Studies in clover soil sickness

Summary The nature of clover soil sickness (CSS) was studied in pot experiments using soils on which berseem had been grown for three, two, one and no years. Both the distribution of CSS with soil depth, and the effect of soil sterilization by dry heat and methyl bromide on the manifestation of CSS in berseem and Persian clover, were studied.CSS factors disappeared in berseem following heat sterilization and in both Persian clover and berseem following methyl bromide treatment.The CSS phenomenon was found in berseem grown on soil from the 0–20-cm and 60–80-cm soil layers of three-year berseem plots. The effect of upper layer-CSS was discernible only after the first harvest, while that of the deep layer one affected growth drastically immediately after germination. Other possible CSS factors are suggested.5012 plant and soilContribution from The Volcani Institute of Agricultural Research, Bet Dagan, Israel, 1971 Series, No. 1884-E. This work was financed by Grant F. G.-IS-222 from the U.S. Dept. Agriculture, under P.L. 480.     

基于Py-GC-MS/MS技术的高寒草原土壤有机质不同组分指纹特征研究

采用热裂解气相色谱质谱联用(Py-GC-MS/MS)技术来研究高寒草原土壤有机质5个密度组分之间的指纹差异。对150种热解产物进行定性定量分析,并将其根据相似的化学性质分为:烷基类化合物、芳烃及多环芳烃、木质素、酚类物质、多糖、含氮化合物及几丁质。研究结果表明:在高寒草原土壤中,F1(密度为小于1.6g/cm~3)组分主要为植物碎屑,虽然该组份在整体土壤中质量含量较少(0.13%)但其有机质含量相对较高(5.7%),该组份中含有较多的木质素及长链烷基类化合物(主要来源于植物),且随着密度的增加,此类化合物的含量逐渐减少。F2(密度为1.6—1.8g/cm~3)、F3(密度为1.8—2.0g/cm~3)及F4(密度为2.0—2.25g/cm~3)3个组分化学性质相似,其有机化合物的含量在密度组分中呈现增加或减少的过渡状态。F5(密度大于2.25g/cm~3)组分是该土壤的主要组成部分,其质量含量高达98%,该组份中的微生物指纹信息(微生物来源的多糖及含氮化合物)均高于前4个组分。同时,芳烃及多环芳烃这类难降解的物质随着密度的增大逐渐累积,在F5组分中富集。     

A new species of Gigaspora from desert soils of Rajasthan,India

A new species of the endogonaceous fungus Gigaspora, isolated from the Indian semi-arid region, is described. The fungus, named G. tuberculata, produces rusty-brown azygospores with septate subtending hypha. The azygospores bear warts all over the outer wall. The shape, size and general appearance of these spores resemble those of Scutellospora persica.Neeraj and A.K. Varma are with the Microbiology Unit, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India; K.G. Mukerji is with the Applied Mycology Laboratory, Botany Department, University of Delhi, Delhi 110 006, India. B.C. Sharma is with the Department of Textile Engineering, Indian Institute of Technology, New Delhi 110 016, India.     

Does root-sourced ABA have a role in mediating growth and stomatal responses to soil compaction in tomato (Lycopersicon esculentum)?

Isogenic wild-type (Ailsa Craig) and abscisic acid (ABA)-deficient mutant (flacca) genotypes of tomato were used to examine the role of root-sourced ABA in mediating growth and stomatal responses to compaction. Plants were grown in uniform soil columns providing low to moderate bulk densities (1.1–1.5 g cm^?3), or in a split-pot system, which allowed the roots to divide between soils of the same or differing bulk density (1.1/1.5 g cm^?3). Root and shoot growth and leaf expansion were reduced when plants were grown in compacted soil (1.5 g cm^?3) but leaf water status was not altered. However, stomatal conductance was affected, suggesting that non-hydraulic signal(s) transported in the transpiration stream were responsible for the observed effects. Xylem sap and foliar ABA concentrations increased with bulk density for 10 and 15 days after emergence (DAE), respectively, but were thereafter poorly correlated with the observed growth responses. Growth was reduced to a similar extent in both genotypes in compacted soil (1.5 g cm^?3), suggesting that ABA is not centrally involved in mediating growth in this severely limiting ‘critical’ compaction stress treatment. Growth performance in the 1.1/1.5 g cm^?3 split-pot treatment of Ailsa Craig was intermediate between the uniform 1.1 and 1.5 g cm^?3 treatments, whereas stomatal conductance was comparable to the compacted 1.5 g cm^?3 treatment. In contrast, shoot dry weight and leaf area in the split-pot treatment of flacca were similar to the 1.5 g cm^?3 treatment, but stomatal conductance was comparable to uncompacted control plants. These results suggest a role for root-sourced ABA in regulating growth and stomatal conductance during ‘sub-critical’ compaction stress, when genotypic differences in response are apparent. The observed genotypic differences are comparable to those previously reported for barley, but occurred at a much lower bulk density, reflecting the greater sensitivity of tomato to compaction. By alleviating the severe growth reductions induced when the entire root system encounters compacted soil, the split-pot approach has important applications for studies of the role of root-sourced signals in compaction-sensitive species such as tomato.     

