Yongli Zhu

An Electrochemical Approach Coupled with Sb Microelectrode to Determine the Activities of Carbonic Anhydrase in the Plant Leaves

The electrochemical approach coupled with Sb microelectrode was developed to determine the carbonic anhydrase activity in a wide range. The sensing response of the microelectrode had a good linear relationship between potential and pH value in barbital buffer. The temperature would not affect the linear relationship. During the determination, the open-circuit potential method was taken to monitor the whole course of the reversible conversion catalyzed by carbonic anhydrase, and then the initial part of uniform velocity from the reaction curve was chosen to calculate the reaction velocity (the time to change one unit of pH). This technique, in comparison with the conventional method was used to determine the activities of bovine red blood cells carbonic anhydrase, foliar carbonic anhydrase and extracellular carbonic anhydrase in some plants. The result showed that the electrochemical approach coupled with Sb microelectrode would obtain more credible, accurate data than the conventional method.

Preliminary Studies on Gross Nitrification, Denitrification and Respiratory Rates in Sediments from a Typical Coastal Wetland, Chongming East Intertidal, Using a Method of BaPS

Drying and re-flooding in coastal wetlands physically response to the periodic semi-lunar and diurnal tides, together with the rising and leaching of salts. This substantially complicates nitrogen transformation in sediments. Sediment and water samples are taken from Chongming east intertidal flat, a typical coastal wetland in China, to investigate gross nitrification, denitrification and respiratory rates under three simulated processes of drying and rewetting, using a method of barometric process separation (BaPS). When moisture of sediment decreases to 30% during drying period, nitrification, denitrification and respiratory rates reach the maximum of 2249, 4149 μg N·kg^-1SDW·h^-1 and 3948 μg C·kg^-1SDW·h^-1, respectively. After then, the rates decrease linearly with the decreasing moisture. During the cycles of semi-lunar tide, the highest nitrification and denitrification rates occur at moisture of 30-35% with a mean of 2809±925 and 4280±115 μg N·kg^-1SDW·h^-1, respectively. In contrast, the respiratory rates reach the highest at 20-40%, varying between 3165-6677 μg C·kg^-1SDW·h^-1. In addition, it is found that BaPS system does not smoothly work when moisture of sediment is above 40%.

Dynamics of phosphorus in water-sediment interface during the courses of proliferating, blooming and decaying of C. Reinhardtii under simulated conditions

Water and sediment samples, collected from Meiliang Bay in Taihu Lake, were employed to investigate the dynamic of phosphorus in water-sediment interface during the courses of proliferating, blooming and decaying of C. Reinhardtii under simulated conditions. Particulate phosphorus released from the decayed algae and sediment increased the availability of phosphorus to algae during the incubation. In addition, the activities of alkaline phosphatase in sediment were enhanced and in turn, it promoted the release of phosphorus under the conditions. It showed that C. Reinhardtii possibly made nutrition preparation to some extent for their proliferating again during water bloom.

Measurement of lettuce leaf chlorophyll content by means of VIS-NIR spectroscopy

Time and fast diagnosis for nitrogen nutrition in vegetables is useful for fertilization management and improving the product quality. In order to develop a method for rapid detection of leaf nitrogen content in lettuce, visible and near infrared (Vis-NIR) spectroradiometer was used to collect the spectral data, and the leaf chlorophyll content were obtained by chlorophyll meter (SPAD 502). Different spectra preprocessing techniques, which included moving average filter (MAF), Savitzky-Golay filter (SGF), first derivative (FD),second derivative (SD), normal normalization (NM) and their combination, were used for select the best chlorophyll content prediction model. And stepwise regression (SWR) and partial least squares regression (PLS) were applied to choose the characteristic wavelengths. It was confirmed that the characteristic wavelength was at 368 nm, 694 nm, 744 nm and 825 nm, respectively. Based on these wavelengths, a linear regression model was performed with correlation coefficient 0.9583 and root mean squared error of prediction (RMSEP) 2.695. Therefore, it was concluded that the Vis-NIR technique could be an available method for rapid detection of lettuce leaf chlorophyll content.

Assaying the Activity of Nitrate and Nitrite Reductases in Sediment from a Eutrophic Lake

Sediment, sampled from Meiliang Bay in Lake Taihu, Eastern China, was employed to investigate the activities of nitrate reductase (Nar) and nitrite reductase (Nir) and their response to toluene. The optimum incubation times for assaying the activity of Nar and Nir in the sediment were 24-27 h and 21-24 h, respectively. Nir activity is easily inhibited by toluene while the Nar activity shows tolerance to toluene. The nitrate or nitrite consumed by potential denitrification in the sediment is 2-5 times greater than that by the dissimilatory reduction of nitrate to ammonia pathway during the incubations.