Inflorescence Differentiation Research Articles

De novo transcriptome assembly reveals characteristics of flower sex determination of Excoecaria agallocha

Key messageMADS-box genes family may play important roles in the flower sex determination in Excoecaria agallocha. A total of 73 MADS-box genes were identified in E. agallocha. De novo transcriptome assembly analysis suggested that AP1/FUL, AP3/PI, AGL104, and SOC1 plays potential roles in E. agallocha flower sex determination.ContextExcoecaria agallocha is a dioecious species containing both male and female individuals producing unisexual flowers. The underlying mechanisms regulating inflorescence differentiation in these species remains poorly understood.AimsFlower development influences reproduction and breeding in E.agallocha, which contributes to ecological restoration in the intertidal zone.MethodsWe performed de novo transcriptome assembly analysis on male and female flowers and leaves from E. agallocha.ResultsWe identified a total of 73 MADS-box genes in the E. agallocha genome, which we grouped into five distinct classes (MIKCc, Mα, Mβ, Mγ, MIKC*) after phylogenetic comparisons with J. curcas homologs. We analyzed expression profiles and suggested AP1/FUL, AP3/PI, AGL104, and SOC1 as candidate regulators of sex determination. In addition, several EaMADS genes were significantly upregulated in flowers compared to leaves.ConclusionOur study represents the first detailed, comprehensive evaluation of the regulation of MADS-box genes associated with sex determination in E. agallocha. The assembled transcriptomic profiles increase the genetic information available for this species and constitute an important contribution to functional studies of inflorescence genes. In turn, this will help exploring the molecular mechanisms underlying the evolution of E. agallocha.

Transcriptome Analysis to Explore the Cause of the Formation of Different Inflorescences in Tomato

The number of inflorescence branches is an important agronomic character of tomato. The meristem differentiation and development pattern of tomato inflorescence is complex and its regulation mechanism is very different from those of other model plants. Therefore, in order to explore the cause of tomato inflorescence branching, transcriptome analysis was conducted on two kinds of tomato inflorescences (single racemes and compound inflorescences). According to the transcriptome data analysis, there were many DEGs of tomato inflorescences at early, middle, and late stages. Then, GO and KEGG enrichments of DEGs were performed. DEGs are mainly enriched in metabolic pathways, biohormone signaling, and cell cycle pathways. According to previous studies, DEGs were mainly enriched in metabolic pathways, and FALSIFLORA (FA) and ANANTHA (AN) genes were the most notable of 41 DEGs related to inflorescence branching. This study not only provides a theoretical basis for understanding inflorescence branching, but also provides a new idea for the follow-up study of inflorescence.

The auxin-responsive transcription factor SlDOF9 regulates inflorescence and flower development in tomato.

Understanding the mechanisms underlying differentiation of inflorescence and flower meristems is essential towards enlarging our knowledge of reproductive organ formation and to open new prospects for improving yield traits. Here, we show that SlDOF9 is a new modulator of floral differentiation in tomato. CRISPR/Cas9 knockout strategy uncovered the role of SlDOF9 in controlling inflorescence meristem and floral meristem differentiation via the regulation of cell division genes and inflorescence architecture regulator LIN. Tomato dof9-KO lines have more flowers in both determinate and indeterminate cultivars and produce more fruit upon vibration-assisted fertilization. SlDOF9 regulates inflorescence development through an auxin-dependent ARF5-DOF9 module that seems to operate, at least in part, differently in Arabidopsis and tomato. Our findings add a new actor to the complex mechanisms underlying reproductive organ differentiation in flowering plants and provide leads towards addressing the diversity of factors controlling the transition to reproductive organs.

Micro-RNA-Regulated SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE (SPL) Gene Expression and Cytokinin Accumulation Distinguish Early-Developing Male and Female Inflorescences in Oil Palm (Elaeis guineensis).

