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1.
基质条件对苦草(Vallisneria natans)生长和形态特征的影响 总被引：3，自引：0，他引：3
通过模拟实验,对不同基质条件下苦草（Vallisneria natans）的形态特征、生物量积累及分配格局进行了研究.结果表明：（1）在营养盐较丰富的湖泥中,苦草的生物量、分株数量和匍匐茎总长度等指标显著大于粘土和沙土,也显著大于营养盐和有机质更高的河泥;（2）沙土中生长的苦草根系纤细,根系直径显著小于其他3种基质类型上的苦草;（3）河泥和沙土上生长的苦草叶绿素含量显著地低于湖泥和粘土上的苦草.因此,基质条件对苦草的生长和形态有较大的影响,苦草在一定程度上能够适应肥沃的基质条件,但当N、P、有机质含量过高时,苦草的生长受到抑制. 相似文献
2.
Dredge samples and photographs from the Blake Plateau, off the southeast coast of the United States, indicate that a layer of manganese oxide forms pavement that may be continuous over an area af about 5000 square kilometers. The manganese pavement grades into round manganese nodules to the south and east and into phosphate nodules to the west. The Gulf Stream probably maintains a very unusual environment that prohibits deposition of clastic sediment and permits accretion of manganese pavements. 相似文献
3.
Sediment accumulation rate curves from 95 drilled cores from the Pacific basin and sea-level curves derived from continental margin seismic stratigraphy show that high biogenous sediment accumulation rates correspond to low eustatic sea levels for at least the last 48 million years. This relationship fits a simple model of high sea levels producing lower land/sea ratios and hence slower chemical erosion of the continents, and vice versa. 相似文献
4.
豆科植物根瘤形成条件初探 总被引：5，自引：0，他引：5
豆科植物的根瘤可以从空气中固定氮气而在贫瘠的土壤中生长。它的形成需要土壤中的根瘤菌或人工培养的根瘤菌与植物共同形成。但根瘤的形成还可由培养根瘤菌的无菌滤液诱导形成,这充分说明根瘤菌生长过程中分泌的某种可溶性物质具有刺激植物形成根瘤的作用,但这种根瘤由于不能形成豆血红蛋白而呈淡绿色或白色,且根瘤中有大量淀粉积累。实验中通过对根瘤的接种、观察、分析,总结了根瘤形成的原因,使我们对根瘤的研究更加深入。 相似文献
5.
Gurnis M 《Science (New York, N.Y.)》1992,255(5051):1556-1558
Dynamic topography resulting from initiation of slab subduction at an ocean-continent margin causes the continental lithosphere to subside rapidly. As subduction continues and the slab shallows, a basin depocenter and forebulge migrate in toward the continental interior. Finally, closure of the ocean basin leads to regional uplift. These active margin processes have commonly been ascribed to supracrustal loading, but numerical modeling shows that dynamic subsidence rates can exceed 100 meters per million years and are similar to rates of sediment accumulation along convergent North American plate margins over the Phanerozoic. 相似文献
6.
The soil actinomycete causing formation of nitrogen-fixing symbiotic nodules on roots of the woody angiosperm Comptonia peregrina (L.) Coult. (Myricaceae) has been isolated from surface-sterilized root nodules after incubation and enzyme maceration. The filamentous bacterium grows slowly in pure culture on a yeast extract medium, producing sporogenous bodies which form large numbers of ovoid spores. Reinfection of sand-grown or aeroponically grown seedlings of Comptonia was achieved repeatedly with inocula prepared from suspensions of the Comptonia isolate. The same actinomycete has been reisolated from these seedling nodules. The induced nodules are highly active in the acetylene-reduction assay, and plants grow vigorously without an exogenous supply of fixed nitrogen. 相似文献
7.
Milliman JD 《Science (New York, N.Y.)》1966,153(3739):994-997
Recrystallized planktonic limestones from two guyots in the North Atlantic are in oxygen-isotopic equilibrium with their present ambient waters, suggesting submarine lithifica tion and recrystallization. The early stages of submarine lithification of carbonates may involve precipitation of, and replacement by, magnesium-rich calcite; with time this may invert to magnesium-poor calcite. This type of lithification probably requires very low rates of sediment accumulation. 相似文献
8.
Radiocarbon dating and sedimentological studies of closely spaced cores indicate movement during the Holocene of sediments on the New Jersey continental slope and upper rise between Wilmington and Lindenkohl canyons. The uneven time-stratigraphic thickness of the late Quaternary sediment sections between cores and the nonuniform deposition rate at any given core site and among core sites show that the sediment blanket in canyon and intercanyon areas has been affected by downslope, gravity-driven pocesses during the Holocene to the present. The reduced rate of deposition on the slope and upper rise between the late Pleistocene and the present is largely due to decreased off-shelf transport in response to the eustatic rise in sea level. Very old radiocarbon dates at core tops result from emplacement of older reworked materials from upslope or from truncation of sections by mass wasting processes exposing older material at the sea floor. These processes also account for an irregular sequence of dated sections within cores and stratigraphic irregularities of the surficial cover from core to core. Marked variability in deposition rates on the slope and upper rise is largely a function of topographic configuration, proximity and accessibility to sediment source, and transport processes seaward of the shelf break. Moreover, higher accumulation rates on the upper rise are attributed primarily to slope bypassing. Bypassing, prevalent during the late Pleistocene, has continued periodically to the present. 相似文献
9.
