马尾松幼苗光合产物的运输与分配特征

【目的】解析光合产物在马尾松幼苗植株中的运输和分配规律,揭示马尾松生产力形成过程,为探讨不同环境干扰下马尾松光合产物分配过程的变化提供参考依据。【方法】采用 13 C同位素脉冲标记法,对1.5年生马尾松幼苗进行标记,标记结束后第0、2、5、17、24、72、120、168、216和 360 h ,按不同部位对马尾松幼苗进行全收获取样,测定 13 C含量,以监测近期合成的光合产物在马尾松幼苗中的运输和分配规律,同时测定光合产物全碳、非结构性碳水化合物(NSC)在各个器官的积累量。【结果】1)标记的光合产物在针叶中合成后,向各库器官的运输量随着时间延长由多逐渐减少,具体表现为标记结束后0~24 h内最多,24~216 h逐渐减少,216 h之后运输完成,且59%以上标记的光合产物在0~24 h内运输到各库器官。2)光合产物运输趋于稳定后,在各器官的分配大小依次为1年生叶>当年生叶>根>茎干>1年生枝>当年生枝,与生物量的分配大小一致,但与库活力大小不同,其库活力依次为当年生叶>当年生枝>1年生叶>根>1年生枝>茎干。3)各器官全碳和NSC积累量的分配与近期合成光合产物的分配大小一致,依次为1年生叶>当年生叶>根>茎干>1年生枝>当年生枝。【结论】马尾松幼苗光合产物运输速率大于0.1 m ·h -1 ,59%以上标记的光合产物在合成后的0~ 24 h 内完成向各个库器官输出。新合成的光合产物在各器官中的积累量表现为功能器官(叶和根)居多,这一分配规律有利于马尾松幼苗阶段的生长。     

陕西关中地区肉牛产地同位素溯源技术初探

为应用牛组织中C、N同位素组成的区域分布和同位素指标溯源肉牛产地,本文利用同位素比率质谱仪(IRMS)对陕西关中不同区县来源的牛尾毛样品的1δ3C和1δ5N值进行检测,通过聚类分析,研究陕西关中地区肉牛组织中同位素组成的区域分布情况。结果表明,杨凌区、眉县牛尾毛样品聚为一类;乾县、永寿县样品聚为一类;麟游县样品聚为一类;扶风县、岐山县和凤翔县分类不十分明显,分散在上述3类中。说明陕西关中不同地区肉牛组织中同位素组成存在差异,利用它们可进行肉牛地域的小范围溯源。     

A comparison of changes in stable isotope ratios in the epidermal mucus and muscle tissue of slow‐growing adult catfish

Although stable isotope analysis is a powerful tool for determining diet, migration patterns and the structure of food webs in aquatic systems, the slow response of isotopic ratios in the widely used muscle tissue often hampers this approach, particularly in slow‐growing or adult fishes. We conducted a diet‐switch experiment to compare the changes in the stable carbon isotope ratio (δ¹³C values) in the epidermal mucus and muscle tissue of five‐year‐old catfish (Silurus asotus). The isotope ratios in noninvasively sampled mucus changed more rapidly than those in the muscle tissue. As isotopic change in mucus was relatively rapid, this technique can be used over a finer timescale than traditional isotopic analyses using the muscle tissue. The isotopic change half‐life in our experimental condition was 200 days, which would not be short enough for some research purposes. Examining mucus along with the muscle would enable food habits of slow‐growing fishes to be determined over different timescales. However, the rate of isotopic change in the mucus was negatively affected by the size of fish and was slower than the previously reported rates in juvenile steelhead. These findings suggest that mucus turnover rates need to be determined prior to the field data interpretation.     

miR-222 enhances HBx-HepG2 cell growth via regulation of BCL2L13 gene

AIM: To investigate the regulation of miR-222 on BCL2L13 gene and its effect on the growth and apoptosis of HBx-HepG2 cells, and to explore the underlying molecular mechanisms. METHODS: The expression level of miR-222 was detected by RT-qPCR. The HBx-HepG2 cell growth was examined by MTT and colony formation assays. The cell cycle and apoptosis were analyzed by flow cytometry. The recombination vector pmirGLO-BCL2L13 was constructed, and dual-luciferase reporter experiment was performed to validate the target of miR-222. RESULTS: The expression level of miR-222 in the HBx-HepG2 cells was significantly higher than that in the L02 cells (P<0.05). Over-expression of miR-222 enhanced HBx-HepG2 cell growth, changed cell cycle, and inhibited apoptosis (P<0.05). Knockdown of miR-222 reduced HBx-HepG2 cell growth, changed cell cycle, and increased cell apoptotic rate (P<0.05). BCL2L13 was down-regulated in the HBx-HepG2 cells as compared with L02 cells (P<0.05), and knockdown of miR-222 in the HBx-HepG2 cells increased the expression level of BCL2L13 (P<0.05). The results of dual-luciferase reporter assay and restore experiment showed that miR-222 negatively regulated the expression of BCL2L13 via targeting 3'UTR of BCL2L13, resulting in the promotion of HBx-HepG2 cell growth. CONCLUSION: miR-222 enhances HBx-HepG2 cell growth via down-regulation of BCL2L13.     

