Differential response of oilseed rape (Brassica napus L.) cultivars to low boron supply

Three experiments were carried out on an alluvial sandy loam (Udifluvent) at Tonglu, Zhejiang Province, P.R. China from 1992 to 1995, to determine the genotypic range in boron (B) efficiency of 16 oilseed rape (Brassica napus L.) cultivars, to identify the B-efficient cultivars and to identify specific responses which can be utilised for selection in a breeding program. The 16 cultivars which included high-quality and conventional types differed significantly in survival, plant height, leaf area, shoot dry weight and seed yield; however, the ranking of the cultivars for their seed yield or other plant traits differed with B treatment. With severe B deficiency (CaCl2 extractable B < 0.26 mg/kg) and no boron applied, none of the cultivars exhibited significant B efficiency, with seed yield <300 kg/ha. With moderate B deficiency (CaCl2 extractable B 0.34 mg/kg or 0.17 kg B/ha applied), seed yield varied significantly among the cultivars from 397 to 1889 kg/ha in year 1 and from 616 to 1260 kg/ha in year 3. Zhongyou 821 and 92-13 were the most B-efficient and Wanyou 324, Huashuang 2 and Su 2051 were the most B-inefficient cultivars under moderate B deficiency. Significant differences were found among the cultivars in leaf B concentration; however, there was no close relationship between leaf B concentration and seed yield responses to B of oilseed cultivars. Of all the growth parameters measured, leaf area was the early indicator best correlated with subsequent seed yield and may be useful for evaluating the response of cultivars to low B supply. Contrary to current opinion, it was also found that high-quality oilseed rape cultivars were not all sensitive to low B supply nor were all conventional cultivars B-efficient.     

Nitrogen use and carbon sequestered by corn rotations in the northern corn belt,U.S

Diversified crop rotation may improve production efficiency, reduce fertilizer nitrogen (N) requirements for corn (Zea mays L.), and increase soil carbon (C) storage. Objectives were to determine effect of rotation and fertilizer N on soil C sequestration and N use. An experiment was started in 1990 on a Barnes clay loam (U.S. soil taxonomy: fine-loamy, mixed, superactive, frigid Calcic Hapludoll) near Brookings, SD. Tillage systems for corn-soybean ( Glycine max [L.] Merr.) rotations were conventional tillage (CS) and ridge tillage (CSr). Rotations under conventional tillage were continuous corn (CC), and a 4-year rotation of corn-soybean-wheat ( Triticum aestivum L.) companion-seeded with alfalfa ( Medicago sativa L.)-alfalfa hay (CSWA). Additional treatments included plots of perennial warm season, cool season, and mixtures of warm and cool season grasses. N treatments for corn were corn fertilized for a grain yield of 8.5 Mg ha(-1) (highN), of 5.3 Mg ha(-1) (midN), and with no N fertilizer (noN). Total (1990-2000) corn grain yield was not different among rotations at 80.8 Mg ha(-1) under highN. Corn yield differences among rotations increased with decreased fertilizer N. Total (1990-2000) corn yields with noN fertilizer were 69 Mg ha-1 under CSWA, 53 Mg ha(-1) under CS, and 35 Mg ha(-1) under CC. Total N attributed to rotations (noN treatments) was 0.68 Mg ha(-1) under CSWA, 0.61 Mg ha(-1) under CS, and 0.28 Mg ha(-1) under CC. Plant carbon return depended on rotation and N. In the past 10 years, total C returned from above- ground biomass was 29.8 Mg ha(-1) under CC with highN, and 12.8 Mg ha(-1) under CSWA with noN. Soil C in the top 15 cm significantly increased (0.7 g kg(-1)) with perennial grass cover, remained unchanged under CSr, and decreased (1.7 g kg(-1)) under CC, CS, and CSWA. C to N ratio significantly narrowed (-0.75) with CSWA and widened (0.72) under grass. Diversified rotations have potential to increase N use efficiency and reduce fertilizer N input for corn. However, within a corn production system using conventional tillage and producing (averaged across rotation and N treatment) about 6.2-Mg ha(-1) corn grain per year, we found no gain in soil C after 10 years regardless of rotation.     

