Atomistic nonlinear carrier dynamics in Ge.

An atomistic technique to successfully demonstrate the ultrafast carrier dynamics in Ge photoconductive samples is reported here. The technique is validated against the experimental findings and with the Drude conductivities. The impact of the various different scattering mechanisms is used to calibrate the experimental results. It is observed that the total scattering rate is not a constant parameter as contrast to Drude model which uses constant scattering rate as the fitting parameter to demonstrate the ultrafast carrier dynamics, but strongly dependent on the applied peak THz field strength. It also contradicts with the relaxation time approximation (RTA) method which uses scattering rate chosen on the empirical basis as the fitting parameter to demonstrate the ultrafast carrier dynamics. On the other hand the limitations and challenges offered by various types of density functional theories (DFT) pose lot of challenges. In current manuscript various types of scattering mechanisms i.e. acoustic, intervalley, Coulomb and impact ionization on the behavior of carrier conductivity are studied in details. The proposed technique has shown capability to extract low and high frequency conductivities accurately which is impossible through the Drude model or DFT based theories. It is observed that the free carrier absorption coefficient depends on the refractive index of the material at low THz frequencies. The solution of Boltzmann transport equation through Monte Carlo technique provides valuable insights for better understanding of ultrafast carrier transportation mechanism. The free carrier absorption spectra are found to be in good agreement with the experimental results at various THz field strengths.

Bark and wood tissues of American elm exhibit distinct responses to Dutch elm disease.

Tolerance to Dutch elm disease (DED) has been linked to the rapid and/or high induction of disease-responsive genes after infection with the fungus Ophiostoma novo-ulmi. Although the fungal infection by O. novo-ulmi primarily takes places in xylem vessels, it is still unclear how xylem contributes to the defense against DED. Taking advantage of the easy separation of wood and bark tissues in young American elm saplings, here we show that most disease-responsive genes exhibited higher expression in wood compared to bark tissues after fungal infection. On the other hand, the stress-related phytohormones were generally more abundant in the bark compared to wood tissues. However, only endogenous levels of jasmonates (JAs), but not salicylic acid (SA) and abscisic acid (ABA) increased in the inoculated tissues. This, along with the upregulation of JA-biosynthesis genes in inoculated bark and core tissues further suggest that phloem and xylem might contribute to the de novo biosynthesis of JA after fungal infection. The comparison between two tolerant elm varieties, 'Valley Forge' and 'Princeton,' also indicated that tolerance against DED might be mediated by different mechanisms in the xylem. The present study sheds some light on the amplitude and kinetics of defense responses produced in the xylem and phloem in response to DED.

Simultaneous induction of jasmonic acid and disease-responsive genes signifies tolerance of American elm to Dutch elm disease.

Dutch elm disease (DED), caused by three fungal species in the genus Ophiostoma, is the most devastating disease of both native European and North American elm trees. Although many tolerant cultivars have been identified and released, the tolerance mechanisms are not well understood and true resistance has not yet been achieved. Here we show that the expression of disease-responsive genes in reactions leading to tolerance or susceptibility is significantly differentiated within the first 144 hours post-inoculation (hpi). Analysis of the levels of endogenous plant defense molecules such as jasmonic acid (JA) and salicylic acid (SA) in tolerant and susceptible American elm saplings suggested SA and methyl-jasmonate as potential defense response elicitors, which was further confirmed by field observations. However, the tolerant phenotype can be best characterized by a concurrent induction of JA and disease-responsive genes at 96 hpi. Molecular investigations indicated that the expression of fungal genes (i.e. cerato ulmin) was also modulated by endogenous SA and JA and this response was unique among aggressive and non-aggressive fungal strains. The present study not only provides better understanding of tolerance mechanisms to DED, but also represents a first, verified template for examining simultaneous transcriptomic changes during American elm-fungus interactions.

Protoplast-to-plant regeneration of American elm (Ulmus americana).

This study describes a protocol for regeneration of plants from cell suspension-derived protoplasts of American elm (Ulmus americana). Efficient protoplast isolation was achieved from a two-phase culture system through the incorporation of 100 µM 2-aminoindan-2-phosphonic acid, with a yield of approximately 2 × 10(6) protoplasts/ml packed cell volume. Isolated protoplasts failed to survive in liquid or alginate bead culture systems but initiated and continued to divide when embedded in low melting point agarose beads. Protoplast-derived callus proliferated and differentiated into shoot buds in response to 10 or 20 µM thidiazuron. Differentiated buds elongated and continued to proliferate on elm shoot medium supplemented with 3.0 µM GA3. The protoplast-derived shoots rooted and acclimatized to greenhouse conditions and continued to grow. This system provides the first protoplast-to-plant regeneration system for American elm and provides a framework for the development of protoplast fusion or genome editing technologies.

