Multiple Inflorescences Research Articles

A malformation of sex-changing plant Arisaema serratum (Araceae) produces both male and female inflorescences

ABSTRACT The genus Arisaema (Araceae) can change sex expression between male and female with increasing plant size (sequential hermaphrodism). As most Arisaema species have only one inflorescence on each individual, sex expression is seemingly determined at the individual level. However, malformations with male and female inflorescences have occasionally been observed. Unfortunately, their developmental origin is unclear because of a lack of detailed descriptions of the shoot structure. To estimate the unit of sex determination in Arisaema, we observed the morphology of an aberrant individual of Arisaema serratum (Thunberg) Schott with multiple inflorescences for three years. In the second year, the aberrant individual produced pure male and female inflorescences. Based on the phyllotactic pattern of this malformation, we estimated that the inflorescences were duplicated due to a broadening of the apical meristem via fasciation. Contrary to other Arisaema plants with multiple inflorescences reported previously, the corm of the aberrant individual did not subdivide nor branch spontaneously after the growing season for three years. Thus, duplicated inflorescences presumably shared the resource supply without physiological partitioning during sex determination. These results imply that sex expression is determined at the inflorescence level but not at the individual or floret levels in dioecious Arisaema.

Developmental Morphology and Anatomy Shed Light on Both Parallel and Convergent Evolution of the Umbellate Inflorescence in Monocots, Underlain by a New Variant of Metatopy.

Inflorescence structure is very diverse and homoplasious, yet the developmental basis of their homoplasy is poorly understood. To gain an understanding of the degree of homology that these diverse structures share, we characterize the developmental morphology and anatomy of various umbellate inflorescences across the monocots and analyzed them in an evolutionary context. To characterize branching order, we characterized the developmental morphology of multiple inflorescences with epi-illumination, and vascular anatomy with Laser Ablation Tomography, a novel high-throughput method to reconstruct three-dimensional vasculature. We used these approaches to analyze the umbellate inflorescences in five instances of presumed homoplasy: in three members of the Amaryllidaceae; in three members of the Asparagaceae, including a putatively derived raceme in Dichelostemma congestum; in Butomus umbellatus (Alismataceae), in Tacca chantrieri (Dioscoreaceae), and in umbellate structure in Fritillaria imperialis (Liliaceae). We compare these with racemes found in three members of the subfamily Scilliioideae (Asparagaceae). We find there are three convergent developmental programs that generate umbellate inflorescences in the monocots, bostryx-derived, cincinnus-derived and raceme-derived. Additionally, among the bostryx-derived umbellate inflorescence, there are three instances of parallel evolution found in the Amaryllidaceae, in two members of Brodiaeoideae (Asparagaceae), and Butomus umbellatus, all of which share the same generative developmental program. We discuss the morphological modifications necessary to generate such complex and condensed structures and use these insights to describe a new variant of metatopy, termed horizontal concaulesence. We contextualize our findings within the broader literature of monocot inflorescence development, with a focus on synthesizing descriptive developmental morphological studies.

Floral scent is different between sexual phases within individuals in a synchronously dichogamous shrub (Canella winterana) but there is no distinct female or male scent profile across individuals

Floral scent is a highly complex and variable floral characteristic that is involved in pollinator attraction. One possible cause for variation in floral scent can be sexual identity of the flower. Here, we examine the floral scent bouquet of a synchronously dichogamous shrub, Canella winterana (L.) Gaertn.We used dynamic headspace extraction and gas chromatography – mass spectroscopy, followed by statistical analysis using non-metric multidimensional scaling, SIMPER, MANOVA, and PERMANOVA to identify and compare the scent profiles of Canella winterana in its female and male phase for multiple individuals as well as multiple inflorescences of a single tree over one cycle of its entire sexual phase transition. The scent profile of C. winterana is composed of 49 volatile organic compounds and dominated by five compounds. We found no evidence for distinct male or female scent profiles; however, there were significant differences in scent emission between different sexes within some individuals. Two compounds explained over half of the variation between sexual stages within individuals. Our exploration of a single tree's sexual phase transition, including neuter phase, found that five compounds dominated the female phase scent bouquet and that female phase was distinct from male and neuter phase. This study offers new insight into the role that variability in floral scent between sexual phases might play in variable pollinator behavioral responses. These results suggest partial support for two distinct hypotheses regarding the differences between the sex phases (1) honest signaling and (2) sexual mimicry.

