Inflorescence Development Research Articles

Stepwise increases in FT1 expression regulate seasonal progression of flowering in wheat (Triticum aestivum).

Flowering is regulated by genes that respond to changing daylengths and temperature, which have been well studied using controlled conditions; however, the molecular processes underpinning flowering in nature remain poorly understood. Here, we investigate the genetic pathways that coordinate flowering and inflorescence development of wheat (Triticum aestivum) as daylengths extend naturally in the field, using lines that contain variant alleles for the key photoperiod gene, Photoperiod-1 (Ppd-1). We found flowering involves a stepwise increase in the expression of FLOWERING LOCUS T1 (FT1), which initiates under day-neutral conditions of early spring. The incremental rise in FT1 expression is overridden in plants that contain a photoperiod-insensitive allele of Ppd-1, which hastens the completion of spikelet development and accelerates flowering time. The accelerated inflorescence development of photoperiod-insensitive lines is promoted by advanced seasonal expression of floral meristem identity genes. The completion of spikelet formation is promoted by FLOWERING LOCUS T2, which regulates spikelet number and is activated by Ppd-1. In wheat, flowering under natural photoperiods is regulated by stepwise increases in the expression of FT1, which responds dynamically to extending daylengths to promote early inflorescence development. This research provides a strong foundation to improve yield potential by fine-tuning the photoperiod-dependent control of inflorescence development.

Does extraction of orchids affect their population structure? Evidence from populations of Laelia autumnalis (Orchidaceae)

Chronic anthropogenic disturbance caused by the extraction of plant sections or entire individuals from wild populations can modify the population structure of the plants. Population structure, plant biomass capital and reproductive probability were compared in five Laelia autumnalis populations under different extraction intensities. For each plant, the number of pseudobulbs was counted and the biomass of each pseudobulb estimated and its live/dead status recorded along with the presence of inflorescence remnants. The live biomass of each plant was related to its total number of pseudobulbs. In populations under greater levels of extraction, the plants accumulate less biomass as they become larger. In populations under lower extraction, there was a greater abundance of small plants (1–9 and 10–18 pseudobulbs). In contrast, populations under higher extraction presented a structure with a greater abundance of large individuals (>19 pseudobulbs). In all populations, the frequency of the remains of inflorescences increases with plant size. In contrast, the development of inflorescences in the study season decreased as the intensity of extraction increased. In conclusion, extraction of Laelia autumnalis plants causes them to accumulate less biomass and become less likely to develop inflorescences as they age, and ultimately modifies their population structure toward an abundance of large, old plants.

COMPOSITUM 1 contributes to the architectural simplification of barley inflorescence via meristem identity signals

Grasses have varying inflorescence shapes; however, little is known about the genetic mechanisms specifying such shapes among tribes. Here, we identify the grass-specific TCP transcription factor COMPOSITUM 1 (COM1) expressing in inflorescence meristematic boundaries of different grasses. COM1 specifies branch-inhibition in barley (Triticeae) versus branch-formation in non-Triticeae grasses. Analyses of cell size, cell walls and transcripts reveal barley COM1 regulates cell growth, thereby affecting cell wall properties and signaling specifically in meristematic boundaries to establish identity of adjacent meristems. COM1 acts upstream of the boundary gene Liguleless1 and confers meristem identity partially independent of the COM2 pathway. Furthermore, COM1 is subject to purifying natural selection, thereby contributing to specification of the spike inflorescence shape. This meristem identity pathway has conceptual implications for both inflorescence evolution and molecular breeding in Triticeae.

