Rorippa Species Research Articles

Phylotranscriptomics provides a treasure trove of flood-tolerance mechanisms in the Cardamineae tribe.

Flooding events are highly detrimental to most terrestrial plant species. However, there is an impressive diversity of plant species that thrive in flood-prone regions and represent a treasure trove of unexplored flood-resilience mechanisms. Here we surveyed a panel of four species from the Cardamineae tribe representing a broad tolerance range. This included the flood-tolerant Cardamine pratensis, Rorippa sylvestris and Rorippa palustris and the flood-sensitive species Cardamine hirsuta. All four species displayed a quiescent strategy, evidenced by the repression of shoot growth underwater. Comparative transcriptomics analyses between the four species and the sensitive model species Arabidopsis thaliana were facilitated via de novo transcriptome assembly and identification of 16 902 universal orthogroups at a high resolution. Our results suggest that tolerance likely evolved separately in the Cardamine and Rorippa species. While the Rorippa response was marked by a strong downregulation of cell-cycle genes, Cardamine minimized overall transcriptional regulation. However, a weak starvation response was a universal trait of tolerant species, potentially achieved in multiple ways. It could result from a strong decline in cell-cycle activity, but is also intertwined with autophagy, senescence, day-time photosynthesis and night-time fermentation capacity. Our data set provides a rich source to study adaptational mechanisms of flooding tolerance.

Complete Plastomes of Ten Rorippa Species (Brassicaceae): Comparative Analysis and Phylogenetic Relationships

The genus Rorippa belongs to the family Brassicaceae, and its members usually have high medicinal value. The genus consists of approximately 75 species and mainly grows in the Northern Hemisphere, occurring in every continent except Antarctica. The taxonomy and phylogenetic relationships of Rorippa are still unsettled, largely due to complex morphological variations in Rorippa, which were caused by frequent hybridization events. Here, we sequenced four complete plastid genomes of Rorippa species by Illumina paired-end sequencing. The four new plastid genomes of Rorippa ranged in total size from 154,671 bp for R. palustris to 154,894 bp for R. sylvestris. There are 130 genes in the four plastomes, embodying 8 rRNA, 37 tRNA, and 85 protein-coding genes. Combining with six published plastid genomes, we carried on comparative and phylogenetic analyses. We found that the ten Rorippa plastid genomes were conservative in gene number and order, total size, genomic structure, codon usage, long repeat sequence, and SSR. Fourteen mutational hotspot regions could be selected as candidate DNA barcoding to distinguish Rorippa plants. The phylogenetic trees clearly identified that ten Rorippa species displayed monophyletic relationships within the tribe Cardamineae based on plastomes and nrDNA ITS sequences. However, there are significant cytonuclear discordances in the interspecific relationships within Rorippa, as well as the intergeneric relationships between Rorippa and its related genera. We inferred that the cytonuclear discordance is most likely a result of interspecific hybridization within Rorippa, as well as intergeneric hybridization with its related genera. These plastid genomes can offer precious information for studies of species authentication, evolutionary history, and the phylogeny of Rorippa.

<strong>A new <em>Rorippa</em> species (Brassicaceae), <em>R. hengduanshanensis</em>, from the Hengduan Mountains in China</strong>

A new species of genus Rorippa, R. hengduanshanensis, from the Hengduan Mountains, is described herein. Comparing the floral structure and overall fruit morphology of R. hengduanshanensis with similar taxa (e.g., R. benghalensis, R. dubia, and R. indica) revealed a series of morphological differences, both qualitative and quantitative. R. hengduanshanensis differs from R. benghalensis in the ebracteate racemes; from R. dubia in the flattened silique, the presence of four petals and the ploidy level (2n=6x=48); and from R. indica in the uniseriate seeds. Phylogenetic analyses using three plastid markers (psbC-trnS, trnG-trnM, and trnL) further revealed clear interspecific divergences that can distinguish R. hengduanshanensis from its morphologically related taxa.