The floral ecology and breeding system of Veratrum virginicum (Melanthiaceae)1

We analyzed the floral biology of a population of the threatened/endangered Veratrum virginicum (L.) W.T. Aiton at the Shaw Nature Reserve (Missouri, USA), comparing our results to the first and only study of this species by Charles Robertson (1896). We confirmed most of Robertson's original descriptions regarding floral presentation, protandry, and insect pollination but found the following new information. Each flower lived 9–11 days and smelled of raw liver and latex. We discerned four floral stages based on gradual changes in style and stamen orientation, which might assist in insect-mediated pollination. We determined that stigmas became receptive by the fifth day of anthesis. The generalist pollination system included three Lasioglossum species (Halictidae) and the beetle Chauliognathus marginatus Fabr. (Cantharidae). Most floral foragers showed a geometric mean of body dimensions between 2–3 mm. Approximately 40% of foraging insects carried heterospecific pollen loads, combining the host flower's pollen with grains from up to seven co-blooming taxa. Field observations suggest that all bees foraged on multiple inflorescences whereas beetles remained on the same inflorescence for hours. Larger Apidae species showed symptoms of nectar poisoning. Epifluorescence showed that flowers exposed to visiting insects contained < 5 pollen tubes per gynoecium. Fruit set was 3% for bagged flowers and 51% for exposed flowers. However, the conversion rate of ovules into seeds was low in both bagged (2%) and exposed (6%) flowers. We interpret low reproductive success as one explanation for current declines in populations of this species.

Systematics of Ledebouria sect. Resnova (Hyacinthaceae: Scilloideae: Massonieae), with a new subtribal classification of Massonieae

The species in Ledebouria sect. Resnova are revised, with an identification key, full nomenclature, descriptions, ecological notes, and illustrations. Sect. Resnova is defined by its deeply campanulate flowers with tepals shortly connate basally and erect throughout or spreading distally; biseriate stamens with white, filiform filaments; sessile or subsessile ovary; and diagnostic seeds, obliquely obovoid with an inflated and invaginated raphe, and a finely puberulous-echinulate testa. Five species are recognised, divided between the monotypic ser. Lachenalioides, diagnosed by larger flowers with multi-nerved tepals, and ser. Resnova, with smaller flowers and uni-nerved tepals. Species in ser. Resnova are distinguished primarily by the presence or absence of hairs on one or both surfaces of the leaves, and by the presence or absence of a pseudopetiole. The new species Ledebouria hardyi J.C.Manning is described for a collection of plants from near Burgersfort in Limpopo with mostly solitary, markedly pseudopetiolate foliage. The species in sect. Resnova are geographically and ecologically separated by altitude and climate. A revised subtribal classification is provided for Massonieae, based on available phylogenetic hypotheses. Three subtribes are recognised: the monotypic Merwillineae is described for the genus Merwilla and is diagnosed by its white ovary and beige seeds; the genus Schizocarphus is transferred to join Ledebouria in Ledebouriinae, which is weakly diagnosed by the development of multiple inflorescences in some species and a flexuous scape; and Lachenaliinae is included within Massoniinae, which comprises all remaining genera in the tribe and is diagnosed by its few to many subglobose seeds per locule and often tunicated bulbs. This classification replaces existing hypotheses, which are inconsistent with available morphological and phylogenetic data.

Reproductive biology of Dyckia excelsa Leme (Bromeliaceae): a xerophyte species from ironstone outcrops in central‐western Brazil

AbstractDyckia is the third most diverse genus from Pitcairnoideae, pollinated mainly by insects and hummingbirds. In this study, we evaluated demography, reproductive biology and pollination of Dyckia excelsa, a saxicolous species typical of ironstone outcrops. It occurs in groupings composed of genets, ramets and seedlings and bloomed several times, principally in September, with fruiting and dispersing of seeds in November. The anthesis is diurnal and flowers remain open for 2 days. Nectar volume decreased during the anthesis, whereas nectar sugar concentration remained constant. Dyckia excelsa is partially self‐compatible and xenogamic; the highest fruit set was observed in the control and cross‐pollination treatments; high seed germination rates were observed in all treatments. Flowers have the ornithophilous syndrome, but hummingbirds, bees and butterflies visited them. The occurrence of groupings with multiple inflorescences could contribute to geitonogamy. The high number of flowers during a year supplies food resources and ensures the fidelity of pollinators.

