Primrose Species Research Articles

Pollinator-mediated selection on flowering start and corolla tube length differed between mating systems in a primrose species

Pollinator-mediated selection on flowering start and corolla tube length differed between mating systems in a primrose species

Effects of storage temperature and pre-treatments on seed germination of Primula mallophylla and P. sertulum (Primulaceae), two narrowly-distributed endemic species from southwest China

Primula mallophylla and P. sertulum are wild ornamental species of south-west China, but the responses of their seeds to storage have not been determined. When seeds were dry-stored for 24 months at room temperature (RT) (ca. 21°C) and at 4°C, germination increased during the first six months, but then decreased over the following 18 months. The decrease in germination was slower for seeds stored at 4°C than for those stored at RT. When seeds of these two species were dry-stored at -20°C for 24 months, germination percentage was significantly higher than that of the control seeds by the sixth month; the high germination percentages persisted at 24 months. In addition, pre-germination treatments (i.e., immersion in 100 μmol L -1 GA3 for 24 hours, cold stratification for 30 days or both) improved the final germination and reduced mean germination time of P. mallophylla seeds stored for 12 months at RT, but not those of P. sertulum. Taken together, storing seeds at -20°C is feasible and convenient for both primrose species; thus, it is possible to safely store seeds for future research and conservation.

Conservation status of Primulaceae, a plant family with high endemism, in China

Primroses, approximately 1000 species from the family Primulaceae, are mostly distributed in subalpine to alpine areas and attract attention due to their high ornamental value. However, they have been increasingly threatened by human activities and climate change in recent decades. China harbours 535 primrose species from 12 genera, most of which are endemic. In this study, we established a distribution database of the primroses in China, then explored the geographic pattern of the richness of primrose species in relation to environmental factors and evaluated their conservation status. The results showed that the primrose richness was highest in the mountainous areas from the eastern Himalayas to the Hengduan Mountains, with habitat heterogeneity (explaining 37.6% of the variance) and temperature seasonality (26.0% of the variance) together explaining this pattern. Furthermore, the richness of endemic and threatened primroses had been strongly affected by the long-term climate change since the Last Glacial Maximum. On average, national nature reserves (NNRs) covered 29.5% of the distribution areas of primroses. However, there were still 97 less-protected species, each of which had a distribution area <2000 km2 covered by NNRs. By analysing this group, we proposed that nature reserves need to be established in several conservation gaps mainly located in Southwest China to protect the primrose species in China.

In Search of High-Yielding and Single-Compound-Yielding Plants: New Sources of Pharmaceutically Important Saponins from the Primulaceae Family.

So far, only a few primrose species have been analyzed regarding their saponin composition and content. Moreover, the roots of only two of them are defined by the European Union (EU) Pharmacopoeia monograph and commercially utilized by the pharmaceutical industry. Thus, this study intended to find some new sources of main triterpene saponins from Primulae radix, namely primulasaponins I and II together with the closely related sakurasosaponin. Using isolated standards, UHPLC-ESI-HRMS served to assess over 155 Primulaceae members qualitatively and quantitatively. Nine examples of plants accumulating over 5% of primulasaponin I in their roots were found. Among them, in one case, it was found as the almost sole secondary metabolite with the concentration of 15–20% (Primula grandis L.). A reasonable content of primulasaponin II was found to be typical for Primula vulgaris Huds. and P. megaseifolia Boiss. & Bal. The sakurasosaponin level was found in seven species to exceed 5%. The finding of new, single and rich sources of the abovementioned biomolecules among species that were never analyzed phytochemically is important for future research and economic benefit. The chemotaxonomic significance of the occurrence of these three saponins in Primulaceae is discussed.

