Phosphorus dynamics in tile-drain flow during storms in the US Midwest

Excess phosphorus (P) in freshwater systems has been associated with eutrophication in agro-ecosystems of the US Midwest and elsewhere. A better understanding of processes regulating both soluble reactive phosphorus (SRP) and total phosphorus (TP) exports to tile-drains is therefore critical to minimize P losses to streams while maintaining crop yield. This paper investigates SRP and TP dynamics at a high temporal resolution during four spring storms in two tile-drains in the US Midwest. Depending on the storm, median concentrations varied between 0.006-0.025 mg/L for SRP and 0.057-0.176 mg/L for TP. For large storms (>6 cm bulk precipitation), for which macropore flow represented between 43 and 50% of total tile-drain flow, SRP transport to tile-drains was primarily regulated by macropore flow. For smaller tile-flow generating events (<3 cm bulk precipitation), for which macropore flow only accounted for 11-17% of total tile-drain flow, SRP transport was primarily regulated by matrix flow. Total P transport to tile-drains was primarily regulated by macropore flow regardless of the storm. Soluble reactive P (0.01-1.83 mg m⁻²/storm) and TP (0.10-8.64 mg m⁻²/storm) export rates were extremely variable and positively significantly correlated to both mean discharge and bulk precipitation. Soluble reactive P accounted for 9.9-15.5% of TP fluxes for small tile-flow generating events (<3 cm bulk precipitation) and for 16.2-22.0% of TP fluxes for large precipitation events (>6 cm bulk precipitation). Although significant variations in tile-flow response to precipitation were observed, no significant differences in SRP and TP concentrations were observed between adjacent tile-drains. Results stress the dominance of particulate P and the importance of macropore flow in P transport to tile-drains in the US Midwest. Although only spring storms are investigated, this study brings critical insight into P dynamics in tile-drains at a critical time of the year for water quality management.     

3种外来树种抗寒性生理指标的比较

以日本厚朴、山樱和美国七叶树的引种实生苗为试材,系统地分析了低温胁迫下其植株的生理生化变化,研究了日本厚朴、山樱和美国七叶树的越冬抗寒机理.试验结果表明,-30 ℃是日本厚朴安全越冬的低温临界值;低温诱导过程中组织中游离脯氨酸含量与外渗电导率变化明显,可以作为鉴定日本厚朴、山樱和美国七叶树抗寒性的生理指标.     

光照条件对参株碳水化合物和人参皂甙含量的影响

本试验测定了５％，２０％，３５％和５０％４种透光棚下人参植株各器官可溶性糖，淀粉和参根皂甙含量的变化。主要结果是：不同光强下人参植株各器官可溶性糖含量无明显差异，淀粉含量则随着光强和增加而增加，在５％和２０％透光棚下，参根皂甙含量随着淀粉含量的增加而增加，并达到最大值；在３５％和５０％透光棚下，参根皂甙含量则随着淀粉含量的增加而下降。参根淀粉含量与参根干重呈显著正相关。     

泽漆化感机理的初步研究

运用室内培养皿生物测定方法,对泽漆的化感作用的研究表明,泽漆水提液对小麦幼苗生长有明显的抑制作用,且抑制强度随浸提液浓度升高而加强,其对小麦根的抑制作用比对苗的抑制作用明显。供试小麦的一些生理测定指标表明,泽漆水提液刺激供试小麦的根系活力增强,可溶性蛋白含量降低,叶绿素含量稍有下降。过氧化氢酶(CAT)活性下降,过氧化物酶(POD)活性和超氧化物歧化酶(SOD)活性明显提高。     

马铃薯离体块茎发育过程中的关键因子及其与蛋白质组分的关系

 利用多元相关、通径分析及线性回归分析等手段 ,针对马铃薯离体块茎发育过程中各影响因子对块茎发育的贡献程度进行分析。结果表明 :平均薯重、质体 Mg2 + - ATP酶活性、质体 Ca2 + - ATP酶活性、线粒体 Mg2 + - ATP酶活性、总可溶性蛋白含量、块茎平均直径、Q酶活性等是影响块茎产量的重要因素 ,其中平均薯重、质体 Mg2 + - ATP酶活性、质体 Ca2 + - ATP酶活性、线粒体 Mg2 + - ATP酶活性等是影响离体块茎发育的关键因子。所得线性回归方程为 :Y=0 .5 2 11+0 .0 5 95 X(1) +0 .8389X(2 ) +0 .0 882 X(3) - 0 .0 0 73X(4) +0 .144 9X(5 ) +0 .35 10 X(6 ) +0 .0 0 31X(7) -0 .0 0 0 0 3X(8) +0 .34 12 X(9) +0 .0 12 7X(10 ) +0 .2 90 4X(11) +0 .0 5 70 X(12 ) +0 .0 15 9X(13) +0 . 35 85 X(14) +0 .0 134 X(15 ) - 0 .10 12 X(16 )。在此基础上 ,对于影响离体块茎发育的各关键因子与块茎蛋白质组分的关系进行分析 ,找到了一些可能与发育中这些重要性状相关的蛋白质组分。即总可溶性蛋白组分中 A4、B1、B8、C8,质体蛋白组分中A4及线粒体蛋白组分中的 A4与 B2等 ,对于马铃薯离体块茎晚期发育具有重要作用。     

小麦籽粒蛋白质组分及其与面条品质的关系

 采用新的蛋白质组分分离方法,对黄淮部分冬麦区25个小麦品种籽粒的单体蛋白含量、可溶性谷蛋白含量、不溶性谷蛋白含量进行了分析,同时对各蛋白质组分与其它蛋白质指标、面条品质的关系进行了研究。结果发现,黄淮冬麦区小麦的平均单体蛋白、可溶性谷蛋白和不溶性谷蛋白的比例为3.7∶1.0∶1.8;与有关文献比较,分析样品的单体蛋白含量偏低,可溶性谷蛋白含量偏高,不溶性谷蛋白含量较低,这可能就是面包小麦和面条小麦在蛋白质组成上的本质区别。单体蛋白对于面条拉伸特性作用小于谷蛋白。可溶性谷蛋白含量、不溶性谷蛋白含量与其它蛋白质     

不同氯化物对土壤铜活性的影响

采用室内培养方法研究了不同氯化物KCl、NH4Cl、MgCl2、CaCl2和FeCl3作为添加剂对土壤中铜的活性影响。结果表明,施用各种添加剂都可增加土壤中水溶态和交换态铜含量以增加土壤铜的活性,且随着投加的氯化物浓度的增加而增加,其中FeCl3对土壤铜的活化能力最强,而KCl对土壤铜的活化能力最弱。     

盐胁迫对NewHy Crested牧草种子萌发的影响

研究不同浓度盐溶液胁迫下NewHy Crested牧草种子发芽率及其萌发过程中淀粉酶活性和可溶性糖含量变化,结果表明,与Hoagland营养液(CK)相比,0.7、1.4 g/100 ml NaCl盐溶液和0.7 g/100 ml土壤浸提液对发芽率影响不显著(P＞0.05),萌发过程中淀粉酶活性、可溶性糖含量未见显著下降(P＞0.05);2.1 g/100 ml NaCl盐溶液和1.4、2.1 g/100 ml胁迫时,发芽率显著下降(P＜0.05),萌发过程中淀粉酶活性、可溶性糖含量亦显著下降.NewHy Crested牧草种子对盐渍生境的适应性较强,能耐受较高盐胁迫.