Sexual differentiation of inflorescences and flowers is important for reproduction and affects crop plant productivity. We report here on a molecular study of the process of sexual differentiation in the immature inflorescence of oil palm (Elaeis guineensis). This species is monoecious and exhibits gender diphasy, producing male and female inflorescences separately on the same plant in alternation. Three main approaches were used: small RNA-seq to characterise and study the expression of miRNA genes; RNA-seq to monitor mRNA accumulation patterns; hormone quantification to assess the role of cytokinins and auxins in inflorescence differentiation. Our study allowed the characterisation of 30 previously unreported palm MIRNA genes. In differential gene and miRNA expression studies, we identified a number of key developmental genes and miRNA-mRNA target modules previously described in relation to their developmental regulatory role in the cereal panicle, notably the miR156/529/535-SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL) gene regulatory module. Gene enrichment analysis highlighted the importance of hormone-related genes, and this observation was corroborated by the detection of much higher levels of cytokinins in the female inflorescence. Our data illustrate the importance of branching regulation within the developmental window studied, during which the female inflorescence, unlike its male counterpart, produces flower clusters on new successive axes by sympodial growth.

A Selection of Reliable Reference Genes for Gene Expression Analysis in the Female and Male Flowers of Salix suchowensis.

Salix is a dioecious plant. Research on the molecular regulation mechanism of male and female inflorescence differentiation and development is necessary to analyze sex differentiation in the willow and the underlying mechanisms of unisexual flower development. However, at present, there are no reference genes suitable for stable expression in the process of willow inflorescence development. In this study, Salix suchowensis was used as the research material, nine candidate reference genes (α-TUB1, α-TUB2, ACT, H2A, DnaJ, CDC2, GAPDH, TIP41, β-TUB) were selected, and qRT-PCR technology was used to detect the expression of each candidate reference gene in female and male flowers at different developmental stages and using five algorithms (geNorm, Normfinder, Delta Ct, BestKeeper, and RefFinder) to comprehensively evaluate the stability of candidate reference genes. The results showed that ACT and DnaJ were stably expressed in all samples and could be used as reference genes. In addition, the reliability of the screening results was further verified via an expression pattern analysis of the CFS gene that encodes flower specific transcription factor in different samples. The stable reference genes selected in this study provide the basis for future research on the expression analysis of functional genes related to the development of male and female flowers of S. suchowensis.

Observation on Flower Bud Differentiation of Crape Myrtle in Red Soil Environment

Flower bud differentiation is a key component of plant blooming biology and understanding how it works is vital for flowering regulation and plant genetic breeding, increasing the number and quality of flowering. Red soil is the most widely covered soil type in the world, and it is also the most suitable soil type for crape myrtle planting. The flower buds of crape myrtle (Lagerstroemia indica) planted in red soil were employed as experimental materials in this study, and the distinct periods of differentiation were identified using stereomicroscopy and paraffin sectioning. We optimized the steps of dehydration, transparency, embedding, sectioning and staining when employing paraffin sections. When seen under a microscope, this optimization can make the cell structure of paraffin sections obvious, the tissue structure complete, and the staining clear and natural. The flower bud differentiation process is divided into 7 periods based on anatomical observations of the external morphology and internal structure during flower bud differentiation: undifferentiated period, start of differentiation period, inflorescence differentiation period, calyx differentiation period, petal differentiation period, stamen differentiation period, and pistil differentiation period. The differentiation time is concentrated from the end of May to mid-June. Crape myrtle flower bud differentiation is a complicated process, and the specific regulatory mechanism and affecting elements need to be investigated further.

SLL1-ZH Regulates Spikelets Architecture and Grain Yield in Rice

The spikelet developmental processes that control structure and floral organ identity play critical roles in rice grain yield formation. In this study, we characterized a novel rice mutant, SLL1-ZH, which exhibits a variety of defective agronomic characters, including semi-dwarf, rolling leaf, deformed panicles, and reduced grains production. Morphological analysis also revealed that the SLL1-ZH mutant shows numerous defects of floral organs, such as cracked glumes, hooked and thin lemmas, shrunken but thickened paleas, an indeterminate number of stamens and stigmas, and heterotopic ovaries. Map-based cloning identified a single nucleotide substitution (C to G) in the first exon of LOC_Os09g23200 that is responsible for the SLL1-ZH phenotype. In addition, qPCR analysis showed a significant change in the relative expression of SLL1-ZH in the mutant during inflorescence differentiation and in the different floral organs. Transcription of rice floral organ development-related factors also changed significantly in the mutant. Therefore, our results suggested that SLL1-ZH plays a great role in plant growth, spikelet development, and grain yield in rice.