Conservation implications of asymmetric introgression and reproductive barriers in a rare primrose species

BackgroundPrimula is a large genus of flowering herbs well known for their heterostyly. Currently few natural hybrids are known and reproductive barriers in this genus in the wild have received little attention. However, there is instance of hybridization between rare and widely-spread species, and conservation implications of such situation is poorly understood. In the present study, we investigated hybridization patterns and reproductive barriers between a wide spread species, Primula poissonii and a rare species P. anisodora, of which only three populations are currently known.ResultsPollinator-mediated reproductive isolation was strong between parental species but not significant between hybrids and parental species. Hand pollination experiments showed significant reduction of both fruit- and seed-set for heterospecific pollination as compared with conspecific pollination for both parental species. Furthermore, hybrids had higher fruit- and seed-set when pollinated with P. anisodora pollen as opposed to P. poissonii pollen. Microsatellites identified backcrosses to P. anisodora in two of the three populations of P. anisodora, and additionally more individuals of P. anisodora showed introgression from P. poissonii than vice versa.ConclusionsThese results provide evidence for potential genetic swamping of the P. anisodora populations, which could pose a serious threat for this locally endemic species.

Nectar robbers influence the trait-fitness relationship of Primula secundiflora.

The trait-fitness relationship influences the strength and direction of floral evolution. To fully understand and predict the evolutionary trajectories of floral traits, it is critical to disentangle the direct and indirect effects of floral traits on plant fitness in natural populations. We experimentally quantified phenotypic selection on floral traits through female fitness and estimated the casual effects of nectar robbing with different nectar robbing intensities on trait-fitness relationships in both the L- (long-style and short-anther phenotype) and S-morph (short-style and long-anther phenotype) flowers among Primula secundiflora populations. A larger number of flowers and wider corolla tubes had both direct and indirect positive effects on female fitness in the P.secundiflora populations. The indirect effects of these two traits on female fitness were mediated by nectar robbers. The indirect effect of the number of flowers on female fitness increased with increasing nectar robbing intensity. In most populations, the direct and/or indirect effects of floral traits on female fitness were stronger in the S-morph flowers than in the L-morph flowers. In addition, nectar robbers had a direct positive effect on female fitness, but this effect varied between the L- and S-morph flowers. These results show the potential role of nectar robbers in influencing the trait-fitness relationships in this primrose species.

Pollinator-mediated selection on floral traits varies in space and between morphs in Primula secundiflora.

Elucidating how variation in selection shapes the evolution of flowers is key to understanding adaptive differentiation processes. We estimated pollinator-mediated selection through female function in L-morph (long-style and short-anther phenotype) and S-morph (short-style and long-anther phenotype) flowers among four Primula secundiflora populations with different pollinator assemblages. Variation in pollinator assemblage strongly contributed to differences in reproductive success among populations and between morphs of the primrose species. A wider corolla tube width was selected in the bumblebee-dominated populations, whereas shorter corolla tube length and wider corolla tube width were selected in the syrphid fly-dominated populations. Morph-specific variation in pollinator-mediated selection on corolla tube length was detected in the syrphid fly-dominated populations. A shorter corolla tube was selected in the L-morph flowers. However, similar selective pressure on this trait was not observed in the S-morph flowers. These results show that variation in pollinator assemblage leads to variation in selection in space and between morphs. The findings highlight the potential forces of different pollinator agents in driving floral evolution in this primrose species.

Germination and Seedling Growth of Water Primroses: A Cross Experiment between Two Invaded Ranges with Contrasting Climates.

Aquatic ecosystems are vulnerable to biological invasions, and will also be strongly impacted by climate change, including temperature increase. Understanding the colonization dynamics of aquatic invasive plant species is of high importance for preservation of native biodiversity. Many aquatic invasive plants rely on clonal reproduction to spread, but mixed reproductive modes are common. Under future climate changes, these species may favor a sexual reproductive mode. The aim of this study was to test the germination capacity and the seedling growth of two water primrose species, Ludwigia hexapetala and Ludwigia peploides, both invasive in Europe and in the United States. We performed a reciprocal transplant of seeds of L. hexapetala and L. peploides from two invasive ranges into experimental gardens characterized by Oceanic and Mediterranean-type climates. Our results showed that higher temperatures increased or maintained germination percentages and velocity, decreased survivorship of germinants, but increased their production of biomass. The origin of the seeds had low impact on L. hexapetala responses to temperature, but greatly influenced those of L. peploides. The invasiveness of water primroses in ranges with Oceanic climates might increase with temperature. The recruitment from seed banks by these species should be considered by managers to improve the conservation of native aquatic and wetland plant species.

