The switch from vegetative growth to reproductive growth, i.e. flowering, is the critical event in a plant’s life. Flowering is regulated either autonomously or by environmental factors; ...photoperiodic flowering, which is regulated by the duration of the day and night periods, and vernalization, which is regulated by low temperature, have been well studied. Additionally, it has become clear that stress also regulates flowering. Diverse stress factors can induce or accelerate flowering, or inhibit or delay it, in a wide range of plant species. This article focuses on the positive regulation of flowering via stress, i.e. the induction or acceleration of flowering in response to stress that is known as stress-induced flowering – a new category of flowering response. This review aims to clarify the concept of stress-induced flowering and to summarize the full range of characteristics of stress-induced flowering from a predominately physiological perspective.
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ABSTRACT
The forecast capability of the first‐flowering date (FFD) over South Korea is evaluated using the seasonal (1‐ to 3‐month lead) prediction from the global Pusan National University (PNU) ...coupled general circulation model (CGCM) v1.1 and regional Weather Research and Forecast (WRF) v3.0 climate models. Gridded data with high spatial (3 km) and temporal (daily) resolution are produced using the physically based dynamical models. Dynamical downscaling is performed using WRF v3.0 with the lateral forcing from hourly outputs of PNU CGCM v1.1. Statistical correction is then used to eliminate systematic bias in the model output. The FFDs of cherry, peach and pear in South Korea are predicted for the decade of 1999–2008 by applying the corrected daily temperature predictions to the phenological thermal‐time model. The WRF v3.0 results reflect the detailed topographical effect, despite having cold and warm biases for warm and cold seasons, respectively. After applying the correction, the mean temperature for early spring (February to April) clearly represents the general pattern of observation, while preserving the advantages of dynamical downscaling. The FFD predictabilities for the three species of trees are evaluated in terms of qualitative, quantitative and categorical estimations. Although FFDs derived from the corrected WRF results well predicted the spatial distribution and the variation of observation, the prediction performance has no statistical significance or appropriate predictability. Even though the upcoming flowering phenology could not be accurately predicted, the present study approach may be helpful in obtaining detailed and useful information about FFD and regional temperature by accounting for physically based atmospheric dynamics.
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The floral transition plays a vital role in the life of ornamental plants. Despite progress in model plants, the molecular mechanisms of flowering regulation remain unknown in perennial plants. Rosa ...chinensis 'Old Blush' is a unique plant that can flower continuously year-round. In this study, gene expression profiles associated with the flowering transition were comprehensively analyzed during floral transition in the rose.
According to the transcriptomic profiles, 85,663 unigenes and 1,637 differentially expressed genes (DEGs) were identified, among which 32 unigenes were involved in the circadian clock, sugar metabolism, hormone, and autonomous pathways. A hypothetical model for the regulation of floral transition was proposed in which the candidate genes function synergistically the floral transition process. Hormone contents and biosynthesis and metabolism genes fluctuated during the rose floral transition process. Gibberellins (GAs) inhibited rose floral transition, the content of GAs gradually decreased and GA2ox and SCL13 were upregulated from vegetative (VM) meristem to floral meristem (FM). Auxin plays an affirmative part in mediating floral transition, auxin content and auxin-related gene expression levels were gradually upregulated during the floral transition of the rose. However, ABA content and ABA signal genes were gradually downregulated, suggesting that ABA passively regulates the rose floral transition by participating in sugar signaling. Furthermore, sugar content and sugar metabolism genes increased during floral transition in the rose, which may be a further florigenic signal that activates floral transition. Additionally, FRI, FY, DRM1, ELIP, COP1, CO, and COL16 are involved in the circadian clock and autonomous pathway, respectively, and they play a positively activating role in regulating floral transition. Overall, physiological changes associated with genes involved in the circadian clock or autonomous pathway collectively regulated the rose floral transition.
Our results summarize a valuable collective of gene expression profiles characterizing the rose floral transition. The DEGs are candidates for functional analyses of genes affecting the floral transition in the rose, which is a precious resource that reveals the molecular mechanism of mediating floral transition in other perennial plants.
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Conservative flowering behaviours, such as flowering during long days in summer or late flowering at a high leaf number, are often proposed to protect against variable winter and spring temperatures ...which lead to frost damage if premature flowering occurs. Yet, due the many factors in natural environments relative to the number of individuals compared, assessing which climate characteristics drive these flowering traits has been difficult. We applied a multidisciplinary approach to 10 winter-annual Arabidopsis thaliana populations from a wide climactic gradient in Norway. We used a variable reduction strategy to assess which of 100 climate descriptors from their home sites correlated most to their flowering behaviours when tested for responsiveness to photoperiod after saturation of vernalization; then, assessed sequence variation of 19 known environmental-response flowering genes. Photoperiod responsiveness inversely correlated with interannual variation in timing of growing season onset. Time to flowering appeared driven by growing season length, curtailed by cold fall temperatures. The distribution of FLM, TFL2 and HOS1 haplotypes, genes involved in ambient temperature response, correlated with growing-season climate. We show that long-day responsiveness and late flowering may be driven not by risk of spring frosts, but by growing season temperature and length, perhaps to opportunistically maximize growth.
