Emergence of Long-Range Angular Correlations in Low-Multiplicity Proton-Proton Collisions

This Letter presents the measurement of near-side associated per-trigger yields, denoted ridge yields, from the analysis of angular correlations of charged hadrons in proton-proton collisions at sqrt[s]=13  TeV. Long-range ridge yields are extracted for pairs of charged particles with a pseudorapidity difference of 1.4<|Δη|<1.8 and a transverse momentum of 1 Collapse

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First Measurement of the |t| Dependence of Incoherent J/ψ Photonuclear Production

The first measurement of the cross section for incoherent photonuclear production of J/ψ vector mesons as a function of the Mandelstam |t| variable is presented. The measurement was carried out with the ALICE detector at midrapidity, |y|<0.8, using ultraperipheral collisions of Pb nuclei at a center-of-mass energy per nucleon pair of sqrt[s_{NN}]=5.02  TeV. This rapidity interval corresponds to a Bjorken-x range (0.3-1.4)×10^{-3}. Cross sections are given in five |t| intervals in the range 0.04<|t|<1  GeV^{2} and compared to the predictions by different models. Models that ignore quantum fluctuations of the gluon density in the colliding hadron predict a |t| dependence of the cross section much steeper than in data. The inclusion of such fluctuations in the same models provides a better description of the data.

ψ(2S) Suppression in Pb-Pb Collisions at the LHC

The production of the ψ(2S) charmonium state was measured with ALICE in Pb-Pb collisions at sqrt[s_{NN}]=5.02  TeV, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity (2.5 Collapse

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Measurements of Groomed-Jet Substructure of Charm Jets Tagged by D^{0} Mesons in Proton-Proton Collisions at sqrt[s]=13 TeV

Understanding the role of parton mass and Casimir color factors in the quantum chromodynamics parton shower represents an important step in characterizing the emission properties of heavy quarks. Recent experimental advances in jet substructure techniques have provided the opportunity to isolate and characterize gluon emissions from heavy quarks. In this Letter, the first direct experimental constraint on the charm-quark splitting function is presented, obtained via the measurement of the groomed shared momentum fraction of the first splitting in charm jets, tagged by a reconstructed D^{0} meson. The measurement is made in proton-proton collisions at sqrt[s]=13  TeV, in the low jet transverse-momentum interval of 15≤p_{T}^{jet ch}<30  GeV/c where the emission properties are sensitive to parton mass effects. In addition, the opening angle of the first perturbative emission of the charm quark, as well as the number of perturbative emissions it undergoes, is reported. Comparisons to measurements of an inclusive-jet sample show a steeper splitting function for charm quarks compared with gluons and light quarks. Charm quarks also undergo fewer perturbative emissions in the parton shower, with a reduced probability of large-angle emissions.

Measurement of the Lifetime and Λ Separation Energy of _{Λ}^{3}H

The most precise measurements to date of the _{Λ}^{3}H lifetime τ and Λ separation energy B_{Λ} are obtained using the data sample of Pb-Pb collisions at sqrt[s_{NN}]=5.02  TeV collected by ALICE at the LHC. The _{Λ}^{3}H is reconstructed via its charged two-body mesonic decay channel (_{Λ}^{3}H→^{3}He+π^{-} and the charge-conjugate process). The measured values τ=[253±11(stat)±6(syst)]  ps and B_{Λ}=[102±63(stat)±67(syst)]  keV are compatible with predictions from effective field theories and confirm that the _{Λ}^{3}H structure is consistent with a weakly bound system.