Staying in the club: Exploring criteria governing metacommunity membership for obligate symbionts under host–symbiont feedback

Metacommunity membership is influenced by habitat availability and trophic requirements. However, for multitrophic horizontally transmitted symbiont communities that are closely associated with hosts, symbiont–host interactions may affect membership criteria in novel ways. For example, failure of beneficial services from symbionts could influence the host, and in turn, the entire community. Understanding such host–symbiont feedback effects on symbiont community membership, symbiont community structure, and function is important for understanding if host–symbiont communities are fundamentally different from more traditional ecological communities.We investigate the membership criteria for a multitrophic insect symbiont community that colonizes host inflorescences at specific developmental stages termed colonization windows. The inflorescences serve as microcosm habitats. Symbionts exhibit a range of interactions from mutualism to parasitism. Hosts exhibit feedback by aborting inflorescences not pollinated by mutualistic symbionts. Habitats are consequently lost for all other symbiont species in such host-derived organs whose development is mutualist-dependent. Using empirical measurements to characterize inflorescence development, we simulate symbiont dispersal colonization across hosts. We vary host densities and lengths of symbiont colonization windows, and track the persistence of each symbiont species in the metacommunity based on its trophic requirements and resource availability within the microcosm.Since the persistence of the microcosm habitat is dictated by pollination performed by the mutualist, the mutualist fared better than all other symbionts. The length of symbiont colonization windows was positively related with colonization success and symbiont persistence. The cumulative length of the colonization windows of prey dictated predator success; diet breadth or prey colonization success did not influence predator persistence. Predators also had a greater host-plant density requirement than prey for persistence in the community. These results offer valuable insights into host densities required for maintaining symbionts, and have implications for multitrophic symbiont community stability.Special constraints can govern symbiont community membership, function and structure and symbiont persistence when host–symbiont feedback impacts host microcosm development.

Flower biology and ontogeny of the tung tree (Vernicia fordii Hemsl.)

Low number of pistillate flowers in the tung tree is a major factor causing the low yield of tung fruits. The tung tree (Vernicia fordii Hemsl.), an economically important woody oil plant, produces excellent fast-drying oil from the seeds which has been used as a protective finish on projects and surfaces for centuries. Knowledge of sex determination and flower development of tung trees is helpful for high-yield cultivation and breeding of new elite cultivars. However, studies on tung flower biology and ontogeny are still lacking. Here, we reported a comprehensive study of the flower biology and ontogeny of the tung tree, focusing on flower cycle, flower morphology and flower development. The inflorescence phenophases of monoecious tung trees were divided into 12 pivotal stages and used as a unique timeline to reference the events registered throughout the flower cycle. Histological studies on sporogenesis and gametogenesis were also conducted. Meanwhile, all the unique events throughout flower cycle were linked together to show the correlation between inflorescence development phenophases, pistillate and staminate flower stages and its embryological development. Tung trees in our plantation were grouped into three major types, i.e., monoecious, gynoecious and androecious trees which produced different number of fruits in each inflorescence. We propose that low number of pistillate flowers in the tung tree is a major factor causing the low yield of tung fruits, and that any measures increasing the number of pistillate flowers would effectively improve the yield of tung fruits.

The study of genetic factors that determine the awned glume trait in bread wheat

Ости – тонкие заостренные отростки, сформированные в дистальной части чешуй колоска соцветия некоторых видов злаков, включая такие экономически значимые культуры, как пшеница мягкая (Triticum aestivum L.) и твердая (T. durum Desf.), ячмень (Hordeum vulgare L.), рис (Oryza sativa L.), рожь (Secale cereal L.). Наличие длинных остей на колосковых чешуях характерно для одного вида пшеницы – T. carthlicum Nevski, киль коло- сковой чешуи которого переходит в длинный остевидный отросток или ость, равную по длине ости цветковой чешуи. Колос T. carthlicum имеет удвоенное число остей, а сам признак получил название «тетраостость» или персикоидность. Ости на месте килевого зубца колосковых чешуй могут формироваться у пшениц T. aestivum и T. aethiopicum, однако такие формы встречаются редко. Особенности развития признака тетраостости и его гене- тические детерминанты изучены мало. В настоящем исследовании рассмотрены особенности развития и насле- дования признака «тетраостость» линии CD 1167-8 мягкой пшеницы T. aestivum c применением классического генетического анализа, молекулярно-генетического картирования и сканирующей электронной микроскопии. Показано, что признак наследуется как рецессивный моногенный. Ген, контролирующий тетраостость линии CD 1167-8, картирован в длинном плече хромосомы 5A c использованием 15K-SNP-микрочипа, содержащего 15 000 ассоциированных с генами SNP пшеницы (Illumina Infinium 15K Wheat Array, TraitGenetics GmbH). Резуль- таты теста на аллелизм продемонстрировали, что изучаемый ген аллелен b1, рецессивному аллелю гена-инги- битора остистости B1 (5AL). Таким образом, ген, контролирующий формирование остей на колосковых чешуях мягкой пшеницы, является рецессивным аллелем гена ингибитора остистости B1. Новый аллель обозначен b1.ag (b1. awned glume). Анализ развивающегося соцветия линии CD 1167-8 с помощью сканирующей электронной микроскопии выявил, что зачатки остей колосковых чешуй формируются по мере развития и роста колосковых чешуй одновременно с развитием остей на цветковых чешуях, различий в развитии остей на цветковых и колосковых чешуях не обнаружено.

