Reproductive Apex Research Articles

Spatio-temporal expression of candidate genes for nectar spur development in Tropaeolum (Tropaeolaceae: Brassicales).

Tropaeolaceae (Brassicales) comprise ~100 species native to South and Central America. Tropaeolaceae flowers have a nectar spur, formed by a late expansion and evagination of the fused proximal region of the perianth (i.e. the floral tube). This spur is formed in the domain of the tube oriented towards the inflorescence axis, which corresponds to the adaxial floral region. However, little is known about the molecular mechanisms responsible for the evolution of spurs in Tropaeolaceae. In this study, we examined the spatio-temporal expression of genes putatively responsible for differential patterns of cell division between the adaxial and abaxial floral regions in Tropaeolaceae. These genes include previously identified TCP and KNOX transcription factors and the cell division marker HISTONE H4 (HIS4). We found a TCP4 homologue concomitantly expressed with spur initiation and elaboration. Tropaeolaceae possess two TCP4-like (TCP4L) copies, as a result of a Tropaeolaceae-specific duplication. The two copies (TCP4L1 and TCP4L2) in Tropaeolum longifolium show overlapping expression in the epidermis of reproductive apices (inflorescence meristems) and young floral buds, but only TlTCP4L2 shows differential expression in the floral tube at early stages of spur formation, restricted to the adaxial region. This adaxial expression of TlTCP4L2 overlaps with the expression of TlHIS4. Later in development, only TlTCP4L2 is expressed in the nectariferous tissue of the spur. Based on these results, we hypothesize that Tropaeolaceae TCP4L genes had a plesiomorphic role in epidermal development and that, after gene duplication, TCP4L2 acquired a new function in spur initiation and elaboration. To better understand spur evolution in Tropaeolaceae, it is critical to expand developmental genetic studies to their sister group, the Akaniaceae, which possess simultaneously an independent duplication of TCP4L genes and a spurless floral tube.

Extrafloral nectar as entrée and elaiosomes as main course for ant visitors to a fireprone, mediterranean-climate shrub.

Thousands of plants produce both extrafloral nectaries (EFNs) on their leaves and nutrient-rich appendages on their diaspores (elaiosomes). Although their individual ecology is well-known, any possible functional link between these structures has almost always been ignored. Here, we recognized their co-presence in the shrub, Adenanthos cygnorum (Proteaceae), and studied their function and interaction. We observed that the same ants frequently visit both structures, seeds are attractive to vertebrate granivores but are released into a leafy cup from where they are harvested by ants and taken to their nests, from which seeds, lacking elaiosomes, germinate after fire. We showed that juvenile plants do not produce EFNs and are not visited by ants. We conclude that EFNs are not just an indirect adaptation to minimize herbivory via aggressive ant visitors (the role of a minority) but specifically enhance reproductive success in two ways: First, by inducing ants to visit the plant as a reliable food source throughout the year. Second, by promoting discovery of the seasonally available, elaiosome-bearing seeds for transport to their nests (the majority of visitors), so avoiding the risk of granivory should seeds instead fall to the ground. Parasitoid wasps play a supporting role in controlling the main insect herbivore whose larvae devour the reproductive apices. Thus, the EFN-elaiosome relationship has three components that enhance species fitness: foliage protection, seed transport, and granivore escape. A similar system has been described only once before (in an unrelated biome) and, consistent with the objectives of ecology as an integrative science, deserves wider study.

Colleters in Mabea fistulifera Mart. (Euphorbiaceae): Anatomy and biology of the secretory process

Mabea is an important neotropical genus of the Euphorbiaceae, whose secretory structure diversity is still little known. Mabea fistulifera Mart., one of the most representative species in the genus, is a pioneer plant that is widely distributed across Brazil and Bolivia. We investigated the distribution, morphology, histochemistry and ultrastructure of colleters, reported for the first time to M. fistulifera, aiming to elucidate the gland functions, exudate nature and secretory activity dynamics. Samples of vegetative and reproductive apices and of leaves at different developmental stages were processed following usual procedures for analysis in light, scanning and transmission electron microscopies. Colleters are present exclusively on leaves, occurring on the adaxial surface and apical region of stipules and on the leaf blade margin. Colleters have protodermal origin and are functional since early leaf differentiation. In the colleter secretory portion, central-axis cells and surface cells have similar origin and structure, both showing numerous mitochondria, dictyosomes, rough endoplasmic reticulum and ribosomes. The translucid secretion is of mucilaginous nature, being formed by polysaccharides, proteins and alkaloids, which is compatible with the observed cellular machinery. The presence of a hygroscopic exudate in contact with developing vegetative and reproductive organs is important for the protection of young tissues against desiccation, especially in view of the fact that the species occurs in open environments, which are subjected to water stress, elevated temperature and high light incidence.