Bulbils in garlic inflorescence: development and virus translocation

Commercial garlic cultivars are propagated only vegetatively. Since viral infection is sheltered in all plant organs, it is transmitted from one generation to another. Bolting varieties of garlic often produce small bulbils in the inflorescence that can be used for propagation. We studied morphological and histological aspects of bulbil differentiation and virus transmission from the mother plant to the next generation. During inflorescence development, flowers differentiate first and then bulbils initiate between flower buds. Lignified vascular cells transport water and nutrients to the differentiating bulbils, together with virus particles that are translocated from the older organs. The two most dangerous potyviruses for garlic, OYDV and LYSV, were detected at the very early stages of garlic inflorescence differentiation, when the vascular system only began to differentiate, and later massive systemic viral infection of the mature bulbils was identified. In spite of common assumption that bulbils produce virus-free regenerants in tissue culture, RT-PCR analysis clearly shows the presence of both viruses in the regenerants originating from young inflorescences. It is concluded that without special means for virus eradication, in vitro propagation from garlic inflorescence or bulbils has no advantage in obtaining virus free propagation material.

ASSESSMENT OF TIMING OF BUD DIFFERENTIATION AND DEVELOPMENT STAGES OF FLOWER INFLORESCENCE IN BLACKBERRY (Rubus spp.) CULTIVARS IN NORTHERN TURKEY

Blackberry (Rubus spp.) production is attracting interest in Turkey’s northern part, but information on timing of bud differentiation and developmental stages of flower inflorescence on next season is limited. The objective of this study was to determine the timing of bud differentiation and development stages of flower inflorescence in 4 biennial fruiting blackberry (Rubus spp.) cultivars (‘Chester’, ‘Dirksen Thornless’, ‘Jumbo’, ‘Bursa 1’) grown in northern Turkey. Axillary bud samples were collected from the middle parts of the one year of lateral branches every 7–15 days from September 2008 to May 2010. Ten development stages were identified from the flower bud differentiation to post-bloom period. The transition from the vegetative to reproductive stage occurred during September to October, with the differentiation of the terminal flower occurring on September 18 in ‘Bursa 1’, October 4–9 in ‘Dirksen Thornless’, October 16–20 in ‘Jumbo’, and October 20–22 in ‘Chester’. In all the examined cultivars, flower development occurred between September and June and lasted for 193–215 days.

Fruit Development in Ficus carica L.: Morphological and Genetic Approaches to Fig Buds for an Evolution From Monoecy Toward Dioecy.

The mechanism behind the bud evolution towards breba or main crop in Ficus carica L. is uncertain. Anatomical and genetic studies may put a light on the possible similarities/differences between the two types of fruits. For this reason, we collected complimentary data from anatomical, X-ray imaging, and genetic techniques. The RNA seq together with structural genome annotation allowed the prediction of 34,629 known genes and 938 novel protein-coding genes. Transcriptome analysis of genes during bud differentiation revealed differentially expressed genes in two fig varieties (Dottato and Petrelli) and in breba and main crop. We chose Dottato and Petrelli because the first variety does not require pollination to set main crop and the latter does; moreover, Petrelli yields many brebas whereas Dottato few. Of the 1,615 and 1,904 loci expressed in Dottato and Petrelli, specifically in breba or main crop, respectively, only 256 genes appeared to be transcripts in both varieties. The buds of the two fig varieties were observed under optical microscope and using 3D X-ray tomography, highlighting differences mainly related to the stage of development. The X-ray images of buds showed a great structural similarity between breba and main crop during the initial stages of development. Analysis at the microscope indicated that inflorescence differentiation of breba was split in two seasons whereas that of main crop started at the end of winter of season 2 and was completed within 2 to 3 months. The higher expression of floral homeotic protein AGAMOUS in breba with respect to main crop, since this protein is required for normal development of stamens and carpels in the flower, may indicate an original role of these fruits for staminate flowers production for pollination of the main crop, as profichi in the caprifig. Several genes related to auxin (auxin efflux carrier, auxin response factor, auxin binding protein, auxin responsive protein) and to GA synthesis (GA20ox) were highly expressed in brebas with respect to main crop for the development of this parthenocarpic fruit.