Effect of Brassica carinata (L.) biofumigants (seed meal) on chickpea wilt (Fusarium oxysporum f.sp. ciceris), growth,yield and yield component in Ethiopia

Pot experiments were carried out in the green house at Amhara Regional Agriculture Research Institute (ARARI) Bahirdar, Ethiopia to evaluate the potential of Brassica carinata cultivars namely; Holleta-l, S-67 and Yellow Dodola in 2007 and 2008. The treatment effects of B. carinata (L.) cultivars Holleta–1, S-67 and Yellow Dodola seed meals on chickpea fusarium wilt (Fusarium oxysporum f.sp. ciceris) were studied. Six rates of seed (0, 5, 10, 15, 20 and 25 g/kg of infested soil) were used. Infested soil without B.carinata cultivars amendments as a control and susceptible check variety JG-62 also without amendments were used in all the experiments. For each seed meal experiment, the treatments were arranged in factorial randomised complete block design in three replications. Data on seedling emergence, wilt incidence, fresh weight, dry weight, pod per plant, seed per pod, hundred seed weight and yield per hectare were collected. The amendments of infested soil with B.carinata cultivars seed meal reduced the incidence of chickpea fusarium wilt and increased yield per hectare. The interaction of the seed meal Holleta-1, S-67 and Yellow Dodola at 10–25 g/kg infested soil were effective in reducing wilt incidences on chickpea. However, the interaction of Yellow Dodola with 20 and 25 g seed meal per kg infested soil were the best combination in reducing significantly wilt incidence. The three cultivars incorporated at different level of doses significantly affected the influence of Fusarium wilt on the fresh weight, dry weight, pod per plant, seed per pod, hundred seed weight and yield per hectare. The highest yield kg/ha was recorded in combination of Yellow Dodola seed meal at 20 and 25 g followed by S-67 and Holleta-1 at 25 g /kg infested soil, respectively. The interaction of Holleta-1 at 5–25 infested soil significantly reduced disease incidence up to 16.7–43.3% and increased yield per hectare with mean by (30%) over the control. Seed meal amendment S-67 significantly reduce disease incidence 26.7–46.7% and increased yield kg/ha with mean by (36.7%) from the unamended control. Yellow dodola reduces disease incidence with 26.7–63.3% and increased yield kg/ha with mean by (45%) from the unamended control. The result indicates the potential of using Brassica crop seed meal amendment as useful component of integrated chickpea wilt management.     

EDTA-assisted heavy-metal uptake by poplar and sunflower grown at a long-term sewage-sludge farm

Little information is available concerning the efficacy of chelates applied to biosolids (sewage-sludge)-treated soil for heavy-metal removal. The purpose of the experiment was to determine the availability to sunflower (Helianthus annuus L.) and hybrid poplar (Populus deltoides Marsh. × P. nigra L.) seedlings, of non-essential (Cd, Ni, Pb) and essential heavy metals (Cu, Fe, Mn, Zn) in field soil injected with biosolids since 1976 and treated with ethylenediamine-tetraacetic acid (EDTA) in 2001. Sunflower was grown at two densities, 20000 and 60000 plants/ha, and poplar at 10000 plants/ha. The tetrasodium salt of EDTA was applied at rates of 0, 0.5, 1, and 2 g EDTA salt per kg surface (25-cm depth) soil. The EDTA did not affect uptake by poplar of the three non-essential (Cd, Ni, Pb) and four essential (Cu, Fe, Mn, Zn) heavy metals. For sunflower, the 1.0 g/kg rate of chelate addition resulted in maximal removal of the three non-essential heavy metals (Cd, Ni, Pb). Uptake of the essential heavy metals by sunflower was little affected by the EDTA. At the 20000 plants/ha density, leaves of sunflower grown with 1.0 g EDTA Na₄2H₂O per kg soil accumulated more Cd, Ni, and Pb than leaves of sunflower grown without the EDTA salt. At this density, concentrations of Cd in leaves of sunflower without EDTA and with 1.0 g/kg EDTA salt were 2.2 and 6.5 g/g, respectively; for Ni, they were 6.7 and 19.2 g/g, respectively; and for Pb, they were 15.6 and 46.9 g/g, respectively. At the 60000 plants/ha density, stems of sunflower grown with 1.0 g EDTA Na₄2H₂O per kg soil accumulated more Cd, Ni, and Pb than stems of sunflower grown without the EDTA salt. At this density, concentrations of Cd in stems of sunflower without EDTA and with 1.0 g/kg EDTA salt were 0.6 and 4.6 g/g, respectively; for Ni, they were 1.7 and 17.6 g/g, respectively; and for Pb, they were 5.2 and 42.8 g/g, respectively. Removal of the non-essential heavy metals by sunflower was greater at the higher plant density (60000 plants/ha) compared to the lower one (20000 plants/ha).     