Selection of the optimal extractant for extracting the complex of biologically active substances from the cowslip leaves and rhizomes with roots

Topicality . Since ancient times the species of Primrose (Primula L.) are used in traditional medicine. There are about 500 species, which are distributed around the globe. In the CIS (Commonwealth of Independent States) countries grows 67 species. The most common is cowslip (Primula veris L.; Primula officinalis Hill.). The decoction of cowslip rhizomes with roots is used in traditional and scientific medicine as an expectorant; the infusion of leaves is used as analgesic and diuretic. In the Ukrainian pharmaceutical market there are no domestic drugs from raw cowslip. Aim. To determine the optimal conditions for obtaining extracts from the cowslip leaves and rhizomes with roots to develop new domestic drugs with anti-inflammatory and expectorant activity. Materials and methods . The object of the research was the cowslip leaves, which were harvested in Ternopil region in 2015 during the mass plants’ flowering, and rhizomes with roots, which were harvested after the death of aerial parts of the plants. Raw material was crushed to the particles of 3-5 mm size. For extraction of biologically active substances from the cowslip leaves, the following solvents were investigated: 20 %, 40 %, 70 % ethanol and hot purified water (80 °C). The ratio of raw material : extractant was 1 : 10. Infused during the day at room temperature, with constant stirring; filtered and condensed on a rotary vacuum evaporator to a thick state at a temperature of 60-70 °C. To select the extractant to obtain substances from the cowslip rhizomes with roots we took 20 %, 30 %, 40 % ethanol. Additionally we received the extract with 20 % ethanol extraction, having moistened the raw material with 95 % ethanol. The ratio of raw material : extractant was 1 : 8. Infused during seven days with compulsory supply of extractant, stirring; filtered and condensed on a rotary vacuum evaporator. Quantitative determination of flavonoids, hydroxycinnamic acids, phenolic compounds and saponins was conducted with spectrophotometric method. The dry residue was determined by gravimetric method as required by State Pharmacopoeia of Ukraine (SPU), oxidative phenols were determined by permanganatometric method. Results and discussion . When studying the effect of extractant upon the degree of biologically active substances extraction from the cowslip leaves, we found that the maximum amount of hydroxycinnamic acids, oxidative phenols and saponins was extracted with ethanol 40 %, representing 25.5 %, 12.13 %, 3.25 % respectively; phenolic compounds and flavonoids – with ethanol 70 % (5.40 % and 12.70 %, respectively); extractive substances with cleared hot water (48.51 %). When extracting biologically active substances from the cowslip rhizomes with roots, we found that the maximum amount of hydroxycinnamic acids and flavonoids was extracted with ethanol 40 %, representing 7.93 % and 1.15 % respectively; phenolic compounds, oxidative phenols and saponins – with ethanol 30 % (2.57 %, 5.03 % and 5.25 % respectively). The content of extractive substances in the studied extracts from the cowslip rhizomes with the roots in all objects was approximately equal. Conclusions . We obtained the extracts from the cowslip leaves and rhizomes with the roots. Thick extract of leaves is a homogeneous viscous brown mass with a greenish tinge, with a bitter and salty taste, with a peculiar pleasant smell, soluble in water and insoluble in ethanol 96 %. Thick extract of rhizomes with roots is a homogeneous viscous dark brown mass, with a bitter taste, with a peculiar pleasant smell, soluble in water and insoluble in ethanol 96 %. It is established that the maximum amounts of hydroxycinnamic acids, oxidative phenols and saponins in extracts from the cowslip leaves was observed with 40 % ethanol extraction; phenolic compounds and flavonoids – 70 % ethanol; extractives – hot clean water. Thus, the optimal content of complex biologically active substances from the cowslip leaves provides 40 % ethanol solution. It is established that the maximum amount of hydroxycinnamic acids and flavonoids in extracts from the cowslip rhizomes with roots was observed with 40 % ethanol extraction; phenolic compounds, saponins, oxidative phenols, extractives – 30 % ethanol. Thus, the optimal content of complex biologically active substances from the cowslip rhizomes with roots provides 30 % ethanol solution.

Unidirectional hybridization and reproductive barriers between two heterostylous primrose species in north-west Yunnan, China.

