Fennoscandian plant communities dominated by the evergreen dwarf shrub Empetrum hermaphroditum Hagerup appear to have negative effects on forest regeneration. Effects of water extracts of leaves of E. hermaphroditum on the development and nitrogen uptake by roots and mycorrhizae (Paxillus involutus Batsch (Fr.)) of Scots pine (Pinus silvestris L.) were studied in a greenhouse experiment. Among seedlings that did not receive E. hermaphroditum extract, mycorrhizal plants grew better than nonmycorrhizal plants and also had a higher shoot to root ratio. Nitrogen uptake per unit root length was 3 times faster in mycorrhizal plants. The uptake of nitrogen was 92 ng∙day−1 per dichotomous tip as compared with 22 ng∙day−1 per nondichotomous root tip (mycorrhizal plants had both dichotomous and nondichotomous tips, whereas uninoculated plants almost exclusively had nondichotomous tips). A low concentration of extract impaired nitrogen uptake in both mycorrhizal and nonmycorrhizal plants. Uptake per unit root length was reduced to one-third and one-tenth in mycorrhizal and nonmycorrhizal plants, respectively. Calculated per dichotomous tip per day, the uptake of nitrogen was reduced to only 0.9 ng. Additions of extract also retarded increases in root length and the numbers of root tips, although less markedly, but the percentage of dichotomous tips was more strongly reduced. Empetrum hermaphroditum extract also strongly inhibited the growth of Paxillus involutus on modified Melin – Norkrans agar medium. The spread of mycorrhizal infection (as indicated by the percentage of dichotomous tips) and uptake of nutrients by roots and mycorrhizae were more sensitive to the extract than seed germination and radicle growth, which were demonstrated to be affected under field conditions. Key words: allelopathy, Empetrum hermaphroditum, forestry, mycorrhiza, nitrogen.
Based on the analysis on the transfer process of benzene hexachloride (HCH), this paper proposed the theory of vertical water body effect, vertical water body cumulative effect, and vertical water body dilutive effect, including definition, main function, and concept model. Furthermore, this paper applied vertical water body effect in analyzing the transfer processes of HCH in Jiaozhou Bay Waters. Results showed that this theory was useful and effective in revealing the changes of HCH under the effects of vertical water body.
Metal-organic frameworks (MOFs), as drug delivery carriers, with high loading capacity and controllable release behavior can provide a more efficacious therapy in cancer treatments. In our work, a novel biocompatible zinc MOF Zn-cpon-1 with the (3,6)-connected rtl 3D topological network was designed and synthesized via employing ClO anion as template. The optically and chemically stable Zn-cpon-1 could be verified as a pH-responsive dual-emission platform and excellent drug delivery carrier with higher 5-fluorouracil (5-FU) (44.75 wt %) loading behavior than 6-mercaptopurine (6-MP) (4.79 wt %) ascribed to the influence of size and shape matching. The multiple interactions between Zn-cpon-1 and 5-FU drug molecules have been discussed and evidenced, which could be quantitatively estimated via the rate constant related to the topological structure. Specially, the gust release behavior of 5-FU@Zn-cpon-1 microcrystal was described and programmed via the Weibull distribution model and could be dual-triggered by the temperature and pH stimulus. This study illustrates that the Zn-cpon-1 without any postmodification performs a favorable potential of being used as biomedical drug delivery alternative carriers in effective drug payload, flexible release administration, and superior dual-stimuli responsiveness.
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