Long-day Photoperiod Research Articles

Longday Photoperiod Accelerates Flowering in Indonesian Non-Flowering Shallot Variety

The shallot flowering ability is essential to increase productivity by assembling superior varieties through the hybridization and botanical seed or true shallot seed (TSS). The photoperiod length greatly influences flowering in shallot, which plays a significant role in the flowering initiation. This research aims to study flowering responses with different photoperiods in shallots. Six shallot varieties: Lokananta, Bima Brebes, Rubaru, Palasa, Biru Lancor, and Batu Ijo, were grown in a greenhouse under a short-day photoperiod, 10 hours of natural condition photoperiod for 60 days. Furthermore, half of the plants are moved to long-day treatment. The temperature during plantation is around from 7-13°C (similar to Indonesia’s upland temperature). The results indicate that long-day photoperiod increased the shallot flowering response on the five shallot varieties tested, except Rubaru. Rubaru could not produce flowers under both photoperiod treatments 120 days after plantation (DAP). Lokananta variety is the most responsive variety to flower, even on short-day photoperiod. Palasa variety, which could not flower under Indonesian photoperiod conditions, could produce flowers on long-day treatment and underplanting conditions at low to moderate temperatures.

静岡県の露地栽培キクおよびその周辺雑草におけるクロゲハナアザミウマの翅型

In 2015–2016, we investigated the wing forms of adult females of Thrips nigropilosus collected from chrysanthemums and nearby weeds in open fields in Shizuoka Prefecture, Central Japan. At all collection sites, the proportion of brachypterous female adults increased in October and February. Therefore, the populations collected in this study were noted to be brachypterous under a short-day photoperiod. Additionally, the proportion of individuals entering reproductive diapause was higher than that under long-day photoperiods.

Comparative transcriptome analysis provides insight into the molecular mechanisms of long-day photoperiod in Moringa oleifera.

The online version contains supplementary material available at 10.1007/s12298-022-01186-4.

Photoperiod controls wing polyphenism in a water strider independently of insulin receptor signalling.

Insect wing polyphenism has evolved as an adaptation to changing environments and a growing body of research suggests that the nutrient-sensing insulin receptor signalling pathway is a hot spot for the evolution of polyphenisms, as it provides a direct link between growth and available nutrients in the environment. However, little is known about the potential role of insulin receptor signalling in polyphenisms which are controlled by seasonal variation in photoperiod. Here, we demonstrate that wing length polyphenism in the water strider Gerris buenoi is determined by photoperiod and nymphal density, but is not directly affected by nutrient availability. Exposure to a long-day photoperiod is highly inducive of the short-winged morph whereas high nymphal densities moderately promote the development of long wings. Using RNA interference we demonstrate that, unlike in several other species where wing polyphenism is controlled by nutrition, there is no detectable role of insulin receptor signalling in wing morph induction. Our results indicate that the multitude of possible cues that trigger wing polyphenism can be mediated through different genetic pathways and that there are multiple genetic origins to wing polyphenism in insects.

Prevention of high temperature induced rosette and flowering acceleration of Dwarf Eustoma ‘Little Belle Blue’ by optimum temperature treatment