Genetic variability in nodulation and root growth affects nitrogen fixation and accumulation in pea

BACKGROUND AND AIMS: Legume nitrogen is derived from two different sources, symbiotically fixed atmospheric N(2) and soil N. The effect of genetic variability of root and nodule establishment on N acquisition and seed protein yield was investigated under field conditions in pea (Pisum sativum). In addition, these parameters were related to the variability in preference for rhizobial genotypes. METHODS: Five different spring pea lines (two hypernodulating mutants and three cultivars), previously identified in artificial conditions as contrasted for both root and nodule development, were characterized under field conditions. Root and nodule establishment was examined from the four-leaf stage up to the beginning of seed filling and was related to the patterns of shoot dry matter and nitrogen accumulation. The genetic structure of rhizobial populations associated with the pea lines was obtained by analysis of nodule samples. The fraction of nitrogen derived from symbiotic fixation was estimated at the beginning of seed filling and at physiological maturity, when seed protein content and yield were determined. KEY RESULTS: The hypernodulating mutants established nodules earlier and maintained them longer than was the case for the three cultivars, whereas their root development and nitrogen accumulation were lower. The seed protein yield was higher in 'Athos' and 'Austin', the two cultivars with increased root development, consistent with their higher N absorption during seed filling. CONCLUSION: The hypernodulating mutants did not accumulate more nitrogen, probably due to the C cost for nodulation being higher than for root development. Enhancing exogenous nitrogen supply at the end of the growth cycle, by increasing the potential for root N uptake from soil, seems a good option for improving pea seed filling.     

Evaluation of high yielding soybean germplasm under water limitation

Limited information is available for soybean root traits and their plasticity under drought stress. To date, no studies have focused on examining diverse soybean germplasm for regulation of shoot and root response under water limited conditions across varying soil types. In this study, 17 genetically diverse soybean germplasm lines were selected to study root response to water limited conditions in clay (trial 1) and sandy soil (trial 2) in two target environments. Physiological data on shoot traits was measured at multiple crop stages ranging from early vegetative to pod filling. The phenotypic root traits, and biomass accumulation data are collected at pod filling stage. In trial 1, the number of lateral roots and forks were positively correlated with plot yield under water limitation and in trial 2, lateral root thickness was positively correlated with the hill plot yield. Plant Introduction (PI) 578477A and 088444 were found to have higher later root number and forks in clay soil with higher yield under water limitation. In sandy soil, PI458020 was found to have a thicker lateral root system and higher yield under water limitation. The genotypes identified in this study could be used to enhance drought tolerance of elite soybean cultivars through improved root traits specific to target environments.     

Wheat Seed Colonized with Atoxigenic Aspergillus flavus: Characterization and Production of a Biopesticide for Aflatoxin Control

Biocontrol of aflatoxin contamination using atoxigenic Aspergillus flavus to competitively exclude aflatoxin-producing strains has previously been reported, and is currently in the third year of commercial-scale tests (treating 50-200 ha per annum). Wheat seed colonized with atoxigenic A. flavus has been used in the commercial trials. Requirements for production of this colonized wheat seed are described and the spore yield of wheat is compared to other substrates. The study suggests that the most cost-effective inoculum production would require colonization of wheat (106 conidia kg -1 of wheat seed) at 25% (w/w) moisture for 18 h at 31 C. To prevent fungal growth and associated wheat aggregation in storage, seed had to be dried below 15% (w/w) moisture, although a moisture content of 35% (w/w) did not reduce viability in sealed containers stored at 18-25 C over an 8-month period. The dry biopesticide had multi-year stability without refrigeration and withstood temperatures of 70 C for 20 min. Sporulation of the product occurred within 3 days at 31 C and 100% relative humidity with yields averaging 4.9 X 109 conidia g -1 by day 7.     

