Journal of Plant Research最新文献

Reproductive interference, an interspecific interaction in reproductive process that exerts an adverse effect, has gained attention as a contributing factor in promoting exclusive distributions between closely related species. However, detailed studies on the possibility of reproductive interference between native plants are still lacking, presumably because strong reproductive interference can rapidly realize exclusive distributions, leaving the two species apparently independent. Salvia japonica and S. lutescens are found in separate localities at a small scale, although their distributions overlap at a large scale. We investigated the possibility of reproductive interference between them through field surveys, hand-pollination experiments, evaluation of hybrid fertility, cpDNA and nrDNA genotyping, and genome-wide DNA analysis. The field survey results did not reveal apparent negative interaction in competition for pollinator services. Mixed pollination with conspecific pollen and counterpart pollen reduced seed set in S. japonica, and hybrid progeny produced by mixed pollination were less than 20% as fertile compared to the pure species. The DNA genotyping results suggested the possibility of hybridization where their distributions overlap, and the genome-wide DNA analysis results showed clear genetic differentiation between the two species as well as the existence of hybrids. These results suggest that bi-directional reproductive interference between S. japonica and S. lutescens may have led to their present separated distributions at a small scale.

Soil salinization has been considered as a major environmental threat to plant growth. Different types of salt in saline soil have different effects on germination and seedling growth. Effect of NaCl on germination and seedling establishment in Suaeda liaotungensis have been reported, but its response to alkali stress remains unclear. Our results showed that brown seeds had higher germination rate, however, black seeds had higher germination recovery percentage under alkali stress. Na₂CO₃ had stronger inhibitory effect on germination and seedling growth than NaHCO₃. As the concentration of alkali stress increased, the ROS level of brown seeds gradually ascended, while that of black seeds decreased first and then ascended. MDA content of dimorphic seeds significantly increased under alkali stress. The trend of SOD, POD and CAT activity between dimorphic seeds was similar under the same type of alkali stress. Alkali stress enhanced proline content of dimorphic seeds, and dimorphic seeds in NaHCO₃ solution had higher proline content than Na₂CO₃ solution. Moreover, radicle and shoot tolerance indexes of seedlings in NaHCO₃ solution were significantly higher than that of Na₂CO₃ solution. Under strong alkali stress, seedlings in NaHCO₃ solution had significantly lower ROS level and MDA content as well as higher antioxidant enzyme activity than Na₂CO₃ solution. This study comprehensively compared the morphological and physiological characteristics in germination and seedlings to better reveal the saline-alkali tolerance mechanisms in S. liaotungensis.

The present study assesses the phylogenetic position of certain Thai members of Gymnema, Gymnemopsis, and Sarcolobus in relation to other known Marsdenieae species. Fifteen accessions newly sequenced from Thailand were added to the dataset of the homologous sequences of 125 accessions of Marsdenieae downloaded from GenBank. In our molecular phylogeny, almost all the delimited major clades and their relationships are largely congruent with those revealed in previous studies. The monophyly of Gymnema (including the former Jasminanthes species) and that of Sarcolobus, as presently circumscribed, are confirmed. The new accessions of these two genera from Thailand are well grouped with the members of their respective genera. Our analyses provide the first molecular evidence for recognition of Gymnemopsis, a small Asian genus that has never been included in the previous phylogenetic studies, as a distinct genus. All elements of Gymnemopsis are retrieved as a well-supported monophyletic group that is strongly supported as sister to Lygisma, another small Asian genus that most closely resembles it in growth habit, color of latex, indumentum on plant parts, corona structure and follicle traits. Combined molecular phylogenetic, morphological and ecological data also support recognition of two new Sarcolobus species from Thailand, Sarcolobus busbanianus sp. nov. and S. flavus sp. nov. Similarities and differences between these new species and their close relative, S. carinatus, are discussed. In addition, this study also reveals the first record for Thailand of Gymnema lacei. Keys to the species of Gymnemopsis (for all members of the genus), Gymnema and Sarcolobus (for Thai members of these genera) are provided.