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Bamboo is a perennial flowering plant with a distinctive life cycle: many bamboo species remain in the vegetative phase for decades, followed by mass synchronous flowering and subsequent death. The ...phenomenon of bamboo flowering is not fully understood, but its periodicity is a major research focus. Here, we collected information on bamboo flowering events by investigating historical documents and field studies at the Bamboo Research Institute of Nanjing Forestry University. We compiled information on more than 630 flowering events, 124 of which accurately recorded the flowering cycle time. We summarized the specific flowering cycles of 85 bamboo species, as well as four kinds of bamboo flowering habits in detail. We present a theory of the bamboo flowering cycle and discuss the reasons for the observed variations in bamboo flowering. This review also introduces two mechanisms by which bamboo forests are rejuvenated after flowering and explains the flowering phenomena of bamboo forests using the bamboo flowering cycle theory. Finally, we present suggestions for forest management strategies. Bamboo flowering is a normal physiological phenomenon, even though it has unique elements compared with flowering in other plants. The results presented here provide valuable reference material for understanding bamboo flowering and its periodicity.
The number of co‐flowering species, floral density and floral trait diversity can be major determinants of pollinator‐mediated plant–plant interactions in a community. However, evaluation of how each ...one of these co‐flowering components affects the pollination success of a single focal plant species, and how these effects vary at different spatial scales, is lacking.
Here, we evaluated the effects of functional diversity (flower morphology and colour), taxonomic diversity (reflecting potential sampling effects) and flower density (conspecific and heterospecific), on the pollinator environment (i.e. visitation rate and pollinator diversity) and pollination success (i.e. pollen load size and number of pollen tubes per style) of Cakile edentula (Brassicaceae). We applied structural equation models (SEMs) at the floral‐neighbourhood (plot level) and community‐wide scales to uncover the factors that mediate co‐flowering community effects on C. edentula pollination success.
We found that co‐flowering community effects at the community level are more important than fine‐scale floral‐neighbourhood differences in mediating plant pollination success in our study species. Increasing plant functional diversity decreased pollinator visitation rate but increased the diversity of pollinator functional groups visiting C. edentula flowers. Taxonomic diversity negatively affected pollinator diversity suggesting that other unmeasured floral traits may be relevant or that single‐species effects (sampling effects) may be important. Overall, our results suggest that functional floral trait diversity in a community may be the most important factor influencing pollination success of species in a community. We also found evidence for intra‐ and interspecific pollinator competition mediated by flower density, but none of these effects seemed to have a significant impact on pollination success.
This study is an important step towards understanding the complexity of co‐flowering community effects on the pollination success of individual plant species at multiple spatial scales. This study further reveals the potential importance of plant functional diversity in a community in helping predict competitive and facilitative interactions in co‐flowering communities.
Synthesis. Floral density and taxonomic and functional co‐flowering diversity are important drivers of pollination success in flowering plants. The effects of the co‐flowering diversity on the pollination success of plant species can largely depend on the spatial scale being studied. Only evaluating the outcomes of pollinator‐mediated plant–plant interactions at multiple stages of the pollination process can lead to a complete understanding of their ecological consequences in nature.
Floral density and taxonomic and functional co‐flowering diversity are important drivers of pollination success in flowering plants. The effects of the co‐flowering diversity on the pollination success of plant species can largely depend on the spatial scale being studied. Only evaluating the outcomes of pollinator‐mediated plant–plant interactions at multiple stages of the pollination process can lead to a complete understanding of their ecological consequences in nature.
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Summary
Molecular genetic studies using Arabidopsis thaliana as a model system have overwhelmingly revealed many important molecular mechanisms underlying the control of various biological events, ...including floral induction in plants. The major genetic pathways of flowering have been characterized in‐depth, and include the photoperiod, vernalization, autonomous and gibberellin pathways. In recent years, novel flowering pathways are increasingly being identified. These include age, thermosensory, sugar, stress and hormonal signals to control floral transition. Among them, hormonal control of flowering except the gibberellin pathway is not formally considered a major flowering pathway per se, due to relatively weak and often pleiotropic genetic effects, complex phenotypic variations, including some controversial ones. However, a number of recent studies have suggested that various stress signals may be mediated by hormonal regulation of flowering. In view of molecular diversity in plant kingdoms, this review begins with an assessment of photoperiodic flowering, not in A. thaliana, but in rice (Oryza sativa); rice is a staple crop for human consumption worldwide, and is a model system of short‐day plants, cereals and breeding crops. The rice flowering pathway is then compared with that of A. thaliana. This review then aims to update our knowledge on hormonal control of flowering, and integrate it into the entire flowering gene network.