Zinc,Iron, Manganese and Copper Uptake Requirement in Response to Nitrogen Supply and the Increased Grain Yield of Summer Maize

The relationships between grain yields and whole-plant accumulation of micronutrients such as zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) in maize (Zea mays L.) were investigated by studying their reciprocal internal efficiencies (RIEs, g of micronutrient requirement in plant dry matter per Mg of grain). Field experiments were conducted from 2008 to 2011 in North China to evaluate RIEs and shoot micronutrient accumulation dynamics during different growth stages under different yield and nitrogen (N) levels. Fe, Mn and Cu RIEs (average 64.4, 18.1and 5.3 g, respectively) were less affected by the yield and N levels. ZnRIE increased by 15% with an increased N supply but decreased from 36.3 to 18.0 g with increasing yield. The effect of cultivars on ZnRIE was similar to that of yield ranges. The substantial decrease in ZnRIE may be attributed to an increased Zn harvest index (from 41% to 60%) and decreased Zn concentrations in straw (a 56% decrease) and grain (decreased from 16.9 to 12.2 mg kg⁻¹) rather than greater shoot Zn accumulation. Shoot Fe, Mn and Cu accumulation at maturity tended to increase but the proportions of pre-silking shoot Fe, Cu and Zn accumulation consistently decreased (from 95% to 59%, 90% to 71% and 91% to 66%, respectively). The decrease indicated the high reproductive-stage demands for Fe, Zn and Cu with the increasing yields. Optimized N supply achieved the highest yield and tended to increase grain concentrations of micronutrients compared to no or lower N supply. Excessive N supply did not result in any increases in yield or micronutrient nutrition for shoot or grain. These results indicate that optimized N management may be an economical method of improving micronutrient concentrations in maize grain with higher grain yield.     

两种农业种植模式对重金属土壤的修复潜力

植物修复农田土壤重金属污染需要经历一个长期的过程,而大部分用来修复的植物都不具备利用价值,不能给当地农民带来经济收入。因此,一些农作物由于其较大的生物量和一定的经济价值,在植物修复土壤重金属污染的应用中受到广泛关注。是在重金属(Cu、Zn、Pb、Cd、As、Hg)复合污染的郴州矿区废弃农田种植油菜、玉米和油葵,研究油菜-玉米和油-油葵两种种植模式对土壤重金属污染的修复潜力。实验结果表明:三种作物在复合污染土壤中对重金属都表现出一定的耐性及吸收积累能力。向日葵的根和叶中重金属Cd、Cu的含量都很高,其中Cd在向日葵的各个部位的富集系数(BCF)及Cu在向日葵的根和叶的富集系数(BCF)都大于1。两种轮作模式对作物的产量没有明显的影响,收获得到的干物质量都很高,每年每公顷分别为油菜16.6t、玉米25.29t、油葵22.5t。两种种植模式都可以对土壤中的重金属进行有效的提取,油菜-油葵种植模式下提取重金属Cu、Pb、Cd、As的量较高,分别为:Cu 2408g hm~(-2)a~(-1),Pb 2027g hm~(-2)a~(-1),Cd 658.5g hm~(-2)a~(-1),As 250g hm~(-2)a~(-1),油菜-玉米模式下Zn和Hg的提取量较高,分别为Zn 4987g hm~(-2)a~(-1)和Hg 7.92g hm~(-2)a~(-1);对于多种重金属复合污染的土壤来说,油菜-油葵的种植模式要优于油菜-玉米的种植模式。总的来说,利用3种作物两两轮作的种植模式,在不影响作物产量的前提下大大的提高了作物对重金属的提取总量。3种作物在收获以后又可以用做工业原料,这就使得当地农民充分利用矿区废弃农田修复污染的同时又能从中获得一定经济效益。     

Enhancing white lupin (Lupinus albus L.) adaptation to calcareous soils through selection of lime-tolerant plant germplasm and Bradyrhizobium strains

Aims

This study aimed to determine whether white lupin adaptation to moderately calcareous soils could be enhanced by lime-tolerant plants and Bradyrhizobium strains.

