Against "silent" retractions in neuroscience.

When an academic paper is published in a journal that assigns a digital object identifier (DOI) to papers, this is a de facto fait accompli. Corrections or retractions are supposed to follow a specific protocol, especially in journals that claim to follow the Committee on Publication Ethics (COPE) guidelines. In this paper, we highlight a case of a new, fully open access neuroscience journal that claims to be COPE-compliant, yet has silently retracted two papers since all records, bibliometrics, and PDF files related to their existence have been deleted from the journal's website. Although this phenomenon does not seem to be common in the neurosciences, we consider that any opaque corrective measures in journals whose papers could be cited may negatively impact the wider neuroscience literature and community. Instead, we encourage transparency in retraction to promote truthfulness and trustworthiness.

Identification of the CONSTANS-like family in Cymbidium sinense, and their functional characterization.

BACKGROUND: Cymbidium sinense is an orchid that is typically used as a potted plant, given its high-grade ornamental characteristics, and is most frequently distributed in China and SE Asia. The inability to strictly regulate flowering in this economically important potted and cut-flower orchid is a bottleneck that limits its industrial development. Studies on C. sinense flowering time genes would help to elucidate the mechanism regulating flowering. There are very few studies on the genetic regulation of flowering pathways in C. sinense. Photoperiod significantly affects the flowering of C. sinense, but it was unknown how the CONSTANS gene family is involved in regulating flowering. RESULTS: In this study, eight CONSTANS-like genes were identified and cloned. They were divided into three groups based on a phylogenetic analysis. Five representative CsCOL genes (CsCOL3/4/6/8/9) were selected from the three groups to perform expression characterization and functional study. CsCOL3/4/6/8/9 are nucleus-localized proteins, and all five CsCOL genes were expressed in all organs, mainly in leaves followed by sepals. The expression levels of CsCOL3/4 (group I) were higher in all organs than other CsCOL genes. Developmental stage specific expression revealed that the expression of CsCOL3/4/9 peaked at the initial flowering stage. In contrast, the transcript level of CsCOL6/8 was highest at the pedicel development stage. Photoperiodic experiments demonstrated that the transcripts of the five CsCOL genes exhibited distinct diurnal rhythms. Under LD conditions, the overexpression of CsCOL3/4 promoted early flowering, and CsCOL6 had little effect on flowering time, whereas CsCOL8 delayed flowering of Arabidopsis thaliana. However, under SD conditions, overexpression of CsCOL4/6/8 promoted early flowering and the rosette leaves growth, and CsCOL3 induced flower bud formation in transgenic Arabidopsis. CONCLUSION: The phylogenetic analysis, temporal and spatial expression patterns, photoperiodic rhythms and functional study indicate that CsCOL family members in C. sinense were involved in growth, development and flowering regulation through different photoperiodic pathway. The results will be useful for future research on mechanisms pertaining to photoperiod-dependent flowering, and will also facilitate genetic engineering-based research that uses Cymbidium flowering time genes.

The plastome reveals new insights into the evolutionary and domestication history of peonies in East Asia.

BACKGROUD: Paeonia holds considerable value in medicinal, ornamental horticultural, and edible oil industries, but the incomplete state of phylogenetic research in this genus poses a challenge to the effective conservation and development of wild germplasm, and also impedes the practical utilization of existing cultivars. Due to its uniparental inheritance and lack of recombination, the plastome (i.e., plastid genome), which is a valuable molecular marker for phylogenetic analyses, is characterized by an appropriate rate of nucleotide evolution. METHODS: In this study, 10 newly assembled data and available reported data were combined to perform a comparative genomics and phylogenetics analysis of 63 plastomes of 16 Paeonia species, primarily from East Asia, which is the origin and diversity center of Paeonia. RESULTS: Ranging between 152,153 and 154,405 bp, most plastomes displayed a conserved structure and relatively low nucleotide diversity, except for six plastomes, which showed obvious IR construction or expansion. A total of 111 genes were annotated in the Paeonia plastomes. Four genes (rpl22, rps3, rps19 and ycf1) showed different copy numbers among accessions while five genes (rpl36, petN, psbI, rpl33 and psbJ) showed strong codon usage biases (ENC < 35). Additional selection analysis revealed that no genes were under positive selection during the domestication of tree peony cultivars whereas four core photosynthesis-related genes (petA, psaA, psaB and rbcL) were under positive selection in herbaceous peony cultivars. This discovery might contribute to the wide adaption of these cultivars. Two types of molecular markers (SSR and SNP) were generated from the 63 plastomes. Even though SSR was more diverse than SNP, it had a weaker ability to delimit Paeonia species than SNP. The reconstruction of a phylogenetic backbone of Paeonia in East Asia revealed significant genetic divergence within the P. ostii groups. Evidence also indicated that the majority of P. suffruticosa cultivars had a maternal origin, from P. ostii. The results of this research also suggest that P. delavayi var. lutea, which likely resulted from hybridization with P. ludlowii, should be classified as a lineage within the broader P. delavayi group. CONCLUSIONS: Overall, this study's research findings suggest that the Paeonia plastome is highly informative for phylogenetic and comparative genomic analyses, and could be useful in future research related to taxonomy, evolution, and domestication.