An empirical correlation between marine barite (BaSO4) accumulation rate in core-top sediment samples from two equatorial Pacific transects (at 140°W and 110°W) and the estimated primary productivity of the overlying water column were used to evaluate glacial to interglacial changes in productivity. Fluctuations in barite accumulation rates down-core indicate that during glacial periods of the past 450,000 years, the productivity in the central and eastern equatorial Pacific was about two times that during intervening interglacial periods. This result is consistent with other evidence that productivity was high in the eastern and central equatorial Pacific during the last glacial. 相似文献
10.
Sediment distribution on the mid-ocean ridges with respect to spreading of the sea floor 总被引：1，自引：0，他引：1
An abrupt change in sediment thickness between the crests and flanks of the mid-ocean ridges can be interpreted as a major discontinuity in the rates either of spreading of the sea floor or of accumulation of sediment. The preferable interpretation of the data is that the process of spreadig of the sea floor is intermittent and that the present cycle of spreading commenced around 10 million years ago. following a long period Of quiescence during which most of the observed sediments were deposited. 相似文献
11.
12.
通过温室盆栽试验,在黑麦草修复重金属(Zn,Pb,Cu,Cd,Ni)——有机物复合污染的城市排污河道疏浚底泥的过程中投加EDTA(1mmol/kg和3mmol/kg),柠檬酸(5mmol/kg和15mmol/kg),DTPA(1mmol/kg和3mmol/kg),研究了对黑麦草生长及重金属积累、底泥特性的影响。结果表明,5mmol/kg的柠檬酸提高了重金属在植物地上部分的积累量,但没有达到显著水平,增大柠檬酸的投加量阻碍了植物的生长、抑制了对重金属的吸收。3mmol/kg的EDTA和DTPA均能提高植物对重金属的积累量,但也降低了植物的叶绿素含量。5mmol/kg的柠檬酸降低了底泥的pH,但其它2种螯合剂对底泥的pH没有明显的影响。3种螯合剂均增加了底泥溶液中重金属的浓度;增大了底泥大颗粒体积百分比,降低了其比表面积和晶格强度,有助于底泥颗粒释放吸附的重金属;提高了底泥中微生物的数量;增加了底泥的TOC含量。5mmol/kg的柠檬酸提高了底泥脲酶的活性,但效果不显著,而其它2种螯合剂均明显降低了脲酶活性,3种螯合剂对过氧化氢酶活性的影响均不明显。 相似文献
13.
Somayajulu BL 《Science (New York, N.Y.)》1967,156(3779):1219-1220
Analyses of beryllium-10 activity in two sections of a manganese nodule indicate an accumulation rate that compares well with such rates measured by other methods on different nodules. The observed specific activity of beryllium-10 in the nodule is in accord with the calculations based on the production of beryllium-10 by cosmic rays in the atmosphere and with the geochnemistry of beryllium in the ocean. 相似文献
14.
Manganese nodules: their evolution 总被引：1，自引：0，他引：1
That manganese nodules and adjacent deep-sea sediments are accumulating manganese at almost the same rate has been established by thorium-230 dating of both sediments and nodules of known manganese content. The rate of manganese deposition is nearly constant over the world oceans. A relatively simple model of nodule evolution explains the distribution of manganese nodules between sediment column and sediment-water interface; the model appears to apply to other trace elements such as copper, nickel, and cobalt. 相似文献
15.
【目的】针对辽宁省花生产地速效钾含量偏低,钾肥施用量不足的现状,探究不同钾水平对花生根系、根瘤特性、主要养分吸收速率以及产量的影响,以期明确最佳的钾肥施用量,为当地的花生生产提供理论依据和参考。【方法】本试验于2018—2019年在沈阳农业大学进行,以农花9号为试材,设0（CK）、112.5 kg·hm-2（T1）、225 kg·hm-2（T2）和337.5 kg·hm-2（T3）4个钾肥处理,采用大田随机区组试验,研究了不同施钾量对花生根系干物质积累、根系形态、根瘤特性、植株养分吸收和产量的影响。【结果】2年试验结果表明,施钾对花生根系干重影响不大,各处理的根系干物质积累量无显著差异;与未施钾肥的CK相比,T2处理的施钾量可显著增加花生的总根长、总根表面积和总根体积;根瘤对钾素较敏感,在施钾量为112.5 kg·hm-2时,根瘤数量及干重在各时期均达到最大,钾素的施入促进了根瘤在花生结荚期的衰老;增施钾肥提高了植株氮、磷、钾素的最大积累速率、平均积累速率和最大积累量,延长了氮和钾的活跃积累期;施钾225 kg·hm-2时单株荚果数等产量构成因素及产量均高于其他处理。【结论】施钾量为225 kg·hm-2（T2）时,最有利于花生根系生长和养分吸收,增产效果最好;在施钾量为112.5 kg·hm-2（T1）时,最有利于根瘤的生长,增产效果次之。 相似文献
16.