The Dynamics of Cytokinin Changes after Grafting of Vegetative Apices on Flowering Rapeseed Plants.

Despite numerous studies, the role of hormones in the induction of shoot apical meristem leading to reproductive development, especially regarding thermoperiodic plants, is still not fully understood. The key problem is separating the effects of the low temperature required for vernalization from those responsible for low temperature stress. An earlier experiment demonstrated the correlation between an increase of cytokinin level in the apical parts of winter rapeseed and the transition time into their reproductive phase during vernalization, i.e., low temperature treatment. From data obtained from the presented experiments, this study aims to contribute to the understanding the role of cytokinins in the induction of flowering based on the grafting of vegetative apical parts of winter rapeseed (scion) on the reproductive (stock) winter and spring genotypes. On the basis of analyses carried out using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry in combination with microscopic observation of changes at the apical meristem, it was indicated that the increase in the amount of trans-zeatin and trans- and cis-zeatin-O-glucoside derivatives appeared in the early stages of apex floral differentiation. During further development, the content of all investigated cytokinins passed through the maximum level followed by their decrease. The final level in reproductive apices was found to be higher than that in vegetative ones.

Sucrose synthesis in Unpollinated ovaries of pomegranate (Punica granatum L.), as well as, in reproductive and vegetative shoot apices

Sugar levels, the enzyme activity of UDP-Glucose Pyrophosphorylase (UGPase) and Sucrose Phosphate Synthase (SPS), key enzymes for sucrose synthesis, and the expression of their respective genes were examined in developing vegetative and reproductive shoot apices and in developing unpollinated ovaries of Pomegranate trees in order to detect differences possibly important for fruit production and plant vigor. The level of total sugars was higher in ovaries, followed by reproductive apices and vegetative apices, suggesting higher energy requirements in the reproductive organs. Moreover, the activities of SPS and UGPase were found to be elevated in the vegetative apices, indicating that sucrose synthesis is possibly differently regulated in comparison to the reproductive organs. Our results suggest that the sink power of each organ primarily regulates the levels of both transported (sucrose, mannitol) and non-transported (fructose, glucose) sugars. However, the endogenous production of sucrose may be a regulatory factor contributing to organ development.

Nitrogen management to optimise canola production in Australia

The expansion of canola production in Australia coincided with an increase in cropping intensity and a reduction in pastures and tillage. These changes mean that nitrogen (N) is often recognised as the most limiting nutrient in canola production, and is the largest single input cost for many growers. Canola responds to added N by producing larger plants that results in a longer leaf area duration, building a larger photosynthetic canopy for seed filling. Although the crop can compensate for poor early growth, a larger canopy is able to compete more effectively against weeds and helps reserve water for crop transpiration rather than soil evaporation. Nitrogen uptake is most rapid during stem elongation, and the N acquired can be remobilised to developing pods and then to seeds. Unlike wheat, N uptake can continue until drought or high temperatures prevent further assimilate supply to the reproductive apex. Data from Australian experiments that measured N uptake over the whole growth period showed that each tonne of seed required ~80 kg N to be taken up, and this forms the basis of a budgeting approach for determining N supply. Typically, added N reduces seed oil concentration at a rate of between –0.03 and –0.13%/kg N. Despite this decline due to added N, oil yield usually increases and the overall value of the crop also increases. Nitrogen has little impact on oil quality or seed glucosinate concentration. The efficiency and effectiveness of N management depends first on selecting a rate appropriate to the water-limited yield potential. Most growers estimate the N rate required using an N budget based on supplying 80 kg N/t less indigenous N supply. The budgeted N can be split over two, three or even more applications with little loss in agronomic efficiency. Splitting application enables growers to make decisions about N when there is more certainty about seasonal conditions. Urea is the most common N source used, and unless there are particular loss processes that are likely to occur, it is cheap and effective. Suggested areas for future N research on canola are to develop tools that can assess in-crop N status, an evaluation of late season N product rate and timing particularly on seed oil concentration, N management for grazed canola, and the development of guidelines to identify, and then address, particular N loss pathways using enhanced efficiency fertilisers.

