On the phylogenetic position of the New Caledonian endemic families Paracryphiaceae, Oncothecaceae, and Strasburgeriaceae: A comparison of molecules and morphology

Following his collecting trips to New Caledonia in 1979 and 1981, William C. Dickison published a series of papers focused on the anatomy, morphology, and systematic relationships of the monogeneric, endemic families Strasburgeriaceae, Oncothecaceae, and Paracryphiaceae. He and his collaborators concluded thatParacryphia, Oncotheca, andStrasburgeria should each be treated as distinct families positioned near Sphenostemonaceae, Theaceae, and Ochnaceae, respectively. These anatomical data proved to be a valuable source of systematic characters, but the precise phylogenetic positions of these enigmatic families continue to be in doubt. In fact, even the ordinal classification of flowering plants published by the Angiosperm Phylogeny Group (APG, 1998) left uncertain the position of two of these three families. More recently, however, phylogenies for eudicots based on multiple-gene data sets firmly place Oncothecaceae within Garryales, a position that has never been suggested previously. In the case of Paracryphiaceae, molecular data support the most often cited, historical placement of the family within Dipsacales. New molecular data presented here support the position of Strasburgeriaceae as sister to Ixerbaceae within Crossosomatales. This is one of several historical placements suggested for the family, but a placement that has not been cited in recent years. A comparison of anatomy/morphology betweenStrasburgeria andIxerba is presented in the context of this molecular phylogenetic hypothesis.     

Floral anatomy and systematic position ofVivianiaceae

The floral anatomy of four species ofViviania has been studied. In the basic floral plan and essential floral anatomical featuresViviana closely resembles theGeraniaceae. Evidence from vegetative and floral anatomy, ultrastructural studies on phloem as well as phytochemistry supports geranialean affinity ofViviania; the placement within thePittosporales sensuHutchinson being unnatural.     

Two tobacco AP1-like gene promoters drive highly specific,tightly regulated and unique expression patterns during floral transition,initiation and development

The genetic engineering of agronomic traits requires an array of highly specific and tightly regulated promoters that drive expression in floral tissues. In this study, we isolated and characterized two tobacco APETALA1-like (AP1-like) promoters (termed NtAP1La and NtAP1Lb1) in transgenic plants using the GUS reporter system, along with tissue-specific ablation analyses. Our results demonstrated that the two promoters are active in floral inflorescences but not in vegetative apical meristems or other vegetative tissues, as reflected by strong GUS staining and DT-A-mediated ablation of apical shoot tips during reproductive but not vegetative growth. We also showed that the NtAP1Lb1 promoter was more active than NtAP1La in inflorescences, as the former yielded higher frequencies and greater phenotypic evidence of tissue ablation compared to the latter. We further revealed that both promoters were uniformly expressed in the meristems of stage 1 and 2 floral buds, but were differentially expressed in floral organs later during development. While NtAP1La was found to be active in stage 4–5 carpels, later becoming confined to ovary tissue from stage 9 onwards, NtAP1Lb1 activity was apparent in all floral organs from stages 3 to 7, becoming completely absent in all floral organs from stage 11 onward. Therefore, it seems that the two tobacco promoters have acquired similar but distinct inflorescence-, floral meristem- and floral organ-specific and development-dependent regulatory features without any leaky activity in vegetative tissues. These features are novel and have rarely been observed in other flower-specific promoters characterized to date. The potential application of these promoters for engineering sterility, increasing biomass production and modifying flower architecture, as well as their putative use in flower-specific transgene excision, will be discussed.     

Floral development and anatomy of Salvadoraceae

Background and Aims

This study is an investigation into the floral development and anatomy of two genera of the small family Salvadoraceae, which belongs to the Brassicales in a clade with Batis and Koeberlinia. Salvadoraceae remains little known, despite its wide distribution in arid areas of the globe. Floral morphological data are scarce, and information on floral anatomy is limited to a single study, although morphological and anatomical characters are now used increasingly as a counterpart of molecular data. There remain a number of controversial morphological questions, such as the fusion of the petals, the number of carpels and the nature of the nectaries.

Methods

Floral anatomy and ontogeny were studied in two species of Salvadora and one species of Dobera. Only for S. persica could a full floral developmental sequence be done.