Ectopic Expression of the Transcriptional Regulator silky3 Causes Pleiotropic Meristem and Sex Determination Defects in Maize Inflorescences.

Maize (Zea mays) is a monoecious plant, in which inflorescence morphogenesis involves complicated molecular regulatory mechanisms. Although many related genes have been cloned, our understanding of the molecular mechanism underlying maize inflorescence development remains limited. Here, we identified a maize semi-dominant mutant Silky3 (Si3), which displays pleiotropic defects during inflorescence development, including loss of determinacy and identity in meristems and floral organs, as well as the sexual transformation of tassel florets. We cloned the si3 gene using a map-based approach. Functional analysis reveals that SI3 is a nuclear protein and may act as a transcriptional regulator. Transcriptome analysis reveals that the ectopic expression of si3 strongly represses multiple biological processes, especially the flower development pathways. RNA in situ hybridization similarly shows that the expression patterns of genes responsible for flower development are changed in the Si3 mutant. In addition, the homeostasis of jasmonic acid and gibberellic acid are altered in the Si3 young tassels, and application of exogenous jasmonic acid can rescue the sex reversal phenotype of Si3 The defects we characterized in various regulatory pathways can explain the complex phenotypes of Si3 mutant, and this study deepens our knowledge of maize inflorescence development.

Inflorescence Development and Floral Organogenesis in Taraxacum kok-saghyz.

Rubber dandelion (Taraxacum kok-saghyz Rodin; TK) has received attention for its natural rubber content as a strategic biomaterial, and a promising, sustainable, and renewable alternative to synthetic rubber from fossil carbon sources. Extensive research on the domestication and rubber content of TK has demonstrated TK’s potential in industrial applications as a relevant natural rubber and latex-producing alternative crop. However, many aspects of its biology have been neglected in published studies. For example, floral development is still poorly characterized. TK inflorescences were studied by scanning electron microscopy. Nine stages of early inflorescence development are proposed, and floral micromorphology is detailed. Individual flower primordia development starts at the periphery and proceeds centripetally in the newly-formed inflorescence meristem. Floral organogenesis begins in the outermost flowers of the capitulum, with corolla ring and androecium formation. Following, pappus primordium—forming a ring around the base of the corolla tube—and gynoecium are observed. The transition from vegetative to inflorescence meristem was observed 21 days after germination. This description of inflorescence and flower development in TK sheds light on the complex process of flowering, pollination, and reproduction. This study will be useful for genetics, breeding, systematics, and development of agronomical practices for this new rubber-producing crop.

