Population genetic structure of Wikstroemia monnula highlights the necessity and feasibility of hierarchical analysis for a highly differentiated species.

Population genetic structure can provide valuable insights for conserving genetic resources and understanding population evolution, but it is often underestimated when using the most popular method and software, STRUCTURE and delta K, to assess. Although the hierarchical STRUCTURE analysis has been proposed early to overcome the above potential problems, this method was just utilized in a few studies and its reliability needs to be further tested. In this study, the genetic structure of populations of Wikstroemia monnula was evaluated by sequencing 12 nuclear microsatellite loci of 905 individuals from 38 populations. The STRUCTURE analysis suggested the most likely number of clusters was two, but using multi-hierarchical structure analysis, almost every population was determined with an endemic genetic component. The latter result is consistent with the extremely low gene flow among populations and a large number of unique cpDNA haplotypes in this species, indicating one level of structure analysis would extremely underestimate its genetic component. The simulation analysis shows the number of populations and the genetic dispersion among populations are two key factors to affect the estimation of K value using the above tools. When the number of populations is more than a certain amount, K always is equal to 2, and when a simulation only includes few populations, the underestimation of K value also may occur only if these populations consist of two main types of significantly differentiated genetic components. Our results strongly support that the hierarchical STRUCTURE analysis is necessary and practicable for the species with lots of subdivisions.

Ternary Pt/SnO(x)/TiO2 photocatalysts for hydrogen production: consequence of Pt sites for synergy of dual co-catalysts.

A variety of ternary nanoheterostructures composed of Pt nanoparticles (NPs), SnOx species, and anatase TiO2 are designed elaborately to explore the effect of interfacial electron transfer on photocatalytic H2 evolution from a biofuel-water solution. Among numerous factors controlling the H2 evolution, the significance of Pt sites for the H2 evolution is highlighted by tuning the loading procedure of Pt NPs and SnOx species over TiO2. A synergistic enhancement of H2 evolution can be achieved over the Pt/SnOx/TiO2 heterostructures formed by anchoring Pt NPs at atomically-isolated Sn-oxo sites, whereas the Pt/TiO2/SnOx counterparts prepared by grafting single-site Sn-oxo species on Pt/TiO2 show a marked decrease in the rate of H2 evolution. The characterization results clearly reveal that the synergy of Pt NPs and SnOx species originates from the vectorial electron transfer of TiO2 → SnOx → Pt occurring on the former, while the latter results from the competitive electron transfer from TiO2 to SnOx and to Pt NPs.

[Effect of NaCl stress on physiological characteristics of Physalis alkekengi var. franchetii test-tube plantlet].

OBJECTIVE: To investigate the effect of NaCl stress on the growth and physiological characteristics of Physalis alkekengi var. franchetii, and to discuss the mechanism of salt tolerance. METHODS: The test-tube plantlet was cultured on the stress medium with NaCl (0.2%~1.0%), the content of proline, soluble sugar, soluble protein, chlorophyll and malondialdthyde (MDA), and membrane relative permeability, as well as the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were determined and analyzed. RESULTS: The average height, stem diameter, root length, number of root and chlorophyll content gradually decreased at salinity less than or equal 0.6% NaCl, then decreased rapidly at salinity greater than or equal 0.8% NaCl, while the root formation was significantly inhibited. The content of free proline and SOD activities always increased with NaCl concentration increasing (0.2%~ 1.0%). Nevertheless, the contents of soluble sugar, soluble protein and the activities of CAT and POD increased firstly and then decreased, but the contents of soluble sugar and soluble protein were higher than those of the control group, whereas the content of MDA and membrane relative permeability accumulated slowly at salinity less than or equal 0.6% NaCl, then increased rapidly at salinity greater than 0.8% NaCl. CONCLUSION: The test-tube plantlet has an adaptability to salty environment at salinity less than or equal 0.6% NaCl, and the test-tube plantlet can alleviate the salty injury by increasing the contents of osmotic regulation substances, such as soluble sugar and soluble protein, decreasing the osmotic potential, and increasing the activities of antioxidant enzymes.

[Study on the optimum combinations of plant hormone in callus culture of Thermopsis lanceolata].

OBJECTIVE: To explore the effects of different hormone combinations on callus induction of Thermopsis lanceolata. METHODS: The effects of different hormone concentrations and ratio on callus induction and subculture multiplication of Thermopsis lanceolata were investigated by orthogonal design methods. RESULTS: The optimal medium of callus induction for hypocotyls explants was MS + 2, 4-D (0.5 mg/L) + BA (1.0 mg/L) + NAA (1.0 mg/L) + IAA (0.5 mg/L). The best medium of callus subculture multiplication for hypocotyl explants was MS with 2,4-D (0.1 mg/L) + BA (0.1 mg/L) + NAA (0.2 mg/L) + IAA (0.5 mg/L) . In the process of callus subculture multiplication, the effect extent of four kinds of hormones for hypocotyl explants was BA > 2,4-D > IAA > NAA. The growth curve of callus culture optimal hormone combination was "S" curve. CONCLUSION: The rapid callus culture system for Thermopsis lanceolata is established for the first time. It provides a new way for protecting and utilizing Thermopsis lanceolata species resources through the modern biotechnology.