Abstract For sample preparation of biological block sectioning, high pressure freezing and freeze substitution (HPF-FS) is a better choice than chemical fixation. Freezing fixation can retain the original structures and preserve the soluble materials, and avoid the disadvantage of chemical fixation. Using high-pressure freezing, plant tissues are more difficult to freeze successfully than animal tissues and microbes because they have cell walls and varying degrees of vacuolation. For plant tissues, including the roots of Arabidopsis thaliana , 1-hexadecene is an ideal cryoprotectant/filler. The ability of highly vacuolated plant tissues (such as mature leaves and petals) to effectively remove intercellular air is crucial for successful high pressure freezing. Using the anthers of Arabidopsis thaliana , the leaves of Brachypodium distachyon , Axonopus compressus and Plantago asiatica , and the petals of Phalaenopsis bellina as examples, we found an effective method to remove air from the intercellular spaces: plant tissue in 1-hexadecene is placed in a vacuum desiccator, and then the air is removed using a vacuum pump, resulting in the release of numerous air bubbles. Plant tissue samples taken at different degassing times are then subjected to high pressure freezing and the subsequent required procedures of sample preparation. Based on the presentation of fine structures, the optimal time for different plant tissues can be determined and shows a positive correction with sample thickness. Good HPF-FS results show that the lipid bilayer within each organelle of the plant cells is clearly visible.
Abstract Physalis gracilis is a wild perennial herb with sweet, orange-colored fruits harvested for household consumption in Mexico. For species with potential for cultivation and nutritional value, a basic information is known their reproductive system. This study aimed to evaluate the reproductive system of P. gracilis and its agronomic performance. Floral longevity and development stages were determined in 30 flower buds until floral senescence, using individuals grown under greenhouse and open-field conditions. Six artificial cross treatments were conducted to characterize the reproductive system, and self-incompatibility and pollen limitation indices were calculated. Stigma receptivity was assessed using hydrogen peroxide. To assess agronomic performance, an open-field crop was established within three accessions, each with 48 individuals (in total 144 plants); six descriptors were evaluated from five fruits per plant per descriptor. Artificial crossing showed that the three accessions exhibited a completely self-incompatible reproductive system; however, it was not pollen limitated. P. gracilis responded positively to agricultural management (93.8% plant survival) and showed a potential average yield of 8.178 t·ha − 1 . Equatorial diameter of the fruit ranged from 11 to 22 mm. The average sweetness was 11.29° Brix, and the pH was 4.18. This study demonstrates that P. gracilis could be a candidate as a new open-field crop with desirable fruit traits, such as weight, size, and sweetness.
French Guiana is one of the earliest regions in the Neotropics where Xylaria species were extensively explored, notably by François Mathias René Leprieur during the 1830s, with many taxa subsequently described as new by Jean Pierre François Camille Montagne. Despite this long history and its clear biogeographical importance, the Xylaria diversity of French Guiana has remained insufficiently documented. Numerous species have been poorly defined, misidentified, or lack molecular data, and no modern, integrative synthesis combining morphology, typification, and phylogenetics has been available for the region. Based on extensive recent field collections by two of us (JF and CL) and a re-examination of historical material, a total of 98 taxa of Xylaria are documented from French Guiana, with X. cantareirensis and X. guadalupensis additionally treated from Brazil and the French West Indies, respectively. Among these, 39 taxa are considered novel to science, including 38 newly described species and one newly recombined name. Multilocus phylogenetic analyses based on protein-coding loci support the separation of the analyzed taxa and clarify relationships among morphologically similar taxa. Of the newly described species, 37 were included in the phylogenetic analyses and are further confirmed as distinct. Several species closely related to X. scruposa are shown to constitute a species complex. Numerous historical names originally reported from French Guiana are re-evaluated through type studies, epitypifications, and critical morphological reassessments. These results highlight the remarkable Xylaria species richness of the region. This study demonstrates that French Guiana harbors a remarkably rich and complex Xylaria diversity that remains only partially resolved. The integration of detailed morphology and molecular phylogenetics reveals a much higher level of diversity than previously recognized and exposes significant taxonomic uncertainty in several species complexes. These findings underscore the need for continued sampling, especially of fresh material suitable for culturing, sequencing, and emphasize the importance of French Guiana as a key region for understanding the taxonomy, evolution, and biogeography of Xylaria in the Neotropics.
Abstract Background Fusarium wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici (FOL) is a serious disease. Host resistance and soil fumigation may reduce the impact of FOL, but the effectiveness may decrease over time due to the diversity and evolution of pathogens. Silicon is the second most abundant element in the Earth’s crust, but has been overlooked in crop protection due to its poor availability to plants. Silicate-solubilizing bacteria (SSB) are reported to enhance soil nutrition, plant growth, and stress tolerance by transforming inorganic silicon into a plant-available form. Hence, SSB with antimicrobial properties can act as green alternatives to fungicides. Therefore, this study aims to isolate rhizospheric SSB and uncover their benefits in crop protection. Results Among thirteen potentially beneficial strains identified through 16S rDNA sequencing, Burkholderia contaminans NRBC (NRBC) and Burkholderia sp. NRBA (NRBA) were chosen for greenhouse experiments to evaluate their effectiveness in promoting plant growth and suppressing FOL (race 2). Under normal greenhouse conditions, the co-application of NRBC and silicon significantly increased shoot dry weight. Under FOL stress, all bacteria-treated groups were taller than the control groups. Bacterial treatments significantly reduced disease incidence and suppressed disease progression with no significant effect of the silicon supplement. The expression profiling of some defense-related genes revealed that soil-inoculation with NRBA and NRBC induced transcriptional patterns consistent with the involvement of salicylic acid (SA) and jasmonic acid/ethylene (JA/ET)-related defense responses. Conclusions SSB isolates, NRBA and NRBC, are effective standalone biocontrol agents for managing Fusarium wilt in tomato. Silicon supplementation did not show the anticipated plant growth promotion of tomato plants and FOL suppression.
Abstract Background Carex subg. Siderosticta is one of the six subgenera recognized in the recently revised infrageneric classification of Carex based on phylogenetic studies. It represents the earliest-diverging lineage within Carex and it is sister to all remaining species in the genus. This morphologically diverse subgenus is distributed across East and Southeast Asia. Historically, the approximately 30 species of this subgenus were assigned to four morphology-based sections, namely Siderostictae , Hemiscaposae , Surculosae , and Hypolytroides . Results Phylogenetic analyses based on three plastid ( matK , ndhF , and rps16 ) and two nuclear (ETS and ITS) DNA markers recovered the four individuals of Carex ensiformis as a strongly supported monophyletic lineage. Micromorphological observations revealed that C. ensiformis differs from the morphologically similar species C. damiaoshanensis in the slightly undulate anticlinal cell walls of the nutlet epidermis and a markedly shorter beak at the nutlet apex. Morphologically, the new species can be distinguished from C. damiaoshanensis by its more numerous inflorescence branches and spikes, as well as smaller utricles, nutlets, and shorter glumes. Conclusions Both morphological and molecular evidence reveal that Carex ensiformis is a new species belonging to subg. Siderosticta from southern China. The discovery of this species enriches our understanding of species diversity and taxonomic complexity within the subgenus, and emphasizes the importance of continued taxonomic studies in this part of Asia.
