Clonal growth of <Emphasis Type="Italic">Typha domingensis</Emphasis> Pers., subject to drawdowns and interference of <Emphasis Type="Italic">Eleocharis mutata</Emphasis> (L.) Roem. et Schult. in a tropical coastal lagoon (Brazil)

This paper presents the results of a study on the clonal growth of Typha domingensis Pers. in the Imboassica lagoon, in the intervals between four drawdowns. Sampling was performed over a period of two years, from permanent quadrats, in the four months after each of the drawdowns. The high mortality of the macrophytes after each drawdown is followed by a period in which the stands recover by producing ramets. The results have shown that the growth areas around the boundary of the stand (boundary band, BB) and one further towards the middle (innermost zone, IZ) show different recovery characteristics. The BB area recovered more quickly after the first drawdown, but both areas had the same accumulated biomass after the third drawdown. At the contact boundary, (CB) with stand of Eleocharis mutata, a decrease in the growth of T. domingensis occurred with a progressive invasion of E. mutata in its stand. After 10 months with no drawdown, T. domingensis produced a large quantity of inflorescences, which indicates recovery. It can therefore be concluded that successive drawdowns may decrease the regeneration ability of T. domingensis, favoring the expansion of E. mutata in the lagoon.     

Prevention of the flowering of a tree,silver birch

Genetic modification of trees presents great advantages but it is hampered by the possible spread of introduced genes to native populations. However, the spread would be prevented if the modified trees would be sterile. We have previously shown that the induction of sterility by the prevention of flowering is possible in tobacco and Arabidopsis by introducing a gene construct composed of the ribonuclease gene BARNASE ligated to the flower-specific promoter of the birch gene BpMADS1. In the present study, we test this gene construct in silver birch (Betula pendula Roth). When this gene construct was introduced into very early-flowering birch clones, 81 kanamycin resistant lines were obtained. In 38 lines, the vegetative development was disturbed, e.g., the leaves were small and the plants were short and bushy or the growth of plants was weak. More importantly, in 7 other lines no male inflorescences formed or they aborted early. If male inflorescences were formed, they did not contain any stamens. The initial growth of these lines was similar to the non-transgenic control lines. Later, however, the growth of the non-flowering lines differed from that of the controls in showing some dichotomic branching and a reduced number of branches. Preliminary results showed that the gene construct can prevent the development of female inflorescences as well. The results show clearly that BpMADS1::BARNASE can prevent the flowering in a tree but the prevention of flowering may cause some side effects. Studies with ordinary birch clones will show whether the side effects are a property of the early flowering clones or all birches.     

Conflict resolution in an ant–plant interaction: Acacia constricta traits reduce ant costs to reproduction

Many plant species attract ants onto their foliage with food rewards or nesting space. However, ants can interfere with plant reproduction when they visit flowers. This study tests whether Acacia constricta separates visiting ant species temporally or spatially from newly opened inflorescences and pollinators. The diurnal activity patterns of ants and A. constricta pollinators peaked at different times of day, and the activity of pollinators followed the daily dehiscence of A. constricta inflorescences. In addition to being largely temporally separated, ants rarely visited open inflorescences. A floral ant repellent contributes to the spatial separation of ants and inflorescences. In a field experiment, ants of four species were given equal access to inflorescences in different developmental stages. On average, the frequency with which ants made initial, antennal contact with the floral stages did not differ, but ants significantly avoided secondary contact with newly opened inflorescences relative to buds and old inflorescences, and old inflorescences relative to buds. Ants also avoided contact with pollen alone, indicating that pollen is at least one source of the repellent. The results suggest A. constricta has effectively resolved the potential conflict between visiting ants and plant reproduction.     

Oviposition preferences and larval performance of a flower-feeding weevil,Coelocephalapion aculeatum, in relation to host development

The oviposition behaviour ofCoelocephalapion aculeatum Fall (Coleoptera: Apionidae), a host specific florivore exploiting an ephemeral resource, was studied in relation to host development. Immature inflorescences of its host, the weedMimosa pigra L. (Mimosaceae), were categorised into 5 developmental stages ranging from first appearance to one day before opening. The duration, weight, percent abortion, and nitrogen content of each stage were measured. Oviposition preferences ofC. aculeatum for all inflorescence stages were determined in multiple choice trials. Newly hatched, larvae were transferred into inflorescences of each stage to determine larval survival as a function of stage. Numbers of eggs laid into inflorescences generally correlated with larval survival except that oviposition was greater in stage 4 inflorescences than expected from the larval survival. Numbers of eggs laid into inflorescences generally correlated with their carrying capacity except that adults avoided stage 5 inflorescences in which larval survival was low. The evolution of oviposition preferences ofC. aculeatum appears to have been influenced by two opposing selective forces. The need to complete development before the inflorescence deteriorated would have selected for oviposition in young inflorescences. The greater availability of food and lower probability of abortion offered by older inflorescences would have selected for oviposition in these. The net outcome of these pressures has resulted in the observed oviposition strategy.     