The objective of this research is to produce dwarf Eustoma grandiflorum (Raf.) Shinn. ‘Little Belle Blue’ potted plants to flower in 130 days after sowing without exhibiting high temperature induced (HTI) rosette. High temperature induced rosette is defined as “the abnormal growth and development of plants exhibiting a compressed stem near the ground after forming 3 – 4 pairs of true leaves resulting from exposure of seedlings to high temperatures, and fail to form elongated internodes and to flower”. The effect of temperature and photoperiod treatments during various growth and development stages was tested on the accelerated flowering without exhibiting the HTI rosette (Expt. 1, 2, 3), and to induce flowering in 130 days preventing the HTI rosette (Expt. 4, 5, 6). The treatments at 32/27 °C (day/night) during 0 – 30 days after sowing (0 – 30D) (32/27 °C/0 – 30D and 27/22 °C/31 – 60D should be avoided because 39% of plants exhibited HTI rosette (Expt. 1). Lower temperatures and shorter periods (24/22 °C/61 – 90D, 24/22 °C/31 – 60D) prevented rosette growth (Expt. 2). The treatment 23/21 °C/34 – 74D is considered acceptable when coupled with 21/19 °C/74 – 115D to promote flowering and to prevent the HTI rosette (Expt. 3). The earliest flowering (157 days) plants without the HTI rosette suggested that temperatures during various 20-day stages are 25/23 °C/0 – 20D, 21/19 °C/21 – 40D, 12/10 °C/61 – 80D, and 25/23 °C/81 – 100D. Early flowering occurred at 12/10 °C/61 – 80D and 25/23 °C/81 – 100D. During these periods, it was considered that flower bud initiation and development might occur, and this effect was especially pronounced in the treatment 25/23 °C/61 – 80D (Expt. 4). Flowering was the earliest (148 days) when 45-day old seedlings after sowing seeds in January were exposed for 30 days (46 – 75D) to a long-day (LD) photoperiod at 21/18 °C (Expt. 5). The total cropping time was reduced to 133 days without inducing HTI rosette and reducing the number of flowers by the following treatments: Sowing seeds as late as February and growing at 23/21 and 25/23 °C/30 – 50D, either under a short-day (SD) or LD/51 – 70D, and growing at 21/19 and 23/21 °C under LD/71 – 90D (Expt. 6). A clear distinction should be made between seedlings exhibiting physiologically normal growth during the vegetative juvenile stages that last about 60 days forming up to 3 to 4 pairs of small leaves and HTI rosette that occurs predominantly when seedlings are exposed to 29/27 °C/34 – 74D. Eustoma grandiflorum is an annual that does not exhibit seed dormancy since germination occurs in 12 – 14 days at 23/21 °C, and ‘Little Belle Blue’ does not require vernalization to induce flowering in 130 days after sowing seeds without exhibiting HTI rosette. Seeds are sown at 21/16 °C/0 – 30D in February and growing at 25/23 °C/31 – 50D, 21/19 °C/51 – 70D/LD, 23/21 °C/71 – 90D/LD, and finally at 23/21 °C/91 – 130D is recommended.

Transcriptomic Analysis of the Interaction Between FLOWERING LOCUS T Induction and Photoperiodic Signaling in Response to Spaceflight.

Spaceflight has an impact on the growth and development of higher plants at both the vegetative stage and reproductive stage. A great deal of information has been available on the vegetative stage in space, but relatively little is known about the influence of spaceflight on plants at the reproductive stage. In this study, we constructed transgenic Arabidopsis thaliana plants expressing the flowering control gene, FLOWERING LOCUS T (FT), together with the green fluorescent protein gene (GFP) under control of a heat shock-inducible promoter (HSP17.4), by which we induced FT expression inflight through remote controlling heat shock (HS) treatment. Inflight photography data showed that induction of FT expression in transgenic plants in space under non-inductive short-day conditions could promote flowering and reduce the length of the inflorescence stem in comparison with that of wild-type plants under the same conditions. Whole-genome microarray analysis of gene expression changes in leaves of wild-type and these transgenic plants grown under the long-day and short-day photoperiod conditions in space indicated that the function of the photoperiod-related spaceflight responsive genes is mainly involved in protein synthesis and post-translation protein modulation, notably protein phosphorylation. In addition, changes of the circadian component of gene expression in response to spaceflight under different photoperiods indicated that roles of the circadian oscillator could act as integrators of spaceflight response and photoperiodic signals in Arabidopsis plants grown in space.

Use of Pyriproxyfen to Induce Oogenesis in Diapausing Megacopta cribraria (Heteroptera: Plataspidae), and Evaluation of Pyriproxyfen-Induced Eggs for Rearing the Parasitoid Paratelenomus saccharalis (Hymenoptera: Scelionidae).