Heteromorphy in flowers has a profound effect on breeding patterns within a species, but little is known about how it affects reproductive barriers between species. The heterostylous genus Primula is very diverse in the Himalaya region, but hybrids there have been little researched. This study examines in detail a natural hybrid zone between P. beesiana and P. bulleyana. Chloroplast sequencing, AFLP (amplified fragment length polymorphism) markers and morphological comparisons were employed to characterize putative hybrids in the field, using synthetic F1s from hand pollination as controls. Pollinator visits to parent species and hybrids were observed in the field. Hand pollinations were conducted to compare pollen tube growth, seed production and seed viability for crosses involving different morphs, species and directions of crossing. Molecular data revealed all hybrid derivatives examined to be backcrosses of first or later generations towards P. bulleyana: all had the chloroplast DNA (cpDNA) of this species. Some individuals had morphological traits suggesting they were hybrids, but they were genetically similar to P. bulleyana; they might have been advanced generation backcrosses. Viable F1s could not be produced with P. bulleyana pollen on P. beesiana females, irrespective of the flower morphs used. Within-morph crosses for each species had very low (<10 %) seed viability, whereas crosses between pin P. bulleyana (female) and pin P. beesiana had a higher seed viability of 30 %. Thus genetic incompatibility mechanisms back up mechanical barriers to within-morph crosses in each species, but are not the same between the two species. The two species share their main pollinators, and pollinators were observed to fly between P. bulleyana and hybrids, suggesting that pollinator behaviour may not be an important isolating factor. Hybridization is strongly asymmetric, with P. bulleyana the only possible mother and all detected hybrids being backcrosses in this direction. Partial ecological isolation and inhibition of heterospecific pollen, and possibly complete barriers to F1 formation on P. beesiana, may be enough to make F1 formation very rare in these species. Therefore, with no F1 detected, this hybrid zone may have a finite life span as successive generations become more similar to P. bulleyana.

SMALL AND UGLY? PHYLOGENETIC ANALYSES OF THE “SELFING SYNDROME” REVEAL COMPLEX EVOLUTIONARY FATES OF MONOMORPHIC PRIMROSE FLOWERS

One of the most common trends in plant evolution, loss of self-incompatibility and ensuing increases in selfing, is generally assumed to be associated with a suite of phenotypic changes, notably a reduction of floral size, termed the selfing syndrome. We investigate whether floral morphological traits indeed decrease in a deterministic fashion after losses of self-incompatibility, as traditionally expected, using a phylogeny of 124 primrose species containing nine independent transitions from heterostyly (heteromorphic incompatibility) to homostyly (monomorphic self-compatibility), a classic system for evolution of selfing. We find similar overall variability of homostylous and heterostylous species, except for diminished herkogamy in homostyles. Bayesian mixed models demonstrate differences between homostylous and heterostylous species in all traits, but net effects across species are small (except herkogamy) and directionality differs among traits. Strongly drift-like evolutionary trajectories of corolla tube length and corolla diameter inferred by Ornstein-Uhlenbeck models contrast with expected deterministic trajectories toward small floral size. Lineage-specific population genetic effects associated with evolution of selfing may explain that reductions of floral size represent one of several possible outcomes of floral evolution after loss of heterostyly in primroses. Contrary to the traditional paradigm, selfing syndromes may, but do not necessarily evolve in response to increased selfing.

Comparative transcriptome analysis and marker development of two closely related Primrose species (Primula poissonii and Primula wilsonii)