Methods

Fourteen landraces from Italy, Morocco and Egypt and some cultivars were grown in moderate-lime (ML) and low-lime (LL) soil with each of two inoculants, one commercial and one including three Bradyrhizobium strains well-nodulating under ML soil (isolated from other lupin species). Grain yield and above-ground biomass were assessed in large artificial environments that mimicked field conditions. Shoot, root and nodulation traits at onset of flowering were studied in a pot experiment.

Results

ML soil severely reduced plant yield, growth and nodulation but increased the harvest index relative to LL. Top-yielding genotypes for grain yield displayed significant rank inversion across soil types (P < 0.05). Lime-tolerant genotypes reduced their nodulation in ML soil less than limesusceptible ones. Some landraces outperformed the reference lime-tolerant cultivar Giza 1 in ML soil. One Italian landrace had a lime-tolerant response across agricultural locations. The Moroccan inoculant provided greater nodulation, more shoot residues but similar grain yield in ML soil, and less grain and shoot residues in LL soil, compared with the commercial inoculant.

Conclusions

Lupin adaptation to ML soil can be improved mainly through selection of lime-tolerant plants.     

Seed bank dynamics of an invasive alien species,Helianthus annuus L.

形成持久种子库的能力是预测物种在新区域成功建群的最佳指标之一。野生向日葵(Helianthus annuus L.)原产于北美，干扰促进了其种子库的形成，并对本地种群的建立和延续起着关键作用。然而，种子库在入侵种群的建立和延续中所起的作用尚不清楚。在本研究中，我们评估了种子库和干扰对几种向日葵生物类型(采集于阿根廷荒地生境中的野生向日葵、野生农田野生向日葵与作物向日葵自然杂交种，以及商业品种的后代)的建立和适应性，以及土壤中种子持久性的作用。在种子库试验中，我们评估了上述材料两年在干扰和未干扰条件下的出苗率、成活率到繁殖率、出苗成活率、每株花序数和每块地的花序数；在种子埋藏试验中，我们评估了其种子在四个春季(6个月、18 个月、30个月和42个月)土壤中的持久性。研究结果表明，总体而言，幼苗在生长期(冬季)出苗较早，且受到干扰促进，尤其是第一年。尽管如此，在两种情况下，每块样地的花序数是相近的，尤其是荒地生境中。第二年，种子库出苗率较低，但成活率较高。在种子掩埋实验中，观察到遗传差异，荒地和野生生境中种子持久性达到42个月，而商业品种后代的种子持久性不超过6个月。在这两项实验中，农田野生型和商业向日葵品种后代生物型表现出一种中间行为。结果表明，野生向日葵和作物野生向日葵杂交种均能在其生长范围之外形成持久的种子库，且干扰可能有助于其在新区域的建立。     

Accumulation of cadmium, zinc, and copper by Helianthus annuus L.: impact on plant growth and uptake of nutritional elements

We investigated the effects on physiological response, trace elements and nutrients accumulation of sunflower plants grown in soil contaminated with: 5 mg kg(-1) of Cd; 5 and 300 mg kg(-1) of Cd and Zn, respectively; 5, 300, and 400 mg kg(-1) of Cd, Zn, and Cu, respectively. Contaminants applied did not produce large effects on growth, except in Cd-Zn-Cu treatment in which leaf area and total dry matter were reduced, by 15%. The contamination with Cd alone did not affect neither growth nor physiological parameters, despite considerable amounts of Cd accumulated in roots and older leaves, with a high bioconcentration factor from soil to plant. By adding Zn and then Cu to Cd in soil, significant were the toxic effects on chlorophyll content and water relations due to greater accumulation of trace elements in tissues, with imbalances in nutrients uptake. Highly significant was the interaction between shoot elements concentration (Cd, Zn, Cu, Fe, Mg, K, Ca) and treatments. Heavy metals concentrations in roots always exceeded those in stem and leaves, with a lower translocation from roots to shoots, suggesting a strategy of sunflower to compartmentalise the potentially toxic elements in physiologically less active parts in order to preserve younger tissues.     