Uncovering the involvement of DoDELLA1-interacting proteins in development by characterizing the DoDELLA gene family in Dendrobium officinale.

BACKGROUND: Gibberellins (GAs) are widely involved in plant growth and development. DELLA proteins are key regulators of plant development and a negative regulatory factor of GA. Dendrobium officinale is a valuable traditional Chinese medicine, but little is known about D. officinale DELLA proteins. Assessing the function of D. officinale DELLA proteins would provide an understanding of their roles in this orchid's development. RESULTS: In this study, the D. officinale DELLA gene family was identified. The function of DoDELLA1 was analyzed in detail. qRT-PCR analysis showed that the expression levels of all DoDELLA genes were significantly up-regulated in multiple shoots and GA3-treated leaves. DoDELLA1 and DoDELLA3 were significantly up-regulated in response to salt stress but were significantly down-regulated under drought stress. DoDELLA1 was localized in the nucleus. A strong interaction was observed between DoDELLA1 and DoMYB39 or DoMYB308, but a weak interaction with DoWAT1. CONCLUSIONS: In D. officinale, a developmental regulatory network involves a close link between DELLA and other key proteins in this orchid's life cycle. DELLA plays a crucial role in D. officinale development.

Characterization of sandalwood (E,E)-α-farnesene synthase whose overexpression enhances cold tolerance through jasmonic acid biosynthesis and signaling in Arabidopsis.

MAIN CONCLUSION: Santalum album (E,E)-α-farnesene synthase catalyzes FPP into (E,E)-α-farnesene. Overexpression of the SaAFS gene positively improved cold stress tolerance through JA biosynthesis and signaling pathways in Arabidopsis. Volatile terpenoids are released from plants that suffer negative effects following exposure to various biotic and abiotic stresses. Recent studies revealed that (E,E)-α-farnesene synthase (AFS) plays a significant role in a plant's defence against biotic attack. However, little is known about whether AFS contributes to plant resistance to cold stress. In this study, a SaAFS gene was isolated from Indian sandalwood (Santalum album L.) and functionally characterized. The SaAFS protein mainly converts farnesyl diphosphate to (E,E)-α-farnesene. SaAFS was clustered into the AFS clade from angiosperms, suggesting a highly conserved enzyme. SaAFS displayed a significant response to cold stress and methyl jasmonate. SaAFS overexpression (OE) in Arabidopsis enhanced cold tolerance by increasing proline content, reducing malondialdehyde content, electrolyte leakage, and accumulating reactive oxygen species. Transcriptomic analysis revealed that upregulated genes related to stress response and JA biosynthesis and signaling were detected in SaAFS-OE lines compared with wild type plants that were exposed to cold stress. Endogenous JA and jasmonoyl-isoleucine content increased significantly in SaAFS-OE lines exposed to cold stress. Collectively considered, these results suggest that the SaAFS gene is a positive regulator during cold stress tolerance via JA biosynthesis and signaling pathways.

How are authors' contributions verified in the ICMJE model?

A recent editorial in Plant Cell Reports reaffirms what has been known for years, namely, that it follows the four ICMJE clauses of authorship. That editorial even provides a "perfect" model contribution statement. In this letter, I argue that in reality and in practice, authorship delimitations are not that clear-cut, nor are all contributions equal or equally weighted. More importantly, I opine that no matter how eloquently an author contribution statement is written, editors have no way to verify the veracity of those claims. In essence, absent authorship contribution verification, the ICMJE guidelines are practically useless. The responsibility for verification, even to determine authorship associated with papermills or the "ghost" contribution of text by AI like ChatGPT, lies entirely with editors and publishers. Although an unpopular meme, there is need for academic publishing to return to a state of no blind trust.

