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Cycas (family Cycadaceae), which spread throughout tropical and subtropical regions, is crucial in conservation biology. Due to subtle morphological variations between species, a solid species-level phylogeny for Cycas is lacking. In the present study, we assembled and analyzed the chloroplast genomes of six Cycas plants, including their genome structure, GC content, and nucleotide diversity. The Cycas chloroplast genome spans from 162,038 to 162,159 bp and contains 131 genes, including 86 protein-coding genes, 37 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Through a comparative analysis, we found that the chloroplast genome of Cycas was highly conserved, as indicated by the contraction and expansion of the inverted repeat (IR) regions and sequence polymorphisms. In addition, several non-coding sites (psbK-psbI, petN-psbM, trnE-UUC-psbD, ndhC-trnM-CAU, and rpl32-trnP-GGG) showed significant variation. The utilization of phylogenetic analysis relying on protein-coding genes has substantiated the division of Cycas primarily into four groups. The application of these findings will prove valuable in evaluating genetic diversity and the phylogenetic connections among closely related species. Moreover, it will provide essential support for the advancement of wild germplasm resources. [ABSTRACT FROM AUTHOR]

Cycadaceae is regarded as one of the largest cycad families. It is made up of 120 species of the single genus Cycas. Genus Cycas is found only in tropical and subtropical climates. They are dioecious plants with male and female reproductive cones. Members of Cycadaceae family are excellent suppliers of a wide range of beneficial phytochemicals however, only a few numbers of species had undergone phytochemical and pharmacological research. A wide battery of metabolites, including flavonoids, biflavonoids, phenolic acids, sterols, amino acids, lignans, and fatty acids, have been isolated and structurally identified from various Cycas species. Since biflavonoids are a defining trait of all cycads, we focused in this review on the various biflavonoids nuclei found in Cycadaceae and their distribution in distinct Cycas species among other isolated secondary metabolites. Therefore, we outlined the various biflavonoids nuclei found in Cycadaceae and their distribution in distinct Cycas species in this review. Additionally, we highlighted the diverse pharmacological effects of different Cycas species that their biflavonoid content can be credited with. [ABSTRACT FROM AUTHOR]

The study of reproductive mechanisms is of particular interest for a real understanding of seed plant evolution. Spermatophytes comprise angiosperms and four orders of gymnosperms (Cycadales, Ginkgoales, Coniferales, and Gnetales) whose main characteristic is the reproduction via seeds. Ginkgo and cycads form a sister clade to the other gymnosperms and occupy a key phylogenetic position in-between the extinct Paleozoic seed ferns and the other extant gymnosperms. This review focuses on the similarities and differences between the reproductive mechanisms of Ginkgo and Cycas, from the morphogenesis of the male and female organs to the pollination and fertilization events. Together with the morphological and cytological description, the latest available molecular data on the reproductive organ development of the two plant genera are discussed. This will, hopefully, pave the path for new studies aiming at filling the gaps in our understanding of the hormonal and genetic regulation of their reproductive mechanisms. The whole reproductive process is presented in detail, providing a comprehensive and organic picture together with complete illustrations and photographic material. Each phase of the reproductive process is dissected, pointing out the main similarities and differences found among the two genera. The comparison comprises the male and female reproductive organs development, with a focus on pollen ontogeny, shape, ultrastructure, and germination as well as ovule development and patterning, female gametophyte formation, and ovule integument differentiation. Particular attention is given to the pollination and fertilization events focusing on the role of reproductive fluids as well as zoogamy. [ABSTRACT FROM AUTHOR]

Endophytes are essential in plant succession and evolution, and essential for stress resistance. Coralloid root is a unique root structure found in cycads that has played a role in resisting adverse environments, yet the core taxa and microbial community of different Cycas species have not been thoroughly investigated. Using amplicon sequencing, we successfully elucidated the microbiomes present in coralloid roots of 10 Cycas species, representing all four sections of Cycas in China. We found that the endophytic bacteria in coralloid roots, i.e., Cyanobacteria, were mainly composed of Desmonostoc_PCC-7422, Nostoc_PCC-73102 and unclassified_f__Nostocaceae. Additionally, the Ascomycota fungi of Exophiala, Paraboeremia, Leptobacillium, Fusarium, Alternaria, and Diaporthe were identified as the core fungi taxa. The Ascomycota fungi of Nectriaceae, Herpotrichiellaceae, Cordycipitaceae, Helotiaceae, Diaporthaceae, Didymellaceae, Clavicipitaceae and Pleosporaceae were identified as the core family taxa in coralloid roots of four sections. High abundance but low diversity of bacterial community was detected in the coralloid roots, but no significant difference among species. The fungal community exhibited much higher complexity compared to bacteria, and diversity was noted among different species or sections. These core taxa, which were a subset of the microbiome that frequently occurred in all, or most, individuals of Cycas species, represent targets for the development of Cycas conservation. [ABSTRACT FROM AUTHOR]

Understanding the genetic structure and differentiation in endangered species is of significance in detecting their phylogenetic relationships and prioritizing conservation. Here we sampled five endangered Cycas species endemic to southwest China and genotyped genetic structure and differentiation among them using the genotyping-by-sequencing (GBS) method. C. hongheensis showed high genetic diversity, but the other four species showed low genetic diversity. The genetic diversity between wild and cultivated populations was similar for C. debaoensis and C. guizhouensis, respectively. Low genetic differentiation and high gene flow were found among C. debaoensis, C. guizhouensis, and C. fairylakea, and C. hongheensis differentiated from them at ~1.74 Mya. TreeMix results showed historic migration events from C. guizhouensis to C. hongheensis, showing southward migration pathways. C. hongheensis showed increased effective population size with time, while the other four species underwent bottleneck events at ~1–5 Mya when continuous cooling events occurred. Our results indicate that the migration, differentiation, and speciation of Cycas species are associated with historical cooling events. [ABSTRACT FROM AUTHOR]

Abstract Background Plastid genomes (plastomes) present great potential in resolving multiscale phylogenetic relationship but few studies have focused on the influence of genetic characteristics of plastid genes, such as genetic variation and phylogenetic discordance, in resolving the phylogeny within a lineage. Here we examine plastome characteristics of Cycas L., the most diverse genus among extant cycads, and investigate the deep phylogenetic relationships within Cycas by sampling 47 plastomes representing all major clades from six sections. Results All Cycas plastomes shared consistent gene content and structure with only one gene loss detected in Philippine species C. wadei. Three novel plastome regions (psbA-matK, trnN-ndhF, chlL-trnN) were identified as containing the highest nucleotide variability. Molecular evolutionary analysis showed most of the plastid protein-coding genes have been under purifying selection except ndhB. Phylogenomic analyses that alternatively included concatenated and coalescent methods, both identified four clades but with conflicting topologies at shallow nodes. Specifically, we found three species-rich Cycas sections, namely Stangerioides, Indosinenses and Cycas, were not or only weakly supported as monophyly based on plastomic phylogeny. Tree space analyses based on different tree-inference methods both revealed three gene clusters, of which the cluster with moderate genetic properties showed the best congruence with the favored phylogeny. Conclusions Our exploration in plastomic data for Cycas supports the idea that plastid protein-coding genes may exhibit discordance in phylogenetic signals. The incongruence between molecular phylogeny and morphological classification reported here may largely be attributed to the uniparental attribute of plastid, which cannot offer sufficient information to resolve the phylogeny. Contrasting to a previous consensus that genes with longer sequences and a higher proportion of variances are superior for phylogeny reconstruction, our result implies that the most effective phylogenetic signals could come from loci that own moderate variation, GC content, sequence length, and underwent modest selection.