Mechanical resistance by an ectorganic soil layer on root development of seedling Pinus sylvestris

We investigated early root development of Pinus sylvestris seedlings in relation to bulk density and natural particle layering in an ectorganic soil layer from a bracken (Pteridium aquilinum) stand. Responses in root development to two levels of bulk density (0.07 and 0.15 g/cm³) in mixed bracken substrate were compared with effects in peat of similar bulk densities, and in sand of three different bulk densities (0.37, 0.52, and 0.67 g/cm³). The effect on root growth of the natural horizontal layering of the organic particles was examined by comparing intact with mixed ectorganic bracken soil profiles of similar bulk densities (resp. 0.09 and 0.07 g/cm³).Root length growth was significantly reduced in the organic and sandy substrates of high bulk density. Root diameter was not affected by bulk density in the organic substrate, but increased with higher bulk density in sand. Preservation of horizontal layering in the intact ectorganic profile significantly reduced root length compared with mixed substrate of similar bulk density.Roots growing in high bulk density, and intact, organic substrate showed increased twisting, which resulted in a smaller depth reached by the root relative to total root length produced. In sand, root twisting did not change with increased bulk density. It is suggested that roots growing through organic substrate follow a path of least resistance. This implies that organic particle size and orientation are more important in determining root development than bulk density.This study points out that the natural layering of organic particles presents another constraint on the establishment of plant species in sites with a well-developed ectorganic soil layer. Disturbance of this layer may therefore enhance establishment of seedlings by reducing the mechanical resistance of the ectorganic soil profile to developing seedling roots.     

Growth,CO2 exchange rate and dry matter partitioning in mungbean (Vigna radiata L.) grown under elevated CO2

This study was conducted to determine the effects of anticipated future level of CO2 on growth and dry matter partitioning of mungbean (Vigna radiata). Plants were grown from seedlings to maturity inside the open top chamber under amhient CO2 (350 +/- 25 microL L(-1)) and elevated CO2 (600 +/- 50 microL L(-1)) at Indian Agricultural Research Institute, New Delhi (India). Plants were harvested at 20, 35 and 50 days after germination. Mungbean plants grown under elevated CO2 concentration resulted in greater photosynthetic rate on a leaflet area basis and no acclimation in photosynthesis was recorded due to high CO2. Plants grown under CO, enrichmcnt were taller and attained greater leaf area along with more dry matter than ambient CO2 grown plants at all growth stages. Response to high CO, depends upon the growth stage of the plant and it was more at early growth stages compared to maturity stages. The high CO2 grown mungbean plants also exhibited increased root growth along with stem and leaves. There was a substantial increase in pod number and seed number/plant under elevated CO2 conditions. The increase in dry matter and growth of root, stem and leaves proved that CO2 enrichment of the atmosphere can stimulate photosynthetic rate which can ultimately lead to an increase in dry matter and growth.     

土壤紧实胁迫对黄瓜根系活力和叶片光合作用的影响

研究了黄瓜(Cucumis sativus L)根系活力和叶片光合作用对土壤紧实胁迫的响应.结果表明:当土壤紧实度增大时,黄瓜根系重量减小,活力下降.同时,叶片的相对电导率(REC)及丙二醛(MDA)含量升高;可溶性蛋白质含量降低;超氧化物歧化酶(SOD)、过氧化物酶(POD)及过氧化氢酶(CAT)活性增强;净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(E)及比叶重(SLW)减小,胞间CO2浓度(Ci)增大.     

Continuous anaerobic phenol degradation using an adapted mixed culture

A mixed culture derived from cow dung and sewage sludge and adapted to phenol was used for anaerobic phenol degradation. The phenol degradation rate depended on the period of adaptation of the mixed culture to phenol. In the continuous process, a higher degradation rate (2500 mg.1^-1 d^-1) and better reactor stability was achieved with a granular activated-carbon-packed bed reactor than with a stirred tank reactor.The authors are with the Department of Biochemical Engineering & Biotechnology, Indian Institute of Technology, Delhi Hauz Khas, New Delhi, India.     