Establishment of invasive and non-invasive reporter systems to investigate American elm-Ophiostoma novo-ulmi interactions.

Dutch elm disease (DED), caused by ascomycete fungi in the Ophiostoma genus, is the most devastating disease of American elm (Ulmus americana) trees. Cerato ulmin (CU), a hydrophobin secreted by the fungus, has been implicated in the development of DED, but its role in fungal pathogenicity and virulence remains uncertain and controversial. Here, we describe reporter systems based on the CU promoter and three reporter proteins (GFP, GUS and LUC), developed as research tools for quantitative and qualitative studies of DED in vitro, in vivo and in planta. A strain of the aggressive species Ophiostoma novo-ulmi was transformed with the reporter constructs using Agrobacterium-mediated transformation and the fungal transformants, namely M75-GFP, M75-GUS and M75-LUC, were examined for mitotic stability after repeated subcultures. The intensity of GFP fluorescence was strong in M75-GFP spores and hyphae, allowing microscopic investigations of spore structure, fungal morphogenesis and fungal development. The interaction of M75-GFP and U. americana callus cells was explored with scanning laser confocal microscopy facilitating qualitative studies on fungal strategies for the invasion and penetration of elm cells. M75-GUS was generated to provide an invasive, yet quantitative approach to study fungal-plant interactions in vitro and in planta. The generation of M75-LUC transformants was aimed at providing a non-destructive quantitative approach to study the role of CU in vivo. The sensitivity, low background signal and linearity of LUC assays all predict a very reliable approach to investigate and re-test previously claimed roles of this CU in fungal pathogenicity. These reporter systems provide new tools to investigate plant-pathogen interactions in this complex pathosystem and may aid in better understanding the development of DED.

Cryopreservation of shoot tips and cotyledons of the north american ginseng (Panax quinquefolius l.).

North American ginseng (NAG) (Panax quinqueolius L.) is a medicinal plant in high demand due to its health benefits. Cryopreservation is a good alternative for long-term conservation of NAG germplasm. Pretreatments of shoot tips (0.8-1 mm) and cotyledons (1-2 mm) on sucrose and abscisic acid (ABA) enriched medium were tested to determine the effects on regrowth following cryopreservation in liquid nitrogen. The maximum regrowth (60 percent) following PVS2 vitrification occurred with shoot tips after three weeks of cold acclimation and pretreatment on sucrose (0.3 M) or a combination of ABA (0.1 M) and sucrose in the third week. Cotyledon recovery was best with the combination pretreatment. Shoot tips showed normal development and cotyledons produced embryogenic callus after the cryopreservation process. This is the first report on cryopreservation of shoot tips and cotyledons of Panax species. This cryopreservation protocol provides a safe long-term storage method for important NAG selections and makes it possible to use cryopreservation for improving the security of NAG germplasm.

Artemisia judaica L.: micropropagation and antioxidant activity.

Artemisia judaica L., an Egyptian medicinal plant used in the treatment of gastrointestinal disorders, was mass-propagated and grown using solid, paper-bridge-support liquid, liquid-flask and bioreactor cultures. The liquid-flask culture using 50 ml MS liquid medium in 250 ml flask yielded significantly greater shoot proliferation than either solid cultures or paper-bridge-support liquid cultures. Increasing flask capacity from 100 to 500 ml improved shoot proliferation and growth. Mass-propagation efficiencies of various bioreactor systems, viz. temporary immersion reactors and bubble column reactors, were also compared. The temporary immersion bioreactor was found to have significant advantages for A. judaica shoot proliferation. The shoot cultures from the temporary immersion reactor formed complete plantlets when subcultured onto a medium containing 1 micromoll(-1) indole-3-butyric acid (IBA), and mature plants were established, acclimatized and thrived in standard greenhouse conditions. Assays of antioxidant activity and total flavonoid content of in vitro and in vivo grown tissues were evaluated as gross parameters of medicinal efficacy. Significantly higher antioxidant activity and flavonoid contents were observed in the tissues of mature greenhouse-grown plants. The efficient in vitro production systems developed in this study provided sterile, consistent tissues for investigation of bioactivity and germplasm conservation of A. judaica.

Incorporation of brewery waste in supplementary feed and its impact on growth in some carps.

Brewery waste (brewer's grains) was used at four different levels (10%, 20%, 30% and 40% w/w) replacing rice bran in fish diet under a semi-intensive culture system and its impact on the growth of catla, Catla catla; rohu, Labeo rohita and mrigal, Cirrhina mrigala, was studied. Growth in terms of body weight gain was maximum in C. catla and L. rohita fed on a diet containing 30% brewery waste in the feed, whereas C. mrigala, fed on a diet containing brewery waste at the above mentioned levels showed poorer growth than the control. A better growth performance was attributed to better absorption and utilization ability.