The regulatory landscape of early maize inflorescence development

BackgroundThe functional genome of agronomically important plant species remains largely unexplored, yet presents a virtually untapped resource for targeted crop improvement. Functional elements of regulatory DNA revealed through profiles of chromatin accessibility can be harnessed for fine-tuning gene expression to optimal phenotypes in specific environments.ResultHere, we investigate the non-coding regulatory space in the maize (Zea mays) genome during early reproductive development of pollen- and grain-bearing inflorescences. Using an assay for differential sensitivity of chromatin to micrococcal nuclease (MNase) digestion, we profile accessible chromatin and nucleosome occupancy in these largely undifferentiated tissues and classify at least 1.6% of the genome as accessible, with the majority of MNase hypersensitive sites marking proximal promoters, but also 3′ ends of maize genes. This approach maps regulatory elements to footprint-level resolution. Integration of complementary transcriptome profiles and transcription factor occupancy data are used to annotate regulatory factors, such as combinatorial transcription factor binding motifs and long non-coding RNAs, that potentially contribute to organogenesis, including tissue-specific regulation between male and female inflorescence structures. Finally, genome-wide association studies for inflorescence architecture traits based solely on functional regions delineated by MNase hypersensitivity reveals new SNP-trait associations in known regulators of inflorescence development as well as new candidates.ConclusionsThese analyses provide a comprehensive look into the cis-regulatory landscape during inflorescence differentiation in a major cereal crop, which ultimately shapes architecture and influences yield potential.

The microvine, a model to study the effect of temperature on grapevine latent bud development and fruitfulness

Aim: The success of inflorescence primordia initiation and differentiation within latent buds (i.e. bud fruitfulness) is a critical issue for grapevine yield sustainability under climate change. The aim of the present study was to track the timing and rate of inflorescence development in latent buds along the cane and to quantify their responses to elevated day/night (D/N) temperatures.Methods and Results: The experiments were conducted under controlled conditions, using the microvine model, which is suitable for establishment in small areas. Two imagery methods for analyzing bud anatomy were assessed: light microscopy and x-ray microtomography. Light microscopy was laborious, but it was the most accurate method for investigating organogenesis in the primordial shoot of the latent bud. In plants grown in a greenhouse (D/N, 25°C/15°C), the number of phytomer primordia in latent buds increased linearly from the apical to the basal buds on the cane. A maximum of six phytomers and two inflorescence primordia were observed beneath the 20th bud position that is, slightly fewer than usually reported with macrovines. The first and second inflorescences started to differentiate at the 14th and 18th bud position, respectively. Temperature increases in the growth chamber (D/N, 20–30°C/15–25°C) only slightly changed the final number of preformed phytomers and the probability of inflorescence primordia differentiation per bud. However, elevated temperature sharply accelerated and thereby shortened development of the latent bud primordial shoot, resulting in differentiation of the first inflorescence primordia straight from the fifth bud position. Based on the spatiotemporal conversion of bud position into thermal time, the first inflorescence started to differentiate 332 growing degree days (°Cd) (or 41 days) after bud emergence at D/N 20°C/15°C, and only 98°Cd (or 5 days) after bud emergence at D/N 35°C/25°C. Finally, the number of preformed phytomers was shown to correlate with primary bud length and cane diameter, independent of temperature. These easily measured variables may be used as indicators of bud developmental stage and potential bud fruitfulness in further studies using the microvine.Conclusions: The microvine appears to be suitable for parameterizing a developmental model of grapevine latent buds under controlled environmental conditions and when evaluating the response to elevated D/N temperatures.Significance and impact of the study: The precise description of the timing and rate of differentiation of phytomers and inflorescences opens new perspectives for understanding the molecular processes underlying the response of bud fruitfulness to environmental constraints.

