Understanding the adaptability of Chionanthus retusus Lindl. et Paxt. to extreme water conditions will help in exploring the potential application of this species in barren mountains. Three-year-old Chionanthus retusus seedlings were used in a greenhouse pot experiment that analyzed the effect of different moisture gradients on growth, photosynthetic and fluorescence characteristics, protective enzyme system, osmotic substance regulation and cell membrane damage. The results indicated that C. retusus can effectively grow at a relative soil water content of 44.6% and above and can maintain growth for 20 days under flooded conditions. Under drought stress, net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and intercellular carbon dioxide concentration (Ci) all showed a trend of gradual decrease. The trend of change was similar under waterlogging conditions. The maximal quantum yield of PSII photochemistry (Fv/Fm), actual photochemical efficiency of PSII (ΦPSII), photochemical quenching coefficient (qP), and electron transport rate (ETR) all decreased as drought deepened. Malondialdehyde (MDA) content decreased first and then increased. However, superoxide dismutase (SOD) activity content, peroxidase (POD) activity content, and proline (Pro) activity content showed a trend of increasing and then decreasing. C. retusus had good adaptability in the slight drought treatment group and flooded treatment group but showed intolerance in the high drought group, which could still last for approximately 21 days. C. retusus was found to have a strong adaptability to water stress and can be used as an afforestation tree in barren mountains.
Real-time and rapid monitoring of the electron transport in nanoscale structures is critical for understanding many fundamental phenomena. However, it is not possible to rapidly record the dynamical current that varied across several orders of magnitude by using a typical linear low-noise current-to-voltage converter due to its fixed gain. In addition, it faces a great challenge in carrying out a dynamical small current measurement by using a commercial source-monitor unit device with both high-precision and high-speed because a high-precision measurement normally requests long integration time, while high-speed sampling demands short integration time. To overcome these challenges, we designed a measurement system with an integrated logarithmic amplifier, which can convert the current/conductance signal (varied across eight orders of magnitude) into an output voltage signal (varied within only one order of magnitude). We successfully applied it for the dynamical conductance measurement of single molecular break junctions in which the current rapidly changed from milliampere (mA) to picoampere (pA) within tens of milliseconds under a fixed bias voltage. It is demonstrated that the intrinsic conductance can be determined accurately independent of the applied bias and the real-time dynamical conductance traces can be precisely recorded with a high-speed sampling ratio. This logarithmic amplifier design and home-made measurement system provide a way to realize a fast measurement (30 kHz) for a rapidly varied current (mA–pA), making it suitable for the characterization of single-molecule junctions during the break process, and show potential for a wide application far beyond molecule electronics.
In order to study the tolerance and removal capability of Salix matsudana to phenol wastewater, we determined the effects of different concentrations of phenol on the photosynthesis, chlorophyll fluorescence parameters and enzyme activities of S. matsudana cut seedlings and their purification effects to phenol using hydroponics. The results show that wastewater containing 30 mg L-1 and 60 mg L-1 phenol increased Pn, Gs and Tr of S. matsudana, however, the maximum photochemical efficiency (Fv/Fm) of PSII changed little. When the concentration of phenol increased to 90 mg L-1-180 mg L-1, Pn and Fv/Fm of S. matsudana were significantly lower than those in the control group, while the Ci increased significantly. The 30 mgL-1-150 mgL-1 of phenol can increase the SOD and POD activities in leaves and roots of S. matsudana and the 180 mgL-1 of phenol decreased their activities. The percent removal of phenol decreased with increasing concentration of phenol ranging from 87% to 98% in 10 days. In conclusion, S. matsudana can be used to purify waste water containing phenol in concentration less than 150 mg L-1.
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