Acridones of Vepris sclerophylla: their C-NMR data

The isolation and ¹³C-NMR data of four acridones from Vepris sclerophylla are reported.     

A new chlorosesquiterpene lactone from Ambrosia maritima

A new chloro-pseudoguaianolide-type sesquiterpene lactone, 11β-hydroxy-13-chloro-11,13-dihydrohymenin (1), was isolated from the Egyptian medicinal plant Ambrosia maritima. The structure was determined by spectroscopic methods, particularly high-resolution ¹H, ¹³C-NMR and 2D ¹H–¹H and ¹H–¹³C COSY NMR analysis.     

Soil organic matter dynamics after the conversion of arable land to pasture

 Conversion of arable land (maize) to pasture will affect the soil organic matter (SOM) content. Changes in the SOM content were studied using a size- and density-fractionation method and ¹³C analysis. Twenty-six years of maize cropping had resulted in a depletion of carbon stored in the macro-organic fractions (>150 μm) and an increase in the <20 μm fraction. Maize-derived carbon in the upper 20 cm increased from 10% in the finest fraction (<20 μm) to 91% in the coarse (>250 μm), light (b.d. <1.13 g cm^–3) fractions. Pasture installation resulted in a rapid recovery of the total SOM content. Up to 90% of the pasture-derived carbon that was mineralized during maize cropping was replaced within 9 years. Especially the medium and coarse size (>150 μm) and light (b.d. <1.13 g cm^–3) fractions were almost completely regenerated by input of root-derived SOM. The amount of medium-weight and heavy macro-organic fractions (>150 μm; b.d. >1.13 g cm^–3) in the 0- to 20-cm layer was still 40–50% lower than in the continuous pasture plots. Average half-life times calculated from ¹³C analyses ranged from 7 years in the light fractions to 56 years in heavy fractions. Fractionation results and ¹³C data indicated that mechanical disturbance (plowing) during maize cropping had resulted in vertical displacement of dispersed soil carbon from the 0- to 20-cm layer down to 60–80 cm. Conversion of arable land to pasture, therefore, not only causes a regeneration of the soil carbon content, it also reduces the risk of contaminant transport by dispersed soil carbon. Received: 10 March 1998     

Carbon input by plants into the soil. Review

The methods used for estimating below‐ground carbon (C) translocation by plants, and the results obtained for different plant species are reviewed. Three tracer techniques using C isotopes to quantify root‐derived C are discussed: pulse labeling, continuous labeling, and a method based on the difference in ¹³C natural abundance in C3 and C4 plants. It is shown, that only the tracer methods provided adequate results for the whole below‐ground C translocation. This included roots, exudates and other organic substances, quickly decomposable by soil microorganisms, and CO₂ produced by root respiration. Advantages due to coupling of two different tracer techniques are shown. The differences in the below‐ground C translocation pattern between plant species (cereals, grasses, and trees) are discussed. Cereals (wheat and barley) transfer 20%—30% of total assimilated C into the soil. Half of this amount is subsequently found in the roots and about one‐third in CO₂ evolved from the soil by root respiration and microbial utilization of rootborne organic substances. The remaining part of below‐ground translocated C is incorporated into the soil microorganisms and soil organic matter. The portion of assimilated C allocated below the ground by cereals decreases during growth and by increasing N fertilization. Pasture plants translocated about 30%—50% of assimilates below‐ground, and their translocation patterns were similar to those of crop plants. On average, the total C amounts translocated into the soil by cereals and pasture plants are approximately the same (1500 kg C ha^—1), when the same growth period is considered. However, during one vegetation period the cereals and grasses allocated beneath the ground about 1500 and 2200 kg C ha^—1, respectively. Finally, a simple approach is suggested for a rough calculation of C input into the soil and for root‐derived CO₂ efflux from the soil.     

两种新型除草剂对麦田恶性杂草防除效果

推广使用高效、安全的麦田除草剂是控制节节麦等麦田恶性杂草严重发生的经济有效的措施之一，本试验采用田间试验方法研究了AEF1300603OF(3％世玛油剂)及WG13A13．6WG对麦田恶性杂革的防治效果。试验结果表明，WG13A13．6WG对麦田杂草防除效果显著，其最佳用量为25～35g／667m^2。在小麦返青期，对节节麦防效达85％～95％，对蜡烛草的防效达85％～90％，对播娘蒿、荠菜的防效达100％，对猪殃殃、婆婆纳等抗性较强的杂革防效也在90％～100％，均高于AEF1300603OF的防除效果。收获首田间调查发现防效趋势与首期调查结果一致。而且WG13A13．6WG防除杂草后使小麦的增产幅度在16．27％～25．48％。