Regeneration of the Egyptian medicinal plant Artemisia judaica L.

An in vitro propagation system for Artemisia judaica L., a traditional Egyptian medicinal plant, has been developed. De novo shoot organogenesis was induced by culturing etiolated hypocotyls and intact seedlings on medium supplemented with thidiazuron [N-phenyl-N'-(1,2,3-thidiazol-yl) urea] via callusing at the cotyledonary notch region. Up to 16 shoots formed per seedling cultured on a medium containing 1 micro mol l(-1) thidiazuron for an optimal duration of exposure of 20 days. Regenerated shoots formed roots when subcultured onto a medium containing 1 micromol l(-1) indole-3-butyric acid. The regeneration protocol developed in this study provides a basis for germplasm conservation and for further investigation of medicinally active constituents of A. judaica.

Thidiazuron induces shoot organogenesis at low concentrations and somatic embryogenesis at high concentrations on leaf and petiole explants of African violet (Saintpaulia ionantha Wendl).

Regeneration via shoot organogenesis and somatic embryogenesis was observed from thidiazuron (TDZ)-treated leaf and petiole explants of greenhouse- and in vitro-grown African violet plants. The response of cultures to other growth regulators over a range of 0.5 microM to 10 microM was 50% less than that observed with TDZ. A comparative study among several cultivars of African violet indicated that "Benjamin" and "William" had the highest regeneration potential. In "Benjamin", higher frequencies of shoot organogenesis (twofold) and somatic embryogenesis (a 50% increase) were observed from in vitro- and greenhouse-grown plants, respectively. At concentrations lower than 2.5 microM, TDZ induced shoot organogenesis, whereas at higher doses (5-10 microM) somatic embryos were formed. These findings provide the first report of simultaneous shoot organogenesis and somatic embryogenesis of African violet explants in response to TDZ.

Potential of Amaranthus seeds in supplementary feed and its impact on growth in some carps.

Amaranthus seeds were used at three different levels (20%, 35%, 50%) in fish diets under a semi-intensive fish culture system and their impact on the growth of common carp, Cyprinus carpio, and rohu, Labeo rohita, was studied. Growth in terms of body weight gain was maximum in fish fed on diets containing 20% Amaranthus seeds, that replaced rice bran and groundnut oil cake in the feed. Overall, the fish fed on diets containing Amaranthus seeds at different levels showed better growth than the control, because of the good-quality proteins available in Amaranthus seeds. In the two species used, L. rohita showed better growth performance than C. carpio.

Impact of pollution on the flesh of some fishes inhabiting river Satluj waters--a biochemical study.

The impact of grossly polluted waters of the Budha Nallah (BN) on the flesh quality of a few fish species inhabiting river Satluj following its confluence with the river has been studied. For flesh quality, levels of extractable proteins (EP), carbohydrate content and total lipid (TL) contents have been compared in Cirrhina mrigala, Cirrhina reba, Crossocheilus latius and Mystus cavasius collected from downstream (DS) region (selected at 40-42 km following confluence of BN with the river) and an upstream (US) region (selected at 8-10 km before the confluence of BN with the river) of river Satluj. The results have shown a significant decline in the EP content, carbohydrates and TL contents in the flesh of these fish species collected from DS region. The functional significance of any decrease/increase in the biochemical parameter (s) has been discussed.

Tryptophan is a precursor for melatonin and serotonin biosynthesis in in vitro regenerated St. John's wort (Hypericum perforatum L. cv. Anthos) plants.

HYPERICUM PERFORATUM: cv. Anthos) is presented. Isotope tracer experiments were performed on plantlets regenerated from thidiazuron-induced stem explants and grown on MS basal medium for 2 months. Radiolabel from 14C-tryptophan was recovered as 14C-indoleacetic acid, 14C-tryptamine, 14C-5-hydroxytryptophan, 14C-serotonin and 14C-melatonin in the treated St. John's wort plantlets. Chromatographic peak identity was confirmed by high performance liquid chromatography-mass spectrometry-mass spectrometry and quantification of melatonin by radioimmunoassay. Significantly more radiolabel was recovered in serotonin relative to melatonin under low light conditions with this ratio being reversed under increased lighting, indicating that the rate of flow through this biosynthetic pathway is regulated, at least in part, by light.

Thidiazuron-induced plant regeneration from hypocotyl cultures of St. John's wort (Hypericum perforatum. cv 'Anthos').