Variations in the naming of malondialdehyde (MDA) in PubMed-, Scopus-, and Web of science-indexed literature.

Malondialdehyde (MDA) is a product of lipid peroxidation that is often determined in abiotic stress-related phytoremediation research. This study assessed (July 14, 2022) the frequency of eight nomenclatural forms of MDA between 2001 and 2021 using three major databases (PubMed, Scopus, and Web of Science (WoS9). The most common form (75,060, 57,874, and 65,663 times in PubMed, Scopus, and WoS, respectively) of MDA was "malondialdehyde", followed by "malonaldehyde" (68,240, 3815, and 2337 times in these three databases, respectively). According to WoS, the journals that used "malondialdehyde" and "malonaldehyde" most frequently were Environmental Science and Pollution Research (Springer-Nature) (587 times) and The Journal of Chemical Physics (AIP Publishing) (57 times). Other less-frequent forms were: malonyldialdehyde, malonic dialdehyde, malon-dialdehyde, malone dialdehyde, malonic aldehyde, and malonodialdehyde. We recommend that the editors of journals that publish papers with themes that are closely associated with plant stress specify in their instructions for authors their journal's preferable nomenclatural form of MDA. The plant abiotic stress community, including phytoremediation specialists, need to debate this topic with the objective of seeking a standardized nomenclatural form of MDA, which would help to fortify the integrity of searches in major databases by allowing all relevant literature to be accurately identified. Novelty statementMalondialdehyde (MDA), a product of lipid peroxidation that is often determined in stress-related phytoremediation research, has various forms to its name. These nomenclatural variations were assessed in PubMed-, Scopus-, and Web of Science-indexed literature. This is the first study to detect, report, quantify and debate these forms of MDA.

Safety & effectiveness of COVID-19 vaccines: A narrative review.

There are currently eight vaccines against SARS-CoV-2 that have received Emergency Use Authorization by the WHO that can offer some protection to the world's population during the COVID-19 pandemic. Though research is being published all over the world, public health officials, policymakers and governments are collecting evidence-based information to establish the public health policies. Unfortunately, continued international travel, violations of lockdowns and social distancing, the lack of mask use, the emergence of mutant strains of the virus and lower adherence by a sector of the global population that remains sceptical of the protection offered by vaccines, or about any risks associated with vaccines, hamper these efforts. Here we examine the literature on the efficacy, effectiveness and safety of COVID-19 vaccines, with an emphasis on select categories of individuals and against new SARS-CoV-2 strains. The literature shows that these eight vaccines are highly effective in protecting the population from severe disease and death, but there are some issues concerning safety and adverse effects. Further, booster shots and variant-specific vaccines would also be required.

Genome-wide identification and analysis of DNA methyltransferase and demethylase gene families in Dendrobium officinale reveal their potential functions in polysaccharide accumulation.

BACKGROUND: DNA methylation is a conserved and important epigenetic modification involved in the regulation of numerous biological processes, including plant development, secondary metabolism, and response to stresses. However, no information is available regarding the identification of cytosine-5 DNA methyltransferase (C5-MTase) and DNA demethylase (dMTase) genes in the orchid Dendrobium officinale. RESULTS: In this study, we performed a genome-wide analysis of DoC5-MTase and DodMTase gene families in D. officinale. Integrated analysis of conserved motifs, gene structures and phylogenetic analysis showed that eight DoC5-MTases were divided into four subfamilies (DoCMT, DoDNMT, DoDRM, DoMET) while three DodMTases were divided into two subfamilies (DoDML3, DoROS1). Multiple cis-acting elements, especially stress-responsive and hormone-responsive ones, were found in the promoter region of DoC5-MTase and DodMTase genes. Furthermore, we investigated the expression profiles of DoC5-MTase and DodMTase in 10 different tissues, as well as their transcript abundance under abiotic stresses (cold and drought) and at the seedling stage, in protocorm-like bodies, shoots, and plantlets. Interestingly, most DoC5-MTases were downregulated whereas DodMTases were upregulated by cold stress. At the seedling stage, DoC5-MTase expression decreased as growth proceeded, but DodMTase expression increased. CONCLUSIONS: These results provide a basis for elucidating the role of DoC5-MTase and DodMTase in secondary metabolite production and responses to abiotic stresses in D. officinale.

