Assessment of sugar maple tree growth in relation to the partitioning of elements in xylem along a soil acidity gradient

Partitioning of elements in tree xylem is being increasingly studied, as it suggests that elements are potentially mobile within the xylem long after their uptake. A recent study revealed that only the most mobile xylem fraction (water-soluble) of base cations (calcium [Ca], magnesium [Mg], and potassium [K]) increased at higher soil acidity, while the two mobile fractions (water- and acid-soluble) of acidic metals—potentially phytotoxic aluminium (Al), cadmium (Cd) and manganese (Mn)—were significantly enhanced on very acid soils. The current paper presents an investigation of soil-wood chemistry relationships with basal area tree growth. It was hypothesized that the growth of sugar maple would be reduced by low base cation and high acidic metal concentrations in the xylem mobile fractions. Sugar maple trees (n = 55) from six watersheds in southern Quebec, Canada were analysed by sequential chemical extractions for the water-soluble, acid-soluble and residual fractions of base cations (Ca, K, Mg) and acidic metals (Al, Cd, Mn) in xylem. Generally, tree growth was positively correlated to concentrations of base cations in wood (ρ = 0.27-0.50) and soil (ρ = 0.41-0.67), and negatively correlated to concentrations of acidic metals in wood (ρ = −0.33 to −0.52) and soil (ρ = −0.67). However, these relations differed depending on the element fraction considered. Water- and acid-soluble xylem concentrations of base cations and Al were among the best predictors of growth trends (R² = 0.46-0.51). The relationship between acidic metals and tree growth is further discussed.     

闽台葡萄种植关键技术比较与合作思考

以2011年5月16日中国农学会葡萄分会和台湾21世纪农业发展基金会在福建省福安市召开的海峡两岸葡萄科技合作恳谈会为契机,总结比较了闽台葡萄种植的五项关键性技术,并对闽台葡萄产业的合作发展提出建议。     

The effect of lime levels on the growth of beans and maize and nodulation of beans in three tropical acid soils

Abstract

A study to investigate the effect of lime on dry matter yield of maize (Zea mays) and beans (Phaseolus vulgaris) and nodulation of beans grown in three tropical acid soils (two humic Nitosols and one humic Andosol) was carried out in a greenhouse. The soils ranged from 4.2 to 5.0 in pH; 1.74 to 4.56 in %C; 21.0 to 32.0 meq/100g in CEC; 5.10 to 8.10 meq/100g in exchange acidity; 0.60 to 3.20 meq/100g in exchangeable (exch.) Al and 0.13 to 0.67 meq/ 100g in exch. Mn.

Exchange acidity and exch. Al decreased with increasing levels of lime in the three soils. Exchangeable Al was reduced to virtually zero at pH 5.5 even in the soils which had appreciable initial amounts. Exchangeable Mn also decreased with increasing levels of lime in the two Nitolsos. Exceptional results, however, were obtained with the Andosol where exch. Mn increased ten‐fold with the first level of lime and then decreased with subsequent levels.

In all the soils, mean dry matter yield of beans and maize, and mean nodule dry weight of beans generally increased significantly with increasing lime levels up to pH value of 6.0. The dry matter yield of beans and maize, and nodule weight of beans, however, decreased progressively with increasing lime levels beyond pH 6.0 value. pH range of 5.5 to 6.0 was considered optimum for the growth of maize and beans, and nodulation of beans in these soils.     

玉米不同自交系幼苗光合对 UV-B 辐射增强的响应

为了探讨玉米不同自交系对UV-B辐射增强的响应，在摸拟光照培养条件下，研究了增强UV-B辐射对玉米不同自交系气体交换参数的影响。结果表明，五叶期UV-B辐射处理6 d后，供试的48个自交系中近一半以上材料的幼苗叶片光合速率、气孔导度和蒸腾速率显著降低10％以上，其材料比例分别为64．6％，47．9％，54．2％；而有62.5％的材料胞间CO2浓度表现为显著增加；相关分析发现，气孔导度与蒸腾速率对UV-B辐射增强的响应值间存在极显著正相关关系；根据气体交换参数对UV-B辐射增强的响应程度将48个材料分成6类，其中对增强UV-B辐射反应比较敏感的材料和能够忍耐UV-B辐射增强的材料均占12．5％。说明玉米不同自交系幼苗叶片气体交换参数对UV-B辐射增强反应敏感程度具有显著的基因型差异，从中能够筛选出对UV-B辐射增强反应敏感和有忍耐能力的材料。     

中缅油气管道国内段砂土液化处理措施

中缅油气管道国内段沿线存在不连续的长距离砂土液化地带,砂土液化是地下管道遭受地震破坏的主要原因之一.为增强管道抵抗土壤液化的能力,通过对砂土液化现象及其危害进行分析,结合油气管道沿线砂土液化特点,对管道敷设深度内有中等、严重砂土液化趋势的地段采取平衡压袋稳管方式进行液化处理.该处理措施具有经济、环保、便于施工、不影响管道主体工程安装和总体工期等特点,而且对于避免和减轻地震灾害,确保油气管道的安全运行具有重要意义,在类似管道工程建设中值得推广应用.(表2,图3,参4)     

气相色谱-电子捕获检测器测定电子废弃物处理场地底泥中的四溴双酚-A

通过优化分析仪器的条件设置，建立了使用气相色谱-电子捕获检测器技术分析四溴双酚-A（TBBP—A）的仪器分析方法。样品采用正己烷索氏提取、硅胶柱分离纯化、外标法定量，结果表明，测定方法在测量范围内具有良好的线性关系，测定的平均回收率为86．8％，检出限为5．0ng／ml，相对标准偏差为3．26％～8．77％：     

Salt‐Induced Regulation of Some Key Antioxidant Enzymes and Physio‐Biochemical Phenomena in Five Diverse Cultivars of Turnip (Brassica rapa L.)

