereas in the Neotropics, some groups continue to also be pollinated by other insect groups and are morphologically less changed.