Cycas (family Cycadaceae), which spread throughout tropical and subtropical regions, is crucial in conservation biology. Due to subtle morphological variations between species, a solid species-level phylogeny for Cycas is lacking. In the present study, we assembled and analyzed the chloroplast genomes of six Cycas plants, including their genome structure, GC content, and nucleotide diversity. The Cycas chloroplast genome spans from 162,038 to 162,159 bp and contains 131 genes, including 86 protein-coding genes, 37 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Through a comparative analysis, we found that the chloroplast genome of Cycas was highly conserved, as indicated by the contraction and expansion of the inverted repeat (IR) regions and sequence polymorphisms. In addition, several non-coding sites (psbK-psbI, petN-psbM, trnE-UUC-psbD, ndhC-trnM-CAU, and rpl32-trnP-GGG) showed significant variation. The utilization of phylogenetic analysis relying on protein-coding genes has substantiated the division of Cycas primarily into four groups. The application of these findings will prove valuable in evaluating genetic diversity and the phylogenetic connections among closely related species. Moreover, it will provide essential support for the advancement of wild germplasm resources.

Luthrodes pandava Horsfield (Lepidoptera: Lycaenidae) has been reported as a pest of cycad plants in the Andaman and Nicobar Islands, India for the first time. Its impact on host species is assessed. Compared to introduced species, endemic cycads appear to be most susceptible to damage by its larvae, feeding on the plant and affecting growth. Larvae damage all above‐ground plant parts. C. dharmrajii L. J. Singh and C. pschannae R.C. Srivast. & L. J. Singh, endemic to the Andaman and Nicobar Islands, are recorded here for the first time as new host plants. [ABSTRACT FROM AUTHOR]

Endophytes are essential in plant succession and evolution, and essential for stress resistance. Coralloid root is a unique root structure found in cycads that has played a role in resisting adverse environments, yet the core taxa and microbial community of different Cycas species have not been thoroughly investigated. Using amplicon sequencing, we successfully elucidated the microbiomes present in coralloid roots of 10 Cycas species, representing all four sections of Cycas in China. We found that the endophytic bacteria in coralloid roots, i.e., Cyanobacteria, were mainly composed of Desmonostoc_PCC-7422, Nostoc_PCC-73102 and unclassified_f__Nostocaceae. Additionally, the Ascomycota fungi of Exophiala, Paraboeremia, Leptobacillium, Fusarium, Alternaria, and Diaporthe were identified as the core fungi taxa. The Ascomycota fungi of Nectriaceae, Herpotrichiellaceae, Cordycipitaceae, Helotiaceae, Diaporthaceae, Didymellaceae, Clavicipitaceae and Pleosporaceae were identified as the core family taxa in coralloid roots of four sections. High abundance but low diversity of bacterial community was detected in the coralloid roots, but no significant difference among species. The fungal community exhibited much higher complexity compared to bacteria, and diversity was noted among different species or sections. These core taxa, which were a subset of the microbiome that frequently occurred in all, or most, individuals of Cycas species, represent targets for the development of Cycas conservation.

Chilades pandava is a dangerous insect pest of Cycas spp., which seriously threatens the growth and development of Cycas plants. On the basis of previous studies, the paper summarized the behaviors of different insect states of C. pandava, such as feeding, flying, resting, mating, spawning, hatching, pupation, eclosion, etc., in order to provide a reference for effective prevention and control of C. pandava. [ABSTRACT FROM AUTHOR]

Understanding the genetic diversity of wild populations is fundamental to conserving species in-situ and ex-situ. To aid conservation plans and to inform ex-situ conservation, we examined the genetic diversity of the cycad Cycas calcicola (Cycadaceae). Samples were collected from wild populations in the Litchfield National Park and Katherine regions in the Northern Territory, Australia. Additional samples were obtained from botanic garden plants that were originally collected in the Katherine region, Daly River and Spirit Hills in the Northern Territory, Australia. Using RADseq we recovered 2271 informative genome-wide SNPs, revealing low to moderate levels of gene diversity (uHe = 0.037 to 0.135), very low levels of gene flow, and significant levels of inbreeding (mean FIS = 0.491). Population structure and multivariate analysis showed that populations fall into two genetic groups (Katherine vs Litchfield + Daly River + Spirit Hills). Genetic differentiation was twice as high between populations of the Katherine and Litchfield regions (FST ~ 0.1) compared to within these two regions (FST ~ 0.05). Increasing population fragmentation together with high levels of inbreeding and very little gene flow are concerning for the future adaptability of this species. The results indicated that the ex-situ collections (1) had significantly lower genetic diversity than the wild populations, and (2) only partly capture the genetic diversity present, particularly because the Litchfield National Park populations are not represented. We recommend that ex-situ collections be expanded to incorporate the genetic diversity found in Litchfield National Park and to increase the number of representatives from Daly River/Spirit Hills, and that in-situ populations from the Katherine and Greater Litchfield regions be conserved as separate management units. [ABSTRACT FROM AUTHOR]

Abstract Background C. panzhihuaensis is more tolerant to freezing than C. bifida but the mechanisms underlying the different freezing tolerance are unclear. Photosynthesis is one of the most temperature-sensitive processes. Lipids play important roles in membrane structure, signal transduction and energy storage, which are closely related to the stress responses of plants. In this study, the chlorophyll fluorescence parameters and lipid profiles of the two species were characterized to explore the changes in photosynthetic activity and lipid metabolism following low-temperature exposure and subsequent recovery. Results Photosynthetic activity significantly decreased in C. bifida with the decrease of temperatures and reached zero after recovery. Photosynthetic activity, however, was little affected in C. panzhihuaensis. The lipid composition of C. bifida was more affected by cold and freezing treatments than C. panzhihuaensis. Compared with the control, the proportions of all the lipid categories recovered to the original level in C. panzhihuaensis, but the proportions of most lipid categories changed significantly in C. bifida after 3 d of recovery. In particular, the glycerophospholipids and prenol lipids degraded severely during the recovery period of C. bifida. Changes in acyl chain length and double bond index (DBI) occurred in more lipid classes immediately after low-temperature exposure in C. panzhihuaensis compare with those in C. bifida. DBI of the total main membrane lipids of C. panzhihuaensis was significantly higher than that of C. bifida following all temperature treatments. Conclusions The results of chlorophyll fluorescence parameters confirmed that the freezing tolerance of C. panzhihuaensis was greater than that of C. bifida. The lipid metabolism of the two species had differential responses to low temperatures. The homeostasis and plastic adjustment of lipid metabolism and the higher level of DBI of the main membrane lipids may contribute to the greater tolerance of C. panzhihuaensis to low temperatures.