Impact of vernalization and heat on flowering induction, development and fertility in root chicory (Cichorium intybus L. var. sativum)

Root chicory (Cichorium intybus var. sativum) is a biennial plant that requires vernalization for flowering initiation. However, we previously showed that heat can induce root chicory flowering independently of vernalization. To deepen our understanding of the temperature control of flowering in this species, we investigated the impact of heat, vernalization and their interaction on flowering induction and reproductive development. Heat increased the flowering percentage of non-vernalized plants by 25% but decreased that of vernalized plants by 65%. After bolting, heat negatively affected inflorescence development, decreasing the proportion of sessile capitula on the floral stem by 40% and the floral stem dry weight by 42% compared to control conditions, although it did not affect the number of flowers per capitulum. Heat also decreased flower fertility: pollen production, pollen viability and stigma receptivity were respectively 25%, 3% and 82% lower in heat-treated plants than in untreated control plants. To investigate the genetic control of flowering by temperature in root chicory, we studied the expression of the FLC-LIKE1 (CiFL1) gene in response to heat; CiFL1 was previously shown to be repressed by vernalization in chicory and to repress flowering when over-expressed in Arabidopsis. Heat treatment increased CiFL1 expression, as well as the percentage of bolting and flowering shoot apices. Heat thus has a dual impact on flowering initiation in root chicory since it appears to both induce flowering and counteract vernalization. However, after floral transition, heat has a primarily negative impact on root chicory reproduction.

Genome-wide identification, phylogeny and expression analysis of the SPL gene family in wheat

BackgroundMembers of the plant-specific SPL gene family (squamosa promoter-binding protein -like) contain the SBP conserved domain and are involved in the regulation of plant growth and development, including the development of plant flowers and plant epidermal hair, the plant stress response, and the synthesis of secondary metabolites. This family has been identified in various plants. However, there is no systematic analysis of the SPL gene family at the genome-wide level of wheat.ResultsIn this study, 56 putative TaSPL genes were identified using the comparative genomics method; we renamed them TaSPL001 - TaSPL056 on their chromosomal distribution. According to the un-rooted neighbor joining phylogenetic tree, gene structure and motif analyses, the 56 TaSPL genes were divided into 8 subgroups. A total of 81 TaSPL gene pairs were designated as arising from duplication events and 64 interacting protein branches were identified as involve in the protein interaction network. The expression patterns of 21 randomly selected TaSPL genes in different tissues (roots, stems, leaves and inflorescence) and under 4 treatments (abscisic acid, gibberellin, drought and salt) were detected by quantitative real-time polymerase chain reaction (qRT-PCR).ConclusionsThe wheat genome contains 56 TaSPL genes and those in same subfamily share similar gene structure and motifs. TaSPL gene expansion occurred through segmental duplication events. Combining the results of transcriptional and qRT-PCR analyses, most of these TaSPL genes were found to regulate inflorescence and spike development. Additionally, we found that 13 TaSPLs were upregulated by abscisic acid, indicating that TaSPL genes play a positive role in the abscisic acid-mediated pathway of the seedling stage. This study provides comprehensive information on the SPL gene family of wheat and lays a solid foundation for elucidating the biological functions of TaSPLs and improvement of wheat yield.

EFFECT OF PRUNING AND ORGANIC FERTILIZATION OVER PRODUCTIVE PARAMETERS OF FOUR MEXICAN PROVENANCES OF Jatropha curcas L.

The performance of Mexican provenances of Jatropha curcas L. under different agropractices has not been very widely investigated in their center of origin. The purpose of this study was to determine the flowering, fruit and seed production performance of four Mexican provenances of J. curcas to pruning and organic fertilization. The evaluated provenances were obtained from the municipalities of Actopan, Tamiahua, Papantla and Amatlán located in southeastern, Mexico. The experimental design considered two factors: provenance and treatment. The treatments were bokashi, vermicompost, pruning, and the control, each one with five individuals per provenance (80 plants). Plants were monitored every week during one productive cycle (April 2016 to January 2017), starting with the development of inflorescences until the harvesting of mature fruits. The seeds obtained from the fruits were dried and weighted to determine plant productivity. The analysis of variance was performed with a significant level of 0.05. Results indicated statistically significant differences between treatments and provenances, but there was no interaction between provenances and treatments. Application of bokashi and vermicompost was statistically similar and allowed the highest productivity, Actopan had the highest productivity (436 g of dried seed by plant), which was 26 % over the control, pruning allowed the highest fruit mooring, but it delayed production by two months, which reduced the total seed productivity (297 g by plant), being statistically similar to the control. We conclude that Mexican provenances have a positive response to organic fertilization and pruning, but pruning reduces its productive period.

