[Responses of Nicotiana tabacum morphology and photosynthetic physiology to reduced ultraviolet-B radiation].

By the method of canopy film-covering to reduce UV-B radiation, this paper studied the responses of the morphology and photosynthetic physiology of Nicotiana tabacum cultivar K326 at its physiological, technical, and physiological-technical transitional maturity stages in high-elevation tobacco-growing area of Yunnan. Three treatments were installed, i.e., reducing 75.74% (T1), 70.08% (T2), and 30.39% (T3) of natural solar UV-B radiation. Reducing UV-B radiation increased the stem height and the internode distance of K326 significantly, with the larger values in T2. Comparing with those under natural UV-B radiation condition, the leaf net photosynthetic rate (Pn), assimilation capacity (AC), water use efficiency (WUE), intrinsic water use efficiency (WUEi), photosynthetic pigments (PP) and flavonoids (FL) contents, and specific leaf mass (SLM) in T1 and T2 all decreased, with larger decrement in T2. The factors affecting the Pn in T, and T2 were stomatal and non-stomatal, and the latter was the main one. The major reason of the lower WUE in T1 and T2 was due to the increase of transpiration rate (Tr) caused by low stomatal regulation capability. In T3, the Pn, AC, WUE, WUEi, and PP increased but the FL and PP decreased to the lowest levels at physiological and transitional maturity stages, and the PP degradation rate was faster at the technical maturity stage.

[Using stable isotope to trace the sources of nitrate in groundwater in Shijiazhuang].

A dual isotope method of measuring both the delta 15N and delta 18O in NO3- was used to discriminate the origin of nitrate and its denitrification in groundwater in Shijiazhuang. Furthermore, the contaminated depth was discussed by tritium. The results show that the ratio of delta 15N/delta 18O in NO3- is close to 2:1, indicating that some denitrification is occurring in this area; The value of delta 15N and delta 18O in NO3- after denitrification are 4.6 per thousand-13.9 per thousand and 1.9 per thousand-7.8 per thousand respectively, which indicates that the main source of nitrate in groundwater are local fertilizer and Animal Waste/Septic Systems. The relationship between NO3- concentration and the depth also shows that the pollution depth is less than 150 m, which is corresponding to the depth of active rechargezone indicated by tritium content. This implies the shallow aquifer above 150m is vulnerable to pollution.

Overproduction of soluble recombinant transglutaminase from Streptomyces netropsis in Escherichia coli.

A novel microbial transglutaminase (TGase) from the cultural filtrate of Streptomyces netropsis BCRC 12429 (Sn) was purified. The specific activity of the purified TGase was 18.2 U/mg protein with an estimated molecular mass of 38 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. The TGase gene of S. netropsis was cloned and an open reading frame of 1,242 bp encoding a protein of 413 amino acids was identified. The Sn TGase was synthesized as a precursor protein with a preproregion of 82 amino acid residues. The deduced amino acid sequence of the mature S. netropsis TGase shares 78.9-89.6% identities with TGases from Streptomyces spp. A high level of soluble Sn TGase with its N-terminal propeptide fused with thioredoxin was expressed in E. coli. A simple and efficient process was applied to convert the purified recombinant protein into an active enzyme and showed activity equivalent to the authentic mature TGase.