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1.
Abstract

An important consideration for milk thistle (Silybum marianum L.) cultivation is regulating development to lengthen the reproductive stage and increase seed yield with high silymarin content. The treatment of milk thistle with foliar fertilizers and growth regulators—thidiazuron (Dropp®), 2,3,5‐triiodobenzoic acid (Tiba®), mepiquat chloride (Pix®), and prohexadione‐Ca (Regalis®)—resulted in an increase in the proportion of mature flower heads. Highest seed yield was observed in plants treated with Pix® and mineral soil fertilization, whereas in plants treated with foliar fertilizers, highest yields were observed with Pix® and Regalis®. The highest content of silymarin was found in plants treated with Dropp® and foliar fertilizer. Generally, treatment of milk thistle with plant‐growth regulators in combination with soil or foliar mineral fertilizers increased the total amount of silymarin by increasing seed yield per hectare.  相似文献   

2.
As part of a research program on the transfer withinfreshwater ecosystems of the radionuclides present inthe weakly radioactive liquid effluents from nuclearpower stations, this article presents an assessment ofthe dynamics of zooplankton contamination from water.The experiments were carried out on young pre-adultdaphnids, placed at a density of 250 individualsL-1, in 0.45 m filtered river water. Inorder to maintain the radionuclide contamination at ahigh level and to limit alterations in the chemicalcharacteristics of the medium, the water was reneweddaily. The dynamics of contamination were described bya one (137Cs) or a two compartmental model(110mAg, 60Co and 54Mn), taking intoaccount the fluctuations of the radionuclideconcentration in the water, as well as the growth rateof the daphnids. The contamination levels weredescribed by the steady state value of theconcentration factor, which was 2870 mL g-1 wetweight, 320 mL g-1 wet weight, 265 mL g-1wet weight and 30 mL g-1 wet weight, for110mAg, 54Mn, 60Co and 137Cs,respectively. During the depuration phase,radioactivity decrease in daphnids was a very fastphenomenon indicating that radionuclide adsorption tothe surface was the major process involved in thecontamination of daphnids. The two correspondinghalf-lives of the depuration kinetics were 10 min and7 d, 20 min and 1 d and 3 hr and 1.5 d for60Co, 110mAg and 54Mn, respectively.The loss of 137Cs was characterised by a singlehalf-life of 0.3 d.  相似文献   

3.
Poly dispersive aerosols of SrCl2, NaI, CsCl having a size distribution of 2.33 m (Activity Median Aerodynamic Diameter, [AMAD]) with a geometric standard deviation of 1.83 m are used for the determination of deposition velocity for 85Sr, 131I and 137Cs aerosols on tropical spinach (Spinicia olericia), radish (Raphanous sative) and beans (Phasolous valugeries) plant leaves. The experiments were carried out in a specially designed exposure chamber to simulate deposition under accidental releases of radioactivity in tropical environment. The rates of particles deposition are expressed as a function of plant surface area and of plant dry weight. The deposition velocities obtained are in the range of 10–6 to 10–7 m/s. These values differ significantly from those in temperate regions. The lower values for deposition velocities (v g) for the tropical environment is attributed due to high humidity. Therefore, the deposition of suspended aerosols on leaf surfaces caused by impaction and Brownian diffusion becomes slower in tropical environment and resulted into lower value of deposition velocities.  相似文献   

4.
Terrain attributes, landform segmentation, and soil redistribution   总被引:4,自引:0,他引:4  
The 137Cs technique has greatly expanded our knowledge of the topography–soil redistribution relationship. For the technique to be useful in upscaling of process models and regional-scale conservation planning, we must be able to show that a consistent relationship exists between 137Cs-derived soil redistribution rates and terrain attributes in a given region. In this paper, the association between 137Cs-derived soil redistribution rates and quantitatively defined landform elements was examined at nine hummocky terrain sites in southern Saskatchewan, Canada. Shoulder (SH) elements with convex plan curvatures had the highest mean soil loss rates of 33 t ha−1 yr−1, followed closely by other SH and backslope (BS) elements. The erosional behavior of level elements (i.e. those with gradients less than 3°) was highly dependent on the specific dispersal area (SDA) of the element—elements with high dispersal areas were dominantly erosional (mean soil loss of 14 t ha−1 yr−1), whereas level elements with low dispersal areas were depositional (mean soil gain of 15 t ha−1 yr−1). Doubly concave footslope (FS) elements had mean soil gain of 10 t ha−1 yr−1. The dispersion of values across the nine sites was much greater for the depositional units than the erosional units, indicating a complex relationship between deposition and terrain attributes in the depositional units. The results clearly indicate that regional-scale patterns of soil redistribution can be developed using the 137Cs technique.  相似文献   