A perennial pseudometallophyte Arabidopsis halleri is frequently infected with cucumber mosaic virus (CMV) in its natural habitat. The purpose of this study was to characterize the effect of CMV infection on the environmental adaptation of its natural host A. halleri. The CMV(Ho) strain isolated from A. halleri was inoculated into clonal virus-free A. halleri plants, and a unique plant-virus system consisting of CMV(Ho) and its natural wild plant host was established. In a control environment with ambient zinc supplementation, CMV(Ho) infection retarded growth in the above-ground part of host plants but conferred strong drought tolerance. On the other hand, in an excess zinc environment, simulating a natural edaphic environment of A halleri, host plants hyperaccumulated zinc and CMV(Ho) infection did not cause any symptoms to host plants while conferring mild drought tolerance. We also demonstrated in Nicotiana benthamiana as another host that similar effects were induced by the combination of excess zinc and CMV(Ho) infection. Transcriptomic analysis indicated that the host plant recognized CMV(Ho) as a mutualistic symbiont rather than a parasitic pathogen. These results suggest a resilient mutualistic interaction between CMV(Ho) and its natural host A. halleri in its natural habitat.

Cloud forests figure as one of the most diverse ecosystems, accounting not only for a high number of plant species but also with a great variety of interactions among them. A common interaction in these forests is the one between vascular epiphytes and their hosts. However, few studies have used the network approach to analyze them. Here, we analyze the horizontal and vertical structure of the vascular epiphyte - host network in a cloud forest in central Mexico. We quantified the number of epiphyte stands on each host both total and per-stratum. Complete network, group, and species metrics were estimated at both levels of analysis. The host - epiphyte networks had relatively low network size but were highly connected; moderately nested, with low specialization, and modularity; but higher vulnerability than generality, and high niche overlap. The community was composed by a high number of generalist species. To our knowledge this is the first study in which network analyses are conducted with standardized data and including all host and epiphyte species in the community. The analyses suggest that the networks are robust, and that functional redundancy might be probable, two advantageous characteristics in a very fragmented and threatened cloud forest.

The Khanka Lowland forest-steppe is the most eastern outpost of the Eurasian steppe biome. It includes unique grassland plant communities with rare steppe species. These coenosis have changed under the influence of anthropogenic activity, especially during the last 100 years and included both typical steppe species and nemoral mesophytic species. To distinguish these ecological groups of plants the random forest method with three datasets of environmental variables was applied. Specifically, a model of classification with the most important bioindices to predict a mesophytic ecological group of plants with a sensitivity greater than 80% was constructed. The data demonstrated the presence of steppe species that arrived at different times in the Primorye Territory. Most of these species are associated with the Mongolian-Daurian relict steppe complex and habit in the Khanka Lowland. Other species occur only in mountains in Primorye Territory and do not persist in the Khanka Lowland. These findings emphasize the presence of relict steppe communities with a complex of true steppe species in the Khanka Lowland. Steppe communities exhibit features of anthropogenic influence definitely through the long land use period but are not anthropogenic in origin. The most steppe species are located at the eastern border of distribution in the Khanka Lowlands and are valuable in terms of conservation and sources of information about steppe species origin and the emergence of the steppe biome as a whole.

The green alga Pediastrum duplex forms colonies through asexual reproduction and has a unique life cycle. To elucidate the mechanisms that regulate the asexual reproductive cycle in P. duplex, we analyzed the effects of light on the processes and gene expression involved in each step of the asexual reproductive cycle, revealing light irradiation to be essential for increasing the number of colonies. Among the processes in the asexual reproductive cycle, the transition from cell hypertrophy to zoospore formation could proceed even in the dark if glucose was added to the medium. Transcriptome analysis revealed that the expression of different groups of genes was significantly promoted or suppressed before and after the number of colonies increased. Our findings indicate that the asexual reproductive cycle of P. duplex includes a process promoted by photosynthesis. This study enhances our understanding of the growth characteristics of P. duplex and other microalgae.

