长春地区不同类型土壤的缓冲性及其影响因素

研究了长春地区主要类型土壤的缓冲性及土壤理化性质对土壤缓冲性的影响。结果表明：5类土壤对酸缓冲性弱程度依次为：黑钙土＞草甸土＞黑土＞白浆土＞暗棕壤；对碱的缓冲性强弱顺序是：草甸土＞白浆土＞暗棕壤＞黑土＞黑钙土；土壤碳酸钙含量、交换性盐基总量、土壤质地和有机质含量对土壤缓冲性的强弱均具有不同程度的影响。     

渠灌区灌溉管理信息化发展模式探讨

探讨了我国渠灌区灌溉管理信息化的发展模式,阐述了灌区进行灌溉管理信息化建设的意义和必要性,构想了灌区灌溉信息网络系统的建网模式和基本框架。     

Limit of T cell tolerance to self proteins by peptide presentation

Cytotoxic T lymphocytes (CTLs) recognize foreign peptides bound to major histocompatibility complex (MHC) class I molecules. MHC molecules can also bind endogenous self peptides, to which T cells are tolerant. Normal mice contained CTLs specific for self peptides that were from proteins of ubiquitous or tissue-restricted expression. In vivo, these endogenous self peptides are not naturally presented in sufficient density by somatic cells expressing MHC class I molecules. They can, however, be presented if added exogenously. Thus, our data imply that CTLs are only tolerant of those endogenous self peptide sequences that are presented by MHC class I-positive cells in a physiological manner.     

Stakeholder participation in agricultural research projects: a conceptual framework for reflection and decision-making

Recent discourse in the field of participatory agricultural research has focused on how to blend various forms and intensities of stakeholder participation with quality agricultural science, moving beyond the simple “farmer-first” ideology of the 1980s and early 1990s. Yet, most existing frameworks of participation in agricultural research still adhere to a linear typology of participatory research with an inherent claim of “the more participation, the better.” In this article, we propose a new framework that looks at participatory research elements along different dimensions and attributes and thus takes into account the diversity and dynamics of agricultural research projects. The framework provides a basis for agricultural researchers engaged in participatory processes with local stakeholders to decide for which issues and in which phases certain participatory elements could be used in a specific research context. Rather than aiming at maximizing the adoption of participatory methods, it can thus become a tool for optimizing the use of participatory approaches in agricultural research. We conclude that this framework can be a starting point for a more thoughtful integration of participatory elements in agricultural research projects that does justice to the multidimensional and dynamic nature of stakeholder participation in varying contexts.     

Two gap genes mediate maternal terminal pattern information in Drosophila

In Drosophila three maternal pattern organizing activities, the anterior, the posterior, and the terminal, establish the anterior-posterior body pattern of the embryo by initiating the spatially restricted activities of the gap class of zygotic segmentation genes. The activities of tailless (tll) and the newly identified gap gene huckebein (hkb) are specifically involved in mediating the maternal terminal information at the posterior end of the blastoderm embryo.     

Expression of beta-nerve growth factor receptor mRNA in Sertoli cells downregulated by testosterone

Nerve growth factor (NGF) is synthesized in male germ cells. The NGF receptor (NGFR) mRNA was found in the Sertoli cells of rat testis. Hypophysectomy increased both NGFR mRNA in testis and the number of NGFR hybridizing cells in seminiferous tubules. This was suppressed by treatment with chorionic gonadotropin or testosterone, but not with follicle-stimulating hormone. The NGFR mRNA also increased after destruction of Leydig cells or blocking of the androgen receptor. This suggests that NGF produced by male germ cells regulates testicular function in an androgen-modulated fashion by mediating an interaction germ and Sertoli cells.     

Product differentiation via corporate social responsibility: consumer priorities and the mediating role of food labels

This article examines quantitatively the determinants of purchase decisions based on corporate social responsibility (CSR), adopting a hierarchical conceptual model of decision making where the key factors are personal concern, information availability and financial considerations. We use best–worst methods to assess consumer priorities (personal concern) for CSR activities in milk production; and elicit consumer interpretation of four labels (organic, Validus, Colorado Proud and rBST free) in terms of CSR and other outcomes (information availability). We then elicit willingness to pay (WTP) for the labels (financial considerations), and estimate regression models to determine how predictive each label perceptual profile is of WTP for milk. Animal welfare and sustainable agricultural practices are the most important activities, and milk labels do convey CSR-related messages. With the exception of the pair animal welfare-Validus, the link between CSR messages and WTP is tenuous. The discussion emphasizes the central role of each label’s perceptual profile in triggering product differentiation among consumers.     

Monitoring of soil organic carbon over 10 years in a Mediterranean silvo-pastoral system: potential evaluation for differential management

Soil organic carbon (SOC) plays a vital role in determining the susceptibility to land degradation. The recommended procedure for the recovery of the characteristic poor soils of the Southern region of Portugal is the installation of grazed permanent pastures and increase of soil fertility. The objectives of this study were: (i) to identify the spatial and temporal patterns of soil nutrients at four points in time over a 10-year period in a perennial pastureland; (ii) to test new tools for survey of the spatial variability of soil nutrients; (iii) to evaluate the potential for differential organic management. A 6 ha permanent bio-diverse pasture field, grazed by sheep and improved by annual application of super phosphate fertilizer, was installed on a shallow soil in Mediterranean conditions. Spatial variability and temporal stability of topsoil macronutrients (phosphorus, nitrogen and potassium), SOC and pH were measured. The results indicate that SOC and pH have great potential for implementing differential management. In the case of SOC, the management classes map shows that over 80 % of the area has temporal stability, while more than 50 % of the area has low levels of SOC (<10 g kg^?1), justifying the potential for differential application of C-rich organic soil amendments. The geospatial measurements of apparent soil electrical conductivity (EC_a) and NDVI index showed significant correlation between these parameters and soil properties, revealing the potential of these tools for producing detailed soil maps, decisive for understanding the changes in soil properties under sustainable management systems.     

Glutathione functions on physiological characters to increase copper-induced corn production

Glutathione (GSH) abundantly presents in plant and affects plants growth and development. To justify if GSH affects copper (Cu)-induced corn production, photosynthesis (Pn) rate, and photosynthetically active radiation (PAR), chlorophyll (Chl) content and Chl fluorescence, relative water content (RWC) and yields were evaluated. Different Cu concentrations (0, 0.2, 1.5 and 3.0 ppm of Zn) with or without 100 µm of N-acetyl cysteine (NAC) were arranged as completely randomize design with 5 replications. Results showed that both NAC and Cu affected plant height and leaf numbers. Copper reduced Pn rate, and PAR and increased RWC but no effect was observed on Chl content and Chl fluorescence in leaves. On the other hand, NAC application increased Pn, PAR, Chl parameters regardless of Cu treatment. In the presence of 1.5 ppm of Cu, corn plants showed improve yield and cob length irrespective to NAC treatment. Taken together, this study suggests that NAC might improve some physiological functions in plants to enhance Cu-induced corn production.