Measurement of the J/ψ Polarization with Respect to the Event Plane in Pb-Pb Collisions at the LHC

We study the polarization of inclusive J/ψ produced in Pb-Pb collisions at sqrt[s_{NN}]=5.02  TeV at the LHC in the dimuon channel, via the measurement of the angular distribution of its decay products. We perform the study in the rapidity region 2.5 Collapse

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First Measurement of Antideuteron Number Fluctuations at Energies Available at the Large Hadron Collider

The first measurement of event-by-event antideuteron number fluctuations in high energy heavy-ion collisions is presented. The measurements are carried out at midrapidity (|η|<0.8) as a function of collision centrality in Pb-Pb collisions at sqrt[s_{NN}]=5.02  TeV using the ALICE detector. A significant negative correlation between the produced antiprotons and antideuterons is observed in all collision centralities. The results are compared with a state-of-the-art coalescence calculation. While it describes the ratio of higher order cumulants of the antideuteron multiplicity distribution, it fails to describe quantitatively the magnitude of the correlation between antiproton and antideuteron production. On the other hand, thermal-statistical model calculations describe all the measured observables within uncertainties only for correlation volumes that are different with respect to those describing proton yields and a similar measurement of net-proton number fluctuations.

Enhanced Deuteron Coalescence Probability in Jets

The transverse-momentum (p_{T}) spectra and coalescence parameters B_{2} of (anti)deuterons are measured in p-p collisions at sqrt[s]=13  TeV for the first time in and out of jets. In this measurement, the direction of the leading particle with the highest p_{T} in the event (p_{T}^{lead}>5  GeV/c) is used as an approximation for the jet axis. The event is consequently divided into three azimuthal regions, and the jet signal is obtained as the difference between the toward region, that contains jet fragmentation products in addition to the underlying event (UE), and the transverse region, which is dominated by the UE. The coalescence parameter in the jet is found to be approximately a factor of 10 larger than that in the underlying event. This experimental observation is consistent with the coalescence picture and can be attributed to the smaller average phase-space distance between nucleons in the jet cone as compared with the underlying event. The results presented in this Letter are compared to predictions from a simple nucleon coalescence model, where the phase-space distributions of nucleons are generated using pythia8 with the Monash 2013 tuning, and to predictions from a deuteron production model based on ordinary nuclear reactions with parametrized energy-dependent cross sections tuned on data. The latter model is implemented in pythia8.3. Both models reproduce the observed large difference between in-jet and out-of-jet coalescence parameters, although the almost flat trend of the B_{2}^{Jet} is not reproduced by the models, which instead give a decreasing trend.

Comparative cryopreservation of indian wild orange (Citrus indica Tanaka) embryonic axes

BACKGROUND

Indian Wild Orange (Citrus indica Tanaka) is an endangered and endemic species from northeast India for which effective ex situ conservation strategies, including embryo cryopreservation, are urgently needed.

MATERIALS AND METHODS

Desiccation tolerance and cryopreservation ability for embryonic axes of Citrus indica was determined using three techniques (air desiccation-freezing, PVS2 vitrification-freezing and encapsulation-dehydration-freezing). Success was assessed as survival and recovery in vitro.

RESULTS

Successful cryopreservation of embryonic axes was achieved using all three methods, with the highest survival achieved when using air desiccation-freezing (90%) followed by encapsulation-dehydration (85%) and PVS2 vitrification cryopreservation (80%). Regeneration levels were lower than survival levels for all three proceedures. Post-cryo regeneration success was: encapsulation-dehydration (64%) > air desiccation-freezing (55%) > PVS2 vitrification (52%).

CONCLUSION

Although there was relatively high post-cryopreservation recovery growth obtained using all the three techniques, the air desiccation-freezing technique is preferred, as it is a simple, practical and reproducible technique for the long-term cryobanking of this important wild species. Doi: 10.54680/fr23310110512.