Evaluation of management strategies for bean leaf beetles (Coleoptera: Chrysomelidae) and Bean pod mottle virus (Comoviridae) in soybean

Cerotoma trifurcata F?rster (Coleoptera: Chrysomelidae) and Bean pod mottle virus (Comoviridae) (BPMV) both can reduce yield and seed quality of soybean, Glycine max (L.) Merr. Field experiments were conducted to evaluate the effects of systemic, seed-applied, and foliar-applied insecticides for the management of this pest complex at three locations in central, northeastern, and northwestern Iowa during 2002-2004. Seed-applied insecticide was evaluated according to a currently recommended management program for Iowa (i.e., insecticide applications that target emerging overwintered beetles, F0, and the first seasonal generation, F1 ). The experimental treatments included seed-applied (thiamethoxam, 0.3-0.5 g [AI] kg(-1)] or clothianidin, 47.32 ml [AI] kg(-1)) and foliar-applied (A-cyhalothrin, 16.83-28.05 g [AI] ha(-1)) or esfenvalerate (43.74-54.69 g [AI] ha(-1)) insecticides. Applications of the foliar insecticides were timed to target F0, F1 or both F0 and F1 populations of C. trifurcata. Our results confirm that insecticides timed at F0 and F1 populations of C. trifurcata can reduce vector populations throughout the growing season, provide limited reduction in virus incidence, and improve both yield and seed coat color. Furthermore, seed-applied insecticides may be the more reliable option for an F0-targeted insecticide if used within this management strategy. An F0-targeted insecticide by itself only gave a yield improvement in one out of eight location-years. However, by adding an F1-targeted insecticide, there was a yield gain of 1.42-1.67 quintal ha(-1), based on contrast comparisons at three location-years.     

Establishment of phosphate-solubilizing strains of Azotobacter chroococcum in the rhizosphere and their effect on wheat cultivars under green house conditions

A pot experiment was conducted in the green house to investigate the establishment of phosphate solubilizing strains of Azotobacter chroococcum, including soil isolates and their mutants, in the rhizosphere and their effect on growth parameters and root biomass of three genetically divergent wheat cultivars (Triticum aestivum L.). Five fertilizer treatments were performed: Control, 90 kg N ha(-1), 90 kg N + 60 kg P2O5 ha(-1), 120 kg N ha(-1) and 120 kg N + 60 kg P2O5 ha(-1). Phosphate solubilizing and phytohormone producing parent soil isolates and mutant strains of A. chroococcum were isolated and selected by an enrichment method. In vitro phosphate solubilization and growth hormone production by mutant strains was increased compared with soil isolates. Seed inoculation of wheat varieties with P solubilizing and phytohormone producing A. chroococcum showed better response compared with controls. Mutant strains of A. chroococcum showed higher increase in grain (12.6%) and straw (11.4%) yield over control and their survival (12-14%) in the rhizosphere as compared to their parent soil isolate (P4). Mutant strain M37 performed better in all three varieties in terms of increase in grain yield (14.0%) and root biomass (11.4%) over control.     

Effect of inorganic fertilizer and farmyard manure on soil physical properties, root distribution, and water-use efficiency of soybean in Vertisols of central India

