Diurnal variation in xylem hydraulic conductivity in white ash (Fraxinus americana L.), red maple (Acer rubrum L.) and red spruce (Picea rubens Sarg.)

Xylem hydraulic conductivity and percentage loss of conductivity (PLC) were measured on a ring-porous ( Fraxinus americana L., white ash), a diffuse porous ( Acer rubrum L., red maple) and a coniferous ( Picea rubens Sarg., red spruce) tree species in a temperate deciduous forest in central Massachusetts, USA. Measurements were made on current and 1-year-old branch segments in the afternoon and on the following morning. Afternoon PLC was 45 to 70% for the current year's extension growth in both white ash and red maple. Morning PLC was significantly lower (10–40%). Conductivity also varied diurnally suggesting, on average, a 50% recovery from cavitation overnight. Red spruce showed lower PLC and conductivity and a less pronounced night-time recovery. Diurnal variation in hydraulic conductivity and PLC suggests that embolism removal occurred in all three species despite the existence of tension within the xylem. Further evidence for embolism removal was observed with an in situ double-staining experiment in which dyes were fed to a transpiring branch during the late afternoon and the following morning. Examination of stem cross-sections showed that a larger number of vessels were conductive in the morning than on the preceding afternoon. Results of this study suggest that hydraulic capacity is highly dynamic and that conductivity measurements reflect a balance between two processes: cavitation and embolism removal.     

Integrated generation of solid fuel and biogas from green cut material from landscape conservation and private households

Green cut material is a potential source of renewable energy which is not fully exploited through conventional energy recovery systems. A new energy conversion process, the integrated generation of solid fuel and biogas from biomass (IFBB), which includes mechanical separation after hydro-thermal conditioning, was investigated. Ash softening temperature and lower heating value of the solid fuel were increased through the IFFB process in comparison to the untreated raw material. The net energy yield of IFBB at 40 °C conditioning temperature ranged between 1.96 and 2.85 kWh kg(-1) dry matter (DM) and for the direct combustion between 1.75 and 2.65 kWh kg(-1) DM. Conversion efficiencies for the IFBB system were 0.42-0.68 and for direct combustion 0.42-0.63. The IFBB system produces storable energy from material which is nowadays not used for energy conversion.     

Phenotypic and genotypic intra-diversity among Anatolian durum wheat “Kunduru” landraces

Kunduru is an important Anatolian landrace having peculiar traits that are appreciated by farmers and breeders. 33 accessions known as Kunduru collected by ICARDA from six geographical provinces of Turkey, were used to study the phenotypic and genotypic intra-diversity. Kunduru landraces exhibited high intra-diversity for most of the studied morphological traits. GPC (12.10–14.90%), vitreousness (75–100%), TKW (31.80–56.70 g), YP (4.70–8.00 ppm), b*-value (14.30–19.50), ash content (1.60–2.0%) and gluten strength (14–60 ml) showed marked variations. Gliadin and glutenin banding patterns showed high polymorphism. 65 alleles were detected with 14 SSR markers, giving a mean of 6.77 alleles per locus. The average PIC value was 0.44 and ranged from 0.11 to 0.70. The average genetic distance between pairs of landraces was 0.47 and ranged between 0.11 and 0.72. This study showed that Kunduru landraces maintains high allelic variation. PCoA indicated that eco-geographical variables have a significant effect on SSR diversity as well as morphological traits. Many of the landraces studied are in danger of disappearing from the local farmers' fields; this study demonstrates the importance of maintaining and conserving this precious genetic resources.     

Light-modulation of nitrate reductase activity in leaves and roots of maize

The nuclear DNA content in ray cells from the 1-year-old vascular cambium of white ash ( Fraxinus americana L.) trees was determined at intervals during the annual cycle of cambial activity and dormancy by using Feulgen microspectrophotometry. By 10 September, these cells had entered dormancy in G₁ with a normal DNA distribution and a minimal average DNA content of 2.65 pg. The average amount of DNA increased to 3.51 pg by 30 November, remained at this elevated value until at least 30 March, when the cambium was still dormant, then declined to the minimum level on 1 May and 10 June, when the cells were mitotically active. The springtime decline appeared to occur both before and during cell division. Between 1 May and 10 June, the prophase (4C) and telophase (2C) DNA contents decreased significantly. The amount of nuclear DNA measured by microspectrophotometry was verified by using flow cytometry and image analysis. The results support the view that there is an annual oscillation in the nuclear genome size of shoot meristematic cells in tree species native to the northern temperate zone.     

藏羚羊冷季对干物质的消化效率

藏羚羊（Pantholops hodgsoni）为青藏高原特有物种,也是世界上最为珍贵和稀有的物种之一。作为青藏高原野生食草动物的典型代表,藏羚羊种群也是构成青藏高原自然生态系统极为重要的组成部分。藏羚羊独特的体态和生理结构,对研究生物适应与进化,尤其是研究高原条件下的生物适应与进化,维护高原地区生态平衡均有极为重要的意义（郑中朝和李宏,2002）。对藏羚羊牧草利用特征的研究对其营养生态学的研究具有重要的科学价值。本文采用藏羚羊饲草中酸不溶灰分作为内源指示剂,对其冷季牧草消化率进行了初步研究,现将结果予以报道。     

火山岩滤料固定化恶臭假单胞菌条件的优化及其吸附铜离子的研究

以多孔介质火山岩滤料为载体,探讨了温度、转速、反应器的底面积等因素对滤料固定化恶臭假单胞菌的影响,比较了固定化恶臭假单胞菌野生菌和重组菌吸附Cu2+的效果.结果表明,火山岩滤料固定化恶臭假单胞菌的最优条件为选择底面积较大的反应器、30℃、静置条件下吸附3.5h.固定化野生菌、重组菌滤料及空白滤料对Cu2+的吸附率依次为:74.76％、89.36％和55.09％.为多孔载体固定化微生物在废水处理中的应用提供了实验依据.     

Estimating the biomass of freshwater mussels (Bivalvia: Unionidae) from shell dimensions

Packs of autumn-shed maple leaves were placed at coal ash effluent-exposed and reference sites in streams on December 5, 1977 and removed after 27 and 96 days. Leaf surface area (cm²/leaf) and disc weight (ash-free dry wt/15 mm disc) were greater at the effluent-exposed site than at the reference site after 96 days (p < .001). ATP content of leaves from the reference stream quadrupled between 27 and 96 days while ATP content of effluent-exposed leaves remained low. Macroinvertebrates colonized the leaf packs in the reference site but were not found on or in effluent-exposed packs. We concluded that leaf processing beyond the leaching of soluble organics did not occur in the effluent-exposed packs owing to reduced colonization and decomposition by fungi. Since stream invertebrates prefer decomposed leaf material and animals grow faster on leaves colonized by microbes, the ash effuent appears to indirectly affect macroinvertebrates by interfering with leaf decomposition and thus reducing the quality of their food.