Key Results

The floral development demonstrates that the ovary of Salvadoraceae is basically bicarpellate and pseudomonomerous with a single locule and parietal placenta. The ovary of Dobera resembles Azima tetracantha in the presence of a false apical septum. Evidence for a staminodial nature of the nectaries is not decisive. In Salvadora petals and stamens are lifted by a short hypanthium.

Conclusions

Salvadoraceae share several morphological and developmental synapomorphies with Batis (Bataceae) and possibly Koeberlinia (Koeberliniaceae), supporting their close relationship as indicated by molecular phylogeny.Key words: Batis, Brassicales, Dobera, Emblingia, floral development, floral anatomy, Koeberlinia, phylogeny, Salvadora, Salvadoraceae, SEM     

Floral and vegetative cues in oil-secreting and non-oil-secreting Lysimachia species

Background and Aims

Unrelated plants pollinated by the same group or guild of animals typically evolve similar floral cues due to pollinator-mediated selection. Related plant species, however, may possess similar cues either as a result of pollinator-mediated selection or as a result of sharing a common ancestor that possessed the same cues or traits. In this study, visual and olfactory floral cues in Lysimachia species exhibiting different pollination strategies were analysed and compared, and the importance of pollinators and phylogeny on the evolution of these floral cues was determined. For comparison, cues of vegetative material were examined where pollinator selection would not be expected.

Methods

Floral and vegetative scents and colours in floral oil- and non-floral oil-secreting Lysimachia species were studied by chemical and spectrophotometric analyses, respectively, compared between oil- and non-oil-secreting species, and analysed by phylogenetically controlled methods.

Key Results

Vegetative and floral scent was species specific, and variability in floral but not vegetative scent was lower in oil compared with non-oil species. Overall, oil species did not differ in their floral or vegetative scent from non-oil species. However, a correlation was found between oil secretion and six floral scent constituents specific to oil species, whereas the presence of four other floral compounds can be explained by phylogeny. Four of the five analysed oil species had bee-green flowers and the pattern of occurrence of this colour correlated with oil secretion. Non-oil species had different floral colours. The colour of leaves was similar among all species studied.

Conclusions

Evidence was found for correlated evolution between secretion of floral oils and floral but not vegetative visual and olfactory cues. The cues correlating with oil secretion were probably selected by Macropis bees, the specialized pollinators of oil-secreting Lysimachia species, and may have evolved in order to attract these bees.     

Anatomy and systematic position of Uldinia (Umbelliferae)

Vegetative, floral and fruit anatomy and morphology ofUldinia, a monotypic hydrocotyloid genus endemic to Australia, are described in detail. These observations, when compared to available reports for other genera of Hydrocotyloideae, indicate thatUldinia is most closely allied to members of Hydrocotyleae—Hydrocotylinae, and, in particular, toTrachymene. Similarities between these two genera include such anatomical and morphological characteristics as habit and leaf morphology, stem anatomy, trichome anatomy, inflorescence morphology, floral morphology, and several details of the floral venation pattern and fruit anatomy. Nevertheless, the nature and development of the fruit wings, the papillae and retrorse barbs of the fruit, the absence of a carpophore, the differences in floral venation at the commissure and in the upper portion of the mericarp, and the orientation of fibers in the endocarp, all provide a basis for the generic distinctness ofUldinia. These comparative studies also point to the need for a possible re-evaluation of relationships within the subtribes of Hydrocotyleae.     

Changes in free and conjugated indole-3-acetic acid during early stage of flower bud differentiation in Polianthes tuberosa

Tuberose (Polianthes tuberosa L. cv. Double) corms at the vegetative, early floral initiation, and flower bud differentiation stages were assayed for free indole-3-acetic acid (IAA), esterified IAA, and peptidyl IAA. The corms in the vegetative stage contained higher free IAA than those from the early floral initiation stage. Free IAA in corm tissues increased 2.7-fold at flower bud differentiation as compared to the vegetative stage. In the vegetative corms, a marked promotion of leaf differentiation was recorded. In contrast, corms from the early floral initiation stage contained less free IAA, whereas esterified IAA and peptidyl IAA increased dramatically. It is concluded that the level of free IAA in vegetative corms is correlated with leaf differentiation, and that the early floral initiation stage is correlated with a reduction in free IAA and an increase in IAA conjugates in the corms. Moreover, increases in free IAA and decreases in IAA conjugates in the floral differentiation stage, as compared to the early floral initiation stage, indicates that free IAA is correlated with flower development.     