Novel inflorescence architecture in gamma radiation-induced faba bean mutant populations

Purpose: Inflorescence architecture is an important trait in the seed production of grain legumes. As several genes are responsible for this trait, any mutation, on these genes, may cause change in the inflorescence architecture. This study was conducted to evaluate inflorescence architecture in faba bean exposed to gamma radiation and to characterize the inflorescence architecture mutants phenotypically.Materials and methods: Faba bean M2 seeds (4898) generated from M1 generation of cultivars Hassawi 2 and ILB4347 were used in this study. M1 seeds were produced by irradiation treatments at two doses of gamma radiations (25 and 50 Gy). Faba bean M2 seeds were planted under field conditions. A total of 4032 mutant plants out of 4898 M2 seeds were evaluated for their inflorescence architecture.Results: A total of 20 determinate mutants were found and classified into four different types. Determinate type 1 was characterized by the formation of single terminal inflorescence on shoot apical meristem (SAM), type 2 by the formation of multiple inflorescences on SEM and generated upper branches that act as indeterminate type. Type 3 was characterized by the formation of a panicle-like inflorescence. While type 4 was characterized by the formation of primary and secondary panicle-like inflorescence. All of the determinate mutant types had shorter plant height and earlier maturity than control indeterminate type but had lower biological yield and seed yield. Among the determinate mutant types, determinate type 1 was only mutant that had a higher harvest index than the control indeterminate type. This promising mutant can be used to further breeding program to increase biological yield and seed yield.Conclusions: This study indicated potential of gamma radiation in inducing novel inflorescence architecture in faba bean. The mutants developed are valuable resources to study genes related to inflorescence architecture through forward genetics approach.

Molecular detection and identification of phytoplasmas in a novel 16SrI subgroup in sunflowers and cocklebur weeds

Sunflowers (Helianthus annuus L.) exhibiting symptoms of stem fasciation and cluster of multiple inflorescences were observed in Baicheng, Jilin province, China. Coincidently, cockleburs (Xanthium strumarium L.), a weed in the sunflower fields, showing similar symptoms were observed as well. Based on successful amplification of 16S rRNA and secY genes of phytoplasmas, the sunflower fasciation disease (SFD) and cocklebur fasciation disease (CFD) were determined to be associated with phytoplasmas. Based on virtual and actual RFLP analysis of the F2nR2 region of the 16S rRNA genes, the SFD and CFD associated phytoplasmas were classified into a novel 16SrI subgroup, designated 16SrI-AI. This was the first report of SFD associated phytoplasma in China, and the first evidence of phytoplasma infecting cocklebur worldwide.

Plant Growth and Agrobacterium-mediated Floral-dip Transformation of the Extremophyte Schrenkiella parvula.

Schrenkiella parvula is an extremophyte adapted to various abiotic stresses, including multiple ion toxicity stresses. Despite high-quality genomic resources available to study how plants adapt to environmental stresses, its value as a functional genomics model and tool has been limited by the lack of a feasible transformation system. In this protocol, we report how to generate stable transgenic S. parvula lines using an Agrobacterium-mediated floral-dip method. We modified the transformation protocol used for A. thaliana to account for unique traits of S. parvula, such as an indeterminate flowering habit and a high epicuticular wax content on leaves. Briefly, S. parvula seeds were stratified at 4 °C for five days before planting. Plants were grown at a photoperiod of a 14 h light and 10 h dark and a 130 µmol m-2s-1 light intensity, at 22 °C to 24 °C. Eight to nine week-old plants with multiple inflorescences were selected for transformation. These inflorescences were dipped in an infiltration solution of Agrobacterium tumefaciens GV3101 carrying the pMP90RK plasmid. We performed two rounds of flower dipping with an interval of three to four weeks to increase the transformation efficiency. The T1 seeds were collected and dried for four weeks in a container with desiccants before germination to screen for candidate transformed lines. Resistance to BASTA was used to screen T1 plants. We sprayed the BASTA solution three times with an interval of three days starting at two week-old plants to reduce false positives. A BASTA drop test was performed on surviving individual plants to identify true positive transformants. The transformation efficiency was 0.033%, yielding 3-4 transgenic plants per 10,000 T1 seeds propagated.