5.
Introduction

Phosphorus applied on a phosphate deficient soil, by increasing the root development of the plant, or by stimulating the soil microflora especially in the rhizosphere, may increase the amount of phosphorus which the plant takes up from the soil. This present paper is a report on a pot culture investigation of such an effect of added phosphorus.  相似文献   

6.
There is a paucity of information on the critical content, threshold levels, uptake, transport, and accumulation of sodium (Na+) and chloride (Cl?) ions in young sunflower plants. Effect of salinity was analyzed in root, stem, leaves, and buds by raising plants in fine sand irrigated with Hoagland's solution and supplemented with 10–160 mM sodium chloride (NaCl) for 30 days. Maximum sensitivity index, reduction in growth, and water content were observed in buds. Maximum Na+ and Cl? contents were obtained in old leaves and stems under low salinity but in roots at high salinity. Uptake, transport, and accumulation rate of Cl? were more than those of Na+, and for both ions they increased with increasing NaCl concentration but decreased with increasing exposure time. Growth reduction at low salinity seems to be because of Cl? toxicity, but Na+ toxicity and water deficiency could also be the causes at high salinity.  相似文献   

7.
Naturally occurring stable isotopes of carbon and nitrogen are powerful tools to investigate food webs, where the ratio of 15N/14N is used to assign trophic levels and of 13C/12C to determine the food source. A shift in δ15N value of 3‰ is generally suggested as mean difference between two trophic levels, whereas the carbon isotope composition of a consumer is assumed to reflect the signal of its diet. This study investigates the effects of food quality, starvation and life stage on the stable isotope fractionation in fungal feeding Collembola. The fractionation of nitrogen was strongly affected by food quality, i.e. the C/N ratio of the fungal diet. Collembola showed enrichment in the heavier isotope with increasing N concentration of the food source. Δ15N varied between 2.4‰, which assigns a shift in one trophic level, and 6.3‰, suggesting a shift in two trophic levels. Starvation up to 4 weeks resulted in an increase in the total δ15N value from 2.8‰ to 4.0‰. Different life stages significantly affected the isotope discrimination by Collembola with juveniles showing a stronger enrichment (Δ15N=4.9‰) compared to adults (Δ15N=3.5‰). Δ13C varied between −2.1‰ and −3.3‰ depending on the food quality, mainly due to compensational feeding on low quality diet. During starvation δ13C value decreased by 1.1‰, whereas the life stage of Collembola had no significant effect on isotopic ratios. The results indicate that the food resource and the physiological status of the consumer have important impact on stable isotope discrimination. They may cause differences in fractionation rate comparable to trophic level shifts, a fact to consider when analysing food web structure.  相似文献   

8.
Nitrogen and carbon dynamics in paddy and upland soils for rice cultivation and in upland soil for corn cultivation was investigated by using 13C and 15N dual-labeled cattle manure compost (CMC). In a soil with low fertility, paddy and upland rice took up carbon and nitrogen from the CMC at rates ranging from 0.685 to 1.051% of C and 17.6–34.6% of N applied. The 13C concentration was much higher in the roots than in the plant top, whereas the 15N concentration differed slightly between them, indicating that organic carbon taken up preferentially accumulated in roots. The 13C recovery in the plant top tended to be higher in upland soil than in paddy soil, whereas 15N applied was recovered at the same level in both paddy and upland soils. In the experiment with organic farming soil, paddy rice took up C and N from the CMC along with plant growth and the final recovery rates of 13C and 15N were 2.16 and 17.2% of C and N applied. In the corn experiment, a very large amount of carbon from the CMC was absorbed, accounting for at least 7 times value for rice. The final uptake rates of 13C and 15N reached about 13 and 10% of C and N applied, respectively. Carbon emission from the CMC sharply increased by 2 weeks after transplanting and the nitrogen emission was very low. It is concluded that rice and corn can take up an appreciable level of carbon and nitrogen from the CMC through roots.  相似文献   