CRISPR/Cas9 editing of wheat TaQ genes alters spike morphogenesis and grain threshability

The TaQ alleles as one of the AP2-like transcription factors in common wheat (Triticum aestivum) play an important role in the evolution of spike characteristics from wild and domesticated emmer to modern wheat cultivars. Its loss-of-function mutant not only changed threshability and spike architecture but also affected plant height, flowering time, and floret structure. However, the comprehensive functions of TaAQ and TaDq genes in wheat have not been fully elucidated yet. Here, CRISPR/SpCas9 was used to edit wheat TaAQ and TaDq. We obtained homozygous plants in the T1 generation with loss of function of only TaAQ or TaDq and simultaneous loss of function of TaAQ and TaDq to analyze the effect of these genes on wheat spikes and floret shapes. The results demonstrated that the TaAQ-edited plants and the TaAQ and TaDq simultaneously-edited plants were nearly similar in spike architecture, whereas the TaDq-edited plants were different from the wild-type ones only in plant height. Moreover, the TaAQ-edited plants or the TaAQ and TaDq simultaneously-edited plants were more brittle than the wild-type and the TaDq-edited plants. Based on the expression profiling, we postulated that the VRN1, FUL2, SEP2, SEP5, and SEP6 genes might affect the number of spikelets and florets per spike in wheat by regulating the expression of TaQ. Combining the results of this report and previous reports, we conceived a regulatory network of wheat traits, including plant height, spike shape, and floral organs, which were influenced by AP2-like family genes. The results achieved in this study will help us to understand the regulating mechanisms of TaAQ and TaDq alleles on wheat floral organs and inflorescence development.

Inflorescence and Flower Development in Orchidantha chinensis T. L. Wu (Lowiaceae; Zingiberales): Similarities to Inflorescence Structure in the Strelitziaceae

Premise of research. The monotypic Lowiaceae remains the least-known family in the plant order Zingiberales, yet it may hold an important key to unraveling the phylogenetic placement of the families Musaceae, Heliconiaceae, Strelitziaceae, and Lowiaceae. After nine phylogenetic studies, the (Lowiaceae, Strelitziaceae) clade is the only stable clade that has emerged in this half of the order. This study was undertaken to verify the unusual inflorescence and flower structure in Orchidantha and to search for new characters that might be used in future phylogenetic analyses. We describe both inflorescence and flower development in a previously unstudied species; confirm inflorescence morphology in the genus; and compare the structure of the inflorescence in the Lowiaceae with that of the Strelitziaceae, its potential sister group.Methodology. Standard collection and SEM procedures were used to collect and prepare the material for study.Pivotal results. The inflorescence of Orchidantha is borne at the end of a vegetative shoot and is composed of two lateral branches that each bear four bracts and a single flower before aborting. The fourth bract and its associated flower form the highly reduced flower cluster (florescence) that characterizes this genus. In technical terms, Orchidantha has a polytelic synflorescence that lacks a main florescence (it has a truncated polytelic synflorescence) and bears solitary flowers in coflorescences on determinate enriching branches. The enriching branches produce a fixed number of bracts before aborting (i.e., they are special paracladia). Many of these features are shared with the Strelitziaceae.Conclusions. Similarities between the Lowiaceae and Strelitziaceae include inflorescence structure; the presence of a long prolongation of the ovary; and a delay in the formation of the third sepal during flower development, a character that is also shared with the Musaceae. Inflorescence and flower structure is now well established in this small but important family.

Fine mapping of qKRN8, a QTL for maize kernel row number, and prediction of the candidate gene.

