Contrasting Patterns of Nucleotide Substitution Rates Provide Insight into Dynamic Evolution of Plastid and Mitochondrial Genomes of Geranium

Geraniaceae have emerged as a model system for investigating the causes and consequences of variation in plastid and mitochondrial genomes. Incredible structural variation in plastid genomes (plastomes) and highly accelerated evolutionary rates have been reported in selected lineages and functional groups of genes in both plastomes and mitochondrial genomes (mitogenomes), and these phenomena have been implicated in cytonuclear incompatibility. Previous organelle genome studies have included limited sampling of Geranium, the largest genus in the family with over 400 species. This study reports on rates and patterns of nucleotide substitutions in plastomes and mitogenomes of 17 species of Geranium and representatives of other Geraniaceae. As detected across other angiosperms, substitution rates in the plastome are 3.5 times higher than the mitogenome in most Geranium. However, in the branch leading to Geranium brycei/Geranium incanum mitochondrial genes experienced significantly higher dN and dS than plastid genes, a pattern that has only been detected in one other angiosperm. Furthermore, rate accelerations differ in the two organelle genomes with plastomes having increased dN and mitogenomes with increased dS. In the Geranium phaeum/Geranium reflexum clade, duplicate copies of clpP and rpoA genes that experienced asymmetric rate divergence were detected in the single copy region of the plastome. In the case of rpoA, the branch leading to G. phaeum/G. reflexum experienced positive selection or relaxation of purifying selection. Finally, the evolution of acetyl-CoA carboxylase is unusual in Geraniaceae because it is only the second angiosperm family where both prokaryotic and eukaryotic ACCases functionally coexist in the plastid.

Genetic structuring, dispersal and taxonomy of the high-alpine populations of the Geranium arabicum/kilimandscharicum complex in tropical eastern Africa

The scattered eastern African high mountains harbor a renowned and highly endemic flora, but the taxonomy and phylogeographic history of many plant groups are still insufficiently known. The high-alpine populations of the Geranium arabicum/kilimandscharicum complex present intricate morphological variation and have recently been suggested to comprise two new endemic taxa. Here we aim to contribute to a clarification of the taxonomy of these populations by analyzing genetic (AFLP) variation in range-wide high-alpine samples, and we address whether hybridization has contributed to taxonomic problems. We identified only two genetic groups. One corresponded to G. kilimandscharicum, which has been reported as exclusively high-alpine and confined to the eastern Rift mountains in East Africa. The other corresponded to G. arabicum, reported from lower altitudes on the same mountains as well as from a wide altitudinal span in Ethiopia and on the western Rift mountains in East Africa. The four populations analyzed of a recently described species from the Bale Mts in Ethiopia were admixed, indicating that they result from recent long-distance dispersal of G. kilimandscharicum from East Africa followed by hybridization with local G. arabicum in naturally disturbed habitats. Some admixture between the two genetic groups was also inferred on other mountains, supporting earlier suggestions of introgression based on morphology. We did not find support for recognition of the recently suggested new subspecies of G. arabicum in Ethiopia. Interestingly, the high-alpine G. kilimandscharicum lacked clear geographic structuring, suggesting a recent history of colonization of the different mountains or extensive intermountain gene flow.

Identification and characterization of the water gap in physically dormant seeds of Geraniaceae, with special reference to Geranium carolinianum

BACKGROUND AND AIMS

Physical dormancy in seeds of species of Geraniaceae is caused by a water-impermeable palisade layer in the outer integument of the seed coat and a closed chalaza. The chalazal cleft has been reported to be the water gap (i.e. location of initial water entry) in innately permeable seeds of Geraniaceae. The primary aim of this study was to re-evaluate the location of the water gap and to characterize its morphology and anatomy in physically dormant seeds of Geraniaceae, with particular reference to G. carolinianum.

METHODS

Length, width, mass, anatomy and germination of two seed types (light brown and dark brown) of G. carolinianum were compared. Location, anatomy and morphology of the water gap were characterized using free-hand and microtome tissue sectioning, light microscopy, scanning electron microscopy, dye tracking, blocking and seed-burial experiments.

KEY RESULTS

Treatment with dry heat caused a colour change in the palisade cells adjacent to the micropyle. When placed in water, the 'hinged valve' (blister) erupted at the site of the colour change, exposing the water gap. The morphology and anatomy in the water-gap region differs from those of the rest of the seed coat. the morphology of the seed coat of the water-gap region is similar in G. carolinianum, G. columbinum, G. molle and G. pusillum and differs from that of the closely related species Erodium cicutarium.

CONCLUSIONS

Dislodgment of swollen 'hinged valve' palisade cells adjacent to the micropyle caused the water gap to open in physically dormant seeds of G. carolinianum, and it was clear that initial water uptake takes place through this gap and not via the chalazal opening as previously reported. This water gap ('hinged valve gap') differs from water gaps previously described for other families in morphology, anatomy and location in the seed coat.

A historical, scientific and commercial perspective on the medicinal use of Pelargonium sidoides (Geraniaceae)

ETHNOPHARMACOLOGICAL CONTEXT: A detailed review of the ethnobotany and commercial history of Pelargonium sidoides is presented, together with a brief summary of pre-clinical and clinical scientific results that support the use of the plant in modern, evidence-based phytomedicines. The aim is to identify the main factors responsible for the success in product development.

MATERIALS AND METHODS

The literature studied includes all modern scientific papers and also old documents and books that are no longer readily accessible.

RESULTS

Available ethnobotanical information shows that several tuberous Pelargonium species (including Pelargonium sidoides) are important traditional medicines with a rich ethnobotanical history. A summary of the interesting history of the commercial development of Stevens' Cure or Umckaloabo in Europe is presented. Scientific evidence for the efficacy of the product, mainly as a treatment for acute bronchitis, is reviewed. These include numerous in vitro studies as well as 18 clinical studies. The botanical identity of the plant and its complex mixture of coumarins and other chemical constituents are summarised.

CONCLUSIONS

The use of Pelargonium stems or tubers for a variety of ailments (including the complications of dysentery) is an important but hitherto under-estimated part of traditional medicine in southern Africa. Key elements in the successful development of Pelargonium sidoides from a profound traditional remedy to a highly successful phytomedicine include the choice of species, a favourable cost-benefit ratio, innovative marketing over many years, good scientific evidence of the botanical and chemical identity of the product and convincing proof of concept.

[Identification on Geranium by X-ray diffraction fourier fingerprint patterns and similarity degree of different fingerprint patterns]

OBJECTIVE

To provide a X-ray diffraction (XRD) new method to identify different of herbal drugs of Geranium.

METHODS

Analyse X-ray diffraction Fourier pattern of 1 plants of Geranium, 7 kinds substitute, and degree of different fingerprint patterns was calculated and analyzed according to the position (2 theta value) of peaks searched.

RESULTS

Obtain the different X-ray diffraction Fourier pattern of 1 kinds plants of Geranium and 7 kinds substitutes of Geranium.

CONCLUSION

This method can be used for indentification on different medicinal material of Geranium.

[Study on morphology of the pollen of 4 species from Geranium in Heilongjiang Province]

Morphology of the pollen of 4 species from Geranium in Heilongjiang province which are G. wilfordii Maxim., G. sibiricum L., G. platyanthum Duthie. and G. dahuricum DC. were observed with optical microscope and scanning electron microscope. The results showed pollen grains of the four species were nearly spherical, with short clavate-shaped, net-shaped and cave-shaped veins on the outer walls and three short-furrow germ pores. Both the clava size and number of clava per unit surface area were different. This paper provided evidences for palynology classification of Geranium.