A field experiment was conducted on a Vertisol for three consecutive years (1998-2000) to study the effects of combined use of inorganic fertilizer (NPK) and organic manure (farmyard manure) on soil physical properties, water-use efficiency, root growth and yield of soybean [Glycine max (L.) Merr.] in a soybean-mustard cropping system. Application of 10 Mg farmyard manure and recommended NPK (NPK+FYM) to soybean for three consecutive years improved the organic carbon content of the surface (0-15 cm) soil from an initial value of 4.4 g kg(-1) to 6.2 g kg(-1) and also increased seed yield and water-use efficiency by 103% and 76%, respectively, over the control. The surface (0-15 cm) soil of the plots receiving both farmyard manure and recommended NPK had larger mean weight diameter (0.50 mm) and a higher percentage of water stable aggregates (55%) than both the inorganically fertilized (NPK) (0.44 mm and 49%) and unfertilized control plots (0.41 mm and 45.4%). The saturated hydraulic conductivity (13.32 x 10(-6) m s(-1)) of the NPK+FYM treatment of the 0-7.5 cm depth was also significantly greater than that of the NPK (10.53 x 10(-6) m s(-1)) and control (8.61 x 10(-6) m s(-1)) treatments. The lowest bulk density (1.18 Mg m(-3)) in the 0-7.5 cm layer was recorded in NPK+FYM whereas it was highest in the control plots (1.30 Mg m(-3)). However, at sub-surface (22.5-30 cm) layer, fertilizer and manure application had little effect on bulk density and saturated hydraulic conductivity. Root length density (RLD) up to the 30 cm depth was highest in the NPK+FYM plots and it was 31.9% and 70.5% more than NPK and control plots. The RLD showed a significant and negative correlation (r=-0.88( * *)) with the penetration resistance.     

Cadmium accumulation in sunflower plants influenced by arbuscular mycorrhiza

In order to investigate the cadmium (Cd) accumulation patterns and possible alleviation of Cd stress by mycorrhization, sunflower plants (Helianthus annuus L.) were grown in the presence or absence of Cd (20 micromol L(-1)) and inoculated or not inoculated with the arbuscular mycorrhizal fungus (AMF) Glomus intraradices. No visual symptoms of Cd phytotoxicity were observed; nevertheless, in non-mycorrhizal plants the presence of Cd decreased plant growth. The addition of Cd had no significant effect on either mycorrhizal colonization or the amount of extra-radical mycelia that was produced by the AMF. Cd accumulated mainly in roots; only 22% of the total Cd absorbed was translocated to the shoots, where it accumulated to an average of 228 mg Cd kg(-1). Although the shoot-to-root ratio of Cd was similar in both the AMF inoculated and non-inoculated plants, the total absorbed Cd was 23% higher in mycorrhizal plants. Cd concentration in AMF extra-radical mycelium was 728 microg g(-1) dry weight. Despite the greater absorption of Cd, mycorrhizal plants showed higher photosynthetic pigment concentrations and shoot P contents. Cd also influenced mineral nutrition, leading to decreased Ca and Cu shoot concentrations; N, Fe and Cu shoot contents; and increased S and K shoot concentrations. Cd induced guaiacol peroxidase activity in roots in both mycorrhizal and non-mycorrhizal plants, but this increase was much more accentuated in non-mycorrhizal roots. In conclusion, sunflower plants associated with G. intraradices were less sensitive to Cd stress than non-mycorrhizal plants. Mycorrhizal sunflowers showed enhanced Cd accumulation and some tolerance to excessive Cd concentrations in plant tissues.     

Phytoextraction of soil trace elements by willow during a phytoremediation trial in Southern Québec,Canada

The phytoextraction of the trace elements (TEs) As, Cd, Cu, Ni, Pb, and Zn by willow cultivars (Fish Creek, SV1 and SX67) was measured during a 3-year field trial in a mildly contaminated soil. Biomass ranged from 2.8 to 4.4 Mg/ha/year at 30,000 plants/ha. Shoots (62%) were the main component followed by leaves (23%) and roots (15%). Biomass was positively linked to soluble soil dissolved organic carbon, K, and Mg, while TEs, not Cd and Zn, had a negative effect. The TE concentration ranking was: Zn > Cu > Cd > Ni, Pb > As, and distribution patterns were: (i) minima in shoots (As, Ni), (ii) maxima in leaves (Cd, Zn), or (iii) maxima in roots (Cu, Pb). Correlations between soil and plant TE were significant for the six TEs in roots. The amounts extracted were at a maximum for Zn, whereas Fish Creek and SV1 extracted more TE than SX67. More than 60% (91–94% for Cd and Zn) of the total TE was in the aboveground parts. Uptake increased with time because of higher biomass. Fertilization, the selection of cultivars, and the use of complementary plants are required to improve productivity and Cd and Zn uptake.     