Effects of Cadmium Stress on Photosynthetic Physiological Characteristics of Two Rorippa Species

The photosynthetic physiological characteristics of Rorippa amphilia and Rorippa sylvestris were studied by pot experiment under Cd stress, and 7 Cd treatments were 0, 1, 5, 10, 50, 100, 200（mg·kg-1）respectively. The results showed that, (1) The Chla, chlb, and Ch(la+b) changed little when the Cd concentration in the soil was less than 100 mg·kg-1. There was no significant difference among the treatments. When Cd concentration was more than or equal to 100 mg·kg-1, all indexes decreased significantly, Chla/b increased gradually with the increase of Cd stressful concentration; (2) Net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) first increased and then decreased with the increase of Cd stressful concentration, while intercellular carbon dioxide concentration (Ci) increased significantly; (3) The photochemical quenching coefficient (qP) and electron transfer rate (ETR) decreased gradually with the increase of Cd stressful concentration, while the non-photochemical quenching coefficient (NPQ) increased with the increase of Cd stress concentration. It indicated that the photosynthetic mechanism of leaves was damaged; the maximum photochemical quantum yield (Fv/Fm) and potential activity (Fv/Fo) of PSII decreased gradually with the increase of Cd stress concentration. When Cd concentration was more than 50 mg·kg-1, the decrease was very obvious, showing photoinhibition. The concentration of Cd below 50 mg·kg-1 had little effect on photosynthesis. These results provide a theoretical application by using these two species of Rorippa to ecological restore the Cd contaminated farmland and abandoned mines.

The Effect of Temperature on Seed Germination and Seedling Growth of Two Invasive Plants in Rorippa

Aims: By studying the response of seed germination and seedling growth of invasive plants, Rorippa amphibia and Rorippa sylvestris, to temperature, the influence of temperature on the invasive ability of two species of Rorippa were further analyzed, which provided a theoretical basis for revealing the diffusion and invasion mechanism of two invasive plants in Rorippa.
 Study Design: Seed germination and seedling growth test of two invasive plants in Rorippa at different temperature was studied by means of laboratory culture. The germination percentage, germination index, germination potential of the seeds and the total leaf number, root length, lateral root number, biomass and root shoot ratio of seedlings were determined.
 Place and Duration of Study: Seeds were collected from the Shenyang Agricultural University of Liaoning Province in July 2018. Experiments were done in the College of Bioscience and Biotechnology, and conducted in April 2019 for a month.
 Methodology: The petri dish method was used at the experiment of seed germination. The seedling growth experiment was carried out by pot sowing.
 Results: At the seedling stage.R. amphibia has the strongest tolerance at 30°C, while the R. sylvestris does at 35°C. The low temperature is more beneficial to the accumulations of the seedlings, R. amphibia is the most tolerant at 25°C, and R. sylvestris is at 30°C at the seedling stage.
 Conclusion: The response of the seeds and seedlings of the two species to temperature was basically the same. Higher temperature promoted seed germination and inhibited seedling growth, while lower temperature inhibited seed germination. The response of seeds and seedlings of R. sylvestris to high temperature makes it more invasive in the process of global warming.

Phenolic profiling of Rorippa palustris (L.) Besser (Brassicaceae) by LC-ESI-MS: Chemosystematic significance and cytotoxic activity

ObjectiveTo investigate the phenolic profile of Rorippa palustris (R. palustris) compared to Egyptian Rorippa species to evaluate their chemosystematic significance as well as screen cytotoxicity of R. palustris extract. MethodsThe chemical components of defatted hydroalcoholic R. palustris extract were analyzed using liquid chromatography-electrospray ionization mass spectrometry technique. The cytotoxic activity was evaluated by using MTT assay against four carcinoma cell lines. ResultsSixteen compounds corresponding to flavonoids (kaempferol and quercetin derivatives), phenolic acids (gallic, coumaric and ferulic acids derivatives) and an anthocyanin (delphinine derivative) were identified or tentatively characterized, of which ten compounds were detected for the first time from R. palustris. Moreover, R. palustris extract showed a moderate activity against MCF7 and A549 cell lines at 100 mg/mL with cell viability of 47.3% and 65.4%, respectively. ConclusionsThe phenolic profile and the morphological characters of R. paluatris seem to be in relation with those of Rorippa indica, which can be considered as an indicative parameter for its medicinal importance.

