Flowers Of Different Species Research Articles

Ornamental plants as vectors of pesticide exposure and potential threat to biodiversity and human health

The production of conventional ornamental plants is pesticide-intensive. We investigated whether pesticide active ingredients (AIs) are still present in ornamentals at the time of purchase and assessed their potential ecotoxicity to non-target organisms. We purchased 1000 pot plants and 237 cut flowers of different species from garden centers in Austria and Germany between 2011 and 2021 and analyzed them for up to 646 AIs. Ecotoxicological risks of AIs were assessed by calculating toxic loads for honeybees (Apis mellifera), earthworms (Eisenia fetida), birds (Passer domesticus), and mammals (Rattus norvegicus) based on the LD50 values of the detected AIs. Human health risks of AIs were assessed on the basis of the hazard statements of the Globally Harmonized System. Over the years, a total of 202 AIs were detected in pot plants and 128 AIs in cut flowers. Pesticide residues were found in 94% of pot plants and 97% of cut flowers, with cut flowers containing about twice as many AIs (11.0 ± 6.2 AIs) as pot plants (5.8 ± 4.0 AIs). Fungicides and insecticides were found most frequently. The ecotoxicity assessment showed that 47% of the AIs in pot plants and 63% of the AIs in cut flowers were moderately toxic to the considered non-target organisms. AIs found were mainly toxic to honeybees; their toxicity to earthworms, birds, and mammals was about 105 times lower. Remarkably, 39% of the plants labeled as “bee-friendly” contained AIs that were toxic to bees. More than 40% of pot plants and 72% of cut flowers contained AIs classified as harmful to human health. These results suggest that ornamental plants are vectors for potential pesticide exposure of consumers and non-target organisms in home gardens.

An Efficient Workflow for Quality Control Marker Screening and Metabolite Discovery in Dietary Herbs by LC-Orbitrap-MS/MS and Chemometric Methods: A Case Study of Chrysanthemum Flowers.

LC-MS is widely utilized in identifying and tracing plant-derived food varieties but quality control markers screening and accurate identification remain challenging. The adulteration and confusion of Chrysanthemum flowers highlight the need for robust quality control markers. This study established an efficient workflow by integrating UHPLC-Orbitrap-MS/MS with Compound Discoverer and chemometrics. This workflow enabled the systematic screening of 21 markers from 10,540 molecular features, which effectively discriminated Chrysanthemum flowers of different species and cultivars. The workflow incorporated targeted and untargeted methods by employing diagnostic product ions, fragmentation patterns, mzCloud, mzVault, and in-house databases to identify 206 compounds in the flowers, including 17 screened markers. This approach improved identification accuracy by reducing false positives, eliminating in-source fragmentation interference, and incorporating partial verification utilizing our established compound bank. Practically, this workflow can be instrumental in quality control, geolocation determination, and varietal tracing of Chrysanthemum flowers, offering prospective use in other plant-derived foods.

Flowering phenology of species with similar flower colours in species-rich communities

Within a community, co-occurring plant species are expected to diverge in floral display or flowering phenology to decrease interspecific competition and thus increase intraspecific pollination. However, co-occurring species can also benefit from floral signal standardisation (similar colour signals among flowers of different species) because it facilitates pollinator attraction. Considering the interaction of flower colour display and flowering phenology, we investigated the visual similarity of rewarding flowers among species from highly diverse tropical and temperate vegetation types. For six groups of co-occurring, closely related bee-pollinated species with similar floral displays from Brazilian campo rupestre (51 species) and Spanish Mediterranean vegetation (30 species), we first investigated whether flower colours can be discriminated by bees based on colour locus distance in the bee vision hexagon. We then tested whether flowering phenology overlapped or was segregated. We found that within both vegetation regions, flower colour was generally not distinguishable within groups by bees. The small perceptual distance of colour loci in the bee visual space did not enable discrimination. The flowering periods of the Mediterranean species overlapped, while the Brazilian campo rupestre species tended to have segregated phenologies. Mediterranean species may benefit from the increased standardisation of signals displayed during the short flowering season, while the sequential flowering phenology of campo rupestre species may decrease interspecific competition and help maintain a recognizable signal for bees over time, favouring flower constancy. We concluded that the standardisation of the floral colour signal within these two species-rich plant communities is advantageous for most of the species studied, despite having different flowering phenologies.