Understanding the genetic structure and differentiation in endangered species is of significance in detecting their phylogenetic relationships and prioritizing conservation. Here we sampled five endangered Cycas species endemic to southwest China and genotyped genetic structure and differentiation among them using the genotyping-by-sequencing (GBS) method. C. hongheensis showed high genetic diversity, but the other four species showed low genetic diversity. The genetic diversity between wild and cultivated populations was similar for C. debaoensis and C. guizhouensis, respectively. Low genetic differentiation and high gene flow were found among C. debaoensis, C. guizhouensis, and C. fairylakea, and C. hongheensis differentiated from them at ~1.74 Mya. TreeMix results showed historic migration events from C. guizhouensis to C. hongheensis, showing southward migration pathways. C. hongheensis showed increased effective population size with time, while the other four species underwent bottleneck events at ~1–5 Mya when continuous cooling events occurred. Our results indicate that the migration, differentiation, and speciation of Cycas species are associated with historical cooling events.

The divergence process of incipient species is fascinating but elusive by incomplete lineage sorting or gene flow. Species delimitation is also challenging among those morphologically similar allopatric species, especially when lacking comprehensive data. Cycas sect. Asiorientales , comprised of C. taitungensis and C. revoluta in the Ryukyu Archipelago and Taiwan, diverged recently with continuous gene flow, resulting in a reciprocal paraphyletic relationship. Their previous evolutionary inferences are questioned from few genetic markers, incomplete sampling, and incomprehensive morphological comparison by a long-term taxonomic misconception. By whole range sampling, this study tests the geographic mode of speciation in the two species of Asiorientales by approximate Bayesian computation (ABC) using genome-wide single nucleotide polymorphisms (SNPs). The individual tree was reconstructed to delimit the species and track the gene-flow trajectory. With the comparison of diagnostic morphological traits and genetic data, the allopatric speciation was rejected. Alternatively, continuous but spatially heterogeneous gene flow driven by transoceanic vegetative dispersal and pollen flow with contrasting population sizes blurred their species boundary. On the basis of morphological, genetic, and evolutionary evidence, we synonymized these two Cycas species. This study highlights not only the importance of the Kuroshio Current to species evolution but also the disadvantage of using species with geographically structured genealogies as conservation units. [ABSTRACT FROM AUTHOR]

Background: Plastid genomes (plastomes) present great potential in resolving multiscale phylogenetic relationship but few studies have focused on the influence of genetic characteristics of plastid genes, such as genetic variation and phylogenetic discordance, in resolving the phylogeny within a lineage. Here we examine plastome characteristics of Cycas L., the most diverse genus among extant cycads, and investigate the deep phylogenetic relationships within Cycas by sampling 47 plastomes representing all major clades from six sections. Results: All Cycas plastomes shared consistent gene content and structure with only one gene loss detected in Philippine species C. wadei. Three novel plastome regions (psbA-matK, trnN-ndhF, chlL-trnN) were identified as containing the highest nucleotide variability. Molecular evolutionary analysis showed most of the plastid protein-coding genes have been under purifying selection except ndhB. Phylogenomic analyses that alternatively included concatenated and coalescent methods, both identified four clades but with conflicting topologies at shallow nodes. Specifically, we found three species-rich Cycas sections, namely Stangerioides, Indosinenses and Cycas, were not or only weakly supported as monophyly based on plastomic phylogeny. Tree space analyses based on different tree-inference methods both revealed three gene clusters, of which the cluster with moderate genetic properties showed the best congruence with the favored phylogeny. Conclusions: Our exploration in plastomic data for Cycas supports the idea that plastid protein-coding genes may exhibit discordance in phylogenetic signals. The incongruence between molecular phylogeny and morphological classification reported here may largely be attributed to the uniparental attribute of plastid, which cannot offer sufficient information to resolve the phylogeny. Contrasting to a previous consensus that genes with longer sequences and a higher proportion of variances are superior for phylogeny reconstruction, our result implies that the most effective phylogenetic signals could come from loci that own moderate variation, GC content, sequence length, and underwent modest selection. [ABSTRACT FROM AUTHOR]

The divergence process of incipient species is fascinating but elusive by incomplete lineage sorting or gene flow. Species delimitation is also challenging among those morphologically similar allopatric species, especially when lacking comprehensive data. Cycas sect. Asiorientales, comprised of C. taitungensis and C. revoluta in the Ryukyu Archipelago and Taiwan, diverged recently with continuous gene flow, resulting in a reciprocal paraphyletic relationship. Their previous evolutionary inferences are questioned from few genetic markers, incomplete sampling, and incomprehensive morphological comparison by a long-term taxonomic misconception. By whole range sampling, this study tests the geographic mode of speciation in the two species of Asiorientales by approximate Bayesian computation (ABC) using genome-wide single nucleotide polymorphisms (SNPs). The individual tree was reconstructed to delimit the species and track the gene-flow trajectory. With the comparison of diagnostic morphological traits and genetic data, the allopatric speciation was rejected. Alternatively, continuous but spatially heterogeneous gene flow driven by transoceanic vegetative dispersal and pollen flow with contrasting population sizes blurred their species boundary. On the basis of morphological, genetic, and evolutionary evidence, we synonymized these two Cycas species. This study highlights not only the importance of the Kuroshio Current to species evolution but also the disadvantage of using species with geographically structured genealogies as conservation units.

The various therapeutic drugs that are currently utilized for the management of cancer, especially breast cancer, are greatly challenged by the augmented resistance that is either acquired or de novo by the cancer cells owing to the long treatment periods. So, this study aimed at elucidating the possible anticancer potential of four compounds 7, 4', 7'', 4'''-tetra- O -methyl amentoflavone, hesperidin, ferulic acid, and chlorogenic acid that are isolated from Cycas thouarsii leaves n -butanol fraction for the first time. The MTT assay evaluated the cytotoxic action of four isolated compounds against MDA-MB-231 breast cancer cells and oral epithelial cells. Interestingly, ferulic acid revealed the lowest IC 50 of 12.52 µg/mL against MDA-MB-231 cells and a high IC 50 of 80.2 µg/mL against oral epithelial cells. Also, using an inverted microscope, the influence of ferulic acid was studied on the MDA-MB-231, which revealed the appearance of apoptosis characteristics like shrinkage of the cells and blebbing of the cell membrane. In addition, the flow cytometric analysis showed that the MDA-MB-231 cells stained with Annexin V/PI had a rise in the count of the cells in the early and late apoptosis stages. Moreover, gel electrophoresis detected DNA fragmentation in the ferulic acid-treated cells. Finally, the effect of the compound was tested at the molecular level by qRT-PCR. An upregulation of the pro-apoptotic genes ( BAX and P53) and a downregulation of the anti-apoptotic gene ( BCL-2 ) were observed. Consequently, our study demonstrated that these isolated compounds, especially ferulic acid, may be vital anticancer agents, particularly for breast cancer, through its induction of apoptosis through the P53-dependent pathway.