Mating system and intrapopulational genetic diversity of Copernicia prunifera (Arecaceae): a native palm from Brazilian semiarid.

The aim of this study was to investigate the mating system and genetic diversity of the palm Copernicia prunifera using inter-simple sequence repeat markers. We found that the C. prunifera has multiple inflorescences with hermaphroditic flowers and pollen viability of 62%. Outcrossing rates at the population level (N = 267) produced a multilocus outcrossing rate (tm) of 0.878 and a single-locus outcrossing rate (ts) of 0.738, indicating that C. prunifera has a mixed mating system that is preferentially allogamous. The rate of mating among relatives (tm - ts) was low, indicating limited outcrossing between closely related individuals. The fixation index between seed trees (F) was negative (0.200), suggesting an absence of inbreeding, while the correlation of selfing (rs) was high (0.914). The values of the diversity indices among adults and progenies did not differ statistically (HE = 0.319 and I = 0.470; HE = 0.337 and I = 0.505, respectively). In testing for the presence of genetic bottlenecks using the infinite allele model and the stepwise mutation model, we observed a reduction in the effective population, as well as a deficit in heterozygosity (P < 0.0001). The results of this study inform management strategies for the conservation and genetic improvement of the C. prunifera palm.

Euscelis incisus(Cicadellidae, Deltocephalinae), a natural vector of 16SrIII-B phytoplasma causing multiple inflorescence disease ofCirsium arvense

We investigated multiple inflorescence disease of Cirsium arvense (CMI) and its association with phytoplasmas of the 16SrIII-B subgroup, potential natural vector(s) and reservoir plant(s). From five locations in northern Serbia, 27 plants of C. arvense, 1 C. vulgare and 3 Carduus acanthoides with symptoms of multiple inflorescences (MIs) were collected and tested for 16SrIII group phytoplasmas. All symptomatic plants were found to be infected. Tentative reservoir plants and insect vectors were collected at a Dobanovci site where the continuous presence of CMI disease was recorded. Among the 19 most abundant plant species submitted to phytoplasma testing, all symptomless, the presence of the 16SrIII group was detected only in two legumes: Lathyrus tuberosus (2/5) and L. aphaca (1/5). Among 19 insect species from six families of Auchenorrhyncha, the deltocephalid leafhopper Euscelis incisus was the only insect carrying a 16SrIII phytoplasma (10% of analysed individuals). Transmission trials were performed with naturally infected E. incisus adults of the summer generation and with a laboratory population reared on red clover. After an acquisition period of 48 h on C. arvense symptomatic for MIs and a latent period of 28 days, 83% of the E. incisus adults (300/360) were infected with CMI phytoplasma. In two transmission tests, the leafhoppers successfully transmitted the phytoplasma to exposed plants (C. arvense and periwinkle), proving its role as a natural vector. Test plants of C. arvense infected with the 16SrIII-B phytoplasma expressed typical symptoms similar to those observed in the field, such as MIs or the absence of flowering, shortened internodes and plant desiccation. Typical symptoms in infected periwinkles were virescence and phyllody. The molecular characterisation of the CMI phytoplasma isolates from diseased and asymptomatic field-collected plants, vectors, and test plants was performed by sequence analyses of the 16S rRNA, rpl22-rps3 and rpl15-secY genes. Phylogenetic analyses of other members of the 16SrIII group of phytoplasmas indicated closest relatedness with clover yellow edge phytoplasma (CYE) of the 16SrIII-B subgroup.

Can a high red: Far red ratio replace temperature-induced inflorescence development in Phalaenopsis?