Simple SummaryRearing of many hymenopteran egg parasitoids requires a reliable supply of host eggs. The parasitoid Paratelenomus saccharalis can be reared on eggs produced from field collected kudzu bug, Megacopta cribraria, however field-collected hosts obtained during reproductive diapause do not readily produce eggs and must be reared under a long day-length photoperiod to terminate diapause. In this study we found that an exogenous application of pyriproxyfen was able to terminate diapause, leading to a significant increase in egg production. The eggs produced by pyriproxyfen-treated M. cribraria were accepted by the egg parasitoid Paratelenomus saccharalis, however parasitoid emergence was reduced when compared to eggs from untreated hosts. When the effects of pyriproxyfen treatment on egg production and parasitoid emergence were evaluated together, the net increase in parasitoid yield due to pyriproxyfen treatment was approximately 87%. This method has the potential to increase parasitoid yield and reduce production costs in egg parasitoid rearing programs.The mass rearing of hymenopteran egg parasitoids requires an abundant supply of host eggs. The onset of reproductive diapause and subsequent decline in egg production poses a challenge for parasitoid rearing when using host colonies augmented by field-collected insects. We investigated the application of pyriproxyfen, a juvenile hormone analog, to induce oviposition in diapausing adult kudzu bugs, Megacopta cribraria (Fabricius) (Heteroptera: Plataspidae), and the use of eggs produced by pyriproxyfen-treated kudzu bugs to rear the egg parasitoid, Paratelenomus saccharalis (Dodd) (Hymenoptera: Scelionidae). The effects of pyriproxyfen and photoperiod treatments on host mortality, egg production, and rates of parasitoid eclosion from the eggs were used to calculate the parasitoid yield for the different treatment regimes. A combination of pyriproxyfen and a long-day photoperiod increased the parasitoid yield by 87% compared to acetone and a long-day photoperiod. The general applicability of JH-analog mediated egg production for parasitoid rearing is discussed.

FLOWERING LOCUS T indel variants confer vernalization-independent and photoperiod-insensitive flowering of yellow lupin (Lupinus luteus L.).

Ongoing climate change has considerably reduced the seasonal window for crop vernalization, concurrently expanding cultivation area into northern latitudes with long-day photoperiod. To address these changes, cool season legume breeders need to understand molecular control of vernalization and photoperiod. A key floral transition gene integrating signals from these pathways is the Flowering locus T (FT). Here, a recently domesticated grain legume, yellow lupin (Lupinus luteus L.), was explored for potential involvement of FT homologues in abolition of vernalization and photoperiod requirements. Two FTa (LlutFTa1a and LlutFTa1b) and FTc (LlutFTc1 and LlutFTc2) homologues were identified and sequenced for two contrasting parents of a reference recombinant inbred line (RIL) population, an early-flowering cultivar Wodjil and a late-flowering wild-type P28213. Large deletions were detected in the 5' promoter regions of three FT homologues. Quantitative trait loci were identified for flowering time and vernalization response in the RIL population and in a diverse panel of wild and domesticated accessions. A 2227bp deletion found in the LlutFTc1 promoter was linked with early phenology and vernalization independence, whereas LlutFTa1a and LlutFTc2 indels with photoperiod responsiveness. Comparative mapping highlighted convergence of FTc1 indel evolution in two Old World lupin species, addressing both artificial selection during domestication and natural adaptation to short season environmental conditions. We concluded that rapid flowering in yellow lupin is associated with the de-repression of the LlutFTc1 homologue from the juvenile phase, putatively due to the elimination of all binding sites in the promoter region for the AGAMOUS-like 15 transcription factor.

Optimization of light and temperature in indoor farming to boost anthocyanin biosynthesis and accumulation in Indigo Rose tomato

