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Despite extensive studies documenting that changes in plant community structure in response to enhanced atmospheric nitrogen (N) deposition were driven by positive effects of N enrichment on rhizome clonal plants in grassland communities, few studies have specifically investigated the responses of rhizome clonal plants to N enrichment in terms of above-and below-ground plant traits.<br>By monitoring above-ground and below-ground plant traits, we investigated long-term (13-year) effects of N addition (64 g m<sup>−2</sup> yr.<sup>−1</sup>) on <i>Leymus chinensis</i>, a rhizome clonal plant, in temperate steppes of northern China.<br>Nitrogen addition enhanced the relative above-ground biomass of <i>L. chinensis</i> from 0.6% (2004) to 75% (2016) in steppe communities. Nitrogen addition enhanced leaf N and chlorophyll concentrations, and specific leaf area, thus leading to a marked increase in photosynthetic rates. Nitrogen addition altered the patterns of carbon allocation, by enhancing the ratios of below-ground to above-ground biomass, while N addition reduced the ratios of rhizome to root biomass. Nitrogen addition modified morphological traits of absorptive fine roots (first two-order roots) by enhancing specific root length and reducing root tissue density and average root diameter. Nitrogen addition significantly shortened rhizome internodes and increased bud density of <i>L. chinensis</i>.<br>Nitrogen addition enhanced <i>L. chinensis</i> resource-acquiring and vegetative reproduction capability, thereby leading to its predominance in the steppe communities.
<p>This issue of the journal <em>Materials for Historical Research on Kanlho</em> (Kan lho'i lo rgyus dpyad gzhi'i yig rigs) provides short histories for over 80 Tibetan Buddhist monasteries in Gannan Tibetan Autonomous Prefecture in Gansu Province, China. (Ben Deitle 2009-07-15)</p>
Four common traditional tibetan medicine prescription preparations "Anzhijinghuasan, Dangzuo, Renqingchangjue and Rannasangpei" in tibetan areas were selected as study objects in the present study. The purpose was to try to establish a kind of wet digestion and flow injection-hydride generation-atomic absorption spectrometry (FI-HAAS) associated analysis method for the content determinations of lead and arsenic in traditional tibetan medicine under optimized digestion and measurement conditions and determine their contents accurately. Under these optimum operating conditions, experimental results were as follows. The detection limits for lead and arsenic were 0.067 and 0.012 µg · mL(-1) respectively. The quantification limits for lead and arsenic were 0.22 and 0.041 µg · mL(-1) respectively. The linear ranges for lead and arsenic were 25-1,600 ng · mL(-1) (r = 0.9995) and 12.5-800 ng · mL(-1) (r = 0.9994) respectively. The degrees of precision(RSD) for lead and arsenic were 2.0% and 3.2% respectively. The recovery rates for lead and arsenic were 98.00%-99.98% and 96.67%-99.87% respectively. The content determination results of lead and arsenic in four traditional tibetan medicine prescription preparations were as fol- lows. The contents of lead and arsenic in Anzhijinghuasan are 0.63-0.67 µg · g(-1) and 0.32-0.33 µg · g(-1) in Anzhijinghua- san, 42.92-43.36 µg · g(-1) and 24.67-25.87 µg · g(-1) in Dangzuo, 1,611. 39-1,631.36 µg · g(-1) and 926.76-956.52 µg- g(-1) in Renqing Changjue, and 1,102.28-1,119.127 µg-g(-1) and 509.96-516.87 µg · g(-1) in Rannasangpei, respectively. This study established a method for content determination of lead and arsenic in traditional tibetan medicine, and determined the content levels of lead and arsenic in four tibetan medicine-prescription preparations accurately. In addition, these results also provide the basis for the safe and effective use of those medicines in clinic.
Zuotai (gTso thal) is a typical representative of Tibetan medicines containing heavy metals, but there is still lack of modem safety evaluation data so far. In this study, acute toxicity test, sub-acute toxicity test, one-time administration mercury distribution experiment, long-term mercury accumulative toxicity experiment and preliminary study on clinical safety of Compound Dangzuo were conducted in the hope of obtain the medicinal safety data of Zuotai. In the acute toxicity test, half of KM mice given the lethal dose of Zuotai were not died or poisoned, and LD50 was not found. The maximum tolerated dose of Zuotai was 80 g x kg(-1). In the subacute toxicity test, Zuotai could reduce ALT, AST, Crea levels in serums under low dose (13.34 mg x kg(-1) x d(-1)) and medium dose (53.36 mg x kg(-1) x d(-1)), with significant difference under low dose, and increase the levels of ALT, AST, MDA, Crea in serums under high dose (2 000 mg x kg(-1) x d(-1)); besides, the levels of BUN and GSH in serums reduced with the increase in dose of Zuotai, indicating a significant dose-effect relationship. In the one-time administration distribution experiment, the content of mercury in rat kidney, liver and lung increased after the one-time administration with Zuotai, with a significant dose-dependent relationship in kidney. In the long-term mercury accumulative toxicity experiment, KM mice were administered with equivalent doses of Zuotai for 4.5 months and then stopped drug administration for 1.5 months. Since the 2.5th month, they showed significant mercury accumulation in kidney, which gradually reduced after drug withdrawal, without significant change in mercury content in liver, spleen and brain and ALT, AST, TBIL, BUN and Crea in serum. At the 4.5th month after drug administration, KM mice showed slight structural changes in kidney, liver and spleen tissues, and gradually recovered to normal after drug withdrawal. Besides, no significant difference in weight gain was found between the Zuotai group and the control group. According to the findings of the clinical safety study of Dangzuo, after subjects administered Dangzuo under clinical dose for one month, their serum biochemical indicators, blood routine indicators and urine routine indicators showed no significant adverse change. This study proved that traditional Tibetan medicine Zuotai was slightly toxic, with a better safety in clinical combined administration and no adverse effects on bodies under the clinical dose and clinical medication cycle. However, long-term high-dose administration of Zuotai may have a certain effect on kidney.;