MICRO-MORPHOLOGICAL OBSERVATIONS ON FLOWER BUD DIFFERENTIATION OF SUPER PREMATURITY CULTIVATED STRAWBERRY

An important step in the cultivation of super prematurity strawberry is how to determine the start of flower bud differentiation (FBD), and this is the premise of planting strawberry at the early stage. The experiments of low-temperature treatment (night temperature was 17-20ÂoC with fluctuations) and short photoperiod treatment (dark length was 16 h) were conducted from 23 June to 24 August, 2011. Apexes were separated under an anatomical microscope every 3-5 days, fixed with FAA, dried at critical point, and observed with a scanning electron microscope. On the basis of the observed micro-morphological characteristics, the whole process of FBD was divided into seven phases: pre-differentiation phase, starting phase, reproductive apex swelling phase, inflorescence differentiation phase, top-flower sepal formation phase, flower petal formation phase, stamen formation phase and stigma formation phase. The flower bud non-differentiation phase was before 29 June, and the top bud was in the state of vegetative growth continually. The starting phase was from 29 June to 3 August, and the top bud turned gradually from sharp, narrow vegetative apex into smooth, broad reproductive apex. The reproductive apex swelling phase was from 3 August to 14 August, and the reproductive apex uplifted and swelled. The inflorescence differentiation phase was from 14 August to 20 August, and top flower primordium and lateral flower primordium gradually appeared during top flower primordium differentiation process. The top flower sepal phase, flower petal formation phase were from 22 to 30 August, the differentiation of sepals (including accessory sepals) and the petals were finished in this phase. The stamen formation phase was from 30 August to 10 September, and two stamen primordia differentiated. Stigma formation phase was from 10 September to 21 September, a large number of stigma primordia uplifted gradually and carpel primordia curled, and the FBD process was complete.

Glandular trichomes in <i>Connarus suberosus</i> (Connaraceae): distribution, structural organization and probable functions.

Connarus suberosus is a typical species of the Brazilian Cerrado biome, and its inflorescences and young vegetative branches are densely covered by dendritic trichomes. The objective of this study was to report the occurrence of a previously undescribed glandular trichome of this species. The localization, origin and structure of these trichomes were investigated under light, transmission and scanning electron microscopy. Collections were made throughout the year, from five adult specimens of Connarus suberosus near Botucatu, São Paulo, Brazil, including vegetative and reproductive apices, leaves and fruits in different developmental stages, as well as floral buds and flowers at anthesis. Glandular trichomes (GTs) occurred on vegetative and reproductive organs during their juvenile stages. The GTs consisted of a uniseriate, multicellular peduncle, whose cells contain phenolic compounds, as well as a multicellular glandular portion that accumulates lipids. The glandular cell has thin wall, dense cytoplasm (with many mitochondria, plastids and dictyosomes), and a large nucleus with a visible nucleolus. The starch present in the plastids was hydrolyzed during the synthesis phase, reducing the density of the plastid stroma. Some plastids were fused to vacuoles, and some evidence suggested the conversion of plastids into vacuoles. During the final activity stages of the GTs, a darkening of the protoplasm was observed in some of the glandular cells, as a programmed cell death; afterwards, became caducous. The GTs in C. suberosus had a temporal restriction, being limited to the juvenile phase of the organs. Their presence on the exposed surfaces of developing organs and the chemical nature of the reserve products, suggest that these structures are food bodies. Field observations and detailed studies of plant-environment interactions, as well as chemical analysis of the reserve compounds, are still necessary to confirm the role of these GTs as feeding rewards.

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.