Physiological and biochemical effect of 24-epibrassinoslide on cold tolerance in maize seedlings

Germination and early seedling growth are important for establishment of maize because maize is chilling sensitive crop and low temperature during early period of growth can be detrimental to subsequent crop growth and productivity. Therefore, it is important to protect maize seedling from cold stress. A study was conducted on induced cold tolerance by 24-epibrassinoslide (EBR) at the Indian Agricultural Research Institute, New Delhi, India. Maize seedlings were raised in green house condition (25/18 °C day-night temperatures). Ten days old seedlings were treated with EBR (0.0, 0.01, 0.1, 1.0 and 10 μM) and then divided into two sets, one set was kept in greenhouse (25/18 °C day-night temperatures) and another was transferred to net house (cold stress). Data on various morpho-physiological traits was recorded after 7, 14 and 21 days of treatment. Exogenous application of 1.0 μM EBR had significant effect on growth and morpho-physiological traits under both conditions. The maize seedlings treated with EBR were more tolerant to cold stress than the untreated one. Significant increase in plant height, dry matter accumulation, chlorophyll content, total soluble proteins and starch contents was observed under both conditions, however, the results were more pronounced under cold stress. 1.0 μ M concentration being the most effective under both conditions. Maintenance of high tissue water content, reduced membrane injury index, increased total chlorophyll, soluble sugar and protein content were taken as the possible indicators of EBR induced chilling tolerance.     

Responses of ectomycorrhizal American elm (Ulmus americana) seedlings to salinity and soil compaction

American elm (Ulmus americana) seedlings were either non-inoculated or inoculated with Hebeloma crustuliniforme, Laccaria bicolor and a mixture of the two fungi to study the effects of ectomycorrhizal associations on seedling responses to soil compaction and salinity. The seedlings were grown in the greenhouse in pots containing non-compacted (0.4 g cm^?3 bulk density) and compacted (0.6 g cm^?3 bulk density) soil and subjected to 60 mM NaCl or 0 mM NaCl (control) treatments for 3 weeks. All three fungal inocula had similar effects on the responses of elm seedlings to soil compaction and salt treatment. In non-compacted soil, ectomycorrhizal fungi reduced plant dry weights, root hydraulic conductance, but did not affect leaf hydraulic conductance and net photosynthesis. When treated with 60 mM NaCl, ectomycorrhizal seedlings had several-fold lower leaf concentrations of Na⁺ compared with the non-inoculated plants. Soil compaction reduced Na⁺ leaf concentrations in non-ectomycorrhizal plants and decreased dry weights, gas exchange and root hydraulic conductance. However, in ectomycorrhizal plants, soil compaction had little effect on the leaf Na⁺ concentrations and on other measured growth and physiological parameters. Our results demonstrated that ECM associations could be highly beneficial to plants growing in sites with compacted soil such as urban areas.     

Meiosis in garden roses

Summary Meiosis in 96 varieties of garden roses was studied. While the euploid numbers were most frequent, in exceptional cases, aneuploid numbers were recorded. Intervarietal variation in chromosome pairing is reflected in the varying degrees of expression of univalents, heteromorphic bivalents, bivalents with double secondary constrictions and multivalents. Supernumerary fragments in addition to the euploid chromosome complement were recorded in three varieties. Three varieties of floribundas and one of hybrid polyanthas were chromosome numerical mosaics.A part of Ph. D. thesis submitted by the senior author to the Post Graduate School, Indian Agricultural Research Institute, New Delhi, India.     

Effect of soil compaction on barley (Hordeum vulgare L.) growth: I. Possible role for ABA as a root-sourced chemical signal

Wild-type (Steptoe) and abscisic acid (ABA)-deficient mutant(Az34) genotypes of barley were grown in compacted soil to examinethe potential role of ABA as a root-to-shoot signal. Root andshoot growth and leaf conductance were all reduced when plantswere grown in compacted soil with a bulk density of 1.7g cm^–3,relative to uncompacted control plants (1.1 g cm^–3. Theseeffects occurred in the absence of detectable changes in leafwater status or foliar abscisic acid (ABA) content. Analysisof Steptoe and Az34 xylem sap showed that the ABA concentrationwas greatly increased at 6 d after emergence (6 DAE) when seedlingswere grown in compacted soil (1.7 g cm^–3); however, ABAconcentrations were never as high in the mutant as in the wildtype. The increase in xylem sap ABA concentration observed athigh bulk density was closely correlated with reductions inleaf conductance, but not leaf area. These increases were transitory,and xylem sap ABA concentrations subsequently decreased towardsthe control level by 18 DAE in both genotypes. The ABA-deficient mutant, Az34, produced a much lower leaf areathan Steptoe at a bulk density of 1.6 g cm^–3. Examinationof epidermal characteristics indicates that this effect resultedmainly from reductions in cell expansion rather than cell division,suggesting that the higher ABA concentrations detected in xylemsap from the wild-type Steptoe may have exerted a positive rolein maintaining leaf expansion in this treatment. The possibleinvolvement of ABA as a root-to-shoot signal mediating the effectsof compaction stress is discussed. Key words: Soil compaction, bulk density, ABA, ABA-deficient mutant, leaf growth     