BackgroundPrimula species are important early spring garden plants with a centre of diversity and speciation in the East Himalaya-Hengduan Mountains in Western China. Studies on population genetics, speciation and phylogeny of Primula have been impeded by a lack of genomic resources. In the present study, we sequenced the transcriptomes of two closely related primrose species, Primula poissonii and Primula wilsonii, using short reads on the Illumina Genome Analyzer platform.ResultsWe obtained 55,284 and 55,011 contigs with N50 values of 938 and 1,085 for P. poissonii and P. wilsonii, respectively, and 6,654 pairs of putative orthologs were identified between the two species. Estimations of non-synonymous/synonymous substitution rate ratios for these orthologs indicated that 877 of the pairs may be under positive selection (Ka/Ks > 0.5), and functional enrichment analysis revealed that significant proportions of the orthologs were in the categories DNA repair, stress resistance, which may provide some hints as to how the two closely related Primula species adapted differentially to extreme environments, such as habitats characterized by aridity, high altitude and high levels of ionizing radiation. It was possible for the first time to estimate the divergence time between the radiated species pair, P. poissonii and P. wilsonii; this was found to be approximately 0.90 ± 0.57 Mya, which falls between the Donau and Gunz glaciation in the Middle Pleistocene. Primers based on 54 pairs of orthologous SSR-containing sequences between the two Primula species were designed and verified. About half of these pairs successfully amplified for both species. Of the 959 single copy nuclear genes shared by four model plants (known as APVO genes), 111 single copy nuclear genes were verified as being present in both Primula species and exon-anchored and intron-spanned primers were designed for use.ConclusionWe characterized the transcriptomes for the two Primula species, and produced an unprecedented amount of genomic resources for these important garden plants. Evolutionary analysis of these two Primula species not only revealed a more precise divergence time, but also provided some novel insights into how differential adaptations occurred in extreme habitats. Furthermore, we developed two sets of genetic markers, single copy nuclear genes and nuclear microsatellites (EST-SSR). Both these sets of markers will facilitate studies on the genetic improvement, population genetics and phylogenetics of this rapidly adapting taxon.

Decrease of sexual organ reciprocity between heterostylous primrose species, with possible functional and evolutionary implications.

Heterostyly is a floral polymorphism that has fascinated evolutionary biologists since Darwin's seminal studies on primroses. The main morphological characteristic of heterostyly is the reciprocal placement of anthers and stigmas in two distinct (distyly) floral morphs. Variation in the degree of intermorph sexual reciprocity is relatively common and known to affect patterns of pollen transfer within species. However, the partitioning of sexual organ reciprocity within and between closely related species remains unknown. This study aimed at testing whether intermorph sexual reciprocity differs within vs. between primrose species that hybridize in nature and whether the positions of sexual organs are correlated with other floral traits. Six floral traits were measured in both floral morphs of 15 allopatric populations of Primula elatior, P. veris and P. vulgaris, and anther-stigma reciprocity was estimated within and between species. A combination of univariate and multivariate approaches was used to test whether positions of reproductive organs were less reciprocal between than within species, to assess correlations between sexual organ positions and other corolla traits, and to quantify differences between morphs and species. The three species were morphologically well differentiated in most floral traits, except that P. veris and P. vulgaris did not differ significantly in sexual organ positions. Overall, lower interspecific than intraspecific sexual organ reciprocity was detected. This decrease was marked between P. elatior and P. vulgaris, intermediate and variable between P. elatior and P. veris, but negligible between P. veris and P. vulgaris. Differences in anther and stigma heights between the analysed primrose species were of the same magnitude or larger than intraspecific differences that altered pollen flow within other heterostylous systems. Therefore, it is possible to suggest that considerable reductions of sexual organ reciprocity between species may lower interspecific pollen flow, with potential effects on reproductive isolation.

Morphological traits and allocation patterns related to stress-tolerance and seed-yield in wild and domesticated evening primrose ( Oenothera L. Onagraceae)

Wild evening primrose species ( Oenothera spp.) native to Argentina, have been suggested as a new crop for irrigated valleys of semi-arid Patagonia. This paper describes patterns of biomass allocation, morphological traits related to stress-tolerance and seed-yield in four species of Oenothera grown in a common garden at three plant densities. Wild and domesticated species are compared. The effect of resource availability on those traits during three phenological stages (vegetative, reproductive and maturity) is described. Native species were characterized by traits related to stress-tolerance (high root allocation and low specific leaf area) during the vegetative stage. This suite of traits resulted in low biomass accumulation and low seed-yield. The domesticated O. biennis was characterized by a combination of traits related to stress-tolerance (low specific leaf area) and high productivity (high leaf allocation and leaf area ratio and low root allocation). Domesticated species accumulated more biomass than natives. Total biomass and total non-structural carbohydrates present in roots were positively correlated to seed-yield. Oenothera biennis showed the highest seed-yield, although this species showed yield instability in response to changes in the environmental quality. No changes in seed-yield in response to plant density were recorded for either O. lamarckiana or native species. Oenothera biennis showed an optimum density of 20 plants m −2 and yielded 260 g m −2, a seed-yield similar to that reported in other countries. Low seed-yield of native species is major drawback that must be overcome. Improving seed-yield in these species could be possible by selection oriented to increase total biomass. Since no detrimental effect of density was found in O. lamarckiana and natives, a higher plant density might increase yield production per unit area.