Optimized Recovery of Cryostored Dormant Buds of Mulberry Germplasm

A two-step freezing cryoprotocol preceded by desiccation to 15 to 25% moisture content was developed and successfully applied to winter dormant buds of mulberry (different Morus spp.) of a core set comprising 238 accessions studies in our laboratory. The survival and recovery percentage of diverse accessions cryobanked for various periods were tested under in vitro conditions, and several factors were analyzed to determine their role in optimizing the recovery of low-viability accessions. The effect of rates of freezing and thawing (both fast and slow), were tested and recovery compared. Recovery conditions such as dark incubation and rehydration in sterile moist moss grass for different durations after cryopreservation led to a higher survival percentage compared to controls. Two different recovery culture media were compared for their efficiency in survival. On average, the survival under in vitro culture conditions using optimized conditions was high: above 60% in majority of the accessions. Dormant buds showed viability in the range of 25 to 100% with an average of 50.4%. The recovery percentage of winter dormant buds after cryopreservation via slow freezing and slow thawing with rehydration by moist moss grass for 2 h was recorded in the range from 63.3 to 90.9% with an average of 81.05%. Without rehydration, it ranged from 50 to 75% with an average of 60.4%. Regeneration of cryopreserved mulberry germplasm after 6 years of storage indicated no survival loss over different years of storage, and 33-40% of the accessions showed viability above 40%, up to a maximum of 100%. Maximum shoot formation (100%) was obtained from Morus alba. The majority of the accessions were rooted in vitro within 20-25 days of subculture in the auxin rich rooting media, except in wild species M. latifolia and M. laevigata, which took longer (45 to 60 days) for root development. All the rooted plantlets were then transferred to the field and successfully established in a glasshouse.

Storage Behavior and Cryopreservation of Citrus cavaleriei, an Endangered, Cold-resistant Species of Northeast India with Exceptionally Large Seeds

BACKGROUND

Ichang Papeda (Citrus cavaleriei H.Lév. ex Cavalerie) is a wild and endangered species of NE India that requires urgent preservation of its genetic resources.

OBJECTIVE

To characterize the storage physiology of the seeds and to cryopreserve the embryo and embryonic axis (EA).

MATERIALS AND METHODS

The morphology and storage physiology of the seeds were determined, and the cryopreservation of embryos and EA attempted using various techniques (viz., air desiccation-freezing, vitrification and encapsulation-dehydration).

RESULTS

Weighing up to 4 g, seeds of Citrus cavaleriei are the largest known in the genus. Based on estimates using the seed coat ratio - seed mass (SCR-SM) model there was a very high probability of seed desiccation intolerance, which was validated physiologically; seeds lost vigour on drying below 30% moisture content (MC) and no seeds germinating after drying to <12% MC. Embryos and EAs could be air dried to 25-30% MC and cryopreserved with c. 50% survival. In contrast, EA optimally exposed to PVS2 (20 min) or encapsulated, sucrose pretreated (0.5 M, 24 h) and dehydrated (6 h) had c. 40% survival after cryopreservation.

CONCLUSION

Citrus cavaleriei produces large, recalcitrant seeds that can, nevertheless, be cryopreserved as embryos or isolated EA after air drying to c. 25-30% MC; encapsulation-dehydration and vitrification provide alternative options for the cryopreservation of EA.

Retraction Note to: Inferring Phylogenetic Relationships of Indian Citron (Citrus medica L.) Based on rbcL and matK Sequences of Chloroplast DNA

The Editor-in-Chief and the publisher have retracted this article [1] because of significant overlap with previously published articles [2-5]. Ajit Uchoi, Surendra Kumar Malik, Ravish Chaudhary, Susheel Kumar, M.R. Rohini, Digvender Pal, and Sezai Ercisli disagree with the retraction. The publisher was not able to get in contact with Rekha Chaudhury, she did not respond to any correspondence about this retraction.

Scanning electron microscopic study on freezing behaviour of tissue cells in dormant bud of mulberry (Morus sp.)

The freezing behaviour studies of dormant buds, were examined, employing scanning electron microscopy (SEM) and light microscopy. The differences and effect of freezing behaviour on dormant buds were observed. The dormant bud primordia of several woody plant species avoid freezing injury by deep supercooling. By slow cooling (5°C/day) of dormant buds to –30°C, all living cells in bud tissues exhibited distinct shrinkage without intracellular ice formation detectable by SEM. However, the recrystallization experiment of these slowly cooled tissue cells, which was done by further freezing of slowly cooled buds with liquid nitrogen (LN) and then rewarming to –10°C, confirmed that some of the cells in the apical meristem, area in which cells had thin walls and in which no extracellular ice accumulated, lost freezable water with slow cooling to –30°C, indicating adaptation of these cells by deep super cooling. Water in plant tissues will not supercool unless heterogeneous ice nucleating substances are absent and the spread of ice from adjacent tissue can be prevented. Deep supercooling could not occur in dormant bud primordia if xylem vessels formed a continuous conduit connecting the dormant bud primordia with the remainder of the plant. If xylem continuity was established, ice could propagate via the vascular system and nucleate the water within the primordia. It is concluded that no extracellular ice crystals accumulated in such tissues containing deep supercooling cells with thin cell walls.