Leaf and calycine colleters in Odontadenia lutea (Apocynaceae - Apocynoideae - Odontadenieae): their structure and histochemistry

The structure and histochemistry of colleters found on the vegetative and floral apices of Odontadenia lutea are described. Colleters occur on vegetative apices starting at the fourth node, with 68 to 80 colleters being found at each node. Each leaf primordium has only one colleter of axillary origin, 3-5 intra-petiolar, and 12-16 inter-petiolar (intra-stipular). There are four types of colleters: standard, bipartite standard, sessile, and bipartite sessile. Colleters on the reproductive apices alternate with the sepals and are sessile, reduced sessile, tripartite laminar sessile, or asymmetrical. All of the colleters have a central nucleus of parenchymatous cells covered by a palisade uniseriate secretory epidermis and a thin cuticle. Secretory idioblasts were observed in the parenchymatous axis. Vascularization was observed only in standard axillary and laminar colleters. Crystals were observed in the parenchyma of the axillary colleter. Histochemical tests demonstrated that there was no rupturing or distension of the cuticle during the secretion process. Mucilage was identified using the PAS reaction as well as by Mayer's reagent and Ruthenium red staining. The calycine colleters had two distinct secretory phases, the first synthesizing mucilage and the second producing phenolic compounds.

Leaf and calycine colleters in Odontadenia lutea (Apocynaceae - Apocynoideae - Odontadenieae): their structure and histochemistry

The structure and histochemistry of colleters found on the vegetative and floral apices of Odontadenia lutea are described. Colleters occur on vegetative apices starting at the fourth node, with 68 to 80 colleters being found at each node. Each leaf primordium has only one colleter of axillary origin, 3-5 intra-petiolar, and 12-16 inter-petiolar (intra-stipular). There are four types of colleters: standard, bipartite standard, sessile, and bipartite sessile. Colleters on the reproductive apices alternate with the sepals and are sessile, reduced sessile, tripartite laminar sessile, or asymmetrical. All of the colleters have a central nucleus of parenchymatous cells covered by a palisade uniseriate secretory epidermis and a thin cuticle. Secretory idioblasts were observed in the parenchymatous axis. Vascularization was observed only in standard axillary and laminar colleters. Crystals were observed in the parenchyma of the axillary colleter. Histochemical tests demonstrated that there was no rupturing or distension of the cuticle during the secretion process. Mucilage was identified using the PAS reaction as well as by Mayer's reagent and Ruthenium red staining. The calycine colleters had two distinct secretory phases, the first synthesizing mucilage and the second producing phenolic compounds.

RNA Content in Relation to Flowering in Sugarcane Varieties

Flowering in sugarcane (Saccharum officinarum L.) is influenced by a number of plant and environmental factors. During the transition from the vegetative to reproductive apex, a number of physiological and biochemical changes occur as in other plants. The RNA content in the shoot apices of nine sugarcane varieties in relation to flowering was studied. The RNA content in the shoot apices of profuse flowering varieties increased at induction over that of the pre-induction stage. The magnitude of increase in the RNA content varied significantly among the varieties. The RNA content at the pre-inductive and the inductive period was positively and significantly associated with flowering.

Coléteres dendróides em Alibertia sessilis (Vell.) K. Schum., uma espécie não-nodulada de Rubiaceae

This paper describes the distribution, structure and histochemistry of the colleters in vegetative and reproductive apices of Alibertia sessilis (Vell.) K. Schum., a native Rubiaceae species of the Brazilian cerrado. In this family, dendroid colleters have been associated with the presence of bacterial nodules in the leaves. Samples were prepared according to common light and scanning electron microscopy techniques, and histochemical assays involved freshly collected material. Colleters are dendroid and occur on the adaxial surface of stipules, bracts and sepals; they consist of a multicellular and multiseriate central axis of parenchymatous nature, covered by digitiform or sharply pointed epidermal cells of irregular sizes, joined together only in the proximal portion and separated from each other in the distal portion. The columnar cells are axially elongated, with thick cell walls, prominent nucleus and reduced cytoplasm, developed vacuole with lipid inclusions and phenolic compounds. The epidermal cells have thin walls, a conspicuous nucleus, abundant cytoplasm and a poorly developed vacuome. The colleters are devoid of cuticle. The secretion is more abundant in the vegetative apex, impregnating the leaf buds and the stipules, forming a spherical cap that is hard, bright, and hydrophobic. In all analyzed samples, the histochemical assays detected polysaccharides, proteins and lipids in the protoplast of both epidermal and columnar cells; phenolic compounds were detected solely in the columnar cells. The resinous nature of the exudate was confirmed with the use of the diethylic ether solvent. Bacterial leaf nodules were not found.