A Distinct Strain of Cowpea mild mottle virus Infecting Soybean in India

Soybean crops showing systemic mottling, mosaic and leaf deformation were observed at high disease incidences (25.1–71.0%) in the kharif season of 2011 and 2012 in the experimental farm of the Indian Agricultural Research Institute (IARI), New Delhi. Symptomatic soybean leaves contained flexuous particles (650 × 12 nm), suggesting an infection by a Carlavirus. The causal virus was characterized as a strain of Cowpea mild mottle virus (CPMMV) on the basis of mechanical inoculation, whitefly transmission, seed transmission and sequencing of the viral genome. This is the first report of natural infection by a distinct strain of CPMMV in soybean in India.     

Influence of soil edaphic factors and their critical limits on seedling emergence of corn (Zea mays L.)

Summary In the present investigation the influence of various soil physical parameters on seeding emergence of corn (Zea mays L.) and their critical limits was studied in order to obtain a proper crop stand. The effect of soil compaction, resulting into various bulk densities on some soil physical properties was also studied. Seedling emergence decreased with increasing bulk density, soil suction, seed placement depth, soil strength and with decreasing oxygen diffusion rates. The critical values for these soil physical parameters were found to be 1.4 g/cm³, 3 atm., 4 cm, 1.0 kg/cm² and 40×10^-8 g O₂/cm²/min bulk density, soil suction, seed placement depth, soil strength and oxygen diffusion rates respectively. Increasing bulk density decreased the soil water content, oxygen diffusion rates and increased the soil strength. re]19751117 Soil Science Department     

Nuclear structure and behaviour in the vegetative hyphae of Pythium aphanidermatum

Nuclear divisions taking place in the hyphae ofPythium aphanidermatum have been described. Typical prophase type of nuclei with elongate chromatin fibres have been observed. Achromatic structures resembling spindle fibres with well defined poles during anaphase configuration have been noticed. A mild pretreatment with acenaphthene vapours proved instrumental in arresting the progress of nuclear division. Stages similar to early and late anaphase and telophase with deeply staining chromosomal masses have been observed. A high concentration of acenaphthene treatment resulted in the formation of giant nuclei.This work is based on a thesis submitted byK. Seshadri in partial fulfilment of the requirements for the M. Sc. degree of the Indian Agricultural Research Institute, New Delhi. His present address is: University Botany Laboratory, Chepauk, Madras-5, India.     

Effect of soil compaction on root growth and uptake of phosphorus

Summary Zea mays L. andLolium rigidum Gaud. were grown for 18 and 33 days respectively in pots containing three layers of soil each weighing 1 kg. The top and bottom layers were 100 mm deep and they had a bulk density of 1200 kg m^–3, while the central layer of soil was compacted to one of 12 bulk densities between 1200 and 1750 kg m^–3. The soil was labelled with³²P and³³P so that the contribution of the different layers of soil to the phosphorus content of the plant tops could be determined. Soil water potential was maintained between –20 and –100 kPa.Total dry weight of the plant tops and total root length were slightly affected by compaction of the soil, but root distribution was greatly altered. Compaction decreased root length in the compacted soil but increased root length in the overlying soil. Where bulk density was 1550 kg m^–3, root length in the compacted soil was about 0.5 of the maximum. At that density, the penetrometer resistance of the soil was 1.25 and 5.0 MPa and air porosity was 0.05 and 0.14 at water potentials of –20 and –100 kPa respectively, and daytime oxygen concentrations in the soil atmosphere at time of harvest were about 0.1 m³m^–3. Roots failed to grow completely through the compacted layer of soil at bulk densities 1550 kg m^–3. No differences were detected in the abilities of the two species to penetrate compacted soil.Ryegrass absorbed about twice as much phosphorus from uncompacted soil per unit length of root as did maize. Uptake of phosphorus from each layer of soil was related to the length of root in that layer, but differences in uptake between layers existed. Phosphorus uptake per unit length of root was higher from compacted than from uncompacted soil, particularly in the case of ryegrass at bulk densities of 1300–1500 kg m^–3.     