The Tulip, Elagance in Stone: An Evaluation on Its Usage on Mosque Decoration (14-18. Centuries)

Türk kültüründe çiçeklere duyulan sevginin İslâmiyet öncesi dönemlerden başlayarak günümüze değin hiç kesintiye uğramadan hatta üzerine koyarak ulaştığı görülür. Özellikle 16. yüzyıldan itibaren bu ilginin sadece çiçek merakı ve sevgisinin ötesine geçip başta sanat dalları olmak üzere birçok alanda somutlaşması, günümüze yüklü bir mirasın ulaşmasına vesile olmuştur. Farklı cinsten birçok çiçeğin bu sevgiden payını aldığı muhakkaktır. Ancak bunların arasında lâlenin ayrıcalıklı bir yerinin olduğunu söylemek gerekir. Roma ve Bizans dönemlerinde bilinmeyen lâlenin Anadolu’ya 12. yüzyılda Türklerle beraber girdiği kabul edilir. Türklerin Anadolu öncesindeki kadim kültürlerinin bir parçası olan lâle, bu coğrafyada yaygınlaşmış, sanattan edebiyata birçok alanda vazgeçilmez motiflerden birisi haline gelmiştir. Lâlenin yaygın olarak kullanıldığı alanlardan birisi mimari süslemedir. Lâle Devri’nde çeşme ve sebiller başta olmak üzere sivil eserlerin taş tezyînâtında yaygın bir biçimde kullanılan lâle, camilerinin taş süslemelerinde ne düzeyde yer almıştır. Makalemiz bu sorunun cevabına yönelik ele alınmıştır. Lâle motifinin camilerin taş süslemesinde kullanımını kronolojik bir düzenle verilmiş böylelikle, 18. yüzyıl camilerinin taş tezyînâtında yaygın olarak karşılaşılan lâle motifinin önceki yüzyıllarda kullanım oranı ortaya koyulmaya çalışılmıştır.

Characterization of an APETALA1 and a FRUITFUL-like homolog in chrysanthemum

MADS box transcription factors encoded by APETALA1/FRUITFUL (AP1/FUL-like) genes are key regulators of flowering in angiosperms. Here, two such genes were isolated from the ornamental species Chrysanthemum morifolium cultivar ‘Jinba’. One of the genes (CmAP1L1) was shown to belong to the AP1 clade, and the other (CmFL2) to the FUL clade. Despite their phylogenetic difference, their transcriptional behavior was similar: in plants prior to flowering, both genes were strongly transcribed in the leaves, while in plants which had reached the reproductive stage, their transcription was most abundant in young buds (2–4 mm in diameter) and was at only a low level in the mature inflorescence. Both proteins were localized in the nucleus as well as in the cell membrane. Their over-expression in both cases accelerated flowering, which was also the case when they were constitutively expressed in Arabidopsis thaliana. While the transcription of CmAP1L1 followed an atypical circadian rhythm, that of CmFL2 was arrhythmic. This work suggested that the AP1/FUL-like genes might play a conserved function in promoting flowering in different species.

Biological Waste Management in the Case of a Pandemic Emergency and Other Natural Disasters. Determination of Bioenergy Production from Floricultural Waste and Modeling of Methane Production Using Deep Neural Modeling Methods