The endophytes of plants are receiving increased attention since they have important functions for improving plant growth and fitness, especially in more challenging environmental conditions. The adaptation of cycads, an ancient gymnosperm taxon, to arid and nutrient-limited habitats is thought to be dependent on their symbiosis with nitrogen-fixing Cyanobacteria. We investigated the endophytic community in seeds, taproots, and young and mature coralloid roots of Cycas dolichophylla using 16S rRNA metabarcoding. Geographically distinct populations were studied in China and Vietnam. Higher endophyte diversity was found in Vietnamese populations than in Chinese ones. A significant difference in the bacterial endophytic community was identified between populations of mature coralloid roots from Chinese and Vietnamese samples, with the predominance of Alpha-, Gamma-, and Beta-Proteobacteria in the Vietnamese samples. Moreover, five core endophytic families, Nostocaceae, Burkholderiaceae, Pseudomonadaceae, Enterobacteriaceae, and Rhizobiaceae were revealed among all the samples. This study offers a robust knowledge of cycad microbial ecology and lends guidelines to the investigation of the adaptation mechanism of cycads in arid and nutrient-poor environments. [ABSTRACT FROM AUTHOR]

The genus Cycas forms one of the oldest plant groups. Cycas are utilized as ornamental plants in urban gardens, so they are found in different cities’ landscapes. At present, Cycas are affected by serious infestations of Aulacaspis yasumatsui (cycad aulacaspis scale; CAS) that eventually lead to the plant’s death. Aulacaspis yasumatsui is native to Thailand and has spread in all continents as an invasive species. To determine the distribution of Aulacaspis yasumatsui in Panama, we sampled 68 sites in 24 municipalities in nine of ten provinces of the Republic of Panama. Our results suggest that Aulacaspis yasumatsui is spread in the low territories of the country; however, we did not observe CAS-infested cycads in the highlands of Panama (> 700 m). Besides the economic loss caused by the death of plants whose price in Panama ranges from tens to hundreds of dollars, Cycas serve as a food supplier to birds and bats in the trophic food web. [ABSTRACT FROM AUTHOR]

Cycads represent one of the most ancestral living seed plants as well as one of the most threatened plant groups in the world. South China is a major center and potential origin of Cycas, the most rapidly diversified lineage of cycads. However, genomic-wide diversity of Cycas remains poorly understood due to the challenge of generating genomic markers associated with their inherent large genomes. Here, we perform a comprehensive conservation genomic study based on restriction-site associated DNA sequencing (RADseq) data in six representative species of Cycas in South China. Consistently low genetic diversity and strong genetic differentiation were detected across species. Both phylogenetic inference and genetic structure analysis via several methods revealed generally congruent groups among the six Cycas species. The analysis with ADMIXTURE showed low mixing of genetic composition among species, while individuals of C. dolichophylla exhibited substantial genetic admixture with C. bifida, C. changjiangensis, and C. balansae. Furthermore, the results from Treemix, f4-statistic, and ABBA-BABA test were generally consistent and revealed the complex patterns of interspecific gene flow. Relatively strong signals of hybridization were detected between C. dolichophylla and C. szechuanensis, and the ancestor of C. taiwaniana and C. changjiangensis. Distinct patterns of demographic history were inferred for these species by Stairway Plot, and our results suggested that both climate fluctuation and frequent geological activities during the late Pleistocene exerted deep impacts on the population dynamics of these species in South China. Finally, we explore the practical implications of our findings for the development of conservation strategies in Cycas. The present study demonstrates the efficiency of RADseq for conservation genomic studies on non-model species with large and complex genomes. Given the great significance of cycads as a radical transition in the evolution of plant biodiversity, our study provides important insights into the mechanisms of diversification in such recently radiated living fossil taxa.

Cycads represent one of the most ancestral living seed plants as well as one of the most threatened plant groups in the world. South China is a major center and potential origin of Cycas , the most rapidly diversified lineage of cycads. However, genomic-wide diversity of Cycas remains poorly understood due to the challenge of generating genomic markers associated with their inherent large genomes. Here, we perform a comprehensive conservation genomic study based on restriction-site associated DNA sequencing (RADseq) data in six representative species of Cycas in South China. Consistently low genetic diversity and strong genetic differentiation were detected across species. Both phylogenetic inference and genetic structure analysis via several methods revealed generally congruent groups among the six Cycas species. The analysis with ADMIXTURE showed low mixing of genetic composition among species, while individuals of C. dolichophylla exhibited substantial genetic admixture with C. bifida , C. changjiangensis , and C. balansae. Furthermore, the results from Treemix, f 4-statistic, and ABBA-BABA test were generally consistent and revealed the complex patterns of interspecific gene flow. Relatively strong signals of hybridization were detected between C. dolichophylla and C. szechuanensis , and the ancestor of C. taiwaniana and C. changjiangensis. Distinct patterns of demographic history were inferred for these species by Stairway Plot, and our results suggested that both climate fluctuation and frequent geological activities during the late Pleistocene exerted deep impacts on the population dynamics of these species in South China. Finally, we explore the practical implications of our findings for the development of conservation strategies in Cycas. The present study demonstrates the efficiency of RADseq for conservation genomic studies on non-model species with large and complex genomes. Given the great significance of cycads as a radical transition in the evolution of plant biodiversity, our study provides important insights into the mechanisms of diversification in such recently radiated living fossil taxa. [ABSTRACT FROM AUTHOR]

Background: C. panzhihuaensis is more tolerant to freezing than C. bifida but the mechanisms underlying the different freezing tolerance are unclear. Photosynthesis is one of the most temperature-sensitive processes. Lipids play important roles in membrane structure, signal transduction and energy storage, which are closely related to the stress responses of plants. In this study, the chlorophyll fluorescence parameters and lipid profiles of the two species were characterized to explore the changes in photosynthetic activity and lipid metabolism following low-temperature exposure and subsequent recovery. Results: Photosynthetic activity significantly decreased in C. bifida with the decrease of temperatures and reached zero after recovery. Photosynthetic activity, however, was little affected in C. panzhihuaensis. The lipid composition of C. bifida was more affected by cold and freezing treatments than C. panzhihuaensis. Compared with the control, the proportions of all the lipid categories recovered to the original level in C. panzhihuaensis, but the proportions of most lipid categories changed significantly in C. bifida after 3 d of recovery. In particular, the glycerophospholipids and prenol lipids degraded severely during the recovery period of C. bifida. Changes in acyl chain length and double bond index (DBI) occurred in more lipid classes immediately after low-temperature exposure in C. panzhihuaensis compare with those in C. bifida. DBI of the total main membrane lipids of C. panzhihuaensis was significantly higher than that of C. bifida following all temperature treatments. Conclusions: The results of chlorophyll fluorescence parameters confirmed that the freezing tolerance of C. panzhihuaensis was greater than that of C. bifida. The lipid metabolism of the two species had differential responses to low temperatures. The homeostasis and plastic adjustment of lipid metabolism and the higher level of DBI of the main membrane lipids may contribute to the greater tolerance of C. panzhihuaensis to low temperatures. [ABSTRACT FROM AUTHOR]