An endangered new species of edible yam (<Emphasis Type="Italic">Dioscorea</Emphasis>, <Emphasis Type="Italic">Dioscoreaceae</Emphasis>) from Western Madagascar and its conservation

Summary  A new species of Dioscorea from Morondava prefecture in Western Madagascar is described. Dioscorea bako Wilkin differs from D. alatipes Burkill & H. Perr. by its usually shallowly and irregularly lobed leaf margins, broader leaf blade (grey-green below), longer petiole and the broadly cuneate area where the petiole is inserted onto the leaf blade in the basal sinus. It is pubescent, especially densely on young shoots and inflorescences. It is endemic to Morondava Préfecture and is endangered under IUCN Red List category criteria (IUCN 2001). The unusual morphological features of its inflorescences, some of which are shared with D. alatipes are discussed. Dioscorea bako is a favoured food source for people of the Menabe region and is reported by them to be increasingly hard to find. Immediate conservation measures are necessary to ensure that it remains extant and, in the medium to long term, research should be undertaken to guide its sustainable utilisation.     

An Efficient Method for the Extraction of High-Quality Fungal Total RNA to Study the <Emphasis Type="Italic">Mycosphaerella fijiensis</Emphasis>–<Emphasis Type="Italic">Musa</Emphasis> spp. Interaction

Efficient RNA isolation is a prerequisite for gene expression studies and it has an increasingly important role in the study of plant–fungal pathogen interactions. However, RNA isolation is difficult in filamentous fungi. These organisms are notorious for their rigid cell walls and the presence of high levels of carbohydrates, excreted from the fungal cells during submerged growth, which interferes with the extraction procedures. Although many commercial kits are already available for RNA isolation, they do not provide, in most cases, enough amount of pure RNA to be used in upstream applications. In the present work, we propose an easy and efficient protocol for isolating total RNA from the filamentous fungus Mycosphaerella fijiensis, the most important foliar pathogen of Musa spp. varieties worldwide. In addition, we applied the proposed protocol to the isolation of total RNA from banana leaves infected with the pathogen. Our methodology was developed based on the SDS method with modifications including a carbohydrate precipitation step. The protocol resulted in high-quality total RNA, from fungal mycelium grown in PDB medium and infected banana leaves, suitable for further molecular studies. The proposed methodology is also applicable to the ascomycete fungus Passalora fulva (syn. Cladosporum fulvum). Aminael Sánchez-Rodríguez and Orelvis Portal contributed equally to the article.     

Fruit-set and seed weight variation inAnthyllis vulneraria subsp.vulgaris (Fabaceae)

Fruit-set and seed weight variation was studied in a population ofAnthyllis vulneraria subsp.vulgaris (Fabaceae) in northwestern Spain. The plants produce several shoots, each bearing two to four inflorescences that open one at a time from bottom to top. Fruit-set, seed-pod weight and seed weight were found to be significantly higher in proximal inflorescences than in distal inflorescences of the same shoot; mean seed weight was up to three times higher in proximal than in distal inflorescences. By contrast, none of the three variables varied significantly among plants or among shoots of the same plant. Similarly, none of the three variables differed significantly between early- and late-flowering plants, or between plants monitored in 1993 and in 1994. These results are compatible with the view that shoots function as semiautonomous units as regards resource allocation, and that within the shoot resources are preferentially allocated to proximal (= early-opening) inflorescences. In the plants studied, the ratio of seed-pod weight to seed weight was fairly constant, suggesting that the pod is important for seed success.     