Kopyor versus macapuno coconuts: are these two edible mutants of Southeast Asia the same?

MAIN CONCLUSION: Kopyor and macapuno are two coconut mutants from Southeast Asia that are often described erroneously or interchangeably mismatched due to a lack of research, so future studies are encouraged. Coconut (Cocos nucifera L.; Arecaceae), a widely distributed plant with popular culinary applications, especially of the endosperm, has several nutritional and medicinal benefits. Two coconut mutants are widely recognized in Southeast Asia, namely kopyor and macapuno, specifically in Indonesia and Philippines, respectively. Kopyor coconut is known for its brittle solid endosperm while macapuno coconut is known for its gelatinous solid endosperm. Both mutant types have many other synonyms in other countries. Over many decades, the biology of macapuno coconut, including endosperm anatomy, histology, cytology, physiology, and genetics have been described, while kopyor coconut is still understudied. However, some literature and websites erroneously describe kopyor as macapuno coconut, or consider them interchangeably, which is an unintentional consequence of insufficient scientific research on these coconut mutants. Additionally, in Indonesia, there is another local mutant in Banten called wax coconut ("kelapa lilin") that some researchers claim as the actual Indonesian macapuno coconut due to its strong resemblance to kopyor coconut. Unfortunately, wax coconut is not only understudied, it is rarely documented. Additional evidence of their differences, in terms of morphological, biochemical and genetic characteristics, is needed. Moreover, clear documentation will also be needed for a better comparison. Understanding the differences between kopyor and macapuno coconuts will not only help to further clarify their scientific description in the literature, but will also guide locals, researchers, and industries to characterize similar mutants, if found in specific regions, for future study and bioprospecting.

Analysis of Chemical Components in the Roots of Eight Intersubgeneric Hybrids of Paeonia.

Paeonia cultivars are famous ornamental plants, and some of them are also traditional Chinese medicinal resources. Intersubgeneric hybrids of Paeonia (IHPs) are formed by the hybridization of herbaceous peony (Paeonia lactiflora) and tree peony (Paeonia×suffruticosa or lutea hybrid tree peony). The phenotypic characteristics of IHPs are similar to those of herbaceous peony, and their root systems are large and vigorous. However, their medicinal value has not been reported yet. In this study, the roots of eight IHP samples were analyzed by high performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS/MS). A total of 18 compounds were identified, including phenols, paeonols, monoterpene glycosides, and tannins. The contents of monoterpene glycosides and tannins in IHPs were higher than herbaceous peony and tree peony, exceeding 44.76 mg/g DW and 11.50 mg/g DW, respectively. Three IHPs, 'Prairie Charm', 'Garden Treasure', and 'Yellow Emperor', with more types and a higher content of medicinal compounds, were screened out by cluster analysis. These IHPs have considerable potential for the development of medicinal resources.

Assessment of physiological and biochemical responses of Amaranthus retroflexus seedlings to the accumulation of heavy metals with regards to phytoremediation potential.

The aim of this research was to assess, under laboratory conditions, how the accumulation of four heavy metals (HMs) (lead (Pb), copper (Cu), nickel (Ni), and zinc (Zn)), prepared as aqueous solutions from 1 µM to 1 mM, affected biochemical and physiological parameters of Amaranthus retroflexus seedlings. Seedlings showed considerably high resistance to all investigated HMs and no significant oxidative stress in leaves. After chronic exposure to high doses of any of the HMs, seedlings remained viable, but with slightly slower axial growth. We propose the use of biochemical indices (lipid peroxidation (LPO) intensity; level of total peroxides) as criteria to assess the adaptive potential of amaranth plants to HMs. These indices had very high correlation coefficients (r) with the accumulation of HMs in A. retroflexus roots, stems and leaves: 0.86-0.89 for malone dialdehyde (MDA) content for Ni and Zn, and 0.79-0.94 for total peroxides (for Cu, Pb, and maximum in Ni). At 1 mM of any HM, seedlings accumulated Pb and Ni at levels of HM-hyperaccumulating species. If soil is contaminated (in terms of maximum permissible concentration, MPC) by Pb (8.2 ± 2.2 MPC) or Ni (3.5 ± 1.0 MPC) (equivalent to 1 mM of the HM in solution), A. retroflexus is a strong candidate for the phytoremediation of Pb- and Ni-contaminated soils.