Genome-wide transcript analysis of inflorescence development in wheat.

The process of inflorescence development is directly related to yield components that determine the final grain yield in most cereal crops. Here, microarray analysis was conducted for four different developmental stages of inflorescence to identify genes expressed specifically during inflorescence development. To select inflorescence-specific expressed genes, we conducted meta-analysis using 1245 Affymetrix GeneChip array sets obtained from various development stages, organs, and tissues of members of Poaceae. The early stage of inflorescence development was accompanied by a significant upregulation of a large number of cell differentiation genes, such as those associated with the cell cycle, cell division, DNA repair, and DNA synthesis. Moreover, key regulatory genes, including the MADS-box gene, KNOTTED-1-like homeobox genes, GROWTH-REGULATING FACTOR 1 gene, and the histone methyltransferase gene, were highly expressed in the early inflorescence development stage. In contrast, fewer genes were expressed in the later stage of inflorescence development, and played roles in hormone biosynthesis and meiosis-associated genes. Our work provides novel information regarding the gene regulatory network of cell division, key genes involved in the differentiation of inflorescence in wheat, and regulation mechanism of inflorescence development that are crucial stages for determining final grain number per spike and the yield potential of wheat.

Reduced Expression of CbUFO Is Associated with the Phenotype of a Flower-Defective Cosmos bipinnatus.

LEAFY (LFY) and UNUSUAL FLORAL ORGANS (UFO) homologous genes have been reported to play key roles in promoting the initiation of floral meristems in raceme- and cyme-type plants. Asteraceae, a large family of plants with more than 23,000 species, has a unique head-like inflorescence termed capitulum. Here, we report a floral defective plant of the garden cosmos named green head (gh), which shows homogeneous inflorescence, indistinguishable inflorescence periphery and center, and the replacement of flower meristems by indeterminate inflorescence meristems, coupled with iterative production of bract-like organs and higher order of inflorescences. A comparison of the LFY- and UFO-like genes (CbFLY and CbUFO) isolated from both the wild-type and gh cosmos revealed that CbUFO may play an important role in inflorescence differentiation into different structures and promotion of flower initiation, and the reduced expression of CbUFO in the gh cosmos could be associated with the phenotypes of the flower-defective plants. Further expression analysis indicated that CbUFO may promote the conversion of inflorescence meristem into floral meristem in early ray flower formation, but does not play a role in its later growth period.

Flower forcing possibilities in Hemerocallis hybrids

Daylilies (Hemerocallis hybrids) are one of the most important ornamental perennial plants nowadays used in gardens and parks. Flower forcing of daylily hybrids in early spring or autumn could broaden their application and marketing possibilities. There is very limited data available on this topic. In our early flower forcing experiment ‘Moonlit Masquerade’, for late flowering ‘Mary Todd’ were used. During the study we have sought answer for the following questions: the amount of growing degree-day required for flower stalk induction and for flowering and whether the day length has an effect on these values or not. In the early flower forcing experiment 4 treatment groups were established: plants of the first treatment group were placed in a moderately heated greenhouse without assimilation lighting. The second treatment group were placed in the same greenhouse but artificial light was used to extend the day length for 15 h. The examination of the third group happened in a plant growth chamber with 15 h day length and a daily average temperature of 20°C was provided for the plants, and there was also a control group in open field environment. For late flowering the bare rooted dormant plants were stored in refrigerator and were planted to open-field in late spring and summer. During the experiments temperature data were logged and plant morphology characteristics were measured in two following year. According to the results it can be stated that the differentiation of inflorescence is not depending on the day length rather on the leaf surface area. Growing degree-day is the main factor which influences the speed of inflorescence development once it has already differentiated, so temperature is the key factor in flower bud opening and it also defines the number of the developing flower buds. The data from late flowering experiment show that bare-rooted daylily plants are suitable for long-term cold storage and this method offers late season flower forcing.