Phalaenopsis is one of the most economically important ornamental crops in the Netherlands, but due to its growth requirements during its various developmental stages, it is a costly crop to grow in terms of energy. Warming the greenhouse in the winter during the vegetative phase, and cooling the greenhouse to 19°C in the summer to induce flowering costs a great deal of energy. Because flower induction is primarily controlled by altering the balance of plant hormones, it might well be possible to steer flower induction by changing the light spectrum instead of changing the temperature. The objective of the present study was to investigate the role of the light spectrum on bud break and inflorescence elongation in Phalaenopsis. To this end an experiment was designed with two Phalaenopsis cultivars, Quincy and Red Stones in a matrix of temperature and spectral treatments. Light treatments were used with a relatively high red to far-red ratio (R:FR) and therefore a high phytochrome photostationary state (PSS) value of 0.85, and with a relatively lower R:FR ratio resulting in a PSS value of 0.71, similar to that of natural daylight. Our hypothesis was that low temperature treatments can, at least partially, be substituted by a light spectrum with a high PSS value in order to suppress apical dominance of the primary flowering inflorescence and thus realize multiple inflorescences. A cooling period (19°C) of 8 weeks always resulted in a high percentage of multiple inflorescences, both from Red Stones as well as Quincy. This implies that a flower induction period of 8 weeks with cooling is effective, regardless of the light spectrum. An induction period of 8 weeks with “red light” always resulted in a high percentage of multiple inflorescences, regardless of the temperature (19 or 22°C). A cooling period (19°C) of 4 weeks followed by 4 weeks 22°C only resulted in a higher percentage of multiple inflorescences under the light spectrum with a high PSS value during the second 4 week-period. This suggests that the plant hormones responsible for bud break and inflorescence elongation, can be stimulated by light with a high PSS value, as well as by a cool phase. In order to stimulate multiple flowering inflorescences, the temperature and/or light spectrum during the second 4-week-period appears to be more important than during the first 4-week-period of the induction phase. Presumably this is due to suppression of the apical dominance of the first emerging inflorescence by low temperature and/or relatively high R:FR ratio during this phase. This also implies that the energy costly cool-induction period during the summer can be replaced, at least in part, by red light or a relatively high R:FR.

Consequences of multiple inflorescences and clonality for pollinator behavior and plant mating.

Angiosperms engage in distributed reproduction, producing sex organs in multiple flowers on one or more inflorescences, including on different physical individuals of clonal plants. We investigated the effects of alternative deployments of artificial flowers for pollinator behavior and simulated pollen dispersal. Plants presented 18 flowers on either one inflorescence (1-I plants) or three inflorescences (3-I plants) spaced either closely or widely. Bees often skipped inflorescences on 3-I plants, visiting an average of 1.5 fewer flowers overall than on 1-I plants. In simulations with all flowers receiving and donating pollen, this behavior caused 7% less geitonogamy for 3-I plants, contradicting a common supposition that clonality increases geitonogamy. Bees generally moved upward within inflorescences and downward between inflorescences. Consequently, in simulations, segregation of pollen receipt to lower flowers and pollen donation to upper flowers reduced self-pollination and enhanced pollen export much more for 1-I plants. Nectar volume per flower had little relevant influence on bee behavior. The observed bee responses and simulated mating results suggest that production of multiple inflorescences and clonality promote pollination quality when flowers simultaneously receive and donate pollen, whereas a single large inflorescence is advantageous when segregation of sex roles among flowers reduces geitonogamy effectively.

The leafy gall syndrome induced byRhodococcus fascians

The Actinomycete Rhodococcus fascians causes the leafy gall syndrome, an infectious plant disease that affects a wide range of plants, primarily dicotyledonous herbs. The syndrome is associated with delayed senescence, loss of apical dominance, activation of dormant axillary meristems, and formation of multiple inflorescences, leading to a stunted and bushy plant appearance. A major breakthrough in the elucidation of the virulence strategy of this pathogen was the discovery of a linear virulence plasmid, pFiD188 for R.fascians strain D188. Upon perception of a compatible host plant, an autoregulatory mechanism mediated by the att operon directs a switch in the bacterial life style from a harmless epiphyte into a pathogenic endophyte and, concomitantly, activates gene expression of the fas operon that encodes a cytokinin biosynthesis pathway. A mixture of five cytokinins determines the cytokinin activity of R.fascians that directly affects plant responses and development. Moreover, the bacterial cytokinins stimulate the host to produce auxins and polyamines, that function as accessory signals to aid in symptom development. The plant reacts against the developmental hijacking by R.fascians by activating a set of counteracting measures that ultimately results in a delicate balance, allowing a long-lasting biotrophic interaction.