Group VII Ethylene Response Factor diversification and regulation in four species from flood‐prone environments

Flooding events negatively affect plant performance and survival. Flooding gradients thereby determine the dynamics in vegetation composition and species abundance. In adaptation to flooding, the group VII Ethylene Response Factor genes (ERF-VIIs) play pivotal roles in rice and Arabidopsis through regulation of anaerobic gene expression and antithetical survival strategies. We investigated if ERF-VIIs have a similar role in mediating survival strategies in eudicot species from flood-prone environments. Here, we studied the evolutionary origin and regulation of ERF-VII transcript abundance and the physiological responses in species from two genera of divergent taxonomic lineages (Rumex and Rorippa). Synteny analysis revealed that angiosperm ERF-VIIs arose from two ancestral loci and that subsequent diversification and duplication led to the present ERF-VII variation. We propose that subtle variation in the regulation of ERF-VII transcript abundance could explain variation in tolerance among Rorippa species. In Rumex, the main difference in flood tolerance correlated with the genetic variation in ERF-VII genes. Large transcriptional differences were found by comparing the two genera: darkness and dark submergence-induced Rumex ERF-VIIs, whereas HRE2 expression was increased in submerged Rorippa roots. We conclude that the involvement of ERF-VIIs in flooding tolerance developed in a phylogenetic-dependent manner, with subtle variations within taxonomic clades.

Learning from nature: the use of non-model species to identify novel acclimations to flooding stress.

Excess water in the form of waterlogged soil or deeper submergence (generically termed 'flooding') influences plant growth, survival and species distribution in many natural ecosystems. It also has a negative impact on crop growth and yield since many agricultural species are flooding intolerant. The often devastating effect of flooding on plant performance is related to its interference with gas exchange between the plant and its environment. This results in energy deficiency and carbohydrate starvation. In the near future, flooding frequency is expected to increase due to global climate change and the human population is expected to increase to ∼9 billion people by 2050. The need for increased agricultural productivity is self-evident and this will require a better mechanistic understanding of the interaction between plants and abiotic stresses such as flooding. We argue that, in seeking this understanding, we should not restrict the research to model species such as rice (Oryza sativa) and Arabidopsis (Arabidopsis thaliana). This is because some stress-tolerance mechanisms are not found in these species. Examples are given of how flooding tolerance is achieved by non-model species of Rumex and Rorippa that have evolved to cope with flooding in natural environments. These findings will add usefully to the spread of resources available to plant breeding programmes aimed at improving flooding tolerance in crop plants.

Root transcript profiling of two Rorippa species reveals gene clusters associated with extreme submergence tolerance.

Complete submergence represses photosynthesis and aerobic respiration, causing rapid mortality in most terrestrial plants. However, some plants have evolved traits allowing them to survive prolonged flooding, such as species of the genus Rorippa, close relatives of Arabidopsis (Arabidopsis thaliana). We studied plant survival, changes in carbohydrate and metabolite concentrations, and transcriptome responses to submergence of two species, Rorippa sylvestris and Rorippa amphibia. We exploited the close relationship between Rorippa species and the model species Arabidopsis by using Arabidopsis GeneChip microarrays for whole-genome transcript profiling of roots of young plants exposed to a 24-h submergence treatment or air. A probe mask was used based on hybridization of genomic DNA of both species to the arrays, so that weak probe signals due to Rorippa species/Arabidopsis mismatches were removed. Furthermore, we compared Rorippa species microarray results with those obtained for roots of submerged Arabidopsis plants. Both Rorippa species could tolerate deep submergence, with R. sylvestris surviving much longer than R. amphibia. Submergence resulted in the induction of genes involved in glycolysis and fermentation and the repression of many energy-consuming pathways, similar to the low-oxygen and submergence response of Arabidopsis and rice (Oryza sativa). The qualitative responses of both Rorippa species to submergence appeared roughly similar but differed quantitatively. Notably, glycolysis and fermentation genes and a gene encoding sucrose synthase were more strongly induced in the less tolerant R. amphibia than in R. sylvestris. A comparison with Arabidopsis microarray studies on submerged roots revealed some interesting differences and potential tolerance-related genes in Rorippa species.