Genus Cycas, Cycadaceae family, contains about 117 species. Nevertheless, few species have been phytochemically and pharmacologically studied. To date Eighty-eight secondary metabolites, including flavonoids, terpenoids, lignans, aromatic acids and sterols were isolated and identified from nineteen Cycas species. Among the isolated compounds flavonoids are the most prevalent metabolites. The extracts as well as pure compounds isolated from Cycas species were reported to exhibit a wide range of biological activities including; antimicrobial, anti-oxidant, antidiabetic, cytotoxic, anthelmintic, analgesic, anti-arthritic, anti-inflammatory and thrombolytic activities. The present review highlights the reported phytochemical content as well as the pharmacological potential of Cycas species. Interestingly, it indicates that; almost all the previous investigation of the biological activity of pure compounds isolated from this genus was directed towards its flavonoid content. Accordingly, more biological studies are needed to figure out the possible role of other isolated compounds in the observed biological activities and/or the reported traditional uses of different Cycas species. Moreover, further studies are required to investigate other unexplored species. [ABSTRACT FROM AUTHOR]

The culture-based approach was used to characterize the fungal endophytes associated with the coralloid roots of the endemic Cycas debaoensis and Cycas fairylakea from various population sites in China. We aim to determine if the assemblages of fungal endophytes inside these endemic plant hosts are distinct and could be explored for bioprospecting. The isolation method yielded a total of 284 culturable fungal strains. Identification based on the analysis of the internal transcribed spacer (ITS) rDNA showed that they belonged to two phyla, five classes, eight orders and 22 families. At least 33 known genera and 62 different species were confirmed based on >97% ITS sequence similarity. The most frequent and observed core taxa in the two host species regardless of their population origin were Talaromyces, Penicillium, Fusarium, Pochonia and Gliocladiopsis. Seventy percent was a rare component of the fungal communities with only one or two recorded isolates. Contrary to common notions, diversity and fungal richness were significantly higher in C. debaoensis and C. fairylakea collected from a botanical garden, while the lowest was observed in C. debaoensis from a natural habitat; this provides evidence that garden management, and to a minor extent, ex-situ conservation practice, could influence fungal endophyte communities. We further selected nineteen fungal isolates and screened for their antagonistic activities via a co-cultivation approach against the phytopathogens, Diaporthe sp. and Colletotrichum sp. Among these, five isolates with high ITS similarity matches with Hypoxylon vinosupulvinatum (GD019, 99.61%), Penicillium sp. (BD022, 100%), Penicillifer diparietisporus (GD008, 99.46%), Clonostachys rogersoniana (BF024, 99.46%) and C. rosea (BF011, 99.1%), which showed exceptional antagonistic activities against the phytopathogenic fungi with a significant inhibition rate of 70–80%. Taken together, our data presented the first and most comprehensive molecular work on culturable fungal endophytes associated with the coralloid roots of cycads. Our study also demonstrated that about 5% of fungal endophytes were not detected by the high-throughput sequencing approach, implying the equal importance of a culture-dependent approach to study fungal communities of cycads. We further highlighted the potential role of endemic and rare plants to discover and isolate unique plant-associated fungal taxa with excellent biocontrol properties. [ABSTRACT FROM AUTHOR]

Barcoding of Cycas pschannae Srivast. & Singh from Andaman & Nicobar Islands was done with the help of rbcL and ITS(Standard Universal Barcode Sequence-CBoL) and submitted to GenBank. Phylogenetic relationship of this species was analyzed and Cladistic study of nine Cycas species from India and adjacent country including Cycas revoluta thunb had been conducted with help of BLAST tool by using rbcL barcode sequence, which reveals that Cycas pschannae has close relation with Cycas circinalis as compared to other Indian species. [ABSTRACT FROM AUTHOR]

Cycads have developed a complex root system categorized either as normal or coralloid roots. Past literatures revealed that a great diversity of key microbes is associated with these roots. This recent study aims to comprehensively determine the diversity and community structure of bacteria and fungi associated with the roots of two Cycas spp. endemic to China, Cycas debaoensis Zhong & Chen and Cycas fairylakea D.Y. Wang using high-throughput amplicon sequencing of the full-length 16S rRNA (V1-V9 hypervariable) and short fragment ITS region. The total DNA from 12 root samples were extracted, amplified, sequenced, and analyzed. Resulting sequences were clustered into 61 bacteria and 2128 fungal OTUs. Analysis of community structure revealed that the coralloid roots were dominated mostly by the nitrogen-fixer Nostocaceae but also contain other non-diazotrophic bacteria. The sequencing of entire 16S rRNA gene identified four different strains of cyanobacteria under the heterocystous genera Nostoc and Desmonostoc. Meanwhile, the top bacterial families in normal roots were Xanthobacteraceae, Burkholderiaceae, and Bacillaceae. Moreover, a diverse fungal community was also found in the roots of cycads and the predominating families were Ophiocordycipitaceae, Nectriaceae, Bionectriaceae, and Trichocomaceae. Our results demonstrated that bacterial diversity in normal roots of C. fairylakea is higher in richness and abundance than C. debaoensis. On the other hand, a slight difference, albeit insignificant, was noted for the diversity of fungi among root types and host species as the number of shared taxa is relatively high (67%). Our results suggested that diverse microbes are present in roots of cycads which potentially interact together to support cycads survival. Our study provided additional knowledge on the microbial diversity and composition in cycads and thus expanding our current knowledge on cycad-microbe association. Our study also considered the possible impact of ex situ conservation on cyanobiont community of cycads. [ABSTRACT FROM AUTHOR]

The present study focuses on investigating the phytochemical screening of indigenous species, C. zeylanica, for the first time. The leaf extracts have been prepared using ultrasound-assisted methods to obtain the best extraction results using different time and temperature conditions such as 30, 60, and 90 min. and 30, 40, and 60 °C, respectively. The results have been optimized using response surface methodology. Under the optimal extraction conditions of 60 °C for 43.57 minutes, an extract was produced with a yield of 0.238 g and a high total phenolic content of 181.1965 mg GAE/g. The total phenolic content has been evaluated and the presence of gallic acid has been confirmed through the HPLC technique. The optimal extract (OE) showed excellent antioxidant activity for the DPPH assay, with an IC 50 of 3.1 μg/ml. Finally, GC-MS profiling has been done to screen the volatile component of the plant extract., (© 2024 Wiley‐VHCA AG, Zurich, Switzerland.)