Anthocyanins are a group of flavonoids that are found ubiquitously in fruits and vegetables. They act as antioxidants in plants and are considered to have potential benefits to human health. The tomato cultivar ‘Indigo Rose’ produces purple-skinned fruits that are rich in anthocyanins in fruit peel. The current study focussed on the detection of anthocyanins and examined the expression profiling of anthocyanin biosynthetic and regulatory genes in Indigo Rose fruits grown under semi-closed greenhouse and fully controlled growth chamber conditions. The anthocyanin content in Indigo Rose fruits grown under growth chamber conditions with a long-day photoperiod and ambient temperature was higher than those grown in the greenhouse with a short-day photoperiod and high temperature. Under indoor growth conditions, moderate to high intensity of artificial light (160−240 µmol m⁻² s⁻¹) and relatively low temperature (20−25 °C) promoted anthocyanin production and accumulation in Indigo Rose fruits. The comparative studies on gene expression under different growth conditions also demonstrate that the expression levels of the structural and regulatory genes in the anthocyanin biosynthetic pathway have a positive correlation with the anthocyanin content in the fruit peel. The growth conditions identified in this study could be used to grow Indigo Rose in indoor farming in Singapore, where the tropical climate makes it challenging to set up a tomato plantation in an open field or greenhouse.

Prospecting the unpredicted potential traits of Cladophialophora chaetospira SK51 to alter photoperiodic flowering in strawberry, a perennial SD plant

Due to the economic importance of strawberry, many countries have established national breeding programs aimed at improving the flowering time and fruiting season to achieve year-round fruit availability. The ability of crops to produce fruits throughout the year with “flowering on command” is still a challenge in strawberry production systems. Although growth promotion by dark septate endophytic (DSE) fungi has been reported, the symbiotic association that alters flowering behaviors in photoperiodic fruit crops has not been studied. Here we established an experimental scheme for inducing the short-day (SD) strawberry cultivar Fragaria vesca to initiate flowering under a long-day (LD) photoperiod in symbiotic association with DSE fungus. We evaluated the relationship between growth-promoting and flower-inducing activities using Pearson's correlation analysis. Symbiotic association with C. chaetospira SK51 markedly stimulated SD strawberry cultivar to initiate early flowering, with the greatest flower induction (94.8%) and highest number of fruits (10.6 fruits/plant) during cultivation under a 16-h LD photoperiod at 23 °C, defined as non-flower-inductive conditions, considered as a new finding. We found that the interactions between C. chaetospira SK51 and strawberry plants markedly contributed to accelerating the earliness of the flowering time, as flower buds were initiated 90 days earlier than in the untreated control. Interestingly, we show that plant response in flowering by co-cultivation of C. chaetospira SK51 is constantly induce under various soil types and pHs. Based on Pearson's correlation coefficient analysis, we suggest that flowering behavior has a weakly non-significant relationship with growth-promoting activities, indicating that the control of flowering has a different or indirect pathway. Strawberry plants in symbiosis with C. chaetospira SK51 might be well-adapted to all regions and help preserve crops resilience against adverse climate conditions. These findings provide an essential resource and new insight for photoperiodic flowering research and innovation that can be adopted to deliver sustainable solutions that eventually will lead to extending and increasing crop production.

Molecular cloning of cryptochrome 1 from Lilium×formolongi and the characterization of its photoperiodic flowering function in Arabidopsis

Lilium × formolongi is an important cut flower species that is able to flower within a year following seed propagation, with flower induction that is very sensitive to the photoperiod. Cryptochromes are blue/UV-A light receptors that regulate many important plant growth and development processes, including photoperiodic flowering. In this study, we isolated the cryptochrome 1 (CRY1) gene from L. × formolongi and analyzed its function in transgenic Arabidopsis. The predicted LfCRY1 protein was strongly homologous to other CRY1 proteins. The transcription of LfCRY1 was induced by blue light, with LfCRY1 exhibiting its highest expression and diurnal expression patterns during the flowering-induction stage under both long-day (LD) and short-day (SD) photoperiods. Overexpression of LfCRY1 in Arabidopsis promoted flowering under LDs but not SDs and inhibited hypocotyl elongation under blue light. The LfCRY1 protein was located in both the nucleus and cytoplasm. LfCRY1 interacted with the important flowering activator LfCOL9 in both yeast and onion cells. These results provide functional evidence for the role of LfCRY1 in controlling photoperiodic flowering under LDs and indicate that LfCRY1 may be a counterpart of AtCRY1. Understanding the role of LfCRY1 in photoperiodic flowering is beneficial for the molecular breeding of lilies with shorter vegetative stages.