Genome-Wide Identification and Analysis of the APETALA2 (AP2) Transcription Factor in Dendrobium officinale.

The APETALA2 (AP2) transcription factors (TFs) play crucial roles in regulating development in plants. However, a comprehensive analysis of the AP2 family members in a valuable Chinese herbal orchid, Dendrobium officinale, or in other orchids, is limited. In this study, the 14 DoAP2 TFs that were identified from the D. officinale genome and named DoAP2-1 to DoAP2-14 were divided into three clades: euAP2, euANT, and basalANT. The promoters of all DoAP2 genes contained cis-regulatory elements related to plant development and also responsive to plant hormones and stress. qRT-PCR analysis showed the abundant expression of DoAP2-2, DoAP2-5, DoAP2-7, DoAP2-8 and DoAP2-12 genes in protocorm-like bodies (PLBs), while DoAP2-3, DoAP2-4, DoAP2-6, DoAP2-9, DoAP2-10 and DoAP2-11 expression was strong in plantlets. In addition, the expression of some DoAP2 genes was down-regulated during flower development. These results suggest that DoAP2 genes may play roles in plant regeneration and flower development in D. officinale. Four DoAP2 genes (DoAP2-1 from euAP2, DoAP2-2 from euANT, and DoAP2-6 and DoAP2-11 from basal ANT) were selected for further analyses. The transcriptional activation of DoAP2-1, DoAP2-2, DoAP2-6 and DoAP2-11 proteins, which were localized in the nucleus of Arabidopsis thaliana mesophyll protoplasts, was further analyzed by a dual-luciferase reporter gene system in Nicotiana benthamiana leaves. Our data showed that pBD-DoAP2-1, pBD-DoAP2-2, pBD-DoAP2-6 and pBD-DoAP2-11 significantly repressed the expression of the LUC reporter compared with the negative control (pBD), suggesting that these DoAP2 proteins may act as transcriptional repressors in the nucleus of plant cells. Our findings on AP2 genes in D. officinale shed light on the function of AP2 genes in this orchid and other plant species.

Potassium-enriched clinoptilolite zeolite mitigates the adverse impacts of salinity stress in perennial ryegrass (Lolium perenne L.) by increasing silicon absorption and improving the K/Na ratio.

Salinity is a major abiotic stress that adversely affects turfgrass growth. Clinoptilolite zeolite, a silicon (Si)-rich mineral, may allow these plants to cope with salinity. Therefore, in the present study, the effects of ordinary clinoptilolite zeolite (OZ) and potassium-enriched clinoptilolite zeolite (K-EZ) on the growth of perennial ryegrass (Lolium perenne L.) were assessed under salinity stress. Perennial ryegrass seeds were cultured in soil mixtures amended, or not, with OZ or K-EZ, then exposed to three salinity levels (0, 50 or 100 mM NaCl) for three months. Control plants were grown in the same soil mixture without zeolites, but not exposed to salinity. In salinity, the application of both types of zeolite significantly decreased Na content by 44.36% and 21.31%, but increased K content by 272.34% and 81.59%, as well as the K/Na ratio by 590.47% and 129.43%, in shoots and roots, respectively, compared to the no-zeolite treatment. Similarly, Si content in shoots increased by 28.33%. Amending the soil mixture with zeolite, especially K-EZ, enhanced relative water content, membrane stability index, total chlorophyll content, total soluble proteins, peroxidase and superoxide dismutase activities but reduced the contents of total soluble carbohydrates, hydrogen peroxide, and malondialdehyde in saline conditions. Shoot and root dry weight, root volume and root/shoot ratio also improved. Soil amendment with both forms of zeolite, as a Si-rich mineral, partially offset the negative impacts of salinity on perennial ryegrass, although K-EZ had more noticeable positive and beneficial effects. The amendment of growth media with zeolite may be an effective sustainable management practice for turfgrass used in landscaping and sports fields exposed to saline water.

Optimizing peer review to minimize the risk of retracting COVID-19-related literature.