Effects of Seed Treatments on Germination of Seed Collected from Native Populations of Oenothera

Oenothera biennis, common evening primrose, is grown commercially for its seed, which contains high levels of gamma-linolenic acid (GLA), a fatty acid with pharmaceutical and dietary importance. Other native species of Oenothera are being evaluated for the presence of GLA in their seed and their potential as a commercial source of GLA. Native evening primrose species have shown slow emergence and low germination percentages. Studies were conducted to determine the effects of chilling, scarification, and priming on germination of seed for six species of native evening primrose. Overall, seed germination was improved by seed treatments. However, responses to the various treatments differed among species.

Comparative Reproductive Biology of Two Alpine Primrose Species

Primula angustifolia and Primula parryi are common alpine primroses in Colorado. We examined the reproductive biology of these species to determine (1) if they were fully distylous (2) what differences in pollinators and in reproductive allocation and success might exist between the species, and (3) whether reproduction was limited by pollen availability during the period of study. We found both taxa to be fully distylous. Primula parryi has numerous, diverse pollinators, a high seed/ovule ratio, and high fecundity. Primula angustifolia has fewer, less diverse pollinators, lower seed/ovule ratios, and lower fecundity. The greater reproductive success of P. parryi may reflect its inflorescence structure and supply of attractants and rewards. Reproduction in both species appears to be limited to some extent by pollen availability, although more so in P. parryi than in P. angustifolia. These results demonstrate while distyly, with obligate outcrossing and reliance on insect pollen vectors, can be a viable reproductive strategy even in a severe environment, it functions differently even in closely related species and understanding individual pollination systems should be a focus for research on other distylous species.

MITOCHONDRIAL HETEROSIS IN MAIZE

MANY hybrids between genetic pure lines in maize exhibit heterosis. The search for the genetic basis of heterosis has been carried on for many years and by many workers. Despite these efforts, an adequate, specific biochemical explanation of heterosis has not been presented. JONES (1952) has noted the interaction of nuclear genes and cytoplasm, as evidenced by differences in reciprocal crosses of corn and other species. WILKIE (1 964) has discussed the physiological complementation of cytoplasms (mitochondria) in producing heterokaryon vigor in micro-organisms. Work with heterotic interspecific hybrids of primrose species has revealed a striking difference between reciprocal hybrids which indicated a cytoplasmic influence on hybrid vigor in this case (OEHLKERS 1964). It has been shown that mitochondria from maize exhibit heterosis in terms of nitrogen content (HANSON, HAGEMAN and FISHER 1960). We demonstrated mitochondrial heterosis in terms of biochemical activity ( MCDANIEL and SARKISSIAN 1966b). Further study showed the mitochondria of a maize hybrid were polymorphic ( SARKISSIAN and MCDANIEL 1967). The combination of mitochondria isolated from the parents of hybrids was found to yield a mitochondrial mixture which showed complementation and approached the activity of mitochondria from the hybrid ( MCDANIEL and SARKISSIAN 1966b; SARKISSIAN and SRIVASTAVA 1967). As mitochondria are of great importance in cellular metabolism, the relation of these subcellular, cytoplasmic organelles to heterosis deserves further study. The oxidation of carbolhydrates, fatty acids and amino acids by the KREBS tricarboxylic acid cycle of the mitochondrion provides much of the ATP needed by the organism for energy-requiring reactions, as well as reduced cofactors and carbon skeletons for syinthetic reactions. Heterosis has been shown to be a phenomenon of growth, being expressed as more rapid growth rates exhibited by heterotic hybrids. As growth is dependent on the production of available energy and utilization of carbon skeletons, and other biochemical products, the rate and efficiency with which the energy captured by photosynthesis can be liberated and used, could be a limiting factor in the growth process. 'This study represents a portion of the dissertation submitted by R. G. NI. to West Virginia University in partial