Adrenal MT1 melatonin receptor expression is linked with seasonal variation in social behavior in male Siberian hamsters

Many animals exhibit pronounced changes in physiology and behavior on a seasonal basis, and these adaptations have evolved to promote survival and reproductive success. While the neuroendocrine pathways mediating seasonal reproduction are well-studied, far less is known about the mechanisms underlying seasonal changes in social behavior, particularly outside of the context of the breeding season. Our previous work suggests that seasonal changes in melatonin secretion are important in regulating aggression in Siberian hamsters (Phodopus sungorus); it is unclear, however, how melatonin acts via its receptors to modulate seasonal variation in social behavior. In this study, we infused a MT1 melatonin receptor-expressing (MT1) or control (CON) lentivirus into the adrenal glands of male Siberian hamsters. We then housed hamsters in long-day (LD) or short-day (SD) photoperiods, administered timed melatonin or control injections, and quantified aggressive and non-aggressive social behaviors (e.g., investigation, self-grooming) following 10 weeks of treatment. LD hamsters infused with the MT1 lentivirus had significantly higher adrenal mt1 expression than LD CON hamsters, as determined via quantitative PCR. While melatonin administration was necessary to induce SD-like reductions in body and relative reproductive mass, only LD hamsters infused with the MT1 lentivirus displayed SD-like changes in social behavior, including increased aggression and decreased investigation and grooming. In addition, SD CON and LD hamsters infused with the MT1 lentivirus exhibited similar relationships between adrenal mt1 expression and aggressive behavior. Together, our findings suggest a role for adrenal MT1 receptor signaling in regulating behavior, but not energetics or reproduction in seasonally breeding species.

Cryptochrome 2 from Lilium × formolongi Regulates Photoperiodic Flowering in Transgenic Arabidopsis thaliana

The photoperiodic flowering pathway is essential for plant reproduction. As blue and ultraviolet-A light receptors, cryptochromes play an important role in the photoperiodic regulation of flowering. Lilium × formolongi is an important cut flower that flowers within a year after seed propagation. Floral induction is highly sensitive to photoperiod. In this study, we isolated the CRYPTOCHROME2 gene (LfCRY2) from L. × formolongi. The predicted LfCRY2 protein was highly homologous to other CRY2 proteins. The transcription of LfCRY2 was induced by blue light. LfCRY2 exhibits its highest diurnal expression during the floral induction stage under both long-day and short-day photoperiods. Overexpression of LfCRY2 in Arabidopsis thaliana promoted flowering under long days but not short days, and inhibited hypocotyl elongation under blue light. Furthermore, LfCRY2 was located in the nucleus and could interact with L. × formolongi CONSTANS-like 9 (LfCOL9) and A. thaliana CRY-interacting basic-helix-loop-helix 1 (AtCIB1) in both yeast and onion cells, which supports the hypothesis that LfCRY2 hastens the floral transition via the CIB1-CO pathway in a manner similar to AtCRY2. These results provide evidence that LfCRY2 plays a vital role in promoting flowering under long days in L. × formolongi.

Cantil - a new organ or a morphological oddity?

Cantil is reported as a new-found organ specific to the model plant Arabidopsis thaliana that is prominent only in short-day-grown wild-type accessions or long-day-grown genetic mutants with delayed vegetative to reproductive transition. Here, we show that cantils (previously known as nubbins) arise as one of the many phenotypic consequences of aneuploidy resulting from chromosome dosage imbalances in Arabidopsis polyaneuploids despite normal reproductive transition in long-day photoperiods. Without a demonstrated function or adaptive significance, we view cantils as a morphological oddity rather than a separate organ, and as a manifestation of physiological perturbations triggered by genetic and environmental factors. We also note a striking phenotypic resemblance between 'cantil' and 'gynophore', a floral morphological structure that is naturally present in the allopolyploid Arabidopsis suecica.