Global warming reduces plant reproductive output for temperate multi‐inflorescence species on the Tibetan plateau

• Temperature is projected to increase more during the winter than during the summer in cold regions. The effects of winter warming on reproductive effort have not been examined for temperate plant species. • Here, we report the results of experimentally induced seasonal winter warming (0.4 and 2.4°C increases in growing and nongrowing seasons, respectively, using warmed and ambient open-top chambers in a Tibetan Plateau alpine meadow) for nine indeterminate-growing species producing multiple (single-flowered or multi-flowered) inflorescences and three determinate-growing species producing single inflorescences after a 3-yr period of warming. • Warming reduced significantly flower number and seed production per plant for all nine multi-inflorescence species, but not for the three single-inflorescence species. Warming had an insignificant effect on the fruit to flower number ratio, seed size and seed number per fruit among species. The reduction in seed production was largely attributable to the decline in flower number per plant. The flowering onset time was unaffected for nine of the 12 species. Therefore, the decline in flower production and seed production in response to winter warming probably reflects a physiological response (e.g. metabolic changes associated with flower production). • Collectively, the data indicate that global warming may reduce flower and seed production for temperate herbaceous species and will probably have a differential effect on single- vs multi-inflorescence species.

Arabidopsis Serine Decarboxylase Mutants Implicate the Roles of Ethanolamine in Plant Growth and Development

Ethanolamine is important for synthesis of choline, phosphatidylethanolamine (PE) and phosphatidylcholine (PC) in plants. The latter two phospholipids are the major phospholipids in eukaryotic membranes. In plants, ethanolamine is mainly synthesized directly from serine by serine decarboxylase. Serine decarboxylase is unique to plants and was previously shown to have highly specific activity to l-serine. While serine decarboxylase was biochemically characterized, its functions and importance in plants were not biologically elucidated due to the lack of serine decarboxylase mutants. Here we characterized an Arabidopsis mutant defective in serine decarboxylase, named atsdc-1 (Arabidopsis thaliana serine decarboxylase-1). The atsdc-1 mutants showed necrotic lesions in leaves, multiple inflorescences, sterility in flower, and early flowering in short day conditions. These defects were rescued by ethanolamine application to atsdc-1, suggesting the roles of ethanolamine as well as serine decarboxylase in plant development. In addition, molecular analysis of serine decarboxylase suggests that Arabidopsis serine decarboxylase is cytosol-localized and expressed in all tissue.

Considerations for evaluating flower abscission in potted plants with multiple inflorescences— Plectranthus as a case study

The ability to protect plants and flowers from the adverse affects of ethylene and sub-optimal transport conditions relies on a thorough understanding of the environmental triggers and subsequent downstream physiological and molecular processes that result in senescence or abscission. Characterising abscission is the essential starting point in this process. In this study we explore additional measures of abscission that provide insight into differential abscission patterns where open flowers or unopened buds are preferentially shed. We examine equations relating to the proportion of open or unopened flowers shed, as well as those that are available for abscission using simulated data. To test these equations, two varieties of potted Plectranthus were subjected to continuous darkness or placed under fluorescent lights. After 96 h, abscission data was calculated using equations. Cultivar P000603 was found to preferentially shed open flowers in both conditions, as indicated by differences in the number of open flowers abscised as a proportion of the total available for abscission. Cultivar P010509 shed open and unopened flowers at similar proportions. These additional measures of abscission enlarge our understanding of this intricate process by providing a more comprehensive and thorough approach to evaluate abscission.

