Search

Appropriate light intensity is favorable for the photosynthesis, biomass accumulation, key enzyme activity, and secondary metabolite synthesis of medicinal plants. This study aims to explore the influence of light intensity on growth and quality of Panax quinquefolius. To be specific, sand culture experiment was carried out in a greenhouse under the light intensity of 40, 80, 120, and 160 μmol·m~(-2)·s~(-1), respectively. The growth indexes, photosynthetic characteristics, content of 6 ginsenosides of the 3-year-old P. quinquefolius were determined, and the expression of ginsenoside synthesis-related enzyme genes in leaves, main roots, and fibrous roots was determined. The results showed that the P. quinquefolius growing at 80 μmol·m~(-2)·s~(-1) light intensity had the most biomass and the highest net photosynthetic rate. The total biomass of P. quinquefolius treated with 120 μmol·m~(-2)·s~(-1) light intensity was slightly lower than that with 80 μmol·m~(-2)·s~(-1). The root-to-shoot ratio in the treatment with 120 μmol·m~(-2)·s~(-1) light intensity was up to 6.86, higher than those in other treatments(Plt;0.05),and the ginsenoside content in both aboveground and underground parts of P. quinquefolius in this treatment was the highest, which was possibly associated with the high expression of farnesylpyrophosphate synthase(FPS), squalene synthase(SQS), squalene epoxidase(SQE), oxidosqualene cyclase(OSC), dammarenediol-Ⅱ synthase(DS), and P450 genes in leaves and SQE and DS genes in main roots. In addition, light intensities of 120 and 160 μmol·m~(-2)·s~(-1) could promote PPD-type ginsenoside synthesis in leaves by triggering up-regulation of the expression of upstream ginsenoside synthesis genes. The decrease in underground biomass accumulation of the P. quinquefolius grown under weak light(40 μmol·m~(-2)·s~(-1)) and strong light(160 μmol·m~(-2)·s~(-1)) was possibly attributed to the low net photosynthetic rate, stomatal conductance, and transpiration rate in leaves. In the meantime, the low expression of SQS, SQE, OSC, and DS genes in the main roots might led to the decrease in ginsenoside content. However, there was no significant correlation between the ginsenoside content and the expression of synthesis-related genes in the fibrous roots of P. quinquefolius. Therefore, the light intensity of 80 and 120 μmol·m~(-2)·s~(-1) is beneficial to improving yield and quality of P. quinquefolius. The above findings contributed to a theoretical basis for reasonable shading in P. quinquefolius cultivation, which is of great significance for improving the yield and quality of P. quinquefolius through light regulation.

Mineral nutrient elements are the key factors to maintain the growth and quality of American ginseng. In order to understand the comprehensive effect of different nutrient elements deficiency on American ginseng, 2-year-old American ginsengs were cultivated by Hoagland solution(CK) or 10 different nutrients deficiency solution in sand culture. During the cultivation, the deficient symptom was observed. The plant height, leaf area, biomass, photosynthetic index, root activity, ginsenoside content were measured. The results showed that N, K or Fe deficiency could lead to leaves of American ginseng yellowing. Deficiency N, K, Ca, Mg and B were the main factors that decrease plant height and leaf area. The biomass of plant decreased significantly in all the nutrient deficient treatments(P0.05)compared with control group, and N, K, Ca or Fe deficiency groups descended over 50%. In the absence of N, K and Fe elements, the P_n, G_s, C_i, T_r and chlorophyll of leaves were decreased mostly. The first three factors decreasing root activity were N, K and Ca deficiency. The effects of nutrient deficiency on saponins of American ginseng were different.Generally, N, P, B, Zn and Cu deficiency resulted the synthesis of saponins decreased significantly(P0.05). This study contributed to clarify the demand characteristics of American ginseng for different nutrient elements,which is of great significance for the diagnose of nutrient deficiency, the rational fertilizer and the improvement of yield and quality of American ginseng.