Inferring Phylogenetic Relationships of Indian Citron (Citrus medica L.) based on rbcL and matK Sequences of Chloroplast DNA

Phylogenetic relationships of Indian Citron (Citrus medica L.) with other important Citrus species have been inferred through sequence analyses of rbcL and matK gene region of chloroplast DNA. The study was based on 23 accessions of Citrus genotypes representing 15 taxa of Indian Citrus, collected from wild, semi-wild, and domesticated stocks. The phylogeny was inferred using the maximum parsimony (MP) and neighbor-joining (NJ) methods. Both MP and NJ trees separated all the 23 accessions of Citrus into five distinct clusters. The chloroplast DNA (cpDNA) analysis based on rbcL and matK sequence data carried out in Indian taxa of Citrus was useful in differentiating all the true species and species/varieties of probable hybrid origin in distinct clusters or groups. Sequence analysis based on rbcL and matK gene provided unambiguous identification and disposition of true species like C. maxima, C. medica, C. reticulata, and related hybrids/cultivars. The separation of C. maxima, C. medica, and C. reticulata in distinct clusters or sub-clusters supports their distinctiveness as the basic species of edible Citrus. However, the cpDNA sequence analysis of rbcL and matK gene could not find any clear cut differentiation between subgenera Citrus and Papeda as proposed in Swingle's system of classification.

An efficient regeneration and rapid micropropagation protocol for Almond using dormant axillary buds as explants

An efficient in vitro protocol was standardized for Almond (Prunus dulcis) propagation using dormant axillary buds as explants. Explants were cultured on Murashige and Skoog (MS) and woody plant medium (WPM) supplemented with different concentration/combination(s) of phytohormones. MS basal medium showed lowest shoot induction and took longest duration for shoot initiation. Multiple shoots were induced in MS medium supplemented with the combination of BAP (0.5 mgL(-1)). Cultures showed poor response for rooting in all combinations of plant growth regulators (PGRs) and took 90 days for initiation. Rooting was higher in half strength of MS than in full-strength. The highest root induction (33.33%) was recorded in half MS medium supplemented with 0.1 mgL(-1) IBA (indole-3-butyric acid) followed by full strength of MS medium (20%) supplemented with IBA (0.1 mgL(-1)). α-Naphthalene acetic acid (NAA) was less effective for rooting than IBA. The highest root induction (25%) was found in half strength of MS medium supplemented with 0.1 mgL(-1) NAA followed by full strength of MS medium (20%). The protocol developed would be of use in mass propagation of almond and also support in vitro conservation.

Genetic Diversity Analysis in wild species of Pongamia pinnata (L.) using RAPD and SRAP markers

Bio -diversityrefers to the variations within the living world while genetic diversity is the sum of genetic characteristics within any species or genus. Genetic diversity serves as a way for populations to adapt to changing environments. With more variation, it is more likely that some individuals in a population will possess variations of alleles that are suited for the environment. Those individuals are more likely to survive to produce offspring bearing that allele. The population will continue for more generations because of the success of these individuals. The extensive literature survey revealed that Pongamia Pinnata L. is an important medicinal plant with diverse pharmacological spectrum. The plant shows the presence of many chemical constituents which are responsible for varied pharmacological and medicinal properties. Furthermore, it also represents a milestone in the field of biofuel industry as one of the most important bio fuel crop. The present investigation was carried out to assess the genetic diversity of 37 wild species of P. pinnata collected from different states from India based on random amplified polymorphic DNA (RAPD) and Sequenced Related Amplified Polymorphism (SRAP) primers. After screening a total of 18 RAPD and 23 SRAP primers were used which gave reproducible amplification banding patterns. In RAPD out of 157 alleles were generated of which 150 were polymorphic across the studied accessions (96.8% polymorphism). For SRAP the total number of amplified products was 145 of which 122 were polymorphic (84.1% polymorphism). The mean polymorphic information content (PIC) for both the markers was 0.77 and 0.68. Variation in combined Jaccard’s coefficient of similarity indicates the high level of genetic variation among the genotypes studied. The overall grouping pattern of clustering corresponds well with the principal component analysis (PCA), confirming patterns of genetic diversity observed among the accessions. 

Genetic diversity and phylogenetic analysis of Citrus (L) from north-east India as revealed by meiosis, and molecular analysis of internal transcribed spacer region of rDNA

The north-eastern region of India is reported to be the center of origin and rich in diversity of Citrus (L.) species, where some wild and endangered species namely Citrus indica, Citrus macroptera, Citrus latipes, Citrus ichagensis and Citrus assamensis exist in their natural and undisturbed habitat. In order to have comprehensive information about the extent of genetic variability and the occurrence of cryptic genomic hybridity between and within various Citrus species, a combined approach involving morphological, cytogenetical and molecular approaches were adopted in the present study. Cytogenetic approaches are known to resolve taxonomic riddles in a more efficient manner, by clearly delineating taxa at species and sub species levels. Male meiotic studies revealed a gametic chromosome number of n = 9, without any evidence of numerical variations. Bivalents outnumbered all other types of associations in pollen mother cells (PMCs) analyzed at diplotene, diakinesis and metaphase I. Univalents were frequently encountered in nine species presently studied, though their presence appropriately did not influence the distributional pattern of the chromosomes at anaphases I and II. The molecular approaches for phylogenetic analysis based on sequence data related to ITS 1, ITS 2 and ITS 1 + 5.8 s + ITS 2 of rDNA using maximum parsimony method and Bayesian inference have thrown light on species inter-relationship and evolution of Citrus species confirming our cytogenetical interpretations. The three true basic species i.e. Citrus medica, Citrus maxima and Citrus reticulata with their unique status have been resolved into distinct clades with molecular approaches as well. C. indica which occupies a unique position in the phylogenetic ladder of the genus Citrus has been resolved as a distinct clade and almost behaving as an out-group. The presences of quadrivalents in C. indica also echo and support its unique position. From our study it is amply clear that C. reticulata also has close relation to C. ichagensis, as these species have clustered together, denoting their close genetic relationship. On the other hand, our studies did not demonstrate a clear differentiation between subgenera Citrus and Papeda at the rDNA level. The combined approach of cytogenetical and molecular analysis did complement our early karyological findings and helped in resolving many a taxonomic riddles.

Long-term, large scale banking of citrus species embryos: comparisons between cryopreservation and other seed banking temperatures

The long-term, large scale application of embryo cryopreservation has been assessed rarely and comparisons of viability loss for partially dried material with conventional seed bank storage conditions infrequently made. Five citrus species were cryopreserved following air drying of embryos (seed minus the testa) and embryonic axes: rough lemon (Citrus jambhiri), pommelo (C. grandis), mandarin (C. reticulata), citron (C. medica) and kagzi lime (C. aurantifolia). Although drying rates to c. 10 percent moisture content (MC) were approximately 10-times faster for isolated axes compared to embryos, the optimum MCs for cryopreservation were generally similar within a species, varying from c. 10 percent (C. jambhiri) to c. 20 percent (C. medica). Nonetheless, the hydration window for cryopreservation of the axis was usually wider than for the embryo. For all species, embryo or axis survival after cryopreservation ranged from 65 to 96 percent (C. medica axes), producing normal healthy seedlings from embryos and plantlets from axes without intervening callus growth in vitro. Whilst partially dried embryos of all five species survived fully liquid nitrogen vapour storage for 120 days, viability loss was rapid at -20 degree C, 5 degree C and ambient temperature, with a maximum interpolated half-life across these temperatures of c. 80 days for C. grandis at 5 degree C. The developed cryopreservation protocols were applied routinely to cryobank 377 accessions of Citrus germplasm from field genebanks, farmer's orchards, semi-wild and wild sources. After an average of 6.3 to 8.4 years cryo-storage, between 69 and 81 percent of accessions per species retained > 70 percent of the viability after desiccation. The results provide irrevocable evidence for the importance of cryopreservation for the banking of seeds of higher plants.