St. John's wort (Hypericum perforatum. cv 'Anthos') is a medicinal plant with evidence of efficacy as an anti-depressant. The present report describes the development of an in vitro regeneration system that utilizes thidiazuron [N-phenyl-N'-(1,2,3-thidiazol-yl)urea] for the induction of de novo shoots on etiolated hypocotyl segments of St. John's wort seedlings. The optimum level of thidiazuron supplementation to the culture medium was 5 µmol·l-1 for a 9-day induction period followed by subculture of induced hypocotyl explants on basal medium. Other plant growth regulators including benzyladenine and indoleacetic acid were not effective in inducing regeneration on St. John's wort hypocotyls. Histological examination of the cultures revealed that the regenerated plants were derived from de novo developed shoots. Transfer of the regenerated shoots into a liquid medium with no plant growth regulators resulted in the rapid and prolific growth of viable plantlets. The rapid and efficient micropropagation system for St. John's wort may be useful for both the genetic improvement of this crop and the production of high-quality phytopharmaceutical preparations for the treatment of neurological disorders.

Inhibitory effect of GA3 on the development of thidiazuron-induced somatic embryogenesis in geranium (Pelargonium xhortorum Bailey) hypocotyl cultures.

Somatic embryogenesis in geranium (Pelargonium xhortorum Bailey cv 'Scarlet Orbit Improved') can be achieved by incubating hypocotyl explants on MS medium supplemented with thidiazuron (TDZ; 10 µM for 3 days followed by subculture on medium devoid of any plant growth regulators. The presence of gibberellins (GAs) during both the induction and expression phases of embryogenesis was significantly detrimental to somatic embryo formation on the hypocotyl explants. The addition of the GA-synthesis inhibitors paclobutrazol, uniconazole or ancymidol during the period of growth and differentiation of somatic embryos increased the number of somatic embryos formed on each explant. However, paclobutrazol added during the period of induction had no significant influence on somatic embryo formation. Results suggest that both exogenously supplied as well as endogenous GAs play a role, albeit a negative one, on somatic embryogenesis of geranium.

Induction of high-frequency somatic embryogenesis in geranium (Pelargonium x hortorum Bailey cv Ringo Rose) cotyledonary cultures.

The cv Ringo Rose of hybrid seed geranium (Pelargonium x hortorum Bailey), previously shown to be recalcitrant in culture, produced somatic embryos when cotyledonary explants were cultured on regeneration medium containing thidiazuron (TDZ), forchlorfenuron (CPPU), or a combination of indole-3-acetic acid and N(6) benzylaminopurine (IAA+BAP). Amendment of the basal medium with TDZ (0.5 µM) was the most effective treatment. Addition of amino acids to the medium promoted the growth of somatic embryos. Retention of the proximal region of the cotyledon was crucial for regeneration, but the removal of the distal 1/3 to 1/2 cotyledon had no significant effect on somatic embryogenesis. Cotyledonary explants formed somatic embryos in higher frequency and much earlier than hypocotyl explants cultured on the same medium. The somatic embryos induced on cotyledonary explants were germinated on basal medium. More than 70% of the somatic embryos were converted into plants and transferred to soil.

Acetylsalicylic acid enhances and synchronizes thidiazuron-induced somatic embryogenesis in geranium (Pelargonium x hortorum Bailey) tissue cultures.

Thidiazuron (TDZ) effectively induced somatic embryogenesis in cultured hypocotyl explants of geranium (Pelargonium x hortorum Bailey) during only a 3-day period of induction. The presence of acetylsalicylic acid (ASA) during this period caused a two-fold increase in the number of somatic embryos and enhanced synchronization of embryo development compared to the TDZ treatment alone. Salicylic acid was ineffective in modulating similar embryogenic responses as ASA. The ASA-induced enhancement and synchronization of somatic embryogenesis could possibly be used as an experimental system to study the interplay of growth regulators in somatic embryogenesis.

Significance of the zygotic seed coat on quiescence and desiccation tolerance of Medicago sativa L. somatic embryos.

The influence of the zygotic seed coat on precocious germination and desiccation tolerance of somatic embryos has been studied using alfalfa (Medicago sativa L.). When cultured in contact with somatic embryos, seed coats at certain developmental stages inhibited precocious germination and induced desiccation tolerance in the somatic embryos. Germination of somatic embryos was inhibited by seed coats at the age of 16-26 days after pollination (DAP) and desiccation tolerance was induced after 20-26 DAP. Both phenomena were related to the synthesis of abscisic acid in the seed coat. The absence of a quiescent phase and desiccation tolerance in alfalfa somatic embryos may be related to the lack of developmental control by the seed coat.

Morphoregulatory role of thidiazuron: morphogenesis of root outgrowths in thidiazuron-treated geranium (Pelargonium x hortorum Bailey).

Root outgrowths formed on the root tissue of geranium (Pelargonium x hortorum Bailey cv. Kim and cv. Shone Helena) