Why do flowers close at night? Experiments with the Lesser celandine Ficaria verna Huds (Ranunculaceae)

Although the mechanisms of flower closure have been widely studied, the evolutionary processes underlying this phenomenon are largely unknown. Open flowers may face a trade‐off between successful pollination/pollen transfer on the one hand and destruction of reproductive organs caused by exogenous factors (e.g. rain) on the other. The cost of flower opening was investigated by treating flowers of the Lesser celandine both in the field and under laboratory conditions. No differences were found in anthesis and reproductive success between treated and untreated flowers in any of the experiments. However, treated flowers in the field experiment suffered from significantly higher predation rates, in all probability caused by slugs and roe deer. It is suggested that flower closure may decrease the rate of being eaten by some herbivores, particularly in early‐spring plants that flower at times of insufficient food availability.     

Reproductive ecology of Viola mirabilis var. subglabra representing intermediate flowering characteristics between stemless and stemmed Viola

Viola (Violaceae) is one of the largest genera in angiosperms. This genus is essentially classified into stemless and stemmed groups based on growth morphology. However, Viola mirabilis var. subglabra is an exception in having intermediate flowering characteristics; cleistogamous (CL) flowers are formed in the axils of stem leaves, whereas chasmogamous (CH) flowers arise from basal rosettes (radical CH (CH(r)) flowers) and also in the axils of the stem (axially CH (CH(a)) flowers). To understand why the pattern of flower production varies in this Viola species, flower production was investigated in 10 Japanese populations from Hokkaido to the western part of Honshu in 2014 and 2015. Furthermore, flower characteristics were also compared between CH(r) and CH(a) flowers in Hokkaido. In this species, the production of CH flowers varied among individuals, and they were categorized into three groups, individuals that produced (i) only CH(r) flowers, (ii) only CH(a) flowers and (iii) both CH flowers. The frequency of these groups differed among populations, but some individuals changed the category between 2014 and 2015. Thus, the production of CH(r) and CH(a) flowers plastically changes depending on individual conditions and/or environmental factors. On the other hand, CH(r) and CH(a) flowers differed in flower size and flowering phenology. These results suggest that two types of CH flowers may play different roles in reproduction in each population, but fruit sets and seed sets did not differ between two types of CH flowers.     

A chalcone isomerase‐like protein enhances flavonoid production and flower pigmentation

Flavonoids are major pigments in plants, and their biosynthetic pathway is one of the best‐studied metabolic pathways. Here we have identified three mutations within a gene that result in pale‐colored flowers in the Japanese morning glory (Ipomoea nil). As the mutations lead to a reduction of the colorless flavonoid compound flavonol as well as of anthocyanins in the flower petal, the identified gene was designated enhancer of flavonoid production (EFP). EFP encodes a chalcone isomerase (CHI)‐related protein classified as a type IV CHI protein. CHI is the second committed enzyme of the flavonoid biosynthetic pathway, but type IV CHI proteins are thought to lack CHI enzymatic activity, and their functions remain unknown. The spatio‐temporal expression of EFP and structural genes encoding enzymes that produce flavonoids is very similar. Expression of both EFP and the structural genes is coordinately promoted by genes encoding R2R3‐MYB and WD40 family proteins. The EFP gene is widely distributed in land plants, and RNAi knockdown mutants of the EFP homologs in petunia (Petunia hybrida) and torenia (Torenia hybrida) had pale‐colored flowers and low amounts of anthocyanins. The flavonol and flavone contents in the knockdown petunia and torenia flowers, respectively, were also significantly decreased, suggesting that the EFP protein contributes in early step(s) of the flavonoid biosynthetic pathway to ensure production of flavonoid compounds. From these results, we conclude that EFP is an enhancer of flavonoid production and flower pigmentation, and its function is conserved among diverse land plant species.     

基于花青素代谢培育蓝色花卉的研究进展

花色是植物吸引昆虫传播花粉的主要因素,对于植物在自然界的生存必不可少,也是观赏植物最重要的性状之一。在蓬勃发展的花卉产业中,色彩各异花卉的培育,可以弥补自然花色的匮乏,但是令人垂涎的蓝色花比较难培育。花色的多样性主要是由花青素及其衍生物的种类和含量等因素决定的,飞燕草色素的合成是形成蓝色花的关键因素,许多植物体内缺少合成飞燕草色素的结构基因。近年来,利用基因工程技术培育蓝色花的研究也时有报道。文中以常见的观赏植物为例,基于花青素代谢调控,从影响飞燕草色素合成的关键因素和不同分子改良途径培育蓝色花等几个方面对植物花朵呈色的机制进行了综述,并展示不同分子育种策略可能在其他领域的应用,为其他植物或经济作物的色泽改良如彩色棉蓝色纤维的培育等提供参考和技术支持。     

二态混合交配系统的适合度优势及其维持机制研究进展

由开花受精花(chasmogamous, CH)和闭花受精花(cleistogamous, CL)构成的二态混合交配系统植物有着特殊的繁殖策略, 对其进行深入研究有助于理解植物交配系统的维持机制、进化趋势以及植物对环境变化的应对策略。本文综述了国内外关于CH-CL系统两型花研究的文献资料, 包括非生物因素和生物因素对该繁育系统两型花的生长、发育及相对比例的影响, 两型花的维持机制及进化意义, 阐明了CH-CL系统的研究现状及科学问题, 重点评述了基于近年来对CH-CL系统研究成果的新认识。作者提出, 精确地检测两种花型的后代在异质生境下以及在生活史的不同阶段的适合度差异是十分必要的; 微环境(种子的散布模式及位置效应)对两型花种子萌发和子代生长发育的影响非常重要; 两型花表达的时空差异(即开花模式及对异质生境的敏感性差异)的表达机制可能与内源激素的水平变化相关; 对于多年生具CL系统植物来说, 不同性质、不同来源的后代在居群中的分布式样及对居群遗传结构的影响很可能是该系统维持的重要机制。因此, 深入研究和科学认识二态混合交配系统对认识整个植物界繁育系统的进化有十分重要的意义。     

Flower preference behaviour of western flower thrips in the Similkameen Valley, British Columbia, Canada

Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), occur on most wildflowers, weed and ground cover flowers in the southern interior of B.C., Canada. Preference by WFT for naturally occurring ground cover blooms was determined in a series of choice trials aimed to examine the potential of using such flowers as trap crops under nectarine trees. The effect of height of flowers above ground level within an orchard was also examined to determine whether this may affect flower attractiveness. Although WFT showed consistent preferences for various flower types, no ground cover grown presently in this region appeared to have potential as an effective trap crop. The density of WFT landing on less preferred flower types was not reduced when more attractive flowers also were present, and WFT were found to distribute evenly over all flowers available. Western flower thrips responded to the density of flowers only in response to highly scented flowers, and were attracted equally to mixtures of colours and single colours of flowers. There was a consistent preference by WFT in the spring for flowers located at ground level.     

Selection of trait combinations through bee and fly visitation to flowers of Polemonium foliosissimum

Pollinators are known to exert natural selection on floral traits, but the extent to which combinations of floral traits are subject to correlational selection (nonadditive effects of two traits on fitness) is not well understood. Over two years, we used phenotypic manipulations of plant traits to test for effects of flower colour, flower shape and their interaction on rates of pollinator visitation to Polemonium foliosissimum. We also tested for correlational selection based on weighting visitation by the amount of conspecific pollen delivered per visit by each category of insect visitor. Although bumblebees were the presumed pollinators, solitary bees and flies contributed substantially (42%) to pollination. In manipulations of one trait at a time, insects visited flowers presenting the natural colour and shape over flowers manipulated to present artificial mutants with either paler colour or a more open or more tubular flower. When both colour and shape were manipulated in combination, selection on both traits arose, with bumblebees responding mainly to colour and flies responding mainly to shape. Despite selection on both floral traits, in a year with many bumblebees, we saw no evidence for correlational selection of these traits. In a year when flies predominated, fly visitation showed a pattern of correlational selection, but not favouring the natural phenotype, and correlational selection was still not detected for expected pollen receipt. These results show that flower colour and shape are subject to pollinator‐mediated selection and that correlational selection can be generated based on pollinator visitation alone, but provide no evidence for correlational selection specifically for the current phenotype.     

Horizontal orientation of zygomorphic flowers: significance for rain protection and pollen transfer

• Floral traits are recognized to have evolved under selection for abiotic and biotic factors. Complex zygomorphic flowers usually face horizontally. It has been proved that a horizontal orientation facilitates pollinator recognition and pollination efficiency, but its significance in adaptation to abiotic factors remains unknown.
• The floral orientation of Abelia × grandiflora naturally varies around horizontal (with an angle of ?30 to +33° between the floral main axis and the horizontal). We examined whether three different floral orientations affected flower thermal conditions, response to rain and pollination.
• Results showed that floral orientation had no effect on diurnal variations in flower temperature. The anthers of all three flower orientations were wetted by rainfall, but the inclined upward‐facing flowers contained significantly more rainwater. The horizontal flowers received significantly higher visitation by hawkmoths and had a higher stigmatic pollen load. In contrast, the upward flower orientation reduced pollination precision, while downward‐facing flowers had decreased pollinator attraction.
• This study indicates that horizontal flowers may have evolved as a trade‐off between rain protection and pollination. Zygomorphic flowers that deviate from a horizontal orientation may have lower fitness because of flower flooding by rainwater and decreased pollen transfer.

     

DOWN THE TUBE: POLLINATORS, PREDATORS, AND THE EVOLUTION OF FLOWER SHAPE IN THE ALPINE SKYPILOT, POLEMONIUM VISCOSUM

Abstract We address how a conflict between pollinator attraction and avoidance of flower predation influences the evolution of flower shape in Polemonium viscosum. Flower shape in P. viscosum is the product of an isometric relationship between genetically correlated (r_A= 0.70) corolla flare and length. Bumblebee pollinators preferentially visit flowers that are more flared and have longer tubes, selecting for a funnel‐shaped corolla. However, flower shape also influences nectar‐foraging ants that sever the style at its point of attachment to the ovary. Surveys of ant damage show that plants having flowers with flared, short corollas are most vulnerable to ant predation. Consistent with this result, the ratio of corolla length to flare is significantly greater in a krummholz (high predation risk) population than in a tundra (low predation risk) population. To explicitly test whether the evolution of a better defended flower would exact a cost in pollination, we created tubular flowers by constricting the corolla during development. Performance of tubular flowers and natural controls was compared for defensive and attractive functions. In choice trials, ants entered control flowers significantly more often than tubular ones, confirming that the evolution of tubular flowers would reduce the risk of predation. However, in a bumblebee‐pollinated population, tubular flowers received significantly less pollen and set fewer seeds than controls. A fitness model incorporating these data predicts that in the absence of the genetic correlation between corolla length and flare, intermittent selection for defense could allow tubular flowers to spread in the krummholz population. However, in the tundra, where bumblebees account for nearly all pollination, the model predicts that tubular flowers should always confer a fitness disadvantage.     

Why flowers close at noon? A case study of an alpine species Gentianopsis paludosa (Gentianaceae)

Repeatable floral closure with diurnal rhythms, that is, flower opening in the morning and closing in the evening, was widely reported. However, the rhythm of flower opening in the morning but closing in the midday received much less attention. Gentianopsis paludosa, Gentianaceae, has an obvious petal movement rhythm opening in the morning and closing at noon at northeast of the Qinghai‐Tibetan Plateau. In this study, we examined the effects of temperature (T), relative humidity (RH), and illumination intensity (II) on G. paludosa''s flower closure. Furthermore, we monitored the environmental changes inside and outside of the flowers, aiming to test the effect of floral closure on the stability of microenvironment inside the flower. Finally, we artificially interrupted temporal petal closure and investigated its effects on reproductive fitness. The results showed that high/low temperature contributed more to the flower closure than low RH, while illumination intensity had no significant effect on it. The medium temperature, relative humidity and illumination intensity (environmental conditions at 10:00) did not delay flower closure when flowers at pre‐closing period or stimulate reopen when flowers full closed. Floral closure provided a stable temperature condition and a higher RH condition inside the flower. Meanwhile, compulsive opening and delayed closure of flowers decreased the seed‐set ratio while no effect was found when flowers were forced to close. We conclude that endogenous rhythm regulates floral closure. The rhythm of petal movement providing a stable microenvironment for G. paludosa, increasing the seed production and saving energy from flower opening maintenance, which might be an adaptive strategy to against unfavorable environmental conditions.     

Flower structure and potential bisexuality in Freycinetia reineckei (Pandanaceae), a species of the Samoa Islands

In Freycinetia reineckei the staminate flower (on the staminate spikes) comprises 3 or 4 (sometimes 2) stamens and a pistillode with 2 (sometimes 4) carpellodes, and the pistillate flower (on the pistillate spikes) is formed of a pistil with 2 (sometimes 4) carpels and of 3 or 4 (sometimes 2) staminodes. This perfect floral homology, also observed in all the other species that were studied with both pistillate and staminate material, strongly suggests that the flower of Freycinetia is basically and potentially bisexual, and may explain the occasional sexual lability and bisexuality of that flower (occurrence of both pistillate and staminate inflorescences, and/or of bisexual inflorescences with bisexual flowers and/or unisexual flowers, on the same individuals) in some species, and also the frequent occurrence of bisexual spikes in this species. These may be partitioned into pistillate, staminate, mixed and sterile zones. In the pistillate zones the flowers have the same aspect and structure as the pistillate flowers. In the staminate zones the flowers generally comprise 3 or 4 (sometimes 2) stamens and a ‘semi-pistil’ some have both stamens and staminodes. The semi-pistils are intermediate between pistils and pistillodes in length, aspect and structure, but always have placentas and ovules. In the mixed zones the flowers are generally formed of a pistil and 3 or 4 (sometimes 2) stamens, and are therefore true hermaphrodite flowers; some have both stamens and staminodes. In the sterile zones the flowers comprise a semi-pistil and 3 or 4 (sometimes 2) staminodes. The staminodes are anatomically very similar to the stamens, especially in the staminate, mixed, and sterile zones, in which they exhibit a wide range of variation in length, aspect and structure. The perfect floral homology as generic character on one hand, and the occasional bisexuality both with and without bisexual flowers and other aspects of sex expression (e.g. occurrence of both pistillate and staminate shoots on the same individuals) in some species on the other hand, seem to indicate that Freycinetia is a basically monoecious, sex changing genus.     

Mimicry in hoverflies (Diptera: Syrphidae): a field test of the competitive mimicry hypothesis

Although most studies on the evolution of mimicry and warningcoloration in insects have considered predators as the majorselective force, it is possible that competition for food resourcescould also facilitate selection for these conspicuous signals.For example, when warningly colored social wasps visit flowers,then they frequently behave aggressively toward heterospecifics,and they also attack and feed on other flying insects. Underthese conditions, a resemblance to a wasp might provide a mimetichoverfly with improved access to floral resources by reducingthe frequency with which it is disturbed by other pollinators.We experimentally evaluated whether wasp-like colors and patternswere important in preventing other flower visitors from sharingthe same flower resource, using pairwise presentations of bothnatural and artificial prey in the field. Flower visitors weremore likely to visit unoccupied flowers compared with the flowerspinned with either natural or artificial specimens in 2 plantspecies with different inflorescences. However, flower visitorsdid not show a significantly reduced rate of visitation to flowerspinned with specimens bearing wasp-like colors and patternscompared with the flowers occupied by similar-sized specimensthat were nonmimetic. Overall, we found no compelling evidencein this study to support the contention that wasp-like warningsignals of hoverflies prevent other flower visitors from sharingflower resources, although insects showed a greater tendencyto avoid visiting flowers pinned with a wasp compared with flowerspinned with a nonmimetic fly.     

Evolution of honest reward signal in flowers

Some flowering plants signal the abundance of their rewards by changing their flower colour, scent or other floral traits as rewards are depleted. These floral trait changes can be regarded as honest signals of reward states for pollinators. Previous studies have hypothesized that these signals are used to maintain plant-level attractiveness to pollinators, but the evolutionary conditions leading to the development of honest signals have not been well investigated from a theoretical basis. We examined conditions leading to the evolution of honest reward signals in flowers by applying a theoretical model that included pollinator response and signal accuracy. We assumed that pollinators learn floral traits and plant locations in association with reward states and use this information to decide which flowers to visit. While manipulating the level of associative learning, we investigated optimal flower longevity, the proportion of reward and rewardless flowers, and honest- and dishonest-signalling strategies. We found that honest signals are evolutionarily stable only when flowers are visited by pollinators with both high and low learning abilities. These findings imply that behavioural variation in learning within a pollinator community can lead to the evolution of an honest signal even when there is no contribution of rewardless flowers to pollinator attractiveness.     

倒地铃花的形态分化与花药结构研究

利用体视显微镜、半薄切片和超薄切片法对倒地铃(Cardiospermum halicacabum Linn.)雄花和假两性花开花过程及花药发育过程进行了观察和比较研究。结果显示:(1)花蕾发育早期,倒地铃雄花和假两性花的花蕾形态没有区别;花蕾发育后期,雄花雌蕊退化,假两性花雌蕊继续发育,花蕾外部形态出现差异;开花时雄花花药开裂,假两性花花药不开裂。(2)倒地铃雄花和假两性花均具四室花药,呈蝶形;花药壁细胞从外到内依次是表皮、药室内壁、中层(2层)和绒毡层;花药壁发育为基本型,绒毡层为单核分泌型,四分体为四面体型,花粉粒两核;开花时雄花和假两性花中层都有残留;小孢子液泡化时,绒毡层开始降解,两核花粉粒时,假两性花绒毡层降解较快。(3)雄花药室内壁次生加厚完全,裂口区发育,连接同侧花粉囊的连接组织降解,花药开裂;假两性花药室内壁次生加厚不完全,具唇形细胞,药隔细胞壁未降解,同侧花粉囊未连通,花药四室,不开裂;假两性花成熟花粉粒细胞质稀少,内壁不完整。本研究结果表明,倒地铃的雄花是由两性花在发育早期雌蕊停止发育形成的,假两性花则由两性花在发育晚期雄蕊功能退化造成的。     

高山植物花形态特征对花温度积累的影响

高山生态系统的低温环境不利于植物繁殖器官的发育和传粉过程,因此能改善花内或花序温度的结构对植物繁殖具有积极意义。该研究利用红外测温仪测量了高寒草甸中64种植物的花温度和叶温度以计算花温度积累,并检测了系统发育、花大小、花对称方式和花大小对花温度积累的影响。结果表明:所测量的64种植物种类,花部温度均高于叶部温度。花温度积累的系统发育信号较弱,表明物种间花温度积累的差异可能主要与不同物种对温度的需求有关。花温度积累与花大小存在显著的正相关关系,且两侧对称花的温度积累比辐射对称花更为迅速,但花对称方式和花颜色对花温度积累并没有显著的影响。该研究结果表明花温度积累在不同植物间存在很大的差异,但这些差异对植物繁殖的实际贡献和意义仍需要进一步验证。     

Florivores on the dioecious shrub Eurya japonica and the preferences and performances of two polyphagous geometrid moths on male and female plants

Flowers of dioecious plants have sexually dimorphic traits that may affect florivore performances, and florivores may have preferences to plant sex that are correlated with their performance on different plant sexes. We investigated the florivory on a polygamodioecious evergreen shrub Eurya japonica in Japan to reveal florivores and their feeding patterns involved in sexually biased florivory on E. japonica flowers. Flowers of E. japonica were infested by lepidopteran and dipteran larvae and hemipteran insects. Lepidopteran larvae were chewers, dipteran larvae were gall makers and hemipteran insects were suckers. Chewed flowers were most frequent among infested flowers. Of florivores, lepidopteran larvae, mostly of Geometridae, were the important florivore that damaged flowers by chewing. Florivores infested male flower buds more often than female flower buds, but only a geometrid larvae Chloroclystis excise, which exclusively uses flower buds, showed the biased infection on male flowers. Rearing experiments for two other geometrid moths which use both leaves and flowers showed that the preference and performance of Ourapteryx nivea that fed mainly leaves did not differ between the plant sexes, whereas the development of Alcis angulifera larvae which fed both leaves and flowers was slower when they fed female than male leaves and flower buds. In addition, A. angulifera larvae fed fewer flower buds on female than on male plants. These results show that the male‐biased florivory on E. japonica trees is attributed mainly to the specialist florivore and also feeding preference for male flowers in an opportunistic florivore that feed both leaves and flowers.     

Patterns of flower morphology and structural changes during interconversion between chasmogamous and cleistogamous flowers in Viola philippica北大核心CSCD

Aims: Viola philippica is a species with a typical chasmogamous-cleistogamous (CH-CL) mixed breeding system. It provides a flower model system to investigate floral organs development under different photoperiods. Morphological changes of intermediate cleistogamous (inCL) flowers have been observed, the trends in variation of changes from CH flowers to CL flowers or from CL flowers to CH flowers have been analyzed, the localized effects of poorly developed stamens and petals in CL and inCL flowers have been identified. This research provided morphology and structural changes with implication for the evolutionary significance of the dimorphic flower formation for further study in dimorphic flower development. Methods: We used methods of anatomy and structural analysis to observe the morphological structures of flowers under different photoperiods. Important findings: Photoperiod played an important role in the development of CH and CL flowers in V. philippica. Under short-day light and intermediate-day light, both CH and inCL flowers developed simultaneously. Most of the floral buds were CH flowers under a photoperiod of short-day light, but most of the floral buds were inCL flowers under mid-day light. Complete CL flowers formed under long-day lights. However, there were a series of transitional types in the number and morphology of stamens and petals among inCL flowers, including five stamens with three petals related to CH flowers and two stamens with one petal related to CL flowers. The former type was dominant under short-day light conditions, and the latter type was dominant under mid-day light. Further more, there were localized effects in stamen and petal development for CL and inCL flowers. The development of ventral lower petal (corresponding to the lower petal with spur of CH flower) and the adjacent two stamens in inCL flowers were best, and the back petal was similar to that of CL flowers, an organ primordium structure. The adjacent stamens with the back petals tended to be poorly developed. In extreme cases, these stamens in inCL flowers had no pollen sac, only a membranous appendage or even a primordium structure. When the plants with CL or CH flowers were placed under short-day light or long-day light, the newly induced flowers all showed a series of inCL flower types, finally the CL flowers transformed into CH flowers, and the CH flowers transformed into CL flowers. This result indicates the gradual effects of different photoperiods on dimorphic flowers development of V. philippica. A long photoperiod could inhibit the development of partial stamens and petals, and a short photoperiod could prevent the suppression of long-day light and promote the development of stamens and petals.     

Is Floral Longevity Influenced by Reproductive Costs and Pollination Success in Cohniella ascendens (Orchidaceae)?

Background and Aims

Although studies have shown that pollen addition and/or removal decreases floral longevity, less attention has been paid to the relationship between reproductive costs and floral longevity. In addition, the influence of reproductive costs on floral longevity responses to pollen addition and/or removal has not yet been evaluated. Here, the orchid Cohniella ascendens is used to answer the following questions. (a) Does experimental removal of flower buds in C. ascendens increase flower longevity? (b) Does pollen addition and/or removal decrease floral longevity, and does this response depend on plant reproductive resource status?

Methods

To study the effect of reproductive costs on floral longevity 21 plants were selected from which we removed 50 % of the developing flower buds on a marked inflorescence. Another 21 plants were not manipulated (controls). One month later, one of four flowers on each marked inflorescence received one of the following pollen manipulation treatments: control, pollinia removal, pollination without pollinia removal or pollination with pollinia removal. The response variable measured was the number of days each flower remained open (i.e. longevity).

Key Results

The results showed significant flower bud removal and pollen manipulation effects on floral longevity; the interaction between these two factors was not significant. Flowers on inflorescences with previously removed flower buds remained open significantly longer than flowers on control inflorescences. On the other hand, pollinated flowers closed much faster than control and removed-pollinia flowers, the latter not closing significantly faster than control flowers, although this result was marginal.

Conclusions

The results emphasize the strong relationship between floral longevity and pollination in orchids, as well as the influence of reproductive costs on the former.Key words: Cohniella ascendens, floral longevity, flower bud removal, pollination, pollinia removal, reproductive costs     

Microbial Community Dysbiosis and Functional Gene Content Changes in Apple Flowers due to Fire Blight

Despite the plant microbiota plays an important role in plant health, little is known about the potential interactions of the flower microbiota with pathogens. In this study, we investigated the microbial community of apple blossoms when infected with Erwinia amylovora. The long-read sequencing technology, which significantly increased the genome sequence resolution, thus enabling the characterization of fire blight-induced changes in the flower microbial community. Each sample showed a unique microbial community at the species level. Pantoea agglomerans and P. allii were the most predominant bacteria in healthy flowers, whereas E. amylovora comprised more than 90% of the microbial population in diseased flowers. Furthermore, gene function analysis revealed that glucose and xylose metabolism were enriched in diseased flowers. Overall, our results showed that the microbiome of apple blossoms is rich in specific bacteria, and the nutritional composition of flowers is important for the incidence and spread of bacterial disease.     

A perfect flower from the Jurassic of China

Flower, enclosed ovule and tetrasporangiate anther are three major characters distinguishing angiosperms from other seed plants. Morphologically, typical flowers are characterised by an organisation with gynoecium and androecium surrounded by corolla and calyx. Theoretically, flowers are derived from their counterparts in ancient ancestral gymnosperms. However, as for when, how and from which groups, there is no consensus among botanists yet. Although angiosperm-like pollen and angiosperms have been claimed in the Triassic and Jurassic, typical flowers with the aforesaid three key characters are still missing in the pre-Cretaceous age, making many interpretations of flower evolution tentative. Thus searching for flower in the pre-Cretaceous has been a tantalising task for palaeobotanists for a long time. Here, we report a typical flower, Euanthus paniigen. et sp. nov., from the Middle–Late Jurassic of Liaoning, China. Euanthus has sepals, petals, androecium with tetrasporangiate dithecate anthers and gynoecium with enclosed ovules, organised just like in perfect flowers of extant angiosperms. The discovery of Euanthus implies that typical angiosperm flowers have already been in place in the Jurassic, and provides a new insight unavailable otherwise for the evolution of flowers.