American ginseng (Panax quinquefolius) is an important medicinal plant cultivated in China since the 1980s. Its dried roots are used for food, health care products, and medicine in China (Yuan et al. 2010). Root rot caused by Fusarium spp. was a major disease, with 33 to 41% incidence surveyed in main production areas of Wendeng County (121.80 °E, 37.09 °N) in Shandong Province, China in 2016 to 2019. Symptoms included soft, water-soaked, dark brown to black lesions on the roots. Lesions progressed and the inner parts gradually disintegrated. One-year-old diseased roots were collected in September 2016. Symptomatic tissues were surface-sterilized in 75% ethanol for 30 s and 0.8% NaOCl for 3 min, rinsed in sterile water, plated on potato dextrose agar (PDA), and incubated at 25°C in darkness. Single colonies were then obtained and transferred to carnation leaf agar (CLA) (Burgess et al. 1993) for growth at 25°C with a 12-h photoperiod. Colonies cultured on PDA for 7 days were white to light pink, turning to apricot pigmentation in color. After 30 days on CLA, the colonies produced elongate, falcate macroconidia having 3 to 5 septa, with a long, tapering and curved apical cell, and having the size ranging from 31.1 to 45.6 μm long x 4 to 4.6 μm wide. Microconidia were zero to 1septate, ellipsoid to ovoid and varied in size from 9.5 to 16.8 μm long x 3 to 3.2 μm wide. Chlamydospores formed abundantly, in chains or clusters. This fungus was identified as F. armeniacum (Burgess et al. 1993). Identification was confirmed by sequencing three DNA regions including the internal spacer ribosomal DNA (ITS), elongation factor 1α and β-tubulin genes (Lu et al. 2019). The three DNA regions (MN417271, MG457199, and MN427653) had 100% homology to the sequences of F. armeniacum (KJ737378, HM744664 and HQ141640) (Wang et al. 2015, Yli-Mattila et al. 2011). Pathogenicity tests were conducted on 1- to 2-year-old bare roots and 2-year-old whole plants. For root inoculation, 14 healthy roots were inoculated with two mycelial PDA plugs/root. After 3 to 10 days at 25°C, all the inoculated roots showed water-soaked and root rot symptoms while no lesions were observed in the control roots. For plant inoculation, eight seedlings planted in pots filled with sterilized soil were inoculated by pouring a conidial suspension of 1×105 conidia/ml at 30 ml/pot. Eight seedlings inoculated with sterilized water served as the controls. After 90 days, only 37.5% of the roots survived with typical root rot symptoms whereas the control plants remained symptomless. F. armeniacum was re-isolated from symptomatic roots but not from the control roots. Besides F. armeniacum, F. solani and F. oxysporum that have been reported to be associated with American ginseng root rot in China and Canada (Reeleder et al. 2002; Punja et al. 2008) were also obtained from the diseased root samples in this study. However, the development of root rot caused by F. armeniacum was much more rapid and its symptoms were more severe. Moreover, F. armeniacum could directly infect American ginseng with no wound requirement. F. armeniacum was previously reported on Glycine max (Leguminosae) (Ellis et al. 2012), Platycodon grandiflorus (Campanulaceae) (Wang et al. 2015) and natural grasses (Poaceae) (Nichea et al. 2015). This is the first report of F. armeniacum causing root rot on American ginseng in China. As this species is more virulent to American ginseng, more research is needed to work on this disease.

Gigaporous poly(styrene-divinylbenzene) (PS) microspheres were hydrophilically modified with natural saccharide to minimize their nonspecific adsorption to proteins. The microspheres were chloroacetylated through Friedel-Crafts acetylation with chloroacetyl chloride, and then coupled with diacetone-D-glucose (DAGlu) through the Williamson reaction, and the protecting groups were removed on DAGlu. Results showed that the PS microspheres were successfully coupled with DAGlu and that the gigaporous structure was well maintained. After hydrophilization (Glu-PS), nonspecific adsorption of proteins on PS microspheres was greatly reduced. The high surface density of hydroxyl groups on Glu-PS microspheres surface make it easy to derivatize the spheres by classical methods. Flow experiments showed that the Glu-PS column had low backpressure, good permeability, and mechanical stability. All results indicate that the Glu-PS microspheres have great potential applications in high-speed protein chromatography. (C) 2012 Elsevier Ltd. All rights reserved.

Living radical polymerization of 3-O-methacryloyl-diaceton-D-glucose was carried out by the atom transfer radical polymerization (ATRP) method with an alkyl halide/copper-complex system. The effect of initiators, catalysts, ligand, and temperature on polymerization was studied in detail. Under the optimum condition, the time-conversion first-order plot was linear and the polydispersity of giycopolymer is relatively low, indicating that the polymerization is well controlled.

A magnetic nano-sized carrier for 10-hydroxycamptothecin (HCPT) was prepared by using Fe(3)O(4) nanoparticles as cores and chitosan (CS) as a polymeric shell by a novel reverse ultrasonic emulsification method. Poly(ethylene glycol) (PEG) chains were then coupled onto the magnetic particles (CS-Fe(3)O(4)) to improve their biocompatibility (PEG-CS-Fe(3)O(4)). HCPT was loaded onto PEG-CS-Fe(3)O(4) by a subtle precipitation method. Under optimum conditions, the CS-Fe(3)O(4) was close to spherical in shape with an average size of 174 nm and a high saturated magnetization. After coupling PEG chains, the unspecific adsorption of bovine serum albumin (BSA) on PEG-CS-Fe(3)O(4) decreased significantly. The drug loading content and loading efficiency were 9.8-11.8% and 49-59% for magnetic composite nanoparticles, respectively. HCPT-loaded magnetic composite nanoparticles showed sustained release profiles up to 48 h, and the cumulative release amount of HCPT from nanoparticles at 45°C increased significantly compared to that at 37°C. Cytotoxicity assay suggests that CS-Fe(3)O(4) does not exhibit noteworthy cytotoxicity against HepG2 cells, but the antitumor activities of HCPT-loaded magnetic composite nanoparticles against HepG2 cells increased significantly in comparison with that of pristine HCPT powder. These results reveal the promising potential of PEG-CS-Fe(3)O(4) as a stable magnetic targeting drug carrier in cancer therapy.