Retractions of COVID-19 literature in both preprints and the peer-reviewed literature serve as a reminder that there are still challenging issues underlying the integrity of the biomedical literature. The risks to academia become larger when such retractions take place in high-ranking biomedical journals. In some cases, retractions result from unreliable or nonexistent data, an issue that could easily be avoided by having open data policies, but there have also been retractions due to oversight in peer review and editorial verification. As COVID-19 continues to affect academics and societies around the world, failures in peer review might also constitute a public health risk. The effectiveness by which COVID-19 literature is corrected, including through retractions, depends on the stringency of measures in place to detect errors and to correct erroneous literature. It also relies on the stringent implementation of open data policies.

Transcriptome sequencing and metabolite profiling analyses provide comprehensive insight into molecular mechanisms of flower development in Dendrobium officinale (Orchidaceae).

KEY MESSAGE: This research provides comprehensive insight into the molecular networks and molecular mechanisms underlying D. officinale flower development. Flowers are complex reproductive organs and play a crucial role in plant propagation, while also providing sustenance for insects and natural bioactive metabolites for humans. However, knowledge about gene regulation and floral metabolomes in flowers is limited. In this study, we used an important orchid species (Dendrobium officinale), whose flowers can be used to make herbal tea, to perform transcriptome sequencing and metabolic profiling of early- and medium-stage flower buds, as well as opened flowers, to provide comprehensive insight into the molecular mechanisms underlying flower development. A total of 8019 differentially expressed genes (DEGs) and 239 differentiated metabolites were found. The transcription factors that were identified and analyzed belong exclusively to the MIKC-type MADS-box proteins and auxin responsive factors that are known to be involved in flower development. The expression of genes involved in chlorophyll and carotenoid biosynthesis strongly matched the metabolite accumulation patterns. The genes related to flavonoid and polysaccharide biosynthesis were active during flower development. Interestingly, indole-3-acetic acid and abscisic acid, whose trend of accumulation was inverse during flower development, may play an important role in this process. Collectively, the identification of DEGs and differentiated metabolites could help to illustrate the regulatory networks and molecular mechanisms important for flower development in this orchid.

Cryopreservation of carnation (Dianthus caryophyllus L.) and other Dianthus species.

MAIN CONCLUSION: This paper reviews the cryopreservation of the ornamental, carnation (Dianthus caryophyllus L.), as an important method for the long-term preservation of this plant's germplasm. Carnation (Dianthus caryophyllus L.) is an important ornamental plant that is used as a potted plant as well as a cut flower. Important Dianthus germplasm would benefit from long-term strategies such as cryopreservation. Unlike the in vitro tissue culture literature of this ornamental, which has been studied in considerable detail, and with several genetic transformation protocols, surprisingly, the literature on its cryopreservation is still fairly scant, with barely two dozen or so studies, mostly having employed shoot tips. Early (< 2007) and more recent (2007-2020) cryopreservation techniques for carnation, including ultra-rapid cooling, encapsulation-vitrification, and encapsulation-dehydration, efficiently replaced programmed slow cooling processes used in early studies in the 1980s. Two large gaps (1997-2006, and 2016-2020) in which no carnation cryopreservation studies were published, requires future studies to cover new knowledge to fill gaps in information. Carnation cryopreservation research would benefit from testing a wide range of in vitro explants, new techniques such as the cryo-mesh, improved regeneration protocols for post-cryopreserved material, and the use of low-temperature storage as a mid- to long-term complementary germplasm storage strategy. This mini-review provides details of what has been achieved thus far and future objectives that could fortify cryopreservation research of this ornamental, as well as provide a robust long-term germplasm repository.

Rafflesia patma Blume flower organs: histology of the epidermis and vascular structures, and a search for stomata.

MAIN CONCLUSION: A histological study of Rafflesia patma revealed the simplicity of a flower's vascular tissue and epidermal features of flower organs, including their structures and pigmentation. Rafflesia is an endophytic holoparasitic plant that infects Tetrastigma. In a previous study, we characterized the shape of the strands of an endophyte (Rafflesia patma Blume) and hypothesized their distribution. In this study, we deepened our analysis by assessing parts of flower tissue sampled during anthesis, performed surface casting of the abaxial and adaxial sides of the perigone lobe to profile their surface features, and histologically characterized the perigone lobe, perigone tube, and central column base, including the anther and cupula region. The objective of these observations was to compare tissues from different organs and the distribution of cells staining positive for tannin, suberin, and lignin. Observable features in this study were vascular and epidermal tissue. We also observed reduced vascular tissue with xylem and vascular parenchyma in multiple organs. The adaxial epidermis found in the perigone lobes and tube had papillate cells, and their function might be to assist with the emission of odor through chemical evaporation. The abaxial epidermis, also found in perigone lobes and tube, had flattened cells. These, combined with the nearby flattened parenchyma cells, especially in the outermost, early perigone lobe, might provide a tougher (stiffer) outer protective barrier for the flower. The accumulation of tannin in perigone lobes might offer protection to the flower from herbivores prior to anthesis. Although a previous observation indicated the possibility of stomata on the surface of Rafflesia flowers, no stomata were found in this study.