9.
ABSTRACT

A study was carried out to determine the influence of nitrogen (N) sources on the growth, nitrate (NO3 ?) accumulation, and macronutrient concentrations of pakchoi (Brassica chinensis L.) in hydroponics. Plants were supplied with NO3 ? and two amino acids (AA), glutamic acid (Glu), and glutamine (Gln), at six NO3 ?-N/AA-N molar ratios: (1) 100:0, (2) 80:20, (3) 60:40, (4) 40:60, (5) 20:80, (6) 0:100. The total N concentration was 12.5 mmol/L for all treatments in nutrient solutions. Both AAs reduced plant growth with decreasing NO3 ?-N/AA-N ratios, but the reduction was for Gln than for Glu. At 80:20 NO3 ?-N: Gln-N ratio, the Gln had no significant effect on pakchoi fresh weights. Decreasing NO3 ?-N/AA-N ratios reduced NO3 ? concentrations in the plant, regardless of AA sources. Adding an appropriate portion of AA-N to nutrient solutions for hydroponic culture increased concentrations of N, phosphorus (P), and potassium (K) in pakchoi shoots. Substituting 20% or less of NO3 ?-N with Gln-N in hydroponic culture will increase the pakchoi quality by reducing NO3 ? concentration and increasing mineral nutrient concentrations in shoots without significant reduction of crop yields.  相似文献   

10.
红壤交换性钙、镁和钾的分布及施肥对其影响   总被引:1,自引:0,他引:1  
A leaching experiment was Carried out with repacked soil columns in laboratory to study the leaching process of a red soil derived from sandstone as affected by various fertilization practices.The treatments were CK(as a control),CaCO3,CaSO4,MgCO3,Ca(H2PO4)2,Urea,KCl,Multiple(a mixture of the above mentioned fertilizers) and KNO3,The fertilizers were added to the bare surface of the soil columns,and then the columns were leached with 120 mL deionized water daily through perstaltic pumps over a period of 92 days,At the end of leaching process,soils were sampled from different depths of the soil profiles ,i.o.,of 92 days,At the end of leaching process,soils were sampled from different depths of the soil profiles,I.e.0-5cm,5-10cm,10-20cm,20-40cm,and 40-60cm,The results showed when applying Ca,Mg,and K to the bare surface of the soil columns,exchangeable Ca^2 ,Mg^2 ,and K^ in the upper layer of the soil profile increased correspondingly,with an extent depending mainly on the application rates of Ca,Mg,and K and showing a downward trend,CaCO3,CaSO4,MgCO3,and Ca(H2PO4)2 treatments had scarcely and effect on movement of exchangeable K^ ,while CaCO3,and CaSO4 treatments singnificantly promoted the downward movement of exchangealble Mg^2 although these two treatments had no obvious effect on leaching losses of Mg,The fact that under Urea treatment,exchangeable Ca^2 and Mg^2 ,were higher as compared to CK treatment showed urea could prevent leaching of exchangeable Ca^2 and Mg^2 ,the obvious downward movement of exchangeable Ca^2 and Mg^2 was noticed in KCl treatment ,In Multiple treatment,the downward movement of exchangeable Ca^2 and Mg^2 was evident,while that of K^ was less evident,Application of KNO3 strongly promoted the downward movement of exchangeable Ca^2 and Mg^2 in the soil profile.  相似文献   