Polycomb-Group Proteins and FLOWERING LOCUS T Maintain Commitment to Flowering in Arabidopsis thaliana

The switch from vegetative to reproductive growth is extremely stable even if plants are only transiently exposed to environmental stimuli that trigger flowering. In the photoperiodic pathway, a mobile signal, florigen, encoded by FLOWERING LOCUS T (FT) in Arabidopsis thaliana, induces flowering. Because FT activity in leaves is not maintained after transient photoperiodic induction, the molecular basis for stable floral commitment is unclear. Here, we show that Polycomb-group (Pc-G) proteins, which mediate epigenetic gene regulation, maintain the identity of inflorescence and floral meristems after floral induction. Thus, plants with reduced Pc-G activity show a remarkable increase of cauline leaves under noninductive conditions and floral reversion when shifted from inductive to noninductive conditions. These phenotypes are almost completely suppressed by loss of FLOWERING LOCUS C (FLC) and SHORT VEGETATIVE PHASE, which both delay flowering and promote vegetative shoot identity. Upregulation of FLC in Pc-G mutants leads to a strong decrease of FT expression in inflorescences. We find that this activity of FT is needed to prevent floral reversion. Collectively, our results reveal that floral meristem identity is at least partially maintained by a daylength-independent role of FT whose expression is indirectly sustained by Pc-G activity.     

Norditerpene alkaloid concentrations in tissues and floral rewards of larkspurs and impacts on pollinators

Plant secondary compounds mediate interactions with insects and other animals. The norditerpene alkaloids are significant secondary compounds in Delphinium (larkspur) species which are divided into two classes: the 7, 8-methylenedioxylycoctonine (MDL-type) and N-(methylsuccinimido) anthranoyllycoctonine (MSAL-type), and are known to be toxic to herbivorous insects and livestock. Alkaloid concentrations were measured in a whole plant context in vegetative and floral tissues as well as rewards (pollen and nectar) in Delphinium barbeyi and Delphinium nuttallianum. Alkaloid concentrations differed between vegetative tissues, floral tissues and floral rewards. Alkaloid concentrations in floral parts were consistent with optimal defense theory, with tissues more closely tied to plant fitness, such as fruits, being more heavily defended than foliage. However, alkaloid concentrations were significantly lower in nectar compared to other tissues. The norditerpene alkaloids influenced the activity of bumble bees, the dominant pollinator of larkspur, but the effects were concentration dependent. Alkaloids in nectar are found at concentrations that have no effect on bee activity; however, if alkaloid concentrations in nectar were similar to those in foliage bee activity would be reduced significantly. These results suggest that nectar with low alkaloid concentrations may be beneficial to plant fitness by limiting adverse effects on pollinator activity.     

Dendroid colleters on vegetative and reproductive apices in Alibertia sessilis (Rubiaceae) differ in ultrastructure and secretion

In this work we compare the structure and secretion of dendroid colleters on stipules, bracts and sepals of Alibertia sessilis, a non-nodulate Rubiaceae species from Brazilian cerrado, with notes on the plant phenology. Samples were processed according to usual methods for anatomy, histochemistry and ultrastructure. Colleters are conical and constituted by a central axis of elongated parenchyma cells from which radiate numerous epidermal cells. Epidermal cells are cylindrical on the vegetative apex and digitiform or bulbous on reproductive apex. Both colleters produce hydrophilic and lipophilic compounds. On the vegetative apex, epidermal cells present numerous well-developed Golgi bodies associated with a network of smooth endoplasmatic reticulum (SER), scarce oil bodies and profiles of rough endoplasmatic reticulum (RER), indicating the involvement of these glands in the production of mainly polysaccharides in addition to protein and lipids. Differently, epidermal cells on bracts and sepals present abundant and prominent oil drops, fewer Golgi bodies and a well developed network of SER with locally dilated cisterns indicating predominance of lipids. Ecrine and granulocrine mechanisms are common to colleters of both apices. We hypothesize that exudates protect vegetative meristems and developing organs against desiccation in the dry season and against insects and pathogens during the wet season. Predominantly lipidic secretion protects the floral organs against dehydration in the dry season and can attract floral visitants. These aspects are relevant if one considers that A. sessilis inhabits the cerrado, an environment characterized by a well-delimited dry season, high irradiance and elevated vapor pressure deficits.     