Influence of resource topography on pollinator flight directionality of two species of bees

Analyses of the search patterns of ApisMellifera workers foraging on artificial inflorescences and Bombus Pennsylvanicusqueens foraging on inflorescences of red clover are used to identify a general rule specifying intrapatch search patterns. Bees land, move about the inflorescences in search of nectar, and come to a last-faced position from which takeoff occurs. Last-faced directions are generated by a forward-moving tendency while probing artificial inflorescences or real florets. This tendency is modulated by restricted bee locomotion, caused by the size and shape of the visited inflorescence and the spatial distribution of florets within such inflorescences. The result is that bees tend to circle inflorescences. The process is terminated with an undefined stopping rule, whereupon bees usually depart in the direction they last face. The last-faced direction is a by-product of intrafloral search and becomes less associated with arrival directions as intrafloral search continues. Pollinator flight directionality is usually represented as a frequency distribution of angular changes in direction which typically has a mean near 0° and a variance that increases with increases in energy gain. We show that these characteristics are artifacts of pooling mirror-image movement data sets;a mean of 0° is the result of canceling the means of the left- and right-hand turns. The putative increased variance associated with energy gain is the result of adding the variances associated with left- and right-handed turns. These computational artifacts may be avoided by changing the sign of the left-handed turns prior to pooling with the right-handed turns (or vice versa). Pooling bee visits based only on the number of florets probed can destroy information relevant to studies examining behavioral mechanisms of flight directionality. Analytical problems encountered when turns exceed 360° are also addressed.     

The bicolor unit — homology and transformation of an inflorescence structure unique to coreMalvales

A broad comparative analysis reveals that the inflorescences of coreMalvales, familiesSterculiaceae, Tiliaceae, Bombacaceae andMalvaceae, include characteristic repeating units. The basic repeating unit is called bicolor unit (afterTheobroma bicolor, where it was first observed). It is determinate and bears three bracts, one of which is invariably sterile, whereas the others subtend lateral cymes or single flowers. Through the demonstration of intermediate steps in closely related taxa the triad of bracts within a bicolor unit and the trimerous malvalean epicalyx are shown to be homologous. Various possibilities for an origin of the bicolor unit are discussed. Bicolor units are variously arranged to form complete inflorescences. In many taxa they are terminal on modules that comprise two (or fewer) prophylls. These modules may be arranged in elongated anthocladia or condensed sympodia, which in turn may constitute components of higher order inflorescence structures. The presence of the bicolor unit or its derivatives linksSterculiaceae, Tiliaceae, Bombacaceae andMalvaceae. It is absent from all other families included in a broader defined orderMalvales and represents one of the rare morphological synapomorphies of coreMalvales. Furthermore, inflorescence morphology provides characters of systematic significance for various taxa within coreMalvales.     

Flower choice by honey bees (Apis mellifera L.): sex-phase of flowers and preferences among nectar and pollen foragers

Bees foraging for nectar should choose different inflorescences from those foraging for both pollen and nectar, if inflorescences consist of differing proportions of male and female flowers, particularly if the sex phases of the flowers differ in nectar content as well as the occurrence of pollen. This study tested this prediction using worker honey bees (Apis mellifera L.) foraging on inflorescences of Lavandula stoechas. Female flowers contained about twice the volume of nectar of male flowers. As one would predict, bees foraging for nectar only chose inflorescences with disproportionately more female flowers: time spent on the inflorescence was correlated with the number of female flowers, but not with the number of male flowers. Inflorescence size was inversely correlated with the number of female flowers, and could be used as a morphological cue by these bees. Also as predicted, workers foraging for both pollen and nectar chose inflorescences with relatively greater numbers of both male and female flowers: time spent on these inflorescences was correlated with the number of male flowers, but not with the number of females flowers. A morphological cue inversely associated with such inflorescences is the size of the bract display. Choice of flowers within inflorescences was also influenced predictably, but preferences appeared to be based upon corolla size rather than directly on sex phase.     

Characterization of rice transformed via an Agrobacterium-mediated inflorescence approach

Rice inflorescences were inoculated with Agrobacterium tumefaciens strain LBA4404 carrying plasmid pJD4 with application of vacuum infiltration. After co-cultivation, callus was initiated and subjected to hygromycin selection, and plants were regenerated from resistant callus lines. Based on the total number of co-cultivated inflorescences bearing flowers 1 to 3 mm in length, the average frequency for recovering independent transgenic rice plants was at least 30%. Seeds from selfed R0 plants were harvested within 6 months after initiation of the experiments. Genomic DNA blot analysis showed that genes in the T-DNA of the binary plasmid were stably integrated into the rice genome, typically at low copy number. In most, but not all, cases the transgene was transmitted to R1 progeny at a frequency characteristic for Mendelian inheritance of a single dominant trait. For selfed progeny of one two-locus insertion line, reactivation of GUS expression was observed for a single copy locus that segregated from a silenced multicopy locus. For this line and some additional plants, fluorescence in situ hybridization was used to visualize the chromosomal location of the transgene insert.     