The literature containing which chemical elements are found in cycad leaves was reviewed to determine the range in values of concentrations reported for essential and beneficial elements. We found 46 of the 358 described cycad species had at least one element reported to date. The only genus that was missing from the data was Microcycas. Many of the species reports contained concentrations of one to several macronutrients and no other elements. The cycad leaves contained greater nitrogen and phosphorus concentrations than the reported means for plants throughout the world. Magnesium was identified as the macronutrient that has been least studied. Only 14 of the species were represented by data from in situ locations, with most of the data obtained from managed plants in botanic gardens. Leaf element concentrations were influenced by biotic factors such as plant size, leaf age, and leaflet position on the rachis. Leaf element concentrations were influenced by environmental factors such as incident light and soil nutrient concentrations within the root zone. These influential factors were missing from many of the reports, rendering the results ambiguous and comparisons among studies difficult. Future research should include the addition of more taxa, more in situ locations, the influence of season, and the influence of herbivory to more fully understand leaf nutrition for cycads. [ABSTRACT FROM AUTHOR]

The number of branches in male and female plants of Cycas micronesica K.D. Hill, Cycas edentata de Laub., Cycas wadei Merr., and Zamia encephalartoides D.W. Stev. were counted in Guam, Philippines, and Colombia, to confirm earlier reports that female plants develop fewer branches than males. Cycas plants produce determinate male strobili and indeterminate female strobili, but Zamia plants produce determinate strobili for both sexes. More than 80% of the female trees for each of the Cycas species were unbranched with a single stem, but more than 80% of the male trees exhibited two or more branches. The mean number of branches on male plants was more than double that of female plants. The number of branches of the Zamia male plants was almost triple that of female plants. Moreover, the Zamia plants produced 2.8-fold greater numbers of branches than the mean of the Cycas plants. Most of Guam's unsexed C. micronesica trees in 2004 were unbranched, but after 15 years of damage from non-native insect herbivores, most of the remaining live trees in 2020 contained three or more branches. The results confirm that male Cycas and Zamia plants produce more branches than female plants and suggest cycad species with determinate female strobili produce more branches on female plants than species with indeterminate female strobili. Our results indicate that the years of plant mortality on Guam due to non-native insect herbivores have selectively killed more female C. micronesica trees. Horticulture and conservation decisions may be improved with this sexual dimorphism knowledge. [ABSTRACT FROM AUTHOR]

Cycadales is an extant group of seed plants occurring in subtropical and tropical regions comprising putatively three families and 10 genera. At least one complete plastid genome sequence has been reported for all of the 10 genera except Microcycas, making it an ideal plant group to conduct comprehensive plastome comparisons at the genus level. This article reports for the first time the plastid genome of Microcycas calocoma. The plastid genome has a length of 165,688 bp with 134 annotated genes including 86 protein-coding genes, 47 non-coding RNA genes (39 tRNA and eight rRNA) and one pseudogene. Using global sequence variation analysis, the results showed that all cycad genomes share highly similar genomic profiles indicating significant slow evolution and little variation. However, identity matrices coinciding with the inverted repeat regions showed fewer similarities indicating that higher polymorphic events occur at those sites. Conserved non-coding regions also appear to be more divergent whereas variations in the exons were less discernible indicating that the latter comprises more conserved sequences. Phylogenetic analysis using 81 concatenated protein-coding genes of chloroplast (cp) genomes, obtained using maximum likelihood and Bayesian inference with high support values (>70% ML and = 1.0 BPP), confirms that Microcycas is closest to Zamia and forms a monophyletic clade with Ceratozamia and Stangeria. While Stangeria joined the Neotropical cycads Ceratozamia, Zamia and Microcyas, Bowenia grouped with the Southern Hemisphere cycads Encephalartos, Lepidozamia and Macrozamia. All Cycas species formed a distinct clade separated from the other genera. Dioon, on the other hand, was outlying from the rest of Zamiaceae encompassing two major clades—the Southern Hemisphere cycads and the Neotropical cycads. Analysis of the whole cp genomes in phylogeny also supports that the previously recognized family—Stangeriaceae—which contained Bowenia and Stangeria, is not monophyletic. Thus, the cp genome topology obtained in our study is congruent with other molecular phylogenies recognizing only a two-family classification (Cycadaceae and Zamiaceae) within extant Cycadales.

Cycas micronesica is a foundation species in several Micronesian islands and its seeds have been a historical source of starch for the island residents. The species has become endangered by invasive specialist insect herbivores and conservationists struggle with the inability to estimate the age of observed seeds. To inform this agenda, we evaluated numerous Cycas micronesica seed traits to determine if any exhibited a relationship with age and a substantial change in absolute value. Of the 30 direct and derived seed traits that we evaluated, most of them were non-linear and exhibited minimal change after about 12 months in age. The only traits that emerged as unambiguous estimators of age were the quotients derived as gametophyte fresh weight/total seed fresh weight and sarcotesta dry weight/sclerotesta dry weight. These two simple metrics can be used to accurately estimate seed age for this arborescent cycad species. [ABSTRACT FROM AUTHOR]

Molecular nitrogen (N2) constitutes the majority of Earth's modern atmosphere, contributing ~0.79 bar of partial pressure (pN2). However, fluctuations in pN2 may have occurred on 107–109 year timescales in Earth's past, perhaps altering the isotopic composition of atmospheric nitrogen. Here, we explore an archive that may record the isotopic composition of atmospheric N2 in deep time: the foliage of cycads. Cycads are ancient gymnosperms that host symbiotic N2‐fixing cyanobacteria in modified root structures known as coralloid roots. All extant species of cycads are known to host symbionts, suggesting that this N2‐fixing capacity is perhaps ancestral, reaching back to the early history of cycads in the late Paleozoic. Therefore, if the process of microbial N2 fixation records the δ15N value of atmospheric N2 in cycad foliage, the fossil record of cycads may provide an archive of atmospheric δ15N values. To explore this potential proxy, we conducted a survey of wild cycads growing in a range of modern environments to determine whether cycad foliage reliably records the isotopic composition of atmospheric N2. We find that neither biological nor environmental factors significantly influence the δ15N values of cycad foliage, suggesting that they provide a reasonably robust record of the δ15N of atmospheric N2. Application of this proxy to the record of carbonaceous cycad fossils may not only help to constrain changes in atmospheric nitrogen isotope ratios since the late Paleozoic, but also could shed light on the antiquity of the N2‐fixing symbiosis between cycads and cyanobacteria. [ABSTRACT FROM AUTHOR]

This study deals with specialized roots of cycads called coralloid roots accommodating a small population of heterotrophic bacteria and significantly abundant endosymbiotic cyanobacteria functioning as nitrogen fixers. This paper aimed to identify what other genes are present in the coralloid roots aside from genes for nitrogen metabolism to determine the functional repertoire of symbiotic coralloid roots. Genomic functional gene profiles were examined using DNA-based microarray GeoChip 5.0. GeoChip analysis suggests that the functional profiles between the two species are highly identical and almost all identified genes present in the coralloid roots were similar. Functional gene inventory identified elevated gene signals for metal homeostasis, carbon metabolism, stress responses, antibiotic resistance, organic contaminant degradation and nitrogen metabolism. This supports the role of symbionts residing in coralloid roots as nitrogen fixers and in increasing host tolerance to various environmental stressors as most genes covering major pathways for nitrogen cycling, metal resistance and toxin degradation were detected in our study. Moreover, indications of active photosynthesis and carbon fixing potential of symbionts in coralloid roots were also evident due to the detection of various carbon cycling genes. This could probably be associated to its apogeotropic growth via phototropism suggesting that symbionts require access to sunlight causing the negative geotropic growth of coralloid roots. [ABSTRACT FROM AUTHOR]