Impact of chelator-induced phytoextraction of cadmium on yield and ionic uptake of maize

Enhanced phytoextraction uses soil chelators to increase the bioavailability of heavy metals. This study tested the effectiveness of ethylenediaminetetraacetic acid (EDTA) and citric acid in enhancing cadmium (Cd) phytoextraction and their effects on the growth, yield, and ionic uptake of maize (Zea mays). Maize seeds of two cultivars were sown in pots treated with 15 (Cd₁₅) or 30 mg Cd kg^?1 soil (Cd₃₀). EDTA and citric acid at 0.5 g kg^?1 each were applied 2 weeks after germination. Results demonstrated that the growth, yield per plant, and total grain weight were reduced by exposure to Cd. EDTA increased the uptake of Cd in shoots, roots, and grains of both maize varieties. Citric acid did not enhance the uptake of Cd, rather it ameliorated the toxicity of Cd, as shown by increased shoot and root length and biomass. Cadmium toxicity reduced the number of grains, rather than the grain size. The maize cultivar Sahiwal-2002 extracted 1.6% and 3.6% of Cd from soil in both Cd+ EDTA treatments. Hence, our study implies that maize can be used to successfully phytoremediate Cd from soil using EDTA, without reducing plant biomass or yield.     

Are “multiple cross-multiple pollen hybrids’ an answer for productive populations in Brassica campestris var. ‘brown sarson’?

Summary A set of complex crosses with multiple crosses as female parents were made using multiple pollen in turnip rape (Brassica campestris L.). These multiple cross — multiple pollen hybrids (mucromphs) were evaluated for a large number of quantitative characters including yield. New methods were proposed to study such genetic material in depth so as to formulate suitable strategies to breed for attractive seed yield.Part of the Ph. D. Thesis of junior author submitted to Indian Agricultural Research Institute, New Delhi     

Limitations of the32P isotope injection technique for the study of the root systems of wheat,mung and cowpeas

Summary The³²P isotope injection technique developed by earlier investigators in graminea has been extensively tested, under irrigated agriculture, using three promising varieties of wheat Pusa Lerma (a single gene dwarf) Sharbati Sonora (a double gene dwarf) and a triple gene dwarf 1634. Field experiments supported by pot experiments using both sand and soil cultures gave identical results.Unlike the wheats with a succulant stem the legumes are fibrous and do not permit injection in the stem. The technique was, therefore, modified and the injection had to be given on the leaf stem instead of the plant stem.While equilibrium in wheat was obtained five days after injection both in pot and field experiments mung behaves in a different manner. In the pot experiments the equilibrium could not be attained till the 12th day while in the field experiments it was attained even on the first day after injection. Mung has a thick tap root surrounded by fine secondary roots. The activity was observed to move very fast in the thick tap root even on the first day while the thin secondary roots showed resistance and attained equilibrium on the 3rd day.The anomaly observed in the pot and field experiments was attributed partly to the differential root growth under the two environments studied and to some extent on the probable loss of fine roots in the collection on the field. However, the plants grown both in pots as well as on the field attained equilibrium on the 12th day. In the case of cowpeas the equilibrium was attained on the 8th day.The period required for attaining uniform distribution of activity thus seems to be a function of the morphology of the plant, the pattern of the root system and the injection technique adopted. As this is a pre-requisite for the quantitative estimation of the roots care has to be taken in perfecting the technique.Part of the thesis for which Ph.D. degree was awarded to K. Vijayalakshmi by the Indian Agricultural Research Institute, New Delhi.Dry Land Agriculture Centre, Hyderabad.Nuclear Research Laboratory, at present International Atomic Energy Agency Expert, Mymensingh, Bangladesh.     

Effect of rates of nitrogen and relative efficiency of sulphur-coated urea and nitrapyrin-treated urea in dry matter production and nitrogen uptake by rice

Summary A field experiment conducted for two rainy seasons (1974 and 1975) on a sandy clay loam soil at the Indian Agricultural Research Institute, New Delhi showed that at 100kg N/ha the apparent recovery of urea nitrogen by the rice crop was only 28%, which was raised to 41.7% by treating urea with Nitrapyrin and to 47.4% by coating urea withneem (Azadirachta indica Juss) cake. The recovery with sulphur-coated urea was 37.7%. Dry matter production nitrogen concentration in plant and uptake by rice were increased as the rate of nitrogen was increased from 0 to 150kg N/ha. Advantage of treating urea with Nitrapyrin or coating withneem cake was seen more in grain than straw yield.