Determination of floral development stages in ‘Cabernet Sauvignon’ (Vitis viniferaL. cv.): highlighting the manifestation of stamens and pistil primordia with new intermediate stages linking the phenological stages

Despite relatively intensive work on the development of inflorescence primordia during grapevine growth in season one, some informational gaps are present in the flower and floral organ development in the season two. In addition, concurrents events of phenology and formation of flowers and floral parts has not been dealt with. With the aid of digital imaging, this research had three objectives; a) describe the developmental events that take place during and after bud break in the buds and in the individual flowers in terms of differentiation, b) match these events with phenological stages, and c) determine size-related growth of the floral organs. After careful dissecting and examination of the samples under microscopy, taken ever 5-10 days between March 20 and May 10 in 2016, the results indicated that highly esteemed works regarding the reproductive anatomy of grapevines needed some additional stages to fully describe events in the stamen and pistil primordia after the appearance of petal primordia. Five intermediate stages were added to the stages of “formation of flowers”. Differentiation of inflorescence and individual flowers occurred in the second season as the buds swelled in the spring. Stamens and pistil could be seen about 3 weeks later and completed their initial growth in another 3 weeks. Flower primordia was visible on April 1 and showed a more than 9-fold increase over the course of 5 to 6 weeks. flowers increased their width and their length more than 9- and 15-fold, respectively, between stage 8.1 (April 1) and 10.3 (May 10). At first, they were wider than they were longer, but at later stages they grew longitudinally. Reproductive organ primordia were visualized around the time of 2-4 leaves separated on the shoots. Signs of generative parts become apparent in late April. Anthers were the smallest in the flower. Filaments, on the other hand, elongated almost 7-fold in a period of 20 days. Gynoecium growth was the most impressive and total pistil length increased from 52.8 to 162 μm, ovary width from 40.4 to 99.8 μm, and stigma diameter from 9.96 to 44.9 μm in twenty days. By the time the pistil took its final shape, 6-8 leaves grew on the shoot during which inflorescence could also be seen.

English

The aim of the present study is to assess the effects of different irrigation blades on the growth and yield of cauliflower cv. Verona CMS. The plants were cultivated in Red-yellow Latosol during the dry period (winter-spring 2014 and 2015), in the Cerrado-Amazon transition region, Middle-Northern of Mato Grasso State, Brazil. The reference evapotranspiration (ETo) was recorded through the Class A pan method by using tank coefficient of (Kp) 0.7795. We assessed the blades of 40, 60, 80, 100 and 120% evapotranspiration of the culture (ETc) by taking into account the cultivation coefficients (Kc) of 0.70 and 0.95 in the vegetative and reproductive phases. With regard to the morphometric variables of the plants (height, stem diameter and number of leaves) there were no significant interactions between assessment time (days after planting) and irrigation blades throughout the crop years. The hydric response functions presented higher yield at repositions from 80% to 100% of ETc. Variations in the irrigation blade did not influence the thermal demands for the inflorescence differentiation period or the inflorescence shape. Increased irrigated blade reduced water use efficiency: 7.4 and 12.4 kg of fresh mass per m³ of irrigated water. Key words: Irrigation management, water response function, degree-days, evapotranspiration.

New phenological growth stages of garlic (Allium sativum)