Wait or escape? Contrasting submergence tolerance strategies of Rorippa amphibia, Rorippa sylvestris and their hybrid

Differential responses of closely related species to submergence can provide insight into the evolution and mechanisms of submergence tolerance. Several traits of two wetland species from habitats with contrasting flooding regimes, Rorippa amphibia and Rorippa sylvestris, as well as F(1) hybrid Rorippa × anceps were analysed to unravel mechanisms underlying submergence tolerance. In the first submergence experiment (lasting 20 d) we analysed biomass, stem elongation and carbohydrate content. In the second submergence experiment (lasting 3 months) we analysed survival and the effect of re-establishment of air contact on biomass and carbohydrate content. In a separate experiment we analysed expression of two carbohydrate catabolism genes, ADH1 and SUS1, upon re-establishment of air contact following submergence. All plants had low mortality even after 3 months of submergence. Rorippa sylvestris was characterized by 100 % survival and higher carbohydrate levels coupled with lower ADH1 gene expression as well as reduced growth compared with R. amphibia. Rorippa amphibia and the hybrid elongated their stems but this did not pay-off in higher survival when plants remained submerged. Only R. amphibia and the hybrid benefited in terms of increased biomass and carbohydrate accumulation upon re-establishing air contact. Results demonstrate contrasting 'escape' and 'quiescence' strategies between Rorippa species. Being a close relative of arabidopsis, Rorippa is an excellent model for future studies on the molecular mechanism(s) controlling these strategies.

Three new phylogenetic lineages are the closest relatives of the widespread species Albugo candida

White blister rust caused by the obligate biotroph Albugo candida ( Albuginaceae; Oomycota) is one of the most notorious and common diseases of Brassicaceae. During the past 5 y, A. candida specimens collected from about 30 host genera were phylogenetically and morphologically investigated in several studies. These not only revealed that A. candida s.str. has a broad host range, encompassing a large number of host plants belonging to Brassicales, but also the presence of previously overlooked species of Albugo with hosts in this order. In this study, we examined specimens from Alyssum, Barbarea, and Rorippa, of which many species were commonly recorded as host plants of A. candida but could not be included in previous works due to the paucity of specimens available. It was revealed that Albugo specimens from Alyssum montanum, Barbarea vulgaris, and various Rorippa species, were placed in three phylogenetically distinct clades, but closer to A. candida s.str. than any previously reported species. Oospores were observed from Albugo specimens parasitic to Rorippa and could be distinguished morphologically from A. candida. Therefore, Albugo rorippae sp. nov. is described and illustrated here. In addition, a key of Albugo species described previously from Brassicales is given. The present study reveals that a large number of Albugo species remain still undiscovered, and that species close to A. candida exist. This could help elucidating the basis of the broad host range of A. candida as opposed to the narrow specialisation that is seemingly present in other species of Albugo on the Brassicaceae.

Rorippa apetala: A new species of Rorippa Scopoli. (Brassicaceae) from Korea

Herein is described a new species of Rorippa (R. apetala, Brassicaceae) discovered on the River Seom-gang in Wonju-si, Gangwon-do, Korea. The new species is distinct from the closely-related species, R. palustris and R. globosa, by having adventitious buds on the surface of rhizome-type roots during the fruiting season, usually absent or rarely 1-4, if present then atrophy petals, obpandurate fruits, and seeds usually empty or rarely 1-2 per locule. The key to these species is provided.

Interspecific hybridization in Rorippa (Brassicaceae): Patterns and processes

The current knowledge on natural hybridization between European lowland Rorippa species is reviewed. Morphological, cytological and molecular markers provide substantial evidence that four Rorippa species (R. amphibia, R. austriaca, R. palustris and R. sylvestris) are involved in hybridization processes. The main factors promoting initial hybridization events between Rorippa species in Europe are (1) natural and anthropogenic habitat disturbance, (2) the invasion of non‐native R. austriaca into western central Europe and (3) the self‐incompatibility system of R. amphibia, R. austriaca and R. sylvestris coupled with clonal growth. Outcomes of hybridization between European Rorippa species show a broad range from incidental hybrids through the formation of hybrid swarms to the evolution of new hybrid taxa. Rorippa × armoracioides is certainly the most successful Rorippa hybrid. It results from hybridization between R. austriaca and R. sylvestris and is known from many localities in the native range of R. austriaca and in regions invaded by R. austriaca. Within this system hybrid zones of different age provide the rare opportunity to analyse different stages of hybrid formation and hybrid speciation in natural populations.