Overexpression of AGAMOUS-LIKE 28 ( AGL28) promotes flowering by upregulating expression of floral promoters within the autonomous pathway

MADS box genes are known to perform important functions in the development of various plant organs. Although the functions of many MADS box genes have previously been elucidated, the biological function of the type I MADS box genes remains poorly understood. In order to understand the function and regulation of the type I MADS box genes, we conducted molecular genetic analyses of AGL28, a member of the Mα class of type I genes. AGL28 was expressed in vegetative tissues in a photoperiod-independent manner, but not within the reproductive apex. This indicates that AGL28 plays a role in the vegetative phase. Overexpression of AGL28 caused precocious flowering via the upregulation of the expression of FCA and LUMINIDEPENDENS ( LD), both floral promoters within the autonomous pathway. However, the loss of AGL28 function did not result in any obvious flowering time phenotype, which suggests that AGL28 may perform a redundant function. Collectively, our data suggest that AGL28 is a positive regulator of known floral promoters within the autonomous pathway in Arabidopsis.

Size and Activity of Shoot Apical Meristems as Determinants of Floret Number in Rice Panicles

The sink capacity (floret number per unit land area) is currently a serious constraint to grain yield production in japonica rice. The size and activity of the early reproductive shoot apex (incipient panicle) are potential determinants of the number of florets generated on the panicle. This hypothesis was tested using eight field-grown japonica rice cultivars (IR65598-112-2, IR65564-44-51, Nipponbare, Akenohoshi, Dobashi 1, Koshihikari, Kochihibiki and Nakateshinsenbon). Using morphometric microscopy, we found that the initial size of the reproductive shoot apex was highly correlated with the number of primary branches, but not with the number of florets per primary branch. The cell division activity of the early reproductive apex examined by in situ hybridization analyses using the histone H4 gene probe as a marker for DNA-replicating cells varied with the cultivar. Akenohoshi had twice as many DNA-replicating cells as Nipponbare and the cell division activity was highly correlated with the number of florets per primary branch, but not with the primary branch number. We concluded that the primary branch number was determined by the initial size of the reproductive apex, and that the floret number per primary branch was determined by the cell division activity in the following apex growth. This result provides the first evidence of a relationship between cell division activity and floret formation in the rice panicle.

Small Inflorescence Bulbils Are Best for Micropropagation and Virus Elimination in Garlic

Garlic (Allium sativum L.) plants were cultured from immature inflorescence bulbils. The primordia of bulbils appeared initially as protuberances on reproductive apices, swelled, and then formed bulbils with protective leaves. Excised bulbils sprouted on Murashige and Skoog's medium with 5.4 μm naphthaleneacetic acid (NAA) and grew into plantlets. The frequency of sprouting in culture increased with the development of bulbils before excision, and immature bulbils 0.4 to 2.4 mm in diameter sprouted at a frequency of >85%. A dot immunoblot assay revealed a remarkable reduction in levels of garlic mite-borne mosaic virus in plantlets grown from immature bulbils, suggesting that such bulbils might be suitable for the propagation of virus-free garlic plants.

Temperature-dependent internode elongation in vegetative plants of Arabidopsis thaliana lacking phytochrome B and cryptochrome 1.

Vegetative plants of Arabidopsis thaliana (L.) Heynh. form a compact rosette of leaves in which internode growth is virtually arrested. Rapid extension of the internodes occurs after flower buds are present in the reproductive apex. Under natural radiation, continuous light from fluorescent lamps, or short photoperiods of light from fluorescent lamps, plants of the phyB cry1 double mutant (lacking both phytochrome B and cryptochrome 1) did not form normal rosettes because all the internodes showed some degree of elongation. Internode elongation was weak in thephyB single mutant and absent in the cry1 mutant, indicating redundancy between phytochrome B and cryptochrome 1. The absence of phytochrome A caused no effects. The failure to form normal rosettes was conditional because internode elongation was arrested at low temperatures in all the mutant combinations. In contrast, the temperature dependence of phytochrome B and cryptochrome 1 effects on hypocotyl growth was weak. The elongation of the internodes in phyB cry1 was not accompanied by early flowering as showed by the lack of effects on the final number of leaves. Apex dissection indicated that in phyB cry1 double mutants internode elongation anticipated the transition from the vegetative to the reproductive stage. Thus, stem growth in Arabidopsis thaliana is not fully dependent on the program of reproductive development.

