Effect of thinning on anatomical adaptations of Norway spruce needles

Conifers and other trees are constantly adapting to changes in light conditions, water/nutrient supply and temperatures by physiological and morphological modifications of their foliage. However, the relationship between physiological processes and anatomical characteristics of foliage has been little explored in trees. In this study we evaluated needle structure and function in Norway spruce families exposed to different light conditions and transpiration regimes. We compared needle characteristics of sun-exposed and shaded current-year needles in a control plot and a thinned plot with 50% reduction in stand density. Whole-tree transpiration rates remained similar across plots, but increased transpiration of lower branches after thinning implies that sun-exposed needles in the thinned plot were subjected to higher water stress than sun-exposed needles in the control plot. In general, morphological and anatomical needle parameters increased with increasing tree height and light intensity. Needle width, needle cross-section area, needle stele area and needle flatness (the ratio of needle thickness to needle width) differed most between the upper and lower canopy. The parameters that were most sensitive to the altered needle water status of the upper canopy after thinning were needle thickness, needle flatness and percentage of stele area in needle area. These results show that studies comparing needle structure or function between tree species should consider not only tree height and light gradients, but also needle water status. Unaccounted for differences in needle water status may have contributed to the variable relationship between needle structure and irradiance that has been observed among conifers.     

城市居民食物氮消费变化特征与趋势预测——以重庆市为例

城市作为全球氮热点区域,其中城市居民食物氮消费对全球氮循环的影响越来越显著,研究其变化特征及趋势,对推动城市低氮生活具有重要意义.以重庆市为例,分析1992年-2012年期间全市城市居民食物氮消费的动态变化,并结合灰色系统GM(1,1)模型,预测未来10年重庆市城市居民食物氮消费总量.研究结果表明:重庆市城市居民食物氮消费从1992年-2012年由22 130.348t增加到60 196.306t,各类食物氮消费结构中粮食消费呈不断下降趋势,蔬菜、乳制品、禽肉类的食物氮消费则呈现上升趋势.模型GM(1,1)预测显示,重庆市城市居民氮消费2022年可能超过90 000t,将进一步威胁城市环境安全,并且人均可支配收入、人均GDP以及高等学历人数比重对其具有较显著的影响.     

Can artificial introductions of diaspore fragments work as a conservation tool for maintaining populations of the rare peatmoss Sphagnum angermanicum?

Species can become regionally rare when limited by the availability of suitable habitats or by limited dispersal ability. We tested if the presence of a rare bryophyte species (Sphagnum angermanicum) was dispersal or habitat limited and at the same time investigated the possibility of establishing new populations of this rare species. Further, we tested how propagule (fragment) size and small scale disturbances affected establishment success. All field experiments were performed by artificially transporting propagules (of various sizes) to new and old sites for the species in Sweden.We show that S. angermanicum is dispersal limited on a regional scale, as no significant differences in establishment success were found between new suitable sites and old occupied sites. The larger the propagule the better was the establishment success; the best establishment success was found when transplanting whole shoots. Disturbances did not increase establishment success, in contrary, when compared to controls success was reduced by the more intensive disturbance treatments. We suggest that disturbance maybe more important for increasing direct dispersal than for making the microhabitat more advantageous for establishment. However, an intermediate disturbance, which slightly reduces the Sphagnum-community length increment, might also be beneficial for the establishment success of S. angermanicum propagules.The reasonably high establishment success of S. angermanicum propagules in new suitable sites suggests that artificial introductions of fragments could be considered as an active management regime for the species if the number of localities continues to decrease.     

Lesions in fetal pigs with transplacentally-induced toxoplasmosis

Two sows (Nos. 1, 2) were each fed 1,000 Toxoplasma gondii oocysts. Sow No. 1 was fed oocysts at 60 day of gestation and was euthanatized 49 days later. Sow No. 2 was fed oocysts at day 45 of gestation and euthanatized 62 days later. Sow No. 1 had eight dead fetuses of which one was mummified and unsuitable for histologic study. Sow No. 2 had 11 fetuses, of which four fetuses were mummified and unsuitable for histologic examination, two fetuses were dead and five were live. Lesions and Toxoplasma parasites were identified in seven fetuses from sow No. 1 and three fetuses from sow No. 2. No lesions were found in four fetuses from sow No. 2. Toxoplasma gondii was present in trophoblasts and produced areas of necrosis of the chorioallantois with focal placental separation. The predominant lesions were necrotizing placentitis, non-suppurative encephalomyelitis, and myocardial degeneration, necrosis and mineralization. Numerous tachyzoites were seen in trophoblast cells lining areolae in placenta.     

The epidemiology and control of swine parasites. Immunity and vaccines

This article discusses the status of two experimental swine helminthic vaccines and how further knowledge of parasite biochemistry and swine immunology and the application of techniques of modern biotechnology may affect their future development.     

Assessment of T lymphocyte responses induced by parasite antigens

Recently developed procedures for the isolation and continuous growth in vitro of T lymphocytes can be used to extend our knowledge of cellular immune responses elicited by parasitic infections. These procedures are adaptable to the study of both the inductive and effector phases of T cell responses. The inductive phase of T cell responses is measured by assessing the level of blastogenesis induced in antigen-primed lymphocyte populations by parasite antigens. The development of limiting dilution analyses and procedures for the repeated in vitro restimulation of such cells have allowed for the quantitation of blastogenic responses, and for the isolation of antigen-reactive T cells. The effector phase of T cell responses is assessed by assays that detect either, cytolytic activity of the antigen-responsive cells, the secretion of lymphokines by the responding cells, or specific or non-specific T cell mediated immunosuppression.     

CpG-oligodeoxynucleotides enhance porcine immunity to Toxoplasma gondii

Protection against a challenge infection with Toxoplasma gondii VEG strain oocysts was examined in pigs after vaccination with T. gondii RH strain tachyzoites with or without a porcine specific synthetic oligodeoxynucleotides (ODN) containing immunostimulatory CpG motifs. Six groups of pigs were immunized with incomplete Freund's adjuvant (IFA) and either vehicle, tachyzoites alone or in combination with three different doses of CpG ODN or with CpG ODN alone. Protection from challenge was significantly (P < 0.05) improved in pigs vaccinated using CpG ODN as an adjuvant with tachyzoites compared to all other groups. The CpG ODN tachyzoite-immunized pigs also had higher serum parasite specific IgG antibody, no clinical signs of disease, and 52% had no demonstrable tissue cysts after the challenge infection. These data indicate that CpG ODN is a potential safe and effective adjuvant for the T. gondii RH strain vaccine in pigs.