Evolutionary Processes Associated with Biological Invasions in the Brassicaceae

This review highlights evolutionary processes in the Brassicaceae which cause, accompany or are a consequence of biological invasions. Case studies in Capsella and Diplotaxis address the genetics of colonising species. The greatest colonising ability in Capsella bursa-pastoris is associated with polyploidy, predominant selfing, and high genetic diversity. Success of colonial populations seems to be due to the introduction of preadapted genotypes. Colonising species in Diplotaxis reveal contrasting evolutionary patterns. Genetic attributes in D. muralis include annuality, polyploidy, and predominant selfing. Very different from Capsella, D. muralis is nearly devoid of genetic diversity as revealed by molecular markers. In contrast to D. muralis, the colonising D. tenuifolia is perennial, diploid, self-incompatible, and displays high genetic diversity. Hybrid speciation, establishment of the hybrids in man-made habitats, stabilisation of their reproductive system, and reproductive isolation from the parent populations were analysed in Cardamine. The Nasturtium example highlights the importance of hybridisation for the evolution of invasiveness. The last case study concentrates on the evolutionary consequences of hybridisation between native and invading Rorippa species. Introgressive hybridisation between the invasive Rorippa austriaca and native Rorippa species is common and widespread in central Europe, and interspecific gene transfer has led to the formation of a new invasive genotype. Each successful invasion presents new aspects and sound case studies are needed in order to understand the ecology and evolution of the colonisation process and to enable us to assess the evolutionary consequences of biological invasions.

Chloroplast DNA Variation and Biogeography in the Genus Rorippa Scop. (Brassicaceae)

Abstract: Phylogenetic relationships and biogeography of 25 Rorippa species were studied using sequences of two non‐coding regions of chloroplast DNA (trnL intron, trnL/F spacer). Our results indicate a close relationship between European (R. islandica ssp. islandica, R. pyrenaica) and North American (R. curvipes, R. sinuata) mountain species. The polyploid European lowland species R. amphibia, R. palustris and R. sylvestris are much younger than the mountain species and have their closest relatives in western Asia and Siberia. Different colonization routes of the southern hemisphere are discussed for Rorippa. Australasia was colonized at least twice, most likely via the Malayan route. A molecular clock approach dates the first colonization to the end of Pliocene or early Pleistocene. R. gigantea reached Australia later in the Pleistocene. Our data provide evidence for an amphitropical disjunction between the South American (R. philippiana) and North American (R. curvisiliqua) species. Long‐distance dispersal via migrating birds is the most likely explanation for this intercontinental disjunction. Two of the analysed African species (R. nudiuscula, R. madagascariensis) have their closest relative (R. austriaca) in eastern Europe and western Asia. The lack of sequence divergence among these species indicates a colonization event probably not earlier than 100 000 years ago.

Introgressive hybridization in Rorippa (Brassicaceae): gene flow and its consequences in natural and anthropogenic habitats.

Introgressive hybridization between three Rorippa species (R. amphibia, R. palustris and R. sylvestris) in northern Germany has been studied using isozymes and noncoding chloroplast DNA (trnL/F spacer). Our results provide substantial evidence for different patterns of gene flow in natural and in anthropogenic environments. Hybridization and bi-directional introgression (chloroplast DNA and allozymes) between R. amphibia and R. sylvestris were detected at the river Elbe, which is one of the last rivers in Central Europe showing a natural dynamic of erosion and sedimentation. The natural dynamic of the Elbe leads to periodic habitat disturbance and the temporal breakdown of ecological isolation barriers between R. amphibia and R. sylvestris. However, the high dynamic does not provide the opportunity for persistence of the morphologically intermediate hybrid R. x anceps (R. amphibia x R. sylvestris). We did not find hybrid zones between R. amphibia and R. sylvestris in the more anthropogenic landscape of northwest Germany. However, contact zones between R. amphibia and R. palustris were detected in drainage ditches in northwest Germany. We found substantial evidence for unidirectional introgression of R. palustris markers (chloroplast DNA and allozymes) into R. amphibia in the man-made habitats. The R. amphibia introgressants in the drainage ditches often showed strongly serrate upper cauline leaves instead of the entire upper cauline leaves typical for R. amphibia. We argue that landscape melioration in northwest Germany, particularly the creation of drainage ditches, favoured both hybrid-zone formation and ecotypic differentiation within R. amphibia.

Genetic diversity within commercial populations of watercress (Rorippa nasturtium-aquaticum), and between allied Brassicaceae inferred from RAPD-PCR

Commercial productivity of watercress (Rorippa nasturtium-aquaticum) can be adversely affected by the pathogenic crook-root fungus, Spongospora subterranea f.sp. nasturti, and watercress viruses. As there are no effective control measures for these diseases, attempts have been made to breed varieties resistant to the crook-root pathogen. This work has been hindered by a lack of knowledge of the genetic base of commercial watercress, and the genetic distance between watercress and allied Brassicaceae which have been identified as candidates for hybridisation programmes. We measured the diversity within these two groups using the RAPD-PCR fingerprinting technique and analysed the data by both distance methods and principal co-ordinate analysis. Little genetic diversity was found within commercial watercress populations. However, watercress formed a unique cluster genetically distinct from other Rorippa species, but equidistant to Cardamine species. It was placed closer to Barbarea verna.

Cochlearia cochlearioides (Brassicaceae) Is a Rorippa

The Indian endemic Cochlearia cochlearioides, initially described as an Alyssum, is transferred to Rorippa, and the new combination R. cochlearioides (Roth) Al-Shehbaz & Jonsell is proposed. Rorippa cochlearioides (Roth) Al-Shehbaz & Jonsell is endemic to India. It has been known under different names in Cochlearia L. and first appeared as C. flava in Roxburgh (1814), but that name remained a nomen nudum until it was validated by Hooker (1852). The species was validly published by Roth (1821) as Alyssum cochlearioides, a legitimate name that was placed in synonymy of the later published and illegitimate C. alyssoides (De Candolle, 1824). Alyssum cochlearioides was then transferred to the monotypic Trochiscus by Schulz (1933) and to Cochlearia by Maheshwari (1957), but it is evident that neither of these generic assignments is appropriate. Perhaps the main reason that Rorippa cochlearioides has been kept for so long in Cochlearia is that it has globose, many-seeded fruits. However, such fruits are found in several species of Rorippa Scopoli, including the Asian R. globosa (Turczaninow ex Fischer & C. A. Meyer) Hayek, the North American R. calycina (Engelmann) Rydberg, R. columbiae (Suksdorf ex Robinson) Suksdorf ex T. J. Howell, R. sphaerocarpa (A. Gray) Britton, and R. subumbellata Rollins, and the eastern Asian-North American R. barbariifolia (DC.) Kitagawa (Jonsell, 1971, 1973; Rollins, 1993). Plants of Rorippa cochlearioides grow in lowland, tropical and subtropical areas of India and are restricted to the Gujarat and Gangetic Plains (Bhaumik, 1993). The species has pinnatifid, nonfleshy, auriculate cauline leaves, yellow flowers, spreading floral parts, terete fruits, obscurely veined thin valves, and up to 80 reddish, reticulate seeds per fruit. This combination of characters is found in many species of Rorippa and does not occur in any species of Cochlearia. Species of Cochlearia are distributed in the arctic, subarctic, and northern latitudes of the north temperate region, and they have more or less fleshy, entire to dentate nonauriculate leaves, white flowers, erect petals and stamens, somewhat narrowly septate fruits, prominently 1-veined thick valves, and often few to several, often tuberculate seeds per fruit. In fact, all the Himalayan species previously assigned to Cochlearia have been or should be transferred to other genera. It is interesting to note that Schulz (1936) placed Rorippa cochlearioides (as Trochiscus) in the tribe Drabeae, a tribe that he separated from the Arabideae primarily on the basis of silicles versus siliques, although he indicated that Nasturtium R. Brown (including Rorippa) is an exception in the Arabideae because it often has silicles. By contrast, Bhaumik (1993) placed the species (as C. cochlearioides) in the Lepidieae, where Cochlearia has been traditionally placed. In our opinion, neither of these tribal dispositions of Rorippa cochlearioides reflects its phylogenetic relationships, and the species should be placed in the same tribe as Rorippa and Nasturtium. To accommodate the species in Rorippa, the following new combination is proposed. Rorippa cochlearioides (Roth) Al-Shehbaz & Jonsell, comb. nov. Basionym: Alyssum cochlearioides Roth, Nov. P1. Sp. 322. 1821. TYPE: India. Benjamin Heyne s.n. (holotype, B-W).

Delimitation of the Genus Nasturtium (Brassicaceae)

Delimitation of the Genus Nasturtium (Brassicaceae)

A reconsideration of Cardamine curvisiliqua and C. gambellii as species of Rorippa (Cruciferae)

A reconsideration of Cardamine curvisiliqua and C. gambellii as species of Rorippa (Cruciferae)