11.
Litter decomposition on the forest floor is an essential process in soil nutrient cycles and formation. These processes are controlled by abiotic factors such as climate and chemical litter quality, and by biotic factors such as microbial community diversity and activity. The aim of this study was to investigate the importance of litter depth with respect to (i) chemical litter quality as evaluated by solid-state 13C NMR, (ii) enzyme activities, and (iii) microbial functional diversity in four different litter layers (OLn, OLv, OF, and OH). A Mediterranean soil profile under an evergreen oak (Quercus ilex L.) forest was used as a model. The recalcitrant OM fraction, corresponding to the deepest layer, showed low enzyme activities. Peroxidases and fluorescein diacetate hydrolases (FDA) were more active in the OLn layer and probably originated largely from plants. High cellulase activity in the OLn and the OLv layers, which are rich in polysaccharides, corresponded with the high content of O-alkyl carbon compounds. Following polysaccharide degradation, laccases and lipases were much more evident in the intermediate layers. This spatial variation in nutrient demand reflected a preferential degradation of the specific plant polymers. Phosphatases were more active along the three upper layers and probably reflected a P limitation during litter degradation. Alkaline/acid (AcPAlP/AcP) ratio increased in the deepest layer, suggesting an increased participation of bacteria AlP in phosphatase pools. Results of BiologTM also indicated spatial variations in microbial functionality. Indeed, FF plates showed the highest functional diversity in the uppermost layer, while ECO plate functional diversity was highest in the intermediate layers. Finally, our results indicated that microbial activity and functional diversity of micro-organisms change with litter depth on a very small scale and vary with chemical organic matter (OM) composition. Thus, the observed increases in the biological variables studied were determined by the evolution of OM chemical structures, the nature and availability in C nutrients, and they ultimately resulted in a progressive accumulation of recalcitrant compounds.  相似文献   

12.
The natural 15N abundances (δ15N values) were measured for nitrate and free and bound amino acids from the leaves of field-grown spinach (Spinacia oleracea L.) and komatsuna (Brassica campestris L.), as well as ureides and free and bound amino acids in the leaves and roots of hydroponically grown soybean (Glycine max L.) totally depending on dinitrogen. Nitrate from the spinach and komatsuna leaves and ureides from leaves and roots of soybean showed higher δ15N values than the total tissue N and N in free or bound amino acid fractions. The δ15N values of individual free and bound amino acids, determined by GC/C/MS using their acetylpropyl derivatives, were similar in leaf tissues except for proline but varied in soybean root tissues. The order of 15N enrichment was similar in the four samples: aspartic acid > glutamic acid > threonine, proline, valine > glycine + alanine +serine, γ-amino butyric acid, and phenylalanine.  相似文献   

13.
以15年生嘎啦苹果/平邑甜茶为试材,采用C、N双标记技术,研究果实发育期不同施氮方式(传统一次性施氮、分次施氮和渗灌施氮,分别用ON、TN和IN表示)对苹果植株碳氮营养吸收、利用、分配、损失及果实产量和品质的影响。结果表明:至果实成熟期,苹果各器官Ndff值均为INTNON,新生器官间(果实、叶片和1年生枝)差异显著。植株全氮量和~(15)N吸收量均以IN处理最大,ON处理最低。与ON处理相比,TN和IN处理~(15)N利用率分别提高了41.63%和68.60%,而~(15)N损失率分别降低了10.60%和18.63%。各处理不同土层~(15)N残留量差异显著,0—40 cm土层~(15)N残留量为INTNON,60—120 cm土层趋势相反。TN和IN处理果实和贮藏器官(多年生枝、中心干和粗根)的~(13)C分配率均显著高于ON处理,而营养器官(叶片和1年生枝)的~(13)C分配率则以ON处理最高,IN处理最低。同时,在IN处理下,苹果产量、硬度、可溶性糖和糖酸比等品质指标均达到最高水平。综上,渗灌施氮通过降低氮素损失,显著促进植株对氮素的吸收利用,并优化光合产物在各器官间分配,从而最有利于苹果产量和品质的提高。  相似文献   