Karyological studies in ten species of Citrus(Linnaeus, 1753) (Rutaceae) of North-East India

Ten Citrus (Linnaeus, 1753) species of North-East India have been karyo-morphologically analysed. All studied species had 2n=18 chromosomes without any evidence of numerical variation. All the chromosomes were found to be of metacentric and sub-metacentric in all the species; the morphology of the chromosomes showing size difference only. Symmetrical karyotype which does not have much difference in the ratio of longest to shortest chromosome in all the species was observed. Three species, Citrus grandis (Osbeck, 1757), Citrus reticulata (Blanco, 1837) and Citrus medica (Linnaeus, 1753) are identified as true basic species from asymmetry studies of karyotypes as they reflect on the primitive nature of their genomes. Citrus indica (Tanaka, 1937)occupies a special taxonomic position within the genus Citrus as a progenitor for other cultivated species.

Magnetic and magnetocaloric properties of nanocrystalline Pr(1-x)A(x)Mn(1-y)Co(y)O3 (A = Ca, Sr) (x = 0.3; y = 0.5) manganites

Structural, magnetic and magnetocaloric properties of sol-gel prepared, nanocrystalline oxides Pr(1-x)A(x)Mn(1-y)Co(y)O3 (A = Ca, Sr) (x = 0.3; y = 0.5) (cubic, space group Fm3m) have been studied. From the X-ray data, the crystallite size of Pro.7Ca0.3Mn0.5Co0,503 and Pr0.7Sr0.3Mn0.5Co0.5O3 samples is found to be approximately 24 nm and approximately15 nm respectively. High resolution transmission electron microscopy image shows average particle size of approximately 34 nm and approximately 20 nm. Magnetization measurements indicate a Curie temperature of approximately 153 K and approximately172 K in applied magnetic field of 100 Oe for Pr0.7Ca0.3Mn0.5Co0.5O3 and Pr0.7Sr0.3Mn0.5Co0.O3 compounds. The magnetization versus applied magnetic field curves obtained at temperatures below 150 K show significant hysteresis and magnetization is not saturated even in a field of 7 T. The magnetocaloric effect is calculated from M versus H data obtained at various temperatures. Magnetic entropy change shows a maximum near T(c) for both the samples and is of the order approximately 2.5 J/kg/K.

An improved pollen collection and cryopreservation method for highly recalcitrant tropical fruit species of mango (Mangifera indica L.) and litchi (Litchi chinensis Sonn.)

An improved method for pollen collection from freshly dehiscing anthers of mango (Mangifera indica L.) and litchi (Litchi chinensis Sonn.) using the organic solvent cyclohexane has been devised. Using this method pollen quantity sufficient for large scale pollinations could be collected and stored for future use. Transport of pollen in viable conditions over long distances, from site of collection (field genebank) to cryolab was successfully devised for both these fruit species. Cryopreservation was successfully applied to achieve long-term pollen storage over periods of up to four years. Pollen viability was tested using in vitro germination, the fluorochromatic reaction (FCR) method and by fruit set following field pollination. On retesting, four year cryostored pollen of different mango and litchi varieties showed high percentage viability as good as fresh control pollens. Pollens of more than 180 cultivars of mango and 19 cultivars of litchi have been stored in the cryogenebank using the technology developed, thus facilitating breeding programmes over the long-term.