Significance Statement
In the view of molecular diversity in plant kingdoms, this paper first focuses on an assessment of photoperiodic flowering in rice (Oryza sativa), and its comparison with that of Arabidopsis thaliana. Furthermore, it aims to update our knowledge on hormonal control of flowering, and integrate it into the entire flowering gene network in plants.
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Species' floral traits and flowering times are known to be the major drivers of pollinator‐mediated plant–plant interactions in diverse co‐flowering communities. However, their simultaneous role in ...mediating plant community assembly and plant–pollinator interactions is still poorly understood. Since not all species flower at the same time, inference of facilitative and competitive interactions based on floral trait distribution patterns should account for fine phenological structure (intensity of flowering overlap) within co‐flowering communities. Such an approach may also help reveal the simultaneous action of competitive and facilitative interactions in structuring co‐flowering communities.
Here we used modularity within a co‐flowering network context, as a novel approach to detect convergent and/or over‐dispersed patterns in floral trait distribution and pollinator sharing. Specifically, we evaluate differences in floral trait and pollinator distribution patterns within (high temporal flowering overlap) and among co‐flowering modules (low temporal flowering overlap). We further evaluate the consistency of observed floral trait and pollinator sharing distribution patterns across space (three geographical regions) and time (dry and rainy seasons).
We found that floral trait similarity was significantly higher in plant species within co‐flowering modules than in species among them. This suggests pollinator facilitation may lead to floral trait convergence, but only within co‐flowering modules. However, our results also revealed seasonal and spatial shifts in the underlying interactions (facilitation or competition) driving co‐flowering assembly, suggesting that the prevalent dominant interactions are not static.
Synthesis. Overall, we provide strong evidence showing that the use of flowering time and floral trait distribution alone may be insufficient to fully uncover the role of pollinator‐mediated interactions in community assembly. Integrating this information along with patterns of pollinator sharing will greatly help reveal the simultaneous action of facilitative and competitive pollinator‐mediated interactions in co‐flowering communities. The spatial and temporal variation in flowering and trait distribution patterns observed further emphasize the importance of adopting a more dynamic view of community assembly processes.
Resumen
Los rasgos florales y el tiempo de floración de las especies, se consideran como de las principales fuerzas que guían las interacciones planta‐planta mediadas por polinizadores. Sin embargo, su papel simultáneo en la mediación del ensamblaje de las comunidades y de las interacciones planta‐polinizadores son poco comprendidas. Debido a que no todas las especies florecen al mismo tiempo, la inferencia sobre interacciones de facilitación o competencia basadas en los patrones de distribución de los caracteres florales, deben considerar la estructura fenológica detallada (intensidad y sobrelapamiento floral) que existe dentro de las comunidades co‐florales. Esta aproximación podría ayudar a revelar la acción simultánea de interacciones de competencia y facilitación en la estructuración de las comunidades.
En este trabajo usamos la modularidad dentro del contexto de redes de co‐floración como una aproximación novedosa para detectar patrones convergentes o de sobre‐dispersión en la distribución de rasgos florales y la compartición de polinizadores. Específicamente evaluamos diferencias en los patrones de distribución de rasgos florales y de polinizadores dentro (alto sobrelapamiento floral) y entre módulos co‐florales (bajo sobrelapamiento floral). Más aún, evaluamos la consistencia espacial (tres regiones geográficas) y temporal (temporada seca y de lluvias) de la distribución observada de los rasgos florales y la compartición de polinizadores.
Encontramos que la similitud de rasgos florales fue significativamente más alta en especies de plantas dentro de módulos co‐florales que entre especies de diferentes módulos. Este resultado sugiere que la facilitación por polinizadores puede llevar a una convergencia de rasgos florales dentro de los módulos co‐florales. Sin embargo, nuestros resultados también revelaron cambios espaciales y temporales en las interacciones subyacentes (facilitación o competencia) que guían el ensamblaje de co‐floración, sugiriendo que las interacciones prevalentes no son estáticas.
Síntesis. Globalmente, en este trabajo proveemos fuertes evidencias de que el uso del tiempo de floración y la distribución de rasgos florales de manera independiente, pueden no ser suficientes para revelar completamente el papel de las interacciones mediadas por polinizadores en el ensamblaje de las comunidades. La integración de esta información con los patrones de compartición de polinizadores ayuda a revelar la acción simultánea de interacciones de facilitación y competencia mediadas por polinizadores en comunidades co‐florales. La variación espacial y temporal en los patrones de distribución de la floración y de los rasgos florales observados, enfatizan la importancia de adoptar una visión más dinámica de los procesos de ensamblaje de las comunidades.
Integrating flowering time and floral trait distribution along with patterns of pollinator sharing will greatly help reveal the simultaneous action of facilitative and competitive pollinator‐mediated interactions in co‐flowering communities. The spatial and temporal variation in flowering and trait distribution patterns observed further emphasize the importance of adopting a more dynamic view of community assembly processes.
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