14.
果园生草对~(15)N利用及土壤累积的影响   总被引:1,自引:0,他引:1  
彭玲  文昭  安欣  姜翰  姜远茂 《土壤学报》2015,52(4):950-956
以2 a生红富士/平邑甜茶为试材,采用15N同位素示踪技术,研究了种植3种牧草(白三叶、鼠茅草和黑麦草)对苹果植株生长,氮素利用、损失及其在0~60 cm土层残留情况的影响。结果表明:与单作苹果相比,生草栽培后苹果植株总鲜重、新梢粗度、新梢长度及根冠比皆成增加的趋势;苹果植株根长、根长密度及根表面积均以种植白三叶处理最大,其次为种植鼠茅草,最低的为单作苹果;不同处理间氮素利用率差异显著,种植白三叶后苹果植株氮素利用率最高,种植鼠茅草次之,单作苹果最低;生草栽培后15N残留主要集中在0~20 cm土层,且其15N残留量显著高于单作苹果。而在20~40 cm及40~60 cm土层15N残留量则以单作苹果最高,种植黑麦草次之,最低的为种植白三叶;生草栽培后氮素损失率为单作苹果种植黑麦草种植鼠茅草种植白三叶。表明种植白三叶、鼠茅草及黑麦草在促进苹果植株氮素利用的同时,也一定程度上减弱了土壤氮素的损失。  相似文献   

15.
This study coupled stable isotope probing with phospholipid fatty acid analysis (13C-PLFA) to describe the role of microbial community composition in the short-term processing (i.e., C incorporation into microbial biomass and/or deposition or respiration of C) of root- versus residue-C and, ultimately, in long-term C sequestration in conventional (annual synthetic fertilizer applications), low-input (synthetic fertilizer and cover crop applied in alternating years), and organic (annual composted manure and cover crop additions) maize-tomato (Zea mays - Lycopersicum esculentum) cropping systems. During the maize growing season, we traced 13C-labeled hairy vetch (Vicia dasycarpa) roots and residues into PLFAs extracted from soil microaggregates (53-250 μm) and silt-and-clay (<53 μm) particles. Total PLFA biomass was greatest in the organic (41.4 nmol g−1 soil) and similar between the conventional and low-input systems (31.0 and 30.1 nmol g−1 soil, respectively), with Gram-positive bacterial PLFA dominating the microbial communities in all systems. Although total PLFA-C derived from roots was over four times greater than from residues, relative distributions (mol%) of root- and residue-derived C into the microbial communities were not different among the three cropping systems. Additionally, neither the PLFA profiles nor the amount of root- and residue-C incorporation into the PLFAs of the microaggregates were consistently different when compared with the silt-and-clay particles. More fungal PLFA-C was measured, however, in microaggregates compared with silt-and-clay. The lack of differences between the mol% within the microbial communities of the cropping systems and between the PLFA-C in the microaggregates and the silt-and-clay may have been due to (i) insufficient differences in quality between roots and residues and/or (ii) the high N availability in these N-fertilized cropping systems that augmented the abilities of the microbial communities to process a wide range of substrate qualities. The main implications of this study are that (i) the greater short-term microbial processing of root- than residue-C can be a mechanistic explanation for the higher relative retention of root- over residue-C, but microbial community composition did not influence long-term C sequestration trends in the three cropping systems and (ii) in spite of the similarity between the microbial community profiles of the microaggregates and the silt-and-clay, more C was processed in the microaggregates by fungi, suggesting that the microaggregate is a relatively unique microenvironment for fungal activity.  相似文献   

16.
The degradation of 2, 4-D, 2, 4, 5-T, and picloram in two Philippine soils was investigated under upland and flooded (submerged) conditions. These herbicides degraded in both upland and flooded Maahas clay and Luisiana clay soils. The rate of degradation of the herbicides was more rapid in the Maahas clay soil than in the Luisiana clay soil. Among the three herbicides, 2, 4-D was the least persistent and picloram was the most persistent in both soils under both submerged and upland conditions. 2, 4, 5-T degraded more actively in the two Philippine soils in this study than studies previously reported in the available literature. The fact that both the 2, 4-D and 2, 4, 5-T did not degrade in sterilized soils during the incubation period suggests that the degradation is due to the microbial activity in the soils.  相似文献   

17.
Total nitrogen (N) concentration (N%), N derived from 15N-fertilizer (Ndff%), amount of 15N uptake (ANU) in main organs (leaves, shoots, roots, fruits), and N use efficiency (NUE) were measured to assess N absorption, distribution, and utilization of Red Fuji apple trees across two years using a 15N-enriched urea method. The N% in leaves and fruits decreased while those in shoots and roots increased in both years. The Ndff% and ANU in roots were highest at fruitlet stage than those in leaves, shoots and fruits at mature stages. This suggested that the absorbed 15N by roots was redistributed to new organs. The N% was lower while Ndff% and ANU were greater in 2008 than 2007. The most 15N absorbed was accumulated in the trunks, main and coarse roots and smaller in the fine roots and biennial branches. The NUE in 2007 and 2008 reached 9.9% and 12.2% respectively.  相似文献   