KEY MESSAGE: qKRN8, a major QTL for kernel row number in maize, was fine mapped to an interval of ~ 520kb on chromosome 8 and the key candidate gene was identified via expression analysis. Kernel row number (KRN) is one of the most important yield-influencing traits and is closely associated with female inflorescence development in maize (Zea mays L.). In this study, an F2:3 population derived from a cross between V54 (low KRN line) and Lian87 (high KRN line) was used to map quantitative trait loci (QTLs) conferring KRN in maize. We identified 12 QTLs for KRN in four environments, each explaining 1.40-14.95% of phenotypic variance. Among these, one novel major QTL (named qKRN8) was mapped to bin 8.03 in all four environments, explaining 8.79-14.95% of phenotypic variation. By combining map-based cloning with progeny testing of recombinants, we ultimately mapped qKRN8 to an ~ 520kb genomic interval, harboring six putative candidate genes. Among them, one candidate gene showed contrasted expression level in immature ears of the near-isogenic lines qKRN8Lian87 and qKRN8V54. These findings should facilitate molecular breeding for KRN and the further identification of the polymorphism underlying this QTL.

OsFD4 promotes the rice floral transition via florigen activation complex formation in the shoot apical meristem.

In rice, the florigens Heading Date 3a (Hd3a) and Rice Flowering Locus T 1 (RFT1), OsFD-like basic leucine zipper (bZIP) transcription factors, and Gf14 proteins assemble into florigen activation/repressor complexes (FACs/FRCs), which regulate transition to flowering in leaves and apical meristem. Only OsFD1 has been described as part of complexes promoting flowering at the meristem, and little is known about the role of other bZIP transcription factors, the combinatorial complexity of FAC formation, and their DNA-binding properties. Here, we used mutant analysis, protein-protein interaction assays and DNA affinity purification (DAP) sequencing coupled to in silico prediction of binding syntaxes to study several bZIP proteins that assemble into FACs or FRCs. We identified OsFD4 as a component of a FAC promoting flowering at the shoot apical meristem, downstream of OsFD1. The osfd4 mutants are late flowering and delay expression of genes promoting inflorescence development. Protein-protein interactions indicate an extensive network of contacts between several bZIPs and Gf14 proteins. Finally, we identified genomic regions bound by bZIPs with promotive and repressive effects on flowering. We conclude that distinct bZIPs orchestrate floral induction at the meristem and that FAC formation is largely combinatorial. While binding to the same consensus motif, their DNA-binding syntax is different, suggesting discriminatory functions.

Cytological Observations and In Vitro Germination of Nipa (Nypa fruticans Wurmb., Arecaceae) Pollen

The staminate rachillae from laterals of nipa (Nypa fruticans Wurmb.) at different stages of inflorescence development were sampled for cytological observations using squash technique, with 2% acetocarmine as the stain. Results showed that the dividing microsporocytes exhibited a tetrad in tetragonal shape enclosed in thick callose walls at the end of meiosis II. The microspore products consisted not only of uninucleate but also of binucleate and trinucleate pollen during anthesis. Meiotic stages were interpreted as highly normal, which suggests high pollen viability. In vitro germination observed every 4-h intervals for 24 h showed that sucrose level at 15% attained significantly highest germination at 53%. The germinated pollen developed a knob protrusion instead of an elongated pollen tube. There was a significant difference in pollen knob length at 15% sucrose measuring 9.6 µm, the longest observed, compared to the control. With significant interaction between sucrose and boron levels, 10% and 15% sucrose levels achieved higher in vitro germination when combined with 0.01% and 0.005% boron, respectively. Indeed, sucrose and boric acid consisting of the liquid medium can initiate nipa pollen germination, confirming earlier results with lower concentrations.