In relation to the situation caused by the pandemic, which may also take place in the future, there is a need to find effective solutions to improve the economic situation of the floristry industry. The production and sale of flowers is time-consuming and long-term. Therefore, any information that causes the impossibility of selling the plants will result in a reduction of profitability or bankruptcy of such companies. Research on rationally utilizing biowaste from plant cultivation as well as unsold flowers for environmental protection and effective use of their potential as a raw material for bioenergy production were examined in this article. The aim of this study was to analyze the energetic potential of the biodegradable fraction of waste from floriculture. The trials included floricultural waste containing the stems, leaves and flowers of different species and hybrid tulips (Tulipa L.), roses (Rosa L.), sunflowers (Helianthus L.) and chrysanthemums (Dendranthema Des Moul.). Their biogas and methane production as well as heat of combustion were determined experimentally. The calorific value was calculated on the basis of results from selected floricultural waste and its chemical composition. The biogas production was tested on different levels of plant material fragmentation (chaff, macerate) in fermentation processes with two ranges of temperature (meso- and thermophilic fermentation). The presented results show that the highest calorific values were determined for dry stems of roses (18,520 kJ/kg) and sunflowers (18,030 kJ/kg). In turn, the lowest were obtained for dried chrysanthemums and tulips, for which the heating value reached 15,560 kJ/kg and 15,210 kJ/kg. In addition, based on one ton of the fresh mass of biowaste from floriculture, the largest biogas production including the control was obtained from the chrysanthemum chaff by mesophilic anaerobic digestion. Moreover, the largest volume of methane was received by thermophilic anaerobic digestion of roses. The highest content of biomethane (56.68%) was reached by thermophilic fermentation of roses. The energy production of the analyzed substrates was also calculated, based on the amount of biogas produced in the containers for anaerobic digestion. Additionally, a deep neural network model, which predicted the production of methane gas, was created. Owing to the properties of the network, the level of significance of variables used for modelling and prediction of biogas production was determined. The neural modelling process was carried out with the use of the H2O program.

The embryo sac development of Manfreda elongata (Asparagaceae)

Manfreda Salisb. belongs to the Asparagaceae family and is a genus of a high ornamental potential due to the beauty and varied morphology of its leaves, as well as it provides flowers of different species throughout the year. In spite of its economic relevance, little is known about its sexual reproduction. This work aimed to characterize the female gametophyte development of Manfreda elongata through a stain-clearing technique of whole ovules and then analyzed by confocal microscopy. The female gametophyte development of M. elongata is of the monosporic Polygonum-type. The megaspore mother cell of M. elongata contains a dense and prominent nucleus, and at megasporogenesis, when meiosis II is completed, linear and T-shaped tetrads of megaspores were observed. Of this, only the megaspore closest to the chalaza remains functional. In the process of megagametogenesis, three rounds of free nuclear mitosis produced an eight-nuclei embryo sac. At maturity, a seven-celled embryo sac is formed by an egg apparatus (egg cell and two synergids) at the micropylar end, a central cell (with a diploid nucleus resulted from the fusion of the two polar nuclei). Thus, at the end of its formation, the female gametophyte development of M. elongata is of the monosporic, Polygonum-type.

HONEY CROP ESTIMATION FROM SPACE: DETECTION OF LARGE FLOWERING EVENTS IN WESTERN AUSTRALIAN FORESTS

Abstract. Recent studies have shown that in the spectral space there is often a better spectral separation between leaves and flowers and even between flowers of different species than between leaves of different species. In this study we assess the ability of satellite remotely sensed data to detect the flowering of Red Gum trees (Corymbia calophylla) in Western Australia, the state’s largest annual honey crop. Spectroradiometer measurements of flowers, leaves and groundcover from Red Gum forests were subjected to ANOVA analysis, which showed that flowers are spectrally different to their environment for 92 % of the wavelengths between 350 nm and 1800 nm. A more detailed assessment, using the JM Distance calculation, showed that the spectra can be reliably separated using 10 % of the wavelengths, with peak separation between 518 nm and 557 nm. To assess the ability of satellite-borne sensors to detect the presence of flowers, the spectroradiometer data were convolved with satellite instruments’ response curves to create synthetic remotely sensed datasets on which JM Distance analysis was performed. MODIS blue bands achieved a median JM Distance of greater than 1.9 and therefore should be able to detect the presence of flowers from the environment. Further assessment showed that the shortest wavelength bands for MODIS, VIIRS and Sentinel 3 all occur where the flower spectra have lower reflectance than their natural background. A sensitivity analysis of percentage flower cover for a pixel showed that the highest sensitivity was obtained by dividing the band closest to 520 nm by the shortest wavelength band for data from these three sources. The MODIS band 10/band 8 metric was tested for its ability to detect flowers in real-world data using 15 years of qualitative honey harvest data from one apiary site as a proxy for flower density. This test was successful as, while there was some overlap between good, moderate and poor years, the poor years could be separated from the other years with nearly 80 % accuracy.

Flowers of Halgania (Ehretiaceae, Boraginales) are set up for being buzzed and the role of intertwining anther trichomes

Flowers that release their powdery pollen by being vibrated through buzzing are morphologically diverse and have evolved many times independently. Most prominently, buzz-pollination is known from Solanum (Solanaceae) defining the “solanoid” flower type by Knut Fægri. The flowers of buzz-pollinated, Australian Halgania resemble the actinomorphic Solanum floral architecture: The plants have a yellow anther cone with an apical pore, protruding from a widely funnel-shaped to rotate, blue to violet corolla. However, Fægri rejected the solanoid flower type for some of the Halgania species due to a contracted inflorescence, a funnel-shaped corolla or an ostensible lack of a female stage. Using light and scanning electron microscopy, we investigated traits referring to the floral architecture of Halgania and compared the flowers of different species. In all investigated species the anthers of the cone are connected via long, intertwined trichomes (denoted “capillinection”) both between the individual anthers and in the central stylar channel. The anther opening is functionally reduced to an apical pore by 1) capillinection and spatial compression of the thecal walls, leaving only small apical slits and 2) by anther appendages that unify the ten slits to a single pore. Halgania flowers are morphologically similar to each other and are buzz-pollinated. We conclude that they are all structurally and functionally matching the flowers of tomato, Solanum lycopersicum, and thus the concept of solanoid flowers as defined by Knut Fægri.

β-Ocimene, a Key Floral and Foliar Volatile Involved in Multiple Interactions between Plants and Other Organisms.

β-Ocimene is a very common plant volatile released in important amounts from the leaves and flowers of many plant species. This acyclic monoterpene can play several biological functions in plants, by potentially affecting floral visitors and also by mediating defensive responses to herbivory. The ubiquity and high relative abundance of β-ocimene in the floral scents of species from most plant families and from different pollination syndromes (ranging from generalism to specialism) strongly suggest that this terpenoid may play an important role in the attraction of pollinators to flowers. We compiled abundant evidence from published studies that supports β-ocimene as a generalist attractant of a wide spectrum of pollinators. We found no studies testing behavioural responses of pollinators to β-ocimene, that could directly demonstrate or deny the function of β-ocimene in pollinator attraction; but several case studies support that the emissions of β-ocimene in flowers of different species follow marked temporal and spatial patterns of emission, which are typical from floral volatile organic compound (VOC) emissions that are involved in pollinator attraction. Furthermore, important β-ocimene emissions are induced from vegetative plant tissues after herbivory in many species, which have relevant functions in the establishment of tritrophic interactions. We thus conclude that β-ocimene is a key plant volatile with multiple relevant functions in plants, depending on the organ and the time of emission. Experimental behavioural studies on pure β-ocimene conducted with pollinating insects will be necessary to prove the assumptions made here.

Molecular Regulation of Flowering Time in Grasses

Flowering time is a key target trait for extending the vegetative phase to increase biomass in bioenergy crops such as perennial C4 grasses. Molecular genetic studies allow the identification of genes involved in the control of flowering in different species. Some regulatory factors of the Arabidopsis pathway are conserved in other plant species such as grasses. However, differences in the function of particular genes confer specific responses to flowering. One of the major pathways is photoperiod regulation, based on the interaction of the circadian clock and environmental light signals. Depending on their requirements for day-length plants can be classified as long-day (LD), short-day (SD), and day-neutral. The CONSTANS (CO) and Heading Date 1 (Hd1), orthologos genes, are central regulators in the flowering of Arabidopsis and rice, LD and SD plants, respectively. Additionally, Early heading date 1 (Ehd1) induces the expression of Heading date 3a (Hd3a), conferring SD promotion and controls Rice Flowering Locus T 1 (RFT1) in LD conditions, independently of Hd1. Nevertheless, the mechanisms promoting flowering in perennial bioenergy crops are poorly understood. Recent progress on the regulatory network of important gramineous crops and components involved in flowering control will be discussed.

Nonrandom genotype distribution among floral hosts contributes to local and regional genetic diversity in the nectar-living yeastMetschnikowia reukaufii

Environmental heterogeneity has been often suggested as a major driving force preserving genetic variation in clonal microorganisms. This study examines this hypothesis for the specialized nectar-dwelling, clonal yeast Metschnikowia reukaufii (Ascomycota, Saccharomycetales). We examined whether M.reukaufii subpopulations associated with flowers of different host plant species, and different individuals of the same host species, differed in genetic characteristics. Amplified fragment length polymorphisms (AFLP) fingerprints of M.reukaufii strains isolated from floral nectar of different host species and individuals sampled at different spatial scales revealed a strong host-mediated component of genetic and genotypic diversity at all scales considered. Genotypes were nonrandomly distributed among flowers of different species and, in the case of the single host species studied in detail (Helleborus foetidus), also among flowers of conspecific individuals coexisting locally. These host-mediated patterns of genetic structuring are compatible with those expected under the diversifying selection hypothesis for the maintenance of local and regional genetic diversity in clonal organisms. It is proposed that a combination of intrafloral selection and biased pollinator-mediated migration may ultimately account for observed host-mediated genetic structuring in populations of M.reukaufii.

Interspecific Pollen Transfer: Magnitude, Prevalence and Consequences for Plant Fitness

Interspecific pollen transfer (IPT) is one of the mechanisms underlying potential competition among plants for pollinators, and it refers to movement of pollen between different plant species by pollinators that visit their flowers simultaneously. Two components of IPT, related to each other, are distinguished: (a) heterospecific pollen deposition (HPD) on conspecific stigmas, which may interfere with fertilization by conspecific pollen; and (b) conspecific pollen loss (CPL) on heterospecific flowers, which may reduce the amount of pollen transferred between conspecific flowers. Thus, IPT may lead to reciprocal losses for male and female functions of the plant, with potentially important ecological and evolutionary consequences. In this review, we explore the magnitude and prevalence of IPT, examining documented mechanisms and evaluating such potential ecological and evolutionary consequences. We compiled existing evidence of interspecific pollinator sharing and interspecific pollinator switching between flowers of different species in natural communities. We evaluated the relative importance of both HPD and CPL from studies comparing these variables in pure vs. mixed floral neighborhoods, analyzing evidence for the claim that IPT is an evolutionary force promoting character displacement in habitat affinity, flowering times, and floral morphology. We also examined the findings of hand-pollination experiments carried out to reveal different mechanisms by which heterospecific pollen can affect performance of native pollen. Finally, we review evidence for impacts of alien plant species on native species' reproduction, and briefly comment on risks of crop-to-wild gene flow imposed by the release of genetically modified (transgenic) crops through IPT.

The role of rainfall and predators in determining synchrony in reproduction of savanna trees in Serengeti National Park, Tanzania

Summary We examined the factors determining synchrony in reproduction in nine Acacia and six other tree species in the Serengeti ecosystem. We test two hypotheses: (i) an abiotic hypothesis where the primary determinant of synchrony is an adaptation to water availability; and (ii) biotic hypotheses where these adaptations to water can be further refined by additional adaptations to avoid predators, or attract seed and fruit dispersers. Flowering and fruiting were recorded monthly for individually marked trees during 1997–2004. Flowering in different species occurs semi‐annually, annually or, in the case of one species, once every 2 years. For most species synchrony of flowering was correlated with seasonal rainfall, with lags related to the mean height of the species; small species flowered during the rains while larger species flowered in the dry season. Fruiting seasons occurred at the end of the rains irrespective of the flowering season. Most species showed flowering synchrony greater than expected from the distribution of rainfall. This may be related to avoidance of insect seed predators through predator satiation. Two Acacias showed multi‐annual fruiting (masting), possibly as a predator avoidance mechanism. Acacia tortilis has two flowering seasons: a dry season flowering with early abortion of pods and a wet season flowering producing successful fruits. Two species of Commiphora appeared to be synchronized so as to attract birds that disperse seeds. Acacia tortilis produced indehiscent pods attractive to ungulates, possibly to kill bruchid beetles during digestion and so increase seed viability. Our results suggest that synchrony in these trees is caused by a strong interaction between abiotic and biotic factors. Closely related species have different reproductive patterns of synchrony that seem to be adapted to different combinations of rainfall, predators and dispersers. Rainfall is the primary determinant but the activities of predators and dispersers increase the degree of synchrony.

Floral mimicry: a fascinating yet poorly understood phenomenon

Flowers of different species that resemble each other are not necessarily mimics. For mimicry to be occurring, the similarity must be adaptive. Unfortunately, no case of floral mimicry has ever been fully verified and it is important that we move beyond these perceived similarities to testing whether they are truly adaptive. Here we explain the differences between Batesian and Müllerian floral mimicry, illustrate what should be done to test mimicry hypotheses, and discuss how interspecific pollen transfer influences the evolution of mimicry.

Foraging dynamics of bumble bees: correlates of movements within and between plant species

What rules determine whether bumble bees continue exploiting plants of the species just visited or switch to another species? To tackle this question, we recorded handling times and flight times from bees foraging in a natural meadow containing five plant species. Inter- and intra-specific plant distances were quantified. The bee-subjective colors of the five species were determined; two of these species had similar colors and structures, while three species were distinct from all others. The following rules were identified: (1) The decision to switch species was correlated with previous flower handling time, which we assume is a function of the reward amount received at the flower. After short handling times, the probability of switching to another species increased, whereas it decreased after long handling times. This difference became even greater if the bee had had a run of several short or several long handling times. (2) Constant flights (those between flowers of the same species) and transition flights (those between flowers of different species) followed stereotyped temporal patterns independent of the distances between flowers. Constant flights within five plant species consistently had median durations of about 2 seconds, whereas median transition times between species took 3–6 seconds. (3) This temporal rule broke down, however, if the flowers of two species had similar colors, in which case transition flights had equal dynamics as constant flights. (4) Bees switched more frequently from rare than from common species but even more frequently between similar species. We conclude that the bees' choices were determined by a set of rules that guided them to stay with the current plant species as long as flowers were rewarding and available within close distance but to switch to another species if flowers offered low rewards or were not encountered at close range

Interspecific diversity and uniformity of flower colour patterns as cues for learned discrimination and innate detection of flowers

The colour patterns of angiosperm flowers visited by bees and hoverflies were shown to provide a dual signalling system, giving the flower-visitors visual orientation cues for the initial detection of flowers, as well as for learned discrimination. Pollinators show an innate response to interspecifically uniform colour signals, which enable them to detect flowers and to orient towards the site of reward. Interspecifically diverse colour signals provide pollinators with cues for learned discrimination between flowers of different species.

Ecological Interactions between Plants and Hummingbirds in a Successional Tropical Community