18.
The 15N natural abundance in Pinus densiflora Sieb. et Zucco that had been inoculated and not inoculated with ectomycorrhizal fungi (Suillus granulatus (L.:Fr.) O. Kuntze) was compared. The inoculated pine needles showed a lower δ15N value, while the uninoculated ones showed a higher δ15N value. Higher δ15N values in the mycelial mat of the ectomycorrhizal fungi compared to those of the inoculated pine needles were also observed. These facts indicate that nitrogen isotope fractionation occurred during the nitrogen transport from mycorrhizal fungi to the host plants.  相似文献   

19.
外源水稻根系和茎叶碳氮在稻田土壤中释放的特征   总被引:2,自引:0,他引:2  
东北地区气候寒冷,稻田土壤休耕期长,多处于冻结状态;水稻生长期短,土壤温度高且季节性淹水。外源水稻秸秆碳氮在东北地区稻田土壤休耕期和水稻生长期不同水热条件下的释放特征尚不完全清楚。通过室外培养试验方法,利用双标记(~(13)C和~(15)N)水稻根系和茎叶示踪技术和稳定同位素质谱分析技术,研究水稻根系和茎叶在稻田土壤中的腐解率、有机碳(氮)释放率的动态变化特征。结果表明:水稻茎叶、根系于秋季添加稻田土壤后,经过寒冷漫长的土壤休耕期(11月至次年5月),S1(标记根系+不标记茎叶)和S2(不标记根系+标记茎叶)处理的秸秆腐解率分别达30.2%和34.5%,水稻根系和茎叶碳释放率分别达30.9%和38.2%,氮释放率分别达7.4%和35.0%。添加一年时,S1和S2处理的秸秆腐解率分别达66.5%和66.6%,水稻根系和茎叶碳释放率分别为63.7%和65.8%,氮释放率分别为28.6%和51.1%,水稻根系氮释放率显著低于水稻茎叶氮释放率(P0.05)。本试验条件下,水稻根系和茎叶添加稻田土壤1年,水稻根系和茎叶的腐解率达65%左右,其碳释放与腐解几乎同步,但氮释放相对缓慢,水稻根系氮释放速度显著低于茎叶氮释放速度,温度升高明显促进了水稻根系和茎叶的腐解及其碳氮释放。  相似文献   

20.
This trial was carried out to study the evolution of the nutrient parameters of the nutrient solution applied to tomato plants (Lycopersicum sculentum Mill. Forteza) cultivated in Mediterranean greenhouse conditions under different fertigation management models. The dynamic model is based on soil water content, which was measured by tensiometers, and on soil solutions obtained with suction cups (porous ceramic cup water samplers). The local traditional method consists of following technical recommendations, and the classical model requires the estimation of Crop Factor (Kc) and knowing the nutrient extraction. Nutrient solution and water applied are functions of the fertigation management criteria. The water used for fertigation was classified as C4-S3 according to the Riverside classification system. The cultivation period lasted from 15 August to 20 April. The nutrient parameters studied in nutrient and soil solution were pH, electrical conductivity (EC), nitrate (NO3 ?), phosphate (H2PO4 ?), potassium (K+), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), and chloride (Cl?). The pH shows similar trends under the different treatments. Electrical conductivity is in the range of 2.8–4.5 dS m?1. Chloride, sodium, magnesium, and sulfate are exclusively modified by the salt concentration in the irrigation water, so it can be assumed that the three treatments vary equally. Nitrate, potassium, phosphate, and calcium are modified depending on each fertigation management method. Soil solution is modified by the nutrient solution applied. Dynamic management allows low nutrient concentration in the nutrient solution to be maintained and keeps soil nutrient concentration low, reducing fertilizer losses and therefore aquifer contamination.  相似文献   

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