A greenhouse experiment was carried out to examine the differential morpho‐physiological responses of five cultivars of turnip (Brassica rapa L.) to salt stress. Five diverse cultivars of turnip (shaljum desi surakh, shaljum purple top, shaljum golden bal, neela shaljum, and peela shaljum) were subjected for 6 weeks to varying levels of NaCl, i.e. 0, 80 and 160 mm in Hoagland’s nutrient solution in sand culture. Imposition of varying levels of salt substantially decreased shoot and root fresh and dry weights, chlorophyll contents, leaf osmotic potential, relative water contents, different gas exchange attributes, total phenolics, malondialdehyde, activities of superoxide dismutase, peroxidase catalase, and leaf and root K⁺ levels while enhanced the proline contents, membrane permeability, level of H₂O₂, leaf and root Na⁺ and Cl^? and leaf Ca²⁺ in all turnip cultivars under study. Of all cultivars, peela shaljum and neela shaljum were consistently higher in their growth than the other turnip cultivars at all salt concentrations of the growth medium. Photosynthetic capacity (A) and stomatal conductance (g_s) were higher in high biomass‐producing cultivars, i.e. peela shaljum and neela shaljum, which provide to be potential selection criteria of salt tolerance in turnip. However, the regulation of antioxidant system was cultivar‐specific under saline conditions.     

Effect of practical diets with different protein levels on the performance of Farfantepenaeus paulensis juveniles nursed in a zero exchange suspended microbial flocs intensive system

Farfantepenaeus paulensis juveniles (72 ± 24 mg), were reared in a suspended microbial flocs system and fed practical diets containing increasing amounts of crude protein (250, 300, 350, 400 and 450 g kg^?1 CP). Development of microbial flocs was promoted by high aeration rates and fertilization with wheat bran and molasses. Flocs were composed of detritus in the form of flocculated matter colonized by heterotrophic bacteria, cocoid and filamentous cyanobacteria, flagellate and ciliate protozoa and rotifers. Proximate composition analysis of the suspended microbial floc showed CP levels of 304 g kg^?1. After 45 days, mean shrimp survival were above 89%, with no significant differences between treatments. Shrimp fed diets with 350 g kg^?1 or higher CP content achieved significant higher (P < 0.05) final weight (0.66–0.68 g), weight gain (0.58–0.61 g) and instantaneous growth rate (0.049–0.050), with feed conversion rates (2.17–2.30) significantly lower (P < 0.05). Results show that, when rearing is carried out in a suspended microbial flocs system, dietary CP levels can be kept at 350 g kg^?1. Furthermore, results confirm that microbial‐based systems allow shrimp culture without compromising the surrounding environment and shows the possible reduction of production costs and fish meal dependence.     

桑叶多糖的分离及红外光谱和气相色谱分析

多糖是桑叶中的重要功能性成分之一。采用水煮提取、乙醇分级沉淀和Sephadex G-100凝胶层析的方法,从桑叶中分离、纯化出3种多糖组分:MPSⅠ、MPSⅡ和MPSⅢ。经红外光谱分析,MPSⅠ不同于MPSⅡ和MPSⅢ,表现出长分子链、β-糖苷键构型和含酰胺基团等特征。气相色谱分析结果显示,L-鼠李糖、D-葡萄糖和D-半乳糖是3种桑叶多糖的共同成分,其中D-葡萄糖和D-半乳糖的构成比例较大,3种桑叶多糖的单糖构成也存在明显差异。     

Responses of leaf photosynthesis and plant growth to altered source–sink balance in a Japanese and a Dutch tomato cultivar

We investigated the effects of altered source/sink ratio by leaf or fruit pruning on leaf photosynthetic characteristics and whole-plant growth of ‘Momotaro York’, a Japanese cultivar, and ‘Dundee’, a Dutch cultivar and verified a hypothesis for sink-limitation of plant growth proposed by Tanaka and Fujita (1974). Plants were grown hydroponically with a high-wire system in a greenhouse for 11 weeks. Light-saturated photosynthesis of young, fully expanded leaves measured at atmospheric CO₂ partial pressure of 37 Pa and at an intercellular CO₂ partial pressure of 20 Pa was not influenced by alteration of source/sink ratio for either cultivar. Although soluble sugars were accumulated in leaves under high source/sink conditions, the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase, a rate-limiting factor for CO₂-limited photosynthesis, was not affected by the altered source–sink balance. Net assimilation rate of a whole plant increased with decreasing source/sink ratio, but this can be accounted for by the changes in light interception per unit leaf area, without taking the source–sink relationship into consideration. It was concluded that the altered source/sink ratio did not change leaf photosynthetic capacity and the sink-limitation hypothesis cannot be applied to either cultivar under the conditions of the present study.