Mutations in Barley Row Type Genes Have Pleiotropic Effects on Shoot Branching

Cereal crop yield is determined by different yield components such as seed weight, seed number per spike and the tiller number and spikes. Negative correlations between these traits are often attributed to resource limitation. However, recent evidence suggests that the same genes or regulatory modules can regulate both inflorescence branching and tillering. It is therefore important to explore the role of genetic correlations between different yield components in small grain cereals. In this work, we studied pleiotropic effects of row type genes on seed size, seed number per spike, thousand grain weight, and tillering in barley to better understand the genetic correlations between individual yield components. Allelic mutants of nine different row type loci (36 mutants), in the original spring barley varieties Barke, Bonus and Foma and introgressed in the spring barley cultivar Bowman, were phenotyped under greenhouse and outdoor conditions. We identified two main mutant groups characterized by their relationships between seed and tillering parameters. The first group comprises all mutants with an increased number of seeds and significant change in tiller number at early development (group 1a) or reduced tillering only at full maturity (group 1b). Mutants in the second group are characterized by a reduction in seeds per spike and tiller number, thus exhibiting positive correlations between seed and tiller number. Reduced tillering at full maturity (group 1b) is likely due to resource limitations. In contrast, altered tillering at early development (groups 1a and 2) suggests that the same genes or regulatory modules affect inflorescence and shoot branching. Understanding the genetic bases of the trade-offs between these traits is important for the genetic manipulation of individual yield components.     

Effects of Surface-Modified Nano-Scale Carbon Black on Cu and Zn Fractionations in Contaminated Soil

Cu contamination soil (547 mg kg^–1) was mixed separately with the surface-modified nano-scale carbon black (MCB) and placed in the ratios (w/w) of 0, 1%, 3%, and 5% in pots, together with 0.33 g KH₂PO₄and 0.35 g urea/pot. Each pot contained 20 ryegrass seedlings (Lolium multiflorum). Greenhouse cultivation experiments were conducted to examine the effect of the MCB on Cu and Zn fractionations in soil, accumulation in shoot and growth of ryegrass. The results showed that the biomass of ryegrass shoot and root increased with the increasing of MCB adding amount (p < 0.05). The Cu and Zn accumulation in ryegrass shoot and the concentrations of DTPA extractable Cu and Zn in soil were significantly decreased with the increasing of MCB adding amount (p < 0.05). The metal contents of exchangeable and bound to carbonates (EC-Cu or EC-Zn) in the treatments with MCB were generally lower than those without MCB, and decreased with the increasing of MCB adding amount (p < 0.05). There was a positive linear correlation between the Cu and Zn accumulation in ryegrass shoot and the EC-Cu and EC-Zn in soil. The present results indicated the MCB could be applied for the remediation the soils polluted by Cu and Zn.     

两个大豆品种在暗棕壤和黑土中的根系形态和根瘤性状

选取黑龙江省2种主要农田土壤类型（暗棕壤和黑土）和2个大豆品种（滴2003-1和合丰25）,采用盆栽试验,分别于大豆第5片复叶展开期、初花期、结荚初期、结荚盛期、鼓粒初期、鼓粒期和完熟期取样,进行根系形态（根干质量、根长、根表面积和平均根直径等）和根瘤性状（根瘤数、根瘤鲜质量和单个根瘤质量）的动态分析,以研究品种和土壤类型对大豆根系形态特征的影响.结果表明：土壤类型对大豆根系形态及结瘤性状均有显著影响,在第5片复叶展开期和初花期,暗棕壤的根系干质量、根长和根表面积低于黑土,而在鼓粒初期后高于黑土,暗棕壤的平均根直径在鼓粒初期后也高于黑土,但土壤类型对根冠比的影响不大;暗棕壤的根瘤数在初花期后明显低于黑土,但根瘤鲜质量和单个根瘤质量高于黑土.不同品种的根系性状在2种土壤上的差异程度不同,与合丰25相比,滴2003-1的根系性状受土壤条件的影响较大.在鼓粒期,根干质量（P<0.05）、根表面积（P<0.05）、根瘤数（P<0.01）及单个根瘤质量（P<0.001）在不同品种与土壤类型间表现出显著的互作效应.