Growth Characteristics of Triticale under Long-Day Photoperiod for Rapid Generation Advancement

Jin-Kyung Cha, Myoung-Ryoul Park, Dongjin Shin, Youngho Kwon, So-Myeong Lee, Jong-Min Ko, Kyeong-Min Kim, and Jong-Hee Lee. Korean J. Breed. Sci. 2021;53:200-5. https://doi.org/10.9787/KJBS.2021.53.3.200

Identification of the blue light intensity administered to one eye required to suppress bovine plasma melatonin and investigation into effects on milk production in grazing dairy cows

Long-day photoperiod is known to positively affect milk production in confinement dairy systems, and it has been hypothesized that pineal melatonin (MT) secretion plays a substantial role in this process. Specialized mammalian photoreceptors that regulate MT secretion are optimally stimulated by short wavelength blue light. We investigated the blue light intensity administered to one eye required to suppress MT secretion in nonlactating dairy cows, and subsequently examined effects on milk production in grazing dairy cows. Following a 14-d light-dark 8:16 h environmental conditioning period, 5 nonlactating Holstein-Friesian cows were exposed to treatments of <1, 70, 125, 175, and 225 lx for 8 additional hours using a 5 × 5 Latin square design. Light was administered via headpieces fitted with light-emitting diodes emitting blue light (465 nm) to the right eye. All cows were then exposed to a light-dark 16:8 h cycle for one night via the indoor lighting system (>200 lx white light). Plasma samples collected at regular intervals were assayed for MT. A dose-dependent effect of light treatment on mean circulating MT concentrations (and 95% CI) was observed [9.4 (7.2, 12.3), 5.0 (3.8, 6.6), 4.4 (3.3, 5.7), 3.3 (2.5, 4.3) and 1.7 (1.3, 2.3) pg/mL for treatments of 0, 70, 125, 175, and 225 lx, respectively. Only the 225 lx treatment acutely suppressed plasma melatonin concentration to levels similar to the light-dark 16:8 h treatment [1.9 (1.4, 2.5) pg/mL]. Forty spring-calving cows were blocked on parity, calving date and Economic Breeding Index for milk production and assigned to the control treatment or blue light to a single eye (LT) treatment from calving through 32 wk of lactation. The cows assigned to LT treatment were fitted with headpieces providing 225 lx of blue light to the right eye from 1700 until 0000 h. Mean milk production (and 95% CI) during 32 wk of lactation was not affected by treatment [20.3 (19.3, 21.3) vs. 20.9 (19.8, 22.0) kg/d, control and LT, respectively]. Within multiparous cows, a treatment by week interaction was detected, whereby LT treatment increased milk production during the first 12 wk of lactation [25.8 (24.3, 27.3) vs. 28.0 (26.5, 29.5) kg/d; +8.5%], but had no effect thereafter. Treatment did not affect plasma insulin-like growth factor 1. We identified the blue light intensity to one eye required to acutely suppress MT concentrations. Transient favorable effects on milk production were observed in multiparous cows. It remains unclear how single-eye blue light treatment affects galactopoiesis in grazing dairy cows, and further research is needed to explore whether this modality of light delivery represents a useful means to aid productivity in pasture-based dairy systems.

Food restriction during development delays puberty but does not affect adult seasonal reproductive responses to food availability in Siberian hamsters (Phodopus sungorus).

Seasonally breeding animals respond to environmental cues to determine optimal conditions for reproduction. Siberian hamsters (Phodopus sungorus) primarily rely on photoperiod as a predictive cue of future energy availability. When raised in long-day photoperiods (>14 h light), supplemental cues such as food availability typically do not trigger the seasonal reproductive response of gonadal regression, which curtails reproduction in unsuitable environments. We investigated whether recognition of food availability as a cue could be altered by a nutritional challenge during development. Specifically, we predicted that hamsters receiving restricted food during development would be sensitized to food restriction (FR) as adults and undergo gonadal regression in response. Male and female hamsters were given either ad libitum (AL) food or FR from weaning until d60. The FR treatment predictably limited growth and delayed puberty in both sexes. For 5 weeks after d60, all hamsters received an AL diet to allow FR hamsters to gain mass equal to AL hamsters. Then, adult hamsters of both juvenile groups received either AL or FR for 6 weeks. Juvenile FR had lasting impacts on adult male body mass and food intake. Adult FR females exhibited decreased estrous cycling and uterine horn mass indiscriminately of juvenile food treatment, but there was little effect on male reproductive measurements. Overall, we observed a delay in puberty in response to postweaning FR, but this delay appeared not to affect seasonal reproductive responses in the long term. These findings increase our understanding of seasonal reproductive responses in a relevant environmental context.