Organographic and ontogenetic studies on the inflorescence ofLespedeza cuneata (Dum.-Cours.) G. Don (Leguminosae)

Structure of inflorescence and its variation were organographically and ontogenetically studied inLespedeza cuneata (Dum.-Cours.) G. Don. An axillary inflorescence of the species forms a compound inflorescence which is composed of three or four component inflorescences. Each component inflorescence bears four (rarely six), three, two, or one flowers. Based on the arrangement of inflorescence phyllomes, the component inflorescence with four flowers is interpreted as a pseudoraceme bearing two shortened lateral shoots (partial inflorescences) each of which has two flowers. The component inflorescence with one flower appears to be terminated by the flower and to compose the cyme. Organographic observations revealed that the terminally located flower is not truly terminal, but axillary in origin. Ontogenetic observations showed that the apices of component inflorescence and partial inflorescence exist in early developmental stages in spite of variation in the form of component inflorescence. The terminally located flower in the cyme-like inflorescence was thus demonstrated to be laterally borne on the partial inflorescence axis. The component inflorescence composing the cyme-like one inL. cuneata is a reduced form in the number of partial inflorescences and of flowers from the pseudoraceme. The cyme-like inflorescence inL. cuneata resembles the inflorescence ofKummerowia.     

The mating system of Hydrophyllum appendiculatum,a protandrous species

Summary The mating system of Hydrophyllum appendiculatum (Hydrophyllaceae), a protandrous, self-compatible, monocarpic plant was examined using progeny arrays assayed at three polymorphic allozyme loci. We were particularly interested in the effect of ecological factors on spatial and temporal variation in outcrossing rates. Multilocus estimates of outcrossing rates in three populations ranged from 0.62–0.81 indicating that the majority of seeds are produced via outcrossing. The population estimates did not differ significantly from each other indicating that there is little or no spatial variation in the mating system of this species. The estimates were, however, significantly less than unity, which demonstrates that although mainly outcrossing, a significant fraction of seeds are produced by selfing. Estimates suggested that biparental inbreeding occurred, although it was statistically significant in only one population. Individuals of H. appendiculatum may remain in anthesis 3–4 weeks and produce up to 30 inflorescences. As a result, the possibility exists for the mating system to vary through the flowering season. Although the mean outcrossing rate was highest in the middle of the flowering phenology than at the beginning or end, there was no evidence for statistically significant temporal heterogeneity. We were also interested in determining if the size of the floral display (number of inflorescences produced by a plant) influenced the outcrossing rate. The results obtained by two different statistical analyses were contradictory; there was a significant positive correlation between size of floral display and outcrossing rate, but the outcrossing rates of large plants (\s> 8 inflorescences) did not differ significantly from small plants (> 8 inflorescences).     

Bat visits to Marcgravia pittieri and notes on the inflorescence diversity within the genus Marcgravia (Marcgraviaceae)

We report bat visits to the inflorescences of Marcgravia pittieri. The animals were videotaped visiting the nectaries of the inflorescences in short hovering flight. Nectarivorous bats caught in front of the inflorescences were Anoura cultrata and Hylonycteris underwoodi (both Phyllostomidae: Glossophaginae). Furthermore, we provide a short overview on inflorescence architecture within the genus Marcgravia with a special focus on functional morphology in chiropterophilous species.     

Oviposition and feeding preferences of a flower-feeding weevil,Coelocephalapion aculeatum, in relation to conspecific damage to its host-plant

The oviposition and feeding preferences ofCoelocephalapion aculeatum Fall (Coleoptera: Apionidae), a host specific florivore ofMimosa pigra L. (Mimosaceae), were studied in relation to conspecific damage to its hostplant. Adults ofC. aculeatum cease ovipositing in inflorescences when the egg load reaches a number consistent with the larval carrying capacity of the inflorescence. The basis for this oviposition deterrence was examined by offering inflorescences damaged by adult feeding alone, larval feeding alone and a combination of adult feeding and oviposition. Adults preferred to oviposit on inflorescences which are not damaged by either adult feeding, larval feeding, or oviposition. No evidence for the existence of an oviposition deterring pheromone (ODP) was found. I suggest that the ability of a single host inflorescence to support the development of many larvae causes selection for the use of these oviposition deterring cues which can convey more quantitative information about the level of previous infestation than can ODPs. Adults fed a similar amount on damaged compared to undamaged inflorescences. These results assisted in the design of host range testing trials and allows predictions to be made about the effectiveness of this insect as a biological control agent.     