Hibiscus is a charismatic genus of the Malvaceae family that is noted for its diversity, lacking identifiable characteristics for distinguishing its various species. Therefore, there is an urgent need to develop authentication methods for genus delimitation and species delineation. The present study aims to discern the taxonomic relationships between the well-known, globally familiar, and economically important five Hibiscus species, namely: H. × rosa-sinensis, H. sabdariffa, H. schizopetalus, H. syriacus and H. tiliaceus based on traditional morphological and anatomical characteristics compared to the contemporary chemotaxonomy. In this context, the leaf-based methanolic extracts of the studied species were analyzed by Gas Chromatography-Mass Spectrometer (GC-MS) to estimate their secondary metabolites similarity. In addition, selected qualitative morphological and anatomical traits including leaf venation patterns, epidermal micromorphology, stomata types and trichomes diversity, petiole serial sectioning (outline, adaxial groove features, vasculature traces arrangement), and midrib characteristics of the studied species were investigated. The results of both chemotaxonomy and traditional taxonomy exhibited a remarkable agreement in the delineation of the five studied species. Specifically, the chemotaxonomy-based dendrogram separates the studied species into two main clusters with the H. sabdariffa as an outlier species in a single cluster and the remaining four species as another cluster with variant distances in its similarity indices. Similarly, the traditional morphological and anatomical characteristics revealed distinct traits for H. sabdariffa compared to the remaining four species. The findings of this study highlight the significance of integrating the structural features with phytochemicals profiling as a potential approach that could be harnessed for the delineation of the taxonomically challenging Hibiscus genus.

The vascular bundle in the ear-internode of maize is a key conduit for transporting photosynthetic materials between "source" and "sink", making it critically important to examine its micro-phenotypes and genetic architecture to identify advantageous characteristics and cultivate high-yielding and high-quality varieties. Unfortunately, the limited observation methods and scope of study precludes any comprehensive and systematic investigations into the microscopic phenotypes and genetic mechanisms of vascular bundle in maize ear-internode. In this study, 47 phenotypic traits were extracted in 495 maize inbred lines using micro computed tomography (Micro-CT) scanning technology and a deep learning-based phenotype acquisition method for stem vascular bundle, which included stem slice-related, epidermis zone-related, periphery zone-related, inner zone-related and vascular bundles-related traits. Phenotypic analysis indicated that there was extensive phenotypic variation of vascular bundle traits in ear-internode, especially that in the inner zone. Of these, 30 phenotypic traits with heritability greater than 0.70 were conducted for GWAS, and a total of 4,225 significant SNPs and 416 candidate genes with detailed functional annotations were identified. Furthermore, 20 genes were highly expressed in stem-related tissues, especially in maize internodes. Functional analysis of candidate genes indicated that the pathways obtained for candidate genes of different trait groups were distinct, mainly involved in vitamin synthesis and metabolism, transport of substances, carbohydrate derivative catabolic process, protein transport and localization, and anatomical structure development. The results of this study will help to further understand the phenotypic traits of stem vascular bundles and provide a reference for revealing the genetic mechanism of maize ear-internode vascular bundles.

Land plants have evolved many systems to adapt to a wide range of environmental stresses. In seed plants, oligogalactolipid synthesis is involved in tolerance to freezing and dehydration, but it has not been analyzed in non-vascular plants. Here we analyzed trigalactosyldiacylglycerol (TGDG) synthesis in Marchantia polymorpha. TGDG is synthesized by galactolipid: galactolipid galactosyltransferase [GGGT; SENSITIVE TO FREEZING2 (SFR2) in Arabidopsis]. We analyzed the subcellular localization and GGGT activity of two M. polymorpha SFR2 homologs (MpGGGT1 and MpGGGT2, each as a GFP-fusion protein) using a transient expression system in Nicotiana benthamiana leaves and found that MpGGGT1-GFP localized in the chloroplast envelope membrane. We produced mutants Mpgggt1 and Mpgggt2 and found that TGDG did not accumulate in Mpgggt1 upon treatment of the thallus with acetic acid. Moreover, growth of Mpgggt1 mutants was impaired by acetic acid treatment. Microscopy revealed that the acetic acid treatment of M. polymorpha plants damaged intracellular membranes. The fact that the effect was similar for wild-type and Mpgggt1 plants suggested that MpGGGT has a role in recovery from damage. These results indicate that MpGGGT plays a crucial role in M. polymorpha growth under conditions of acid stress, which may have been encountered during the ancient terrestrial colonization of plants.