Floral activity in solutions of deoxyribonucleic Acid extracted from tobacco stems

For Nicotiana tabacum cv. Wis. 38 plants, the capabilities of solutions containing DNA, extracted from either homogenates of stems in a floral state or nuclei of stems in a vegetative state, to effect flowering of vegetative plants have been studied. Previous work indicates that the DNA from homogenates of stems in a floral state is mainly nuclear. If DNA solutions are supplied to axillary buds of vegetative plants and if the axillary buds are defoliated every 4th day for 12 days, the buds supplied a solution of DNA from stems in a floral state initiate flowers under noninductive conditions, and the buds supplied a solution of DNA from stems in a vegetative state remain vegetative. Heating and rapidly cooling a solution of DNA from stems in a floral state enhances its floral activity. Heating and cooling a DNA solution also results in novel flowers showing up in many treated plants. Novel flowers are more striking in the offspring than in the parents. The capabilities of heated-cooled DNA solution to initiate flowers in noninductive conditions and to cause novel flowers are eliminated completely by treating (before heating and cooling) the DNA solution with deoxyribonuclease. Heated-cooled solutions of DNA extracted from nuclei of either vegetative stems or vegetative leaves contain no floral activity.     

Relationship between seasonal progression of floral meristem development and <Emphasis Type="Italic">FLOWERING LOCUS T</Emphasis> expression in the deciduous tree <Emphasis Type="Italic">Fagus crenata</Emphasis>

Estimating the timing of flower bud formation in plants is essential to identify environmental factors that regulate floral transition. The presence of winter dormancy between the initiation of flowers and anthesis, characteristic of most trees in the temperate forests, hampers accurate estimation of the timing of floral transition. To overcome this difficulty, expression levels of flowering-time genes could be used as indicators of the timing of floral transition. Here, we evaluated the usefulness of molecular markers in estimating the timing of floral transition in Fagus crenata, a deciduous tree that shows intermittent and synchronized flowering at the population level. We selected FLOWERING LOCUS T (FT) as a candidate molecular marker and quantified the expression levels of its ortholog in F. crenata (FcFT). Subsequently, we analyzed the relationship between morphogenetic changes that occur between the vegetative state of the buds and the initiation of floral organs, and compared the FcFT expression levels in reproductive and vegetative buds, collected from spring to autumn. FcFT expression in leaves peaked at least two weeks before the morphological changes associated with flowering were visible in the buds in late July. FcFT expression levels were significantly higher in the reproductive buds than in the vegetative buds in July. These results suggest that the FcFT expression in July is a reliable indicator of the timing and occurrence of floral transition. This study highlights the utility of molecular tools in unraveling reproductive dynamics in plants, in combination with ecological and physiological approaches.     

COMPARATIVE ANATOMY OF EUCRYPHIACEAE

Aspects of vegetative and floral morphology and anatomy of five species of Eucryphia Cav. are described. Differences in wood structure, type and complexity of petiole and leaf vascularization, presence or absence of complex abaxial cuticular protrusions on the leaves, and patterns of floral vasculature are useful in species delimitation. Anatomical data are in agreement with the inclusion of Eucryphiaceae in the Rosales near Cunoniaceae.     

Anatomy and histochemistry of the nectaries of Rodriguezia venusta (Lindl.) Rchb. f. (Orchidaceae)

Orchidaceae is one of the largest angiosperm families. Although extensively studied, reports of anatomy of secretory structures of orchids are relatively scarce. Rodriguezia venusta is an epiphytic orchid occurring in Brazil and Peru that has floral and extrafloral nectaries. This study describes the structure and the histochemistry of these secretory structures. Floral and extrafloral nectary samples were obtained from R. venusta plants that were collected in a gallery forest in the State of Bahia, Brazil, and grown in a greenhouse. Theses samples were fixed and processed according to routine procedures in plant anatomy and histochemistry or for scanning electron microscopy. The extrafloral nectaries occur on the edge and sub-edge of young leaves and at the basal portion of bracts that subtend the floral buds. They are structurally very similar, being formed by a nectary parenchyma and a simple epidermis with stomata (“non-structured nectaries”). The floral nectary is inserted at the floral receptacle fused with the labellum base, between this structure and the two inferior connate sepals. This nectary consists of an epidermis with numerous specific nectar secreting trichomes, a subnectary and a nectary parenchyma abundantly supplied by vascular terminations. Its structure is complex and distinct from other floral nectaries described for Orchidaceae.