A test of the effect of floral color change on pollination effectiveness using artificial inflorescences visited by bumblebees

Floral color change has been recognized as a pollination strategy, but its relative effectiveness has been evaluated insufficiently with respect to other floral traits. In this study, effects of floral color change on the visitation pattern of bumblebees were empirically assessed using artificial flowers. Four inflorescence types were postulated as strategies of flowering behavior: type 1 has no retention of old flowers, resulting in a small display size; type 2 retains old flowers without nectar production; type 3 retains old flowers with nectar; and type 4 retains color-changed old flowers without nectar. Effects of these treatments varied depending on both the total display size (single versus multiple inflorescences) and the pattern of flower-opening. In the single inflorescence experiment, a large floral display due to the retention of old flowers (types 2-4) enhanced pollinator attraction, and the number of flower visits per stay decreased with color change (type 4), suggesting a decrease in geitonogamous pollination. Type-4 plants also reduced the foraging time of bees in comparison with type-2 plants. In the multiple inflorescence experiment, the retention of old flowers did not contribute to pollinator attraction. When flowering occurred sequentially within inflorescences, type-4 plants successfully decreased the number of visits and the foraging time in comparison with type-2 plants. In contrast, floral color change did not influence the number of visits, and it extended the foraging time when flowering occurred simultaneously within inflorescences but the opening of inflorescences progressed sequentially within a plant. Therefore, the effectiveness of floral color change is highly susceptible to the display size and flowering pattern within plants, and this may limit the versatility of the color change strategy in nature.

First report of multiple inflorescence disease of Cirsium arvense and its association with a 16SrIII‐B subgroup phytoplasma in Serbia

Multiple inflorescences on Cirsium arvense (Asteraceae) have always been attributed to the presence of eriophyid mites, since their first record in 1892 (Petanovićet al., 1997). Plants showing symptoms of varying intensity were recorded from more than 10 sites in northern Serbia between 2001 and 2003. Affected plants showed irregular growth, atypical branching with small leaves, shortened internodes, hardening of the green inflorescence and reduced vigour, as well as either chlorosis or reddish-brown discoloration of the leaves and stems. Plants that reached flowering sometimes had multiple inflorescences. In the field the disease persists for years, increasing slowly around the original infection focus. Infected plants senesce prematurely, inhibiting both seed production and rhizome propagation, which markedly reduces the C. arvense population. DNA was extracted from eight samples of fresh leaf midribs and multiple inflorescences from affected plants, and from similar tissues of four plants without symptoms. This DNA was used as template in a nested PCR using universal phytoplasma primers P1/P7, followed by primers F1/B6 (band 1700 bp) and then primers R16F2/R2 (Duduk et al., 2004). Subsequent RFLP analyses with HpaII, TruI and HhaI restriction endonucleases were carried out. All samples from plants with symptoms were PCR positive, while those from the four symptomless plants were negative. RFLP patterns from the R16F2/R2 amplicons were identical to those of clover yellow edge phytoplasma (subgroup 16SrIII-B) but different from the TruI and HpaII profiles obtained using a reference strain of peach X disease. These results were confirmed using primers R16(III)F2/R1, which are specific for group 16SrIII phytoplasmas and which amplify an ≈800 bp product (Lee et al., 1994). This is the first report of multiple inflorescence disease of Cirsium in Serbia and of its association with phytoplasmas belonging to rRNA group 16SrIII-B. These phytoplasmas have recently been identified in plants with similar symptoms in Hungarian vineyards (Palermo et al., 2004) and in other herbaceous or woody host species.

Ectopic expression of a Eucalyptus grandis SVP orthologue alters the flowering time of Arabidopsis thaliana.

A new MADS-box gene, EgrSVP was isolated from vegetative tips of Eucalyptus grandis Hill ex Maiden saplings. This gene was expressed in vegetative tissues such as shoots, leaves and roots, as well as in unopened floral buds. DNA sequence alignments indicate that EgrSVP shares the highest level of sequence identity with PkMADS1, JOINTLESS, IbMADS3 and SVP. Phylogenetically, it is grouped in the JOINTLESS clade, the members of which share similar expression patterns. Transgenic Arabidopsis thaliana (L.) Heynh. plants overexpressing EgrSVP, exhibited a variety of altered phenotypes, including homeotic floral organ transformation, indeterminate floral development, multiple inflorescences and coflorescences, and some degree of late flowering.The nucleotide sequence data reported will appear in the GenBank Nucleotide Database under the accession number AY263809.