At Monteverde, Costa Rica, 10 successional plant species used 14 hummingbird species for pollination. Displacement among flowering seasons suggests that the plants influenced hummingbirds to abandon another. There was no evidence that the flowering of one plant influenced hummingbirds to abandon another Pollination is simultaneously flowering plants likely suffered nonetheless, since birds tended to move indiscriminately among flowers of different species and could lose much pollen between successive visits to conspecific plants. This may have led to scatter in flowering peaks by favoring the quick establishment of plant colonists with unique flowering seasons over colonists whose flowering seasons coincided with those of established species. The continuous supply of nectar provided by staggered flowering peaks maintained a continuous supply of hummingbirds competing for nectar. Even inconspicuous plants with few flowers received sufficient hummingbird visits for moderate to high potential rates of outbreeding. At large, flower—laden trees and shrubs, hummingbirds defending feeding territories evidently effected much inbreeding, but movements of intruders between territories kept inbreeding from becoming absolute. Nectar secretion rates varied widely among flowers of each of the 5 plant species in which nectar volume was measured. Many flowers produced little or no nectar, while a few secreted quite copious volumes. This "bonanza" pattern may benefit plants by reducing caloric expenditures on nectar while increasing the duration of hummingbirds' foraging bouts. The latter possibility was tested and verified experimentally with artificial flowers exposed to a free—living hummingbird on Trinidad, West Indies. When pollinators are abundant, plants with "bonanza" patterns can attract consistent visitors and rare, inconspicuous plants can count on consistent service. At Monteverde, the unspecialized, opportunistic nature of both plants and birds assured abundant hummingbirds and resulted in a well—integrated complex of plants and pollinators despite the transient nature of the successional habitats.

BEE FLOWERS: A HYPOTHESIS ON FLOWER VARIETY AND BLOOMING TIMES.

In arctic (Kevan, 1972), temperate (Lovell, 1903), and tropical regions, the flowers of different species of plants in a given habitat at any one time usually exhibit a variety of colors, scents, morphologies, and blooming times. Bees are the primary pollinators of many of them (Baker and Hurd, 1968). Adaptations of given species of plants to specific pollinators (MMuller, 1881; Knuth, 1909; van der Pijl, 1961; van der Pijl and Dodson, 1966; Grant and Grant, 1965; Faegri and van der Pijl, 1971), to an array of generalized pollinators, or to differences in pollinator behavior (Macior, 1970, 1971) probably do not account for all of the extraordinary array of forms, colors and scents of the bee-pollinated flowers in a given habitat. Those commonly visited by bumblebees alone may be white, red, yellow, purple, ultraviolet, green, or blotched and streaked with a variety of colors. The flowers may be zygomorphic (Werth, 1949), platformshape, or equipped with varying numbers of lobed and unlobed petals. The key to the evolution of different types of flowers is usually considered to reside in the preferences and the flowerconstancy of the pollinators. The flowerconstancy of bees, and its probable impact on plant speciation has been discussed (Grant, 1949; Grant, 1950; Manning, 1956a; Free, 1966). However, little is known about the selective pressures producing the variety of flowers upon which flower-constancy is based. It is rarely possible to witness selection, but inferences of differential selection exerted by pollinators can sometimes be made from careful studies of the interactions of flower-visitors and plants in a given area. The studies of Clarkia bees of the western United States (MacSwain et al., 1973) and of bumblebees on Pedicularis in the Rocky Mountains (Macior, 1970, 1971) serve as good examples. It is necessary to determine what affects flower choice and flower fidelity of the foragers in the presence of numerous species of sympatric plants. This paper concerns the functional significance in the variety and in the assortment of flowers visited primarily by bumblebees in one habitat in Maine. The observations from this area may serve as a model applicable to other plant assemblages and pollinators.

Relazioni ormonali nello sviluppo dell'ovario delle orchidee i. effetto in vivo del trattamento con auxine

Abstract HORMONAL RELATIONS IN THE DEVELOPMENT OF ORCHID OVARY. I. - THE EFFECTS OF TREATMENTS WITH AUXINS ON THE INTACT PLANT. — The flowers of different species of Orchids have been treated with auxins, pure or in solutions, and with pollen from the same or a different species. The auxin treatment consistently induces the elongation of the column and the growth of the ovary. The treatment with the most active of the auxins used (pure NAA) induces necrosis of the column; in this case, growth of the ovary can last for more than one year, till ripening of the fruit. Morever, the interruption of development at any stage, is more frequent. The stimulation of the ovary can be obtained also with the introduction of auxin into wounds at the basis of the column. In Zygopetalum NAA induces parthenocarpy but not adventive embriony which is induced with exogenous pollen.