应恢复赤车属头序赤车组和头序赤车

头序赤车的特征在于其具花序托和总苞的雌头状花序,根据此一特征即可将它与赤车属的其它所有种区别开。因此,在2002年被错误归并为异名的此赤车属进化种,以及根据其建立的单种进化组头序赤车组在该文中予以恢复。     

The inflorescences structure of Cyperus L. section Luzuloidei Kunth (Cyperaceae)

In the present work the inflorescences of 12 species of Cyperus sect. Luzuloidei Kunth sensu Kükenthal were analyzed using the methodology and terminology of Troll's school. All the inflorescences studied are polytelic (indeterminate). The inflorescences are anthela-like or capitate, and can be terminal or pseudolateral. Below the main florescence a paracladial zone is present. In this zone three types of branching were observed, i.e. normal, accessory-axillar and prophyllar branching, whose position vary among the different species. In the paracladial zone a subzone of long paracladia and a subzone of short paracladia were observed. In the short paracladial subzone the spikelets are clustered in fascicles, which can be serial, prophyllar or mixed. Variation in length and position of pherophylls, length of prophyll, number and degree of branching were noticed. The systematic value of the inflorescences in the section Luzuloidei is discussed.     

Prevention of flower formation in dicotyledons

Prevention of flower formation is important, for example for preventing the spread of transgenes from genetically modified plants or the spread of non-native species, for increasing vegetative growth or preventing the formation of allergenic pollen. The aim of this study was to determine whether flowering of dicotyledonous plants can be prevented by genetic manipulation without harmful effects on vegetative growth. Here we describe isolation of the BpMADS1 gene (similar to SEP3, formerly AGL9) from birch and show that it is expressed only in the inflorescences. In tobacco and Arabidopsis, the expression of BpMADS1::GUS was also virtually inflorescence-specific. Transgenic tobacco and Arabidopsis containing a BpMADS1::BARNASE construct grew well. In one tobacco line the formation of the inflorescence was completely prevented; in several other lines the flowers lacked stamens and carpels and therefore were sterile. The final dry weights of the shoots of the sterile tobacco lines were 140–200% of those of controls. In Arabidopsis, some of the transgenic lines containing the BpMADS1::BARNASE construct formed inflorescences. Some of these lines formed never flowers and some others formed occasionally single fertile flowers. Some other lines did not form inflorescences, but formed up to about one hundred leaves, even in long-day conditions. These results suggest that formation of flowers or inflorescences in widely different dicotyledonous plants could be prevented using the BpMADS1::BARNASE construct and that prevention of flowering may lead to increased vegetative mass.     

Pollination ecology of Yucca elata

The pollination biology of a population of 250 Yucca elata (Liliaceae) plants was studied in southern New Mexico. Yucca elata and the prodoxid yucca moth Tegeticula yuccasella have a mutualistic association that is essential for the successful sexual reproduction of both species. However, a wide range of other invertebrate species visit flowers during the day and at night. Our aim was to quantify the role of yucca moths and other invertebrate visitors in pollination and fruit set, using manipulative field experiments. Inflorescences were bagged during the day or night (N=12 inflorescences) to restrict flower visitors to either nocturnal or diurnal groups. Yucca moths were active exclusively nocturnally during the flowering period and thus did not visit inflorescences that were unbagged during the day. None of the 4022 flowers exposed only to diurnal visitors set fruit, whereas 4.6% of the 4974 flowers exposed only to nocturnal visitors (including yucca moths) produced mature fruit. The proportion of flowers producing fruit in the latter treatment was not significantly different from unbagged control inflorescences. In a series of experimental manipulations we also determined that: (1) flowers opened at dusk and were open for two days on average, but were only receptive to pollen on the first night of opening; (2) pollen must be pushed down the stigmatic tube to affect pollination; and (3) most plants require out-cross pollination to produce fruit. The combination of these results strongly suggests that yucca moths are the only species affecting pollination in Y. elata, and that if another species was to affect pollination, it would be a rare event.     

Hormone-regulated inflorescence induction and TFL1 expression in Arabidopsis callus in vitro

To study hormone-regulated inflorescence development, we established the in vitro regeneration system of Arabidopsis inflorescences in the presence of cytokinin and auxin. Media containing a combination of thidiazuron (TDZ) and 2,4-dichlorophenoxyacetic acid (2,4-D) were used to induce callus formation. Higher frequencies of calli were obtained by using the inflorescence stems as explants. After transferring the calli to media containing a combination of zeatin and indole-3-acetic acid (IAA), the inflorescences were induced from the calli. The morphology of regenerated inflorescences was similar to that of inflorescences in plants; however, flowers of regenerated inflorescences often lacked a few floral organs. Furthermore, TFL1, a gene involved in floral transition in Arabidopsis, was activated during the inflorescence induction. Our results suggest that the TFL1 gene plays an important role in hormone-regulated inflorescence formation.