Genotypic Variability in Biomass Protein and Nucleic Acids in Four Linum Species to Sodicity Stress

Differences in gas exchange parameters i.e. carbon exchange rate (CER), transpiration (Tr), water vapor conductance (g) were investigated, under a controlled environment, in a semi-dwarf (SD) Triticum aestivum line, its tall (TL) near isoline and the Payne (PA) variety characterized by small leaves. The plants were maintained in: (a) optimal substrate moisture condition (CTR); (b) salinized by watering with a 0.12 m NaCl solution (SLT); (c) water stressed by withholding waterings during a period of six days (STR); (d) stressed and salinized during the same period and with the same saline solution (S + S). CER and Tr were negatively affected by the stresses; SLT and S + S treatments had a higher WUE compared to their respective controls CTR and STR.
SD line had a better performance in terms of CER and WUE, particularly when water and salt stresses interacted. Leaf anatomy and assimilation/internal CO₂ concentration curves contributed to explaining the SD performance.     

建筑物的机械排烟

本文作者从实际经验出发,详细阐述了建筑物的机械排烟原理及设计施工,管理中的各项注意事项。     

Stoffbildung, CO2-Gaswechsel, Kohlenhydrat- und Stickstoffgehalt von Winterweizen bei erhöhter CO2-Konzentration und Trocken-streß

Dry Matter Production, CO₂ Exchange, Carbohydrate and Nitrogen Content of Winter Wheat at Elevated CO₂ Concentration and Drought Stress
Methods of mathematical modelling and simulation are being used to an increasing degree in estimating the effects of rising atmospheric CO₂ concentration and changing climatic conditions on agricultural ecosystems. In this context, detailed knowledge is required about the possible effects on crop growth and physiological processes. To this aim, the influence of an elevated CO₂ concentration and of drought stress on dry matter production, CO₂ exchange, and on carbohydrate and nitrogen content was studied in two winter wheat varieties from shooting to milk ripeness. Elevated CO₂ concentration leads to a compensation of drought stress and at optimal water supply to an increase of vegetative dry matter and of yield to the fourfold value. This effects were caused by enhanced growth of secondary tillers which were reduced in plants cultivated at atmospheric CO₂ concentration. Analogous effects in the development of ear organs were influenced additionally by competitive interactions between the developing organs. The content and the mass of ethanol soluble carbohydrates in leaves and stems were increased after the CO₂ treatment and exhausted more completely during the grain filling period after drought stress. Plants cultivated from shooting to milk ripeness at elevated CO₂ concentration showed a reduced response of net photosynthesis rate to increasing CO₂ concentration by comparison with untreated plants. The rate of dark respiration was increased in this plants.     

Long-term application of animal slurries to grassland alters soil cation balance

Abstract. Soil samples from a 32-year grassland field experiment were taken from 0–5, 5–10, and 10–15 cm soil depths in February 2002. Plots received annual treatments of unamended control, mineral fertilizer, three rates of pig slurry and three rates of cow slurry, each with six replicates. Samples were analysed for cation exchange capacity (CEC), exchangeable cations (Na⁺, K⁺, Ca²⁺, Mg²⁺), pH and Olsen P. Exchangeable sodium percentage (ESP) was calculated as a sodicity indicator. Mean ESP was generally greater for slurry treatments than the control, with a trend of increasing ESP with application rate. This was particularly marked for cow slurry. At 0–5 cm depth ESP increased from 1.18 in the control to 1.75 at the highest rate of pig slurry and 5.60 at the highest rate of cow slurry. Similar trends were shown for CEC, exchangeable Na⁺, K⁺ and Mg²⁺, Ca²⁺ and Olsen P. The build-up of soil P due to slurry applications, together with this combination of physical and chemical factors, may increase the risk of P loss to surface waters, particularly from soils receiving high rates of cow slurry.     

不同生长年限王草的营养价值研究

本文对生长第1、2、3年的王草在100cm高度时刈割的营养成分及其体外干物质、有机物降解率进行分析研究。结果表明:不同生长年限王草第1年的粗蛋白质显著高于第2、3年(P<0.05),而中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)显著低于第3年(P<0.05)。干物质、有机物的降解率第1年最高,第3年的最低,但差异不大。     

Growth- and leaf-temperature effects on photosynthesis of sweet orange seedlings infected with Xylella fastidiosa

The effects of growth and leaf temperature on photosynthesis were evaluated in sweet orange seedlings ( Citrus sinensis cv. Pera) infected with Xylella fastidiosa (the bacterium that causes citrus variegated chlorosis, CVC). Measurements of leaf gas exchange and chlorophyll  a fluorescence were taken at leaf temperatures of 25, 30, 35 and 40°C in healthy and infected (without visible symptoms) seedlings submitted to two temperature regimes (25/20 or 35/20°C, day/night), not simultaneously. The CO₂ assimilation rates ( A ) and stomatal conductance ( g _s) were higher in healthy plants in both temperature regimes. Values for A and g _s of infected and healthy plants were higher in the 35/20°C regime, decreasing with leaf temperature increase. In addition, differences between healthy and infected plants were higher at 35/20°C, while no differences in chlorophyll  a fluorescence parameters were observed except for potential quantum efficiency of photosystem II, which was higher in infected plants. Low A values in infected plants were caused by low g _s and probably by biochemical damage to photosynthesis. The high alternative electron sink of infected plants was another effect of reduced A . Both high growth and high leaf temperatures increased differences in A between healthy and infected plants. Therefore this feature may be partially responsible for lower growth and/or productivity of CVC-affected plants in regions with high air temperature.     

京西稻的百年传承与发展

京西稻是清康熙、雍正、乾隆等亲自选育的优良品种,在与紫禁城并重的"三山五园"政治中心内外种植,具有多重价值属性,属于皇家御稻.从2000年起,基于北京水资源匮乏等原因,京西稻种植面积大幅度降至134 hm2左右,处于濒危状态.在保护传承过程中,京西稻入选中国重要农业文化遗产目录.在新修订的《北京历史文化名城保护条例》中...     

池塘和稻田养殖模式下克氏原螯虾肌肉和肝脏营养成分比较

通过对池塘和稻田2种养殖模式下克氏原螯虾(Procambarus clarkii)的肌肉常规营养成分进行测定,同时,对肌肉和肝胰腺的氨基酸和脂肪酸组成进行测定,从而对其营养品质进行分析评价.结果显示,2种养殖模式下克氏原螯虾粗蛋白和粗脂肪无显著性差异(P＞0.05),池塘养殖模式下水分显著高于稻田模式(P＜0.05),...