Cycadales is an extant group of seed plants occurring in subtropical and tropical regions comprising putatively three families and 10 genera. At least one complete plastid genome sequence has been reported for all of the 10 genera except Microcycas, making it an ideal plant group to conduct comprehensive plastome comparisons at the genus level. This article reports for the first time the plastid genome of Microcycas calocoma. The plastid genome has a length of 165,688 bp with 134 annotated genes including 86 protein-coding genes, 47 non-coding RNA genes (39 tRNA and eight rRNA) and one pseudogene. Using global sequence variation analysis, the results showed that all cycad genomes share highly similar genomic profiles indicating significant slow evolution and little variation. However, identity matrices coinciding with the inverted repeat regions showed fewer similarities indicating that higher polymorphic events occur at those sites. Conserved non-coding regions also appear to be more divergent whereas variations in the exons were less discernible indicating that the latter comprises more conserved sequences. Phylogenetic analysis using 81 concatenated protein-coding genes of chloroplast (cp) genomes, obtained using maximum likelihood and Bayesian inference with high support values (>70% ML and = 1.0 BPP), confirms that Microcycas is closest to Zamia and forms a monophyletic clade with Ceratozamia and Stangeria. While Stangeria joined the Neotropical cycads Ceratozamia, Zamia and Microcyas, Bowenia grouped with the Southern Hemisphere cycads Encephalartos, Lepidozamia and Macrozamia. All Cycas species formed a distinct clade separated from the other genera. Dioon, on the other hand, was outlying from the rest of Zamiaceae encompassing two major clades--the Southern Hemisphere cycads and the Neotropical cycads. Analysis of the whole cp genomes in phylogeny also supports that the previously recognized family--Stangeriaceae--which contained Bowenia and Stangeria, is not monophyletic. Thus, the cp genome topology obtained in our study is congruent with other molecular phylogenies recognizing only a two-family classification (Cycadaceae and Zamiaceae) within extant Cycadales. [ABSTRACT FROM AUTHOR]

Biomass has rich porous texture and unique physical and chemical properties, so it is widely used to enhance the electrochemical performances of lithium-sulfur batteries. In this paper, porous biochar is fabricated by easily obtained folium cycas. Acetic acid (HAc) is used to clean the ash content in cavity and solve the problem of pore blockage. The results showed that the folium cycas biochar (FCB) treated with HAc increased the specific surface area by 44.7% (2954 m2/g) and the cumulative pore volume by 67.5% (1.39 cm3/g). The FCB has rich nano-scale meso/microporous tubular pores which provide a natural high-efficiency space for sulfur storage and buffer the volume expansion, so that the prepared composite cathode material of FCB/S has a first discharge capacity of up to 1317 mAh/g and stable at 910 mAh/g after 5 cycles. The capacity can still reach 790 mAh/g after 200 cycles with an attenuation rate of only 0.068% for each cycle. [ABSTRACT FROM AUTHOR]

Premise Cycas is an important gymnosperm genus, and the most diverse of all cycad genera. The C. taiwaniana complex of species are morphologically similar and difficult to distinguish due to a lack of genomic resources. Methods We characterized the transcriptomes of two closely related and endangered Cycas species endemic to Hainan, China: C. hainanensis and C. changjiangensis. Three single‐copy nuclear genes in the C. taiwaniana complex were sequenced based on these transcriptomes, enabling us to evaluate the species boundaries using the multispecies coalescent method implemented in the Bayesian Phylogenetics and Phylogeography program. Results We obtained 68,184 and 81,561 unigenes for C. changjiangensis and C. hainanensis, respectively. We identified six positively selected genes that are mainly involved in stimulus responses, suggesting that environmental adaptation may have played an important role in the relatively recent divergence of these species. The similar KS distribution peaks at 1.0 observed for the paralogs in the two species indicate a common whole‐genome duplication event. Our species delimitation analysis indicated that the C. taiwaniana complex consists of three distinct species, which correspond to the previously reported morphological differences. Discussion Our study provides valuable genetic resources for Cycas species and guidance for the taxonomic treatment of the C. taiwaniana complex, as well as new insights into evolution of species within Cycas.

The spores of 11 species of Lomariocycas that grow in America were studied: Lomariocycas aurata , L. columbiensis , L. cycadifolia , L. insularis , L. magellanica , L. moritziana , L. rufa, L. schomburgkii, L. shaferi , L. underwoodiana and L. werckleana. The study was performed with light microscope (LM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The spores are monolete of 61–100 μm in equatorial diameter and 40–79 μm in polar diameter. The exospore is 1.5–4.8 μm thick and in section is two-layered. The perispore is folded, two types of folds were observed in the different species analyzed and also they could be fused in different ways. In section, it is 0.5–13.8 μm thick and is two-layered. The outer layer is single stratified and the inner layer is three-stratified. The spores of some species are illustrated and described for the first time. Moreover, the sporoderm ultrastructure of L. underwodiana was not studied until now. The differences found in perispore morphology and ultrastructure could be valuable characters for systematic and phylogenetic purposes. • The spores of Lomariocycas from America are folded. • Two types of folds are defined: (1) narrow and high, (2) wide and robust. • The two types of folds could be partially or totally fused. • The spores of some species are illustrated and described for the first time. • In the species analyzed the sporoderm ultrastructure is similar. [ABSTRACT FROM AUTHOR]

Crystalline, pasting and thermal properties and antioxidant activity of starch isolated from queen sago seed by using different isolation methods such as water steeping, alkali steeping and enzymatic extraction methods were evaluated. The properties studied include, chemical composition, morphology, swelling, solubility, color, X-ray diffraction (XRD), texture, pasting (RVA), total phenolic content, antioxidant activity and thermal (DSC) properties. Among the isolation methods, enzymatic extraction method is efficient as compared to alkali and water steeping method. Enzymatically extracted sago starch (ES) showed highest yield, L* value, swelling, solubility and lower non starch components. ES formed harder gel as compared to alkali steeped sago starch (AS) and water steeped sago starch (WS). SEM showed presence of more agglomerated granular structure in AS. ES showed highest peak, trough and break down viscosity. Setback and final viscosity was highest for AS. Isolation methods affected on the total phenolic content and antioxidant activity of queen sago seed starch. Highest gelatinization enthalpy of AS was correlated with higher relative crystallinity and presence of more agglomerated structure. The queen sago seed starch isolated by enzymatic extraction method has better properties and industrial relevance. [ABSTRACT FROM AUTHOR]

In this study, a novel composited catalyst (AgFe/biochar) was synthesized using sago cycas as carbon sources by a simple method and then used to activate peroxydisulfate for the degradation of Acid Orange II. The Ag0 in the AgFe/biochar was formed in the presence of biochar whereas the bimetallic oxide (AgFeO 2) was produced in the absence of biochar, which was attributed to the role of defect in biochar. This novel catalyst exhibited remarkably higher catalytic activity, as compared to other catalysts. The scavenging experiments and electron spin resonance results indicated that it coexisted the radical and non-radical species. It is confirmed that Ag+/ Ag0, Fe3+/Fe2+, defective sites and oxygen-containing groups in biochar were demonstrated to be extremely essential in the activating peroxydisulfate. This work not only offered a feasible approach for the synthesis of novel AgFe/biochar composites but also provided a useful method for the activation of peroxydisulfate to effectively remove organic pollutants in wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