Transgenic tobacco over-expressing a homeobox gene shows a developmental interaction between leaf morphogenesis and phyllotaxy.

The tobacco gene, NTH1, encodes a polypeptide of 326 amino acids and is a member of the class1 KN1-type family of homeobox genes. Expression of NTH1 has mainly been observed in vegetative and reproductive shoot apices, not observed in roots or expanded leaves. Over-expression of NTH1 in transgenic plants caused abnormal leaf morphology, consisting of wrinkling and curvature. Interestingly, the direction of leaf curvature tended to be conserved among almost all of the leaves in any given transformant. In transgenic plants exhibiting clockwise or anticlockwise phyllotaxy, leaves curved to the right or left, respectively, when looking from the shoot apex toward the base. Micro-surgical experiments demonstrated that the presence of the shoot apex is necessary for the development of leaf curvature, indicating that the order of formation of leaves on the stem (the generative spiral) affects leaf development. We found a correlation between the severity of leaf curvature and the value of the plastochron ratio, a parameter of phyllotaxy. Transformants with more severe phenotypes had larger plastochron ratios. From these findings, we discuss the possibility that an increase in the plastochron ratio, caused by over-expression of NTH1 in the shoot apex, may be involved in leaf curvature.

Growth of Near-isogenic Wheat Lines Differing in Development—Spaced Plants

Abstract The relationship between phenological development in wheat (Triticum aestivumL.) and growth was studied to determine if the switch from a vegetative to a reproductive apex increases plant growth rate. Plant partitioning and relative growth rates during vegetative and pre-flowering reproductive periods were determined in two sets of near-isogenic lines differing in phenological development. Spaced plants were grown in two photoperiods (15 and 10 h) to increase the range of development rates. Lines within each isogenic set and photoperiod treatment did not differ in whole plant growth rate despite large differences in developmental rate. In addition, the partitioning of biomass between roots and shoots was also similar. The transition of the apex from vegetative to reproductive mostly affected the partitioning of shoot biomass into leaf (blades) and stems (rest of the shoot). A longer time to reach floral initiation was associated with the production of more, and larger, leaves as well as more tillers. This resulted in large differences in leaf area between isolines. However, at the whole plant level, all lines accumulated biomass at the same rate with time. The early flowering lines compensated for their reduced leaf area by having a higher net assimilation rate and were thereby able to maintain the same relative growth rate as their later flowering counterparts.

ニンニク, ネギ, アサツキの花序の分化発達過程と花序型

Morphological development of inflorescences and types among garlic, Japanese bunching onion and asatsuki (Allium schoenoprasum L. var. foliosum Regel) was examined with a scanning electron microscope.1. A spathe primordium from the receptacle emerged as a circular (ring) protuberance surrounding a shoot apex. The ring of tissue increased in height on both sides from which true leaves arose.2. Reproductive apices of fertile and sterile complete-bolting garlics first divided into equal parts. On each half of the apex, flower primordia formed regularly into a dichasial cyme, and subsequently the whole apex developed into a compound inflorescence composed of two dichasial cymes. When the inflorescence elongated, it acquired the appearance of a determinate umbel.3. Some of flowers of the fertile garlic lines and almost all of the sterile complete-bolting garlic cultivars aborted. The dichasial cyme lost its shape as the flowers aborted.4. In Japanese bunching onion and asatsuki, flower initiation occurred first on the center of the reproductive apex and proceeded toward the circumference, but the order of flower initiation and the disposition of flowers exhibited no regularity. The mature inflorescences of these two Allium species also had the shape of a determinate umbel.5. That the initiation time, location, and bracteole number and position of bulbils were different from those of flowers, suggests that the bulbils differentiated independently of flowers.