Shoot tip necrosis of in vitro plant cultures: a reappraisal of possible causes and solutions.

MAIN CONCLUSION: Shoot tip necrosis is a physiological condition that negatively impacts the growth and development of in vitro plant shoot cultures across a wide range of species. Shoot tip necrosis is a physiological condition and disorder that can arise in plantlets or shoots in vitro that results in death of the shoot tip. This condition, which can spread basipetally and affect the emergence of axillary shoots from buds lower down the stem, is due to the cessation of apical dominance. STN can occur at both shoot multiplication and rooting stages. One of the most common factors that cause STN is nutrient deficiency or imbalance. Moreover, the presence or absence of plant growth regulators (auxins or cytokinins) at specific developmental stages may impact STN. The cytokinin to auxin ratio within an in vitro plant can be modified by varying the concentration of cytokinins used in the culture medium. The supply of nutrients to in vitro shoots or plantlets might also affect their hormonal balance, thus modifying the occurrence of STN. High relative humidity within culture vessels and hyperhydricity are associated with STN. An adequate supply of calcium as the divalent cation (Ca2+) can hinder STN by inhibiting the accumulation of phenolic compounds and thus programmed cell death. Moreover, the level of Ca2+ affects auxin transport and ethylene production, and higher ethylene production, which can occur as a result of high relative humidity in or poor ventilation of the in vitro culture vessel, induces STN. High relative humidity can decrease the mobility of Ca2+ within a plant, resulting in Ca2+ deficiency and STN. STN of in vitro shoots or plantlets can be halted or reversed by altering the basal medium, mainly the concentration of Ca2+, adjusting the levels of auxins or cytokinins, or modifying culture conditions. This review examines the literature related to STN, seeks to discover the associated factors and relations between them, proposes practical solutions, and attempts to better understand the mechanism(s) underlying this condition in vitro.

Smoking Prevalence and COVID-19 in Europe.

INTRODUCTION: This ecological study investigates the association between smoking prevalence and COVID-19 occurrence and mortality in 38 European nations as of May 30, 2020. METHODS: Data were collected from Our World in Data. Regression analysis was conducted to adjust for potential confounding factors such as economic activity (gross domestic product), the rate of COVID-19 testing, and the stringency of COVID-19 control policies. RESULTS: There was a statistically significant negative association between smoking prevalence and the prevalence of COVID-19 across the 38 European nations after controlling for confounding factors (p = 0.001). A strong association was found between the prevalence of COVID-19 per million people and economic activity (p = 0.002) and the rate of COVID-19 testing (p = 0.0006). Nations with stricter policy enactment showed fewer COVID-19 cases per million people, but the association was not significant (p = 0.122). Delaying policy enactment was associated with a greater prevalence of COVID-19 (p = 0.0535). Evidence of a direct association between smoking prevalence and COVID-19 mortality was not found (p = 0.626). There was a strong positive association between COVID-19 mortality rate and the prevalence of COVID-19 cases (p < 0.0001) as well as the proportion of the population over 65 years of age (p = 0.0034) and a negative association with the rate of COVID-19 testing (p = 0.0023). CONCLUSIONS: We found a negative association between smoking prevalence and COVID-19 occurrence at the population level in 38 European countries. This association may not imply a true or causal relationship, and smoking is not advocated as a prevention or treatment of COVID-19. IMPLICATIONS: Given the evidence of this ecological study, and of several other studies that found an underrepresentation of smoking prevalence in hospitalized cases, it may be worth examining, in laboratory experiments and controlled human trials, if nicotine offers any protection against COVID-19. Most importantly, to date, no study, including this one, supports the view that smoking acts as a treatment intervention or prophylaxis to reduce the impact or ameliorate the negative health impacts of COVID-19.