A developmental approach expanding the knowledge of inflorescence diversity in subtribe Eleusininae (Chloridoideae: Poaceae)

Abstract Subtribe Eleusininae (Chloridoideae, Poaceae) comprise 237 species with little morphological diversity in inflorescence structure. This diversity may be explained by an evolution from complex (pyramidal, highly branched) to simpler (digitate, barely branched) morphologies. However, only mature specimens have been studied; the developmental analyses of the inflorescences are rare. We analysed the inflorescence, spikelet and flower development of 17 species of Eleusininae using scanning electron microscopy. In the early stages of the transition to flowering of the studied species, the inflorescence meristem elongates initiating primary branches acropetally. The differentiation of these branches along the main axis is either basipetal or amphipetal. Although the initiation of secondary branches along primary branches may be acropetal or amphipetal, their differentiation follows an amphipetal direction. The florets in spikelets are initiated acropetally. We found abnormal orientation of stamens and gynoecium in florets of Leptochloa chloridiformis. The analysis of the ontogeny has enriched current knowledge of inflorescences in the subtribe. In addition, the developmental patterns revealed the existence of more than one developmental pattern leading to similar mature inflorescence forms. The results will support future efforts on postulating trends of developmental patterns across Poaceae.

Endogenous phytohormones and the expression of flowering genes synergistically induce flowering in loquat

Flowering is an important process for the reproduction of higher plants. Up to this point, the studies on flowering have mostly focused on the model plant Arabidopsis thaliana, and the flowering mechanism of fruit trees remains mostly unknown. The diversity of the flowering time of loquat (Eriobotrya japonica Lindl.) makes it an ideal material to study the regulation of flowering. In this study, we first observed the inflorescence bud differentiation in two varieties of loquat that had different blooming times (cv. Dawuxing (E. japonica), that blooms in the fall and cv. Chunhua (E. japonica×Eriobotrya bengalensis Hook. f.) that blooms in the spring) and found that the starting time of inflorescence bud differentiation and the speed of inflorescence development were responsible for the difference in blooming times. The determination of endogenous phytohormones by high performance liquid chromatography (HPLC) indicated that abscisic acid (ABA), zeatin (ZT), and gibberellin (GA3) promoted flowering in loquat, while indole-3-acetic acid (IAA) was mainly involved in inflorescence bud differentiation in Chunhua. A transcription level analysis illustrated that multiple flowering-related genes could respond to different signals, integrate to the TFL1, AP1 and FT genes, and then synergistically regulate flowering in loquat. Thus, this study provides a new insight into flowering regulation mechanisms in loquat.

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

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

V-Mango: a functional-structural model of mango tree growth, development and fruit production.

Background and AimsMango (Mangifera indica L.) is the fifth most widely produced fruit in the world. Its cultivation, mainly in tropical and sub-tropical regions, raises a number of issues such as the irregular fruit production across years, phenological asynchronisms that lead to long periods of pest and disease susceptibility, and the heterogeneity of fruit quality and maturity at harvest. To address these issues, we developed an integrative functional–structural plant model that synthesizes knowledge about the vegetative and reproductive development of the mango tree and opens up the possible simulation of cultivation practices.MethodsWe designed a model of architectural development in order to precisely characterize the intricate developmental processes of the mango tree. The appearance of botanical entities was decomposed into elementary stochastic events describing occurrence, intensity and timing of development. These events were determined by structural (position and fate of botanical entities) and temporal (appearance dates) factors. Daily growth and development of growth units and inflorescences were modelled using empirical distributions and thermal time. Fruit growth was determined using an ecophysiological model that simulated carbon- and water-related processes at the fruiting branch scale.Key ResultsThe model simulates the dynamics of the population of growth units, inflorescences and fruits at the tree scale during a growing cycle. Modelling the effects of structural and temporal factors makes it possible to simulate satisfactorily the complex interplays between vegetative and reproductive development. The model allowed the characterization of the susceptibility of mango tree to pests and the investigatation of the influence of tree architecture on fruit growth.ConclusionsThis integrative functional–structural model simulates mango tree vegetative and reproductive development over successive growing cycles, allowing a precise characterization of tree phenology and fruit growth and production. The next step is to integrate the effects of cultivation practices, such as pruning, into the model.