AbstractThe advantages of using Biologische Bundesanstalt, Bundessortenamt and Chemische Industrie (BBCH) phenological scales are well‐known in the field of agronomy. Currently, specific scales exist for the majority of crops. Although garlic has international importance due to its worldwide cultivation, a specific phenological scale has not been developed; in general, garlic is integrated into the BBCH description for onion. While garlic and onion belong to the same genus, this generalisation should be avoided due to their many differences. The means of propagation of garlic is vegetative, from cloves of the previous cycle, and the concurrence of the bulbing phase and the emergence of the inflorescence (bolting types) cause garlic to perpetually remain in a ‘second year stage’ of its biological cycle. In contrast, onions and other bulbous Liliaceae that produce seeds undergo biannual development. In addition to this complexity, its physiological complex is strongly influenced by environmental factors, such as temperature and photoperiod; distinct conditions are required for overlapping or simultaneously occurring phases (bulbing/flowering). Nevertheless, ambiguity and lack of consensus exist concerning the start of different phenological phases due to the complex morphology of the bulb (composed of a bulb of bulbs/cloves). During bulbing, for example, two distinct, consecutive processes are involved: the differentiation of lateral buds and inflorescence (bolting types) and the thickening of the storage leaf of each bud (cloves). In the present study, an extended BBCH scale was developed for garlic (Allium sativum). Seven principal growth stages divided into secondary growth stages are described in detail and are represented by a two‐ or three‐digit code. Descriptions begin with garlic cloves in a stage of dormancy, destined for planting and end with complete bulb maturity. The most complex growth stages of garlic were described from a morphological and physiological perspective, that is complete bolting types (hard‐neck cultivars). Illustrations of different stages are included to clarify the application of the code system. The proposed BBCH garlic scale aims to fill gaps in the knowledge of this important crop and will serve as a useful tool for researchers, technicians and farmers. Thus, experimental findings may be standardised and complementary, which may lead to improvements in management practices and their comparisons.

Life cycle and reproductive botany of Scilla hyacinthoides, a Mediterranean geophyte

The Mediterranean region is abundant with geophyte species, many of which have been developed as ornamentals. In recent years attempts were made to grow Scilla hyacinthoides L. (Asparagaceae, subfamily Scilloideae) commercially, both as a cut flower and as a water-saving ornamental geophyte. Optimizing commercial production of S. hyacinthoides requires the study of growth and development of the vegetative plant, as well as the control of flower bud initiation and development.Like most Mediterranean plants, S. hyacinthoides life cycle is attuned to the annual rhythm which alternates between hot and dry summer, and cool and rainy winter. Plants are dormant during summer. In autumn the apical meristem becomes active and either begins producing leaves for the next season, or initiates inflorescence development. After the onset of inflorescence development, a new apical meristem is formed at the axil of the youngest leaf. Frequently, two apices are formed; one of them becomes a daughter bulb. Intrabulb development of the inflorescence was studied by histology and electron microscopy. The flowering occurs in spring. Floral initiation is temperature-dependent and is inhibited by low temperatures, but inflorescence differentiation and elongation is inhibited by high temperatures. Flowers are self-incompatible and exhibit several polymorphic traits, probably important in pollinator attraction. In summary, current research provides a basis for future studies on the florogenesis and ecophysiology in Scilla, as well as enabling future fine tuning of cultivation protocols for the flower industry.

Study on Petal-Sepal Mutant of Sunflower (<i>Helianthus annuus</i>) after Space Mutation

In this paper, we studied the morphological, histological and photosynthetic characteristics of the stably inherited sunflower petal-sepal mutant, and it was obtained by the space radiation-induced mutagenesis. Afterwards, we got following results: 1) The morphological characteristics represented that the inflorescence of petal-sepal mutant maintained the appearance and structure of capitulum, whereas no explicit tubular flower or ligulate flower was differentiated. 2) The histological characteristics revealed that the petal-sepal mutant only completed the inflorescence development and the differentiation of sepal primordia and inflorescence primordia, without entering the differentiation stage of tubular flower primordia, ligulate flower primordia, stamen primordia or pistil primordia. 3) The photosynthetic characteristics showed that the photosynthetic rate, transpiration and stomatal conductance of petal-sepal mutant were relatively weaker than the control plants. In the end, we concluded that the petal-sepal mutant of sunflower had only inflorescence differentiation, while several mutant genes were caused by radiation-induced mutation, which entered an infinitely recurrent development process rather than the floral differentiation stage. We also observed a few chloroplast structures in the paraffin section, combined with the results of photosynthetic characteristics of petal-sepal mutant, and then we believed that the inflorescence of petal-sepal mutant was involved in photosynthesis to accumulate energy for plant growth.