Improved critical current density of MgB2--carbon nanotubes composite

In the present study, we report a systematic study of doping/admixing of carbon nanotubes (CNTs) in different concentrations in MgB2. The composite material corresponding to MgB2-x at.% CNTs (35 at.% > or = x > or = 0 at.%) have been prepared by solid-state reaction at ambient pressure. All the samples in the present investigation have been subjected to structural/microstructural characterization employing XRD, Scanning electron microscopic (SEM), and Transmission electron microscopic (TEM) techniques. The magnetization measurements were performed by Physical property measurement system (PPMS) and electrical transport measurements have been done by the four-probe technique. The microstructural investigations reveal the formation of MgB2-carbon nanotube composites. A CNT connecting the MgB2 grains may enhance critical current density due to its size (approximately 5-20 nm diameter) compatible with coherence length of MgB2 (approximately 5-6 nm) and ballistic transport current carrying capability along the tube axis. The transport critical current density (Jct) of MgB2 samples with varying CNTs concentration have been found to vary significantly e.g., Jct of the MgB2 sample with 10 at.% CNT addition is approximately 2.3 x 10(3) A/cm2 and its value for MgB2 sample without CNT addition is approximately 7.2 x 102 A/cm2 at 20 K. In order to study the flux pinning effect of CNTs doping/ admixing in MgB2, the evaluation of intragrain critical current density (JJ) has been carried out through magnetic measurements on the fine powdered version of the as synthesized samples. The optimum result on Jc is obtained for 10 at.% CNTs admixed MgB2 sample at 5 K, the Jc reaches approximately 5.2 x 10(6) A/cm2 in self field, -1.6 x 10(6) A/cm2 at 1 T, approximately 2.9 x 10(5) A/cm2 at 2.6 T, and approximately 3.9 x 10(4) A/cm2 at 4 T. The high value of intragrain Jc in 10 at.% CNTs admixed MgB2 superconductor has been attributed to the incorporation of CNTs into the crystal matrix of MgB2, which are capable of providing effective flux pinning centres. A feasible correlation between microstructural features and superconducting properties has been put forward.

Morphohistobiochemical characteristics of embryogenic and nonembryogenic callus cultures of sweet potato (Ipomoea batatas L.)

Ipomoea batatas callus culture raised in a medium supplemented with 2,4-D (2,4-dichlorophenoxy acetic acid) alone or 2,4-D in combination with benzyl adenine, were found to be embryogenic. Supplementation of exogenous chemicals, such as 5 g/l NaCI or 0.7 g/l proline together with a mild dose of 0.2 mg/l 2,4-D, enhanced somatic embryogenesis significantly in all the genotypes tested. Morphological, growth, physiological, histological, and biochemical characteristics of the embryogenic callus were different from the nonembryogenic callus. The former was compact, slow growing, and nodular compared with the fast growing, fragile, nonembryogenic callus. The embryogenic callus tissue had more dry matter, protein and reducing sugar contents compared with the less embryogenic callus. The somatic embryogenic response remained steady in the cultures for up to 96 weeks.

Plant regeneration via somatic embryogenesis in pigeonpea (Cajanus cajan L. Millsp)

Efficient plant regeneration via somatic embryogenesis has been developed in pigeonpea. Cotyledon and leaf explants from 10-day-old seedlings produced embryogenic callus and somatic embryos when cultured on Murashige and Skoog (MS) medium supplemented with 10 µM thidiazuron (TDZ). Subsequent withdrawal of TDZ from the induction medium resulted in the maturation and growth of the embryos into plantlets on MS basal medium. The rooted plantlets were transferred and acclimatized on vermiculite where they showed normal morphological characters.

Plant regeneration from various expiants of cultivated Piper species

Morphogenetic potential of root, leaf, node and internode expiants of 3 cultivated Piper species was investigated to develop a reliable plant regeneration protocol. P. longum (pipli) was the most responsive followed by P. betle (betel vine) and P. nigrum (black pepper). In P. longum the highest number of shoot buds was produced on root expiants followed by node, internode and leaf expiants. In P. betle and P. nigrum adventitious shoot buds differentiated only from internodal and nodal ring regions, respectively. Histological examination in P. longum showed that adventitious shoot buds originate directly from the cortical cells of the root and the internode without an intervening callus phase. Benzyladenine was superior to kinetin for shoot induction and its optimum concentrations for P. longum, P. betle and P. nigrum were 1-2, 10 and 10 μM, respectively. Shoot elongation and rooting were achieved in B5 medium containing 0.5 μM benzyladenine and 1 μM indoleacetic acid, respectively. Regenerated plants were established in soil.