Cycadophytes comprise ancient lineages of seed plants, and include Cycadales and Bennettitales. In this study, Phasmatocycas mazongshanensis sp. nov., represented by megasporophylls, is reported from the Lower Cretaceous of the Beishan area in Gansu Province, Northwest China. Based on the strip-shaped megasporophylls and ovules in two symmetrical rows, Phasmatocycas mazongshanensis is supposed to be closely related to Paleozoic primitive Cycadales. In addition, fossil leaves Pterophyllum beishanensis sp. nov. and Nilssoniopteris binggouensis are studied on leaf morphological and epidermal features. Syndetocheilic stomatal apparatus, thickened guard cells and curved anticlinal walls, all three features were observed on the epidermis, indicating that the leaves should be assigned to Bennettitales. The female reproductive organs of cycadophytes can be classified into four lineages: Phasmatocycas mode, Williamsonia mode, Cycas mode, and Zamia mode. Moreover, Phasmatocycas mazongshanensis is considered to be the lastest fossil record of Paleozoic-grade Cycadales. The reproduction of Phasmatocycas has previously been restricted to the Permian, but the new species, Phasmatocycas mazongshanensis , have been discovered from the Lower Cretaceous demonstrating its resurgence after a long absence from the stratigraphic record. [ABSTRACT FROM AUTHOR]

Trends in published cycad research within various fields of study were determined using proceedings from international conferences on cycad biology and Google Scholar to access the primary literature. Both search methods indicated that phylogeny, systematics and ecology are strongly represented in recent cycad literature, while there is a need for more research in horticulture and pathology, reviews and clarification of correspondence between current and discontinued species designations.

The literature containing which chemical elements are found in cycad leaves was reviewed to determine the range in values of concentrations reported for essential and beneficial elements. We found 46 of the 358 described cycad species had at least one element reported to date. The only genus that was missing from the data was Microcycas. Many of the species reports contained concentrations of one to several macronutrients and no other elements. The cycad leaves contained greater nitrogen and phosphorus concentrations than the reported means for plants throughout the world. Magnesium was identified as the macronutrient that has been least studied. Only 14 of the species were represented by data from in situ locations, with most of the data obtained from managed plants in botanic gardens. Leaf element concentrations were influenced by biotic factors such as plant size, leaf age, and leaflet position on the rachis. Leaf element concentrations were influenced by environmental factors such as incident light and soil nutrient concentrations within the root zone. These influential factors were missing from many of the reports, rendering the results ambiguous and comparisons among studies difficult. Future research should include the addition of more taxa, more in situ locations, the influence of season, and the influence of herbivory to more fully understand leaf nutrition for cycads.

The United States is currently home to five native cycad species. We provide a discussion on these five cycad species to illuminate how evolutionary and geopolitical processes influence phytogeography and published checklists of threatened plants. The number of threatened species in need of protection within any given country is a product of speciation that is contingent with evolutionary processes. However, this number may change instantaneously along with shifting of geopolitical boundaries brought about by armed conflict between rival states and multilateral negotiations. There are five contemporary cycad species within the United States, and the various historical bilateral and multilateral agreements that have generated this list are reviewed. Three of these five cycad species are threatened and in need of urgent protection. A discussion on the history of United States cycads as a microcosm of worldwide conservation issues is presented, with a focus on how federal conservation endeavors of individual nations may influence the world’s biodiversity crisis.

The number of branches in male and female plants of Cycas micronesica K.D. Hill, Cycas edentata de Laub., Cycas wadei Merr., and Zamia encephalartoides D.W. Stev. were counted in Guam, Philippines, and Colombia, to confirm earlier reports that female plants develop fewer branches than males. Cycas plants produce determinate male strobili and indeterminate female strobili, but Zamia plants produce determinate strobili for both sexes. More than 80% of the female trees for each of the Cycas species were unbranched with a single stem, but more than 80% of the male trees exhibited two or more branches. The mean number of branches on male plants was more than double that of female plants. The number of branches of the Zamia male plants was almost triple that of female plants. Moreover, the Zamia plants produced 2.8-fold greater numbers of branches than the mean of the Cycas plants. Most of Guam’s unsexed C. micronesica trees in 2004 were unbranched, but after 15 years of damage from non-native insect herbivores, most of the remaining live trees in 2020 contained three or more branches. The results confirm that male Cycas and Zamia plants produce more branches than female plants and suggest cycad species with determinate female strobili produce more branches on female plants than species with indeterminate female strobili. Our results indicate that the years of plant mortality on Guam due to non-native insect herbivores have selectively killed more female C. micronesica trees. Horticulture and conservation decisions may be improved with this sexual dimorphism knowledge.

Leaf gas-exchange responses to shadefleck-sunfleck and sun-cloud transitions were determined for in situ Cycas micronesica K.D. Hill plants on the island of Guam to add cycads to the published gymnosperm data. Sequential sunfleck-shadefleck transitions indicated understory leaves primed rapidly but open field leaves primed slowly. Time needed to reach 90% induction of net CO2 assimilation (PN) was 2.9 min for understory leaves and 13.9 min for open field leaves. Leaf responses to sun-cloud transitions exhibited minimal adjustment of stomatal conductance, so PN rapidly returned to precloud values following cloud-sun transitions. Results indicate bi-directional leaf acclimation behavior enables mature C. micronesica trees to thrive in deep understory conditions in some habitats and as emergent canopy trees in other habitats. These data are the first nonconifer gymnosperm data; the speed of gas-exchange responses to rapid light transitions was similar to some of the most rapid angiosperm species described in the literature. [ABSTRACT FROM AUTHOR]

Premise of research. The armored scale Aulacaspis yasumatsui Takagi has invaded numerous geographic regions to devastate cultivated populations of Cycas L. and the native population of Cycas micronesica K.D. Hill on the islands of Guam and Rota. Questions remain as to how this small hemipteran insect can so rapidly kill a large cycad tree. One possibility is depletion of nonstructural carbohydrates (NSCs) until the storage pool can no longer sustain plant viability.Methodology. We infested Cycas revoluta Thunberg plants with A. yasumatsui and harvested whole plants periodically until plant mortality at week 60. Harvested plants were separated into leaves, stems, and roots, and tissue was frozen and then lyophilized. The dry mass of each organ was measured, and then fructose, glucose, maltose, starch, and sucrose were quantified. Concentration and total pool size within each organ were calculated for each NSC.Pivotal results. Concentration and total pool of all five NSCs were greatest in stems. Concentrations exhibited linear or quadratic declines with time of infestation for all NSCs and organs, with the exception of glucose in stems and maltose in leaves. The total pool of all five NSCs declined linearly or quadratically in all three organs, with the exception of maltose in leaves. Initial plant dry mass of 152 g was 23% NSC, and ending plant dry mass of 59 g was 26% NSC. Carbohydrate stoichiometry shifted in favor of sugars over starch, and sugar stoichiometry shifted in favor of hexoses over disaccharides as time of infestation progressed.Conclusions. These results are consistent with carbohydrate depletion as the mechanism that explains rapid Cycas tree mortality during chronic A. yasumatsui infestation. This is the first demonstration of stress-induced expenditures of carbohydrates by cycads. [ABSTRACT FROM AUTHOR]