本实验以042B 的 DNA 转化 ROG31细胞,在以0.2 mol/L NaCl 为选择标记的YMA 培养基上,获得37个耐盐的菌落,纯化后又经30代的转管移植,有8株转化子获得了稳定的耐盐性,再将这8株转化子回接红豆草植株,得到1株耐0.4 mol/L NaCl 和固氮能力较好的红豆草根瘤菌 ROt6。供体菌042B 和转化子 ROt1和 ROt6在0.3 mol/L NaCl 培养基中生长时,细胞内积累大量谷氨酸。 相似文献
17.
Growth in vitro of cells from hyperplastic nodules of liver induced by 2-fluorenylacetamide or aflatoxin B1 总被引：1，自引：0，他引：1
M Slifkin L P Merkow M Pardo S M Epstein J Leighton E Farber 《Science (New York, N.Y.)》1970,167(916):285-287
Cell suspensions obtained from hyperplastic nodules induced in rat liver by either of the two hepatic carcinogens, 2-fluorenylacetamide or aflatoxin B(1), show growth when cultured in vitro. No growth of cells from liver adjacent to the hyperplastic nodules or from liver of control rats has been obtained so far under comparable conditions. Hepatocarcinoma cells induced by 2-fluorenylacetamide grow readily in vitro but behave differently. These findings suggest that some nonmalignant cells capable of growth in vitro arise during liver carcinogenesis prior to the appearance of unequivocal cancer. Cultures of such cells may offer new avenues for the study of liver carcinogenesis. 相似文献
18.
Features exhibited by a large number of sea floor photographs together with the dating of 187 sediment cores from the southeast Indian Ocean have revealed extensive manganese nodule development and sediment erosion in deep basinal areas. The most extensive nodule field, with an area of 10(6) square kilometers, occurs in the northwestern sector of the South Australian Basin and is named the Southeast Indian Ocean Manganese Pavement. The crests and flanks of the adjacent mid-ocean ridge are, in contrast, free of nodules and marked by much less dynamic bottom water conditions. 相似文献
19.
以第四纪红壤和河潮土进行盆栽试验，探讨了氯化铵不同用量对小白菜产量和品质的影响．结果表明：合理施用氯化铵，小白菜产量增加，可溶性糖含量上升，两者均达极显著水平．氯化铵的最高施用量约３７５ｋｇ／ｈｍ２；采用氯化铵做氮肥，能有效降低小白菜体内硝酸盐积累量，试验中所有小白菜鲜样品的硝酸盐（ＮＯ－３）含量均在４３２ｍｇ／ｋｇ以下，符合食用的硝酸盐控制标准；土壤中氯离子含量在３００ｍｇ／ｋｇ左右时，小白菜能正常生长，过量使用氯化铵将产生小白菜氯中毒 相似文献
20.
为探究典型湿地挺水植物香蒲(Typha angustifolia L.)在砷(As)污染下的生长状况,以及香蒲中As的累积与迁移特征,设置As0、As50、As150、As600 4个梯度As污染生境,对应底泥中As含量分别为0、50、150、600 mg·kg-1,探析As胁迫下生命周期内(生长期、成熟期、萎黄期)香蒲的生长发育、As累积特征及其对土壤中As的提取效果。结果表明:在4种程度As胁迫下香蒲均能完成生命周期,结出种子柱头。生长期,As50处理香蒲根系耐性指数最高,达到132.38%;As150处理香蒲生物量为19.12 g,较As0处理高出34.08%;As600处理生物量积累为12.35 g,较As0处理减少13.39%,此时香蒲根系耐性指数最小,为65.23%。成熟期,As50处理香蒲生物量累积最大,达到72.23 g,较As0处理高出28.70%,此时香蒲根系耐性指数最高,为149.25%;As600处理生物量积累最低,香蒲根系耐性指数最小。萎黄期,As50处理香蒲生物量累积最高,达到79.23 g,较As0处理高出23.94%,此时香蒲根系耐性指数最高,达到119.28%;As600处理下生物量积累最低,较As0处理下降13.47%。在香蒲生长的3个阶段,底泥As含量为0 ~50 mg·kg-1时香蒲叶片谷胱甘肽活性最高;As50和As150处理的PSⅡ光合反应系统最大光合潜力(Fv/Fm)均高于As0处理,而As600处理下香蒲Fv/Fm最低,此时叶片超氧化物歧化酶活性和丙二醛含量最高;香蒲地下部对As的生物富集系数大于地上部,植株间转运系数为0.09~1.10,香蒲对底泥中As的固定率大于去除率,提取量和单位面积迁移量与底泥中As含量呈极显著正相关。说明香蒲可以耐高浓度As胁迫并正常生长,对As污染湿地底泥有良好的修复效果,可以将香蒲作为As污染湿地植物建群种,香蒲生长达到萎黄期之前增加对香蒲的收获和更换次数可以获得更好的修复效果。 相似文献