Thermography as a tool to monitor the velvet temperature and ossification stage of fallow deer (Dama dama) antlers under normal and modified photoperiodic conditions

An increase in testosterone levels affects the shedding of velvet which, in turn, influences the behaviour of farm-raised fallow deer bucks. Consequently, the welfare of the farmed animals can be considerably improved by controlling the timing of the velvet shedding period. The aim of this study was to analyse changes in the velvet temperature and the timing of the velvet shedding in farm-raised fallow deer bucks exposed to a modified photoperiod. A total of 28 bucks were examined. The experimental group was subjected to an experimentally modified photoperiod before the direct observations and measurements of the antler temperatures with a thermal imaging camera. The acquired thermograms were useful for analysing the stages and the rate of the antler growth and for predicting the timing of the velvet shedding. The introduction of a long-day photoperiod in spring affected the growth and ossification of the antlers as well as the velvet shedding. The optimal time for antler cutting can be planned based on the identified changes in the velvet temperature in different parts of the antler.

Beyond the Genetic Pathways, Flowering Regulation Complexity in Arabidopsis thaliana

Flowering is one of the most critical developmental transitions in plants’ life. The irreversible change from the vegetative to the reproductive stage is strictly controlled to ensure the progeny’s success. In Arabidopsis thaliana, seven flowering genetic pathways have been described under specific growth conditions. However, the evidence condensed here suggest that these pathways are tightly interconnected in a complex multilevel regulatory network. In this review, we pursue an integrative approach emphasizing the molecular interactions among the flowering regulatory network components. We also consider that the same regulatory network prevents or induces flowering phase change in response to internal cues modulated by environmental signals. In this sense, we describe how during the vegetative phase of development it is essential to prevent the expression of flowering promoting genes until they are required. Then, we mention flowering regulation under suboptimal growing temperatures, such as those in autumn and winter. We next expose the requirement of endogenous signals in flowering, and finally, the acceleration of this transition by long-day photoperiod and temperature rise signals allowing A. thaliana to bloom in spring and summer seasons. With this approach, we aim to provide an initial systemic view to help the reader integrate this complex developmental process.

Stevia rebaudiana (Bert.) Bertoni cultivated under different photoperiod conditions: Improving physiological and biochemical traits for industrial applications

Stevia rebaudiana is an important industrial crop due to the accumulation of high amounts of steviol glycosides (SG - natural sweeteners) in its leaves. S. rebaudiana cultivation has faced some pushbacks since this species is highly responsive to environmental factors, such as light availability. Sixty days after sowing, plants were transferred to different photoperiod conditions (12/12 h, 15/9 h, and 16/8 h of light/dark). Leaf extracts of plants growing at the 16/8 h photoperiod showed greater accumulation of antioxidant-like metabolites as compared to the other two photoperiods, which might be explained by the total phenolic content of the extracts. Additionally, plants growing at the 16/8 h photoperiod showed increased SOD activity as compared to plants growing at the 15/9 h photoperiod, which in turn showed higher SOD activity than plants growing at the 12/12 h photoperiod. It seems that SOD isoforms act synergically with phenolic compounds to prevent possible damages caused by reactive oxygen species that are produced in plants growing at long-day photoperiods. Sixteen metabolites were identified by Nuclear Magnetic Resonance in the leaf and stem extracts. Alanine, formate, choline, kaempferol-3-O-β-d-glucopyranoside-7-O-α-l-rhamnopyranoside, and gallic acid seems to contribute to maintain stevia homeostasis under unfavorable conditions. Furthermore, the accumulation of SGs and other bioactive compounds in S. rebaudiana in response to different photoperiods provides important leads for the improvement of its large-scale cultivation, as well as for the extraction and purification of phytochemicals with industrial interest.