土壤酸度和施用石灰对澳洲坚果幼苗中铝,钙和锰浓度的影响

澳洲坚果(Macadamia integrifolia)在世界许多地区己逐渐成为一种重要的园艺作物。但是,有关这种作物营养状况方面的知识,特别是在不利的土壤条件下的营养状况的资料却不多。为了弥补这方面的不足,布置了一个盆栽试验,以研究铝、锰和钙(土壤酸度和施用石灰)对澳洲坚果幼苗的影响。试验中采用了三种矿物成分和土壤肥力各异的土壤,根据石灰需要量曲线对土壤 PH 进行调节,以便每种土壤都获得几种 PH 值水平(4.5—7.5)。对土壤溶液和新近完全成熟的叶片的化学成分进行定期监测,用以评价作物的生长反应。试验结果表明,当叶片的铝大于275毫克/千克和土壤溶液中的铝超过1.2毫克/升时对澳洲坚果幼苗的生理过程不利。而且,铝似乎还会减少植株对锰的吸收,尽管澳洲坚果叶片中可以积累1200毫克/千克的锰而不出现中毒症状,植株体内的钙需要量尚不明确,但是,在高度风化的氧化土中,当土壤溶液含钙160毫克/升[相当于0.9cmol(+)/千克交换性钙或 CEC的10%]时可望获得最大的生长量。     

Calcium addition at the Hubbard Brook Experimental Forest increases sugar storage, antioxidant activity and cold tolerance in native red spruce (Picea rubens)

In fall (November 2005) and winter (February 2006), we collected current-year foliage of native red spruce (Picea rubens Sarg.) growing in a reference watershed and in a watershed treated in 1999 with wollastonite (CaSiO(3), a slow-release calcium source) to simulate preindustrial soil calcium concentrations (Ca-addition watershed) at the Hubbard Brook Experimental Forest (Thornton, NH). We analyzed nutrition, soluble sugar concentrations, ascorbate peroxidase (APX) activity and cold tolerance, to evaluate the basis of recent (2003) differences between watersheds in red spruce foliar winter injury. Foliar Ca and total sugar concentrations were significantly higher in trees in the Ca-addition watershed than in trees in the reference watershed during both fall (P=0.037 and 0.035, respectively) and winter (P=0.055 and 0.036, respectively). The Ca-addition treatment significantly increased foliar fructose and glucose concentrations in November (P=0.013 and 0.007, respectively) and foliar sucrose concentrations in winter (P=0.040). Foliar APX activity was similar in trees in both watersheds during fall (P=0.28), but higher in trees in the Ca-addition watershed during winter (P=0.063). Cold tolerance of foliage was significantly greater in trees in the Ca-addition watershed than in trees in the reference watershed (P<0.001). Our results suggest that low foliar sugar concentrations and APX activity, and reduced cold tolerance in trees in the reference watershed contributed to their high vulnerability to winter injury in 2003. Because the reference watershed reflects forest conditions in the region, the consequences of impaired physiological function caused by soil Ca depletion may have widespread implications for forest health.     

Influence of Portland cement amendment on soil pH and residual soil termiticide performance

Soil adjacent to new brick veneer work is likely to have a higher pH owing to the mixture of cement with the soil. In the Gainesville, FL, area, soil samples taken from such locations had a range of pH values from 9.0 to 10.1; similar soils used in bioassays had a pH of 5.6 before the addition of cement. Addition of 15 mg of Portland cement to 33 g of soil increased the pH to 6, and addition of 291 mg of Portland cement increased the pH to 9. The pH of soil amended with cement was stable for the first 5 months. After 10 months, soil pH values decreased from alkaline to near neutral in all cases. Eastern subterranean termite workers, Reticulitermes flavipes (Kollar), were exposed to the treated soil at pH 6-9 for 24 h, and percentage mortality was recorded at 5 days, 5 months and 10 months. Termite mortality significantly decreased at higher soil pHs for bifenthrin, chlorpyrifos, fipronil and imidacloprid treatments at 5 months and similarly for bifenthrin, permethrin, chlorpyrifos, fipronil and imidacloprid treatments at 10 months. There was an inverse linear relationship between soil pH and mortality. Increased soil pH diminished residual activity of termiticide in the following order: imidacloprid > fipronil > chlorpyrifos = bifenthrin > permethrin > cypermethrin.     

Experimental reproduction of severe disease in CD/CD pigs concurrently infected with type 2 porcine circovirus and porcine reproductive and respiratory syndrome virus

Three-week-old cesarean-derived colostrum-deprived (CD/CD) pigs were inoculated with porcine circovirus type 2 (PCV2, n = 19), porcine reproductive and respiratory syndrome virus (PRRSV, n = 13), concurrent PCV2 and PRRSV (PCV2/PRRSV, n = 17), or a sham inoculum (n = 12) to compare the independent and combined effects of these agents. Necropsies were performed at 7, 10, 14, 21, 35, and 49 days postinoculation (dpi) or when pigs became moribund. By 10 dpi, PCV2/PRRSV-inoculated pigs had severe dyspnea, lethargy, and occasional icterus; after 10 dpi, mortality in this group was 10/11 (91%), and all PCV2/ PRRSV-inoculated pigs were dead by 20 dpi. PCV2-inoculated pigs developed lethargy and sporadic icterus, and 8/19 (42%) developed exudative epidermitis; mortality was 5/19 (26%). PRRSV-inoculated pigs developed dyspnea and mild lethargy that resolved by 28 dpi. Microscopic lesions consistent with postweaning multisystemic wasting syndrome (PMWS) were present in both PCV2- and PCV2/PRRSV-inoculated pigs and included lymphoid depletion, necrotizing hepatitis, mild necrotizing bronchiolitis, and infiltrates of macrophages that occasionally contained basophilic intracytoplasmic inclusion bodies in lymphoid and other tissues. PCV2/ PRRSV-inoculated pigs also had severe proliferative interstitial pneumonia and more consistent hepatic lesions. The most severe lesions contained the greatest number of PCV2 antigen-containing cells. PRRSV-inoculated pigs had moderate proliferative interstitial pneumonia but did not develop bronchiolar or hepatic lesions or lymphoid depletion. All groups remained seronegative to porcine parvovirus. The results indicate that 1) PCV2 coinfection increases the severity of PRRSV-induced interstitial pneumonia in CD/CD pigs and 2) PCV2 but not PRRSV induces the lymphoid depletion, granulomatous inflammation, and necrotizing hepatitis characteristic of PMWS.     

发酵条件和时间对红茶质量的影响

根据茶黄素、鲜爽度和感官评价，在发酵的初始阶段使用暖气会降低红茶质量，但能提高茶红素和颜色水平。与发酵110分钟相比，短发酵时间(90分钟)生产的红茶茶黄素水平较高，茶红素和颜色较低。发酵条件(如温度和湿度)和时间对平淡红茶的咖啡碱水平和香味质量参数无显影响，尽管在发酵的初始阶段，在暖发酵条件下，挥发性芳香化合物总量提高。尽管在连续发酵器的不同部分使用温度稳定的空气，但随着发酵时间的延长，茶胚温度仍然降低。然而，在不供给空气的最后一个发酵器中，随着发酵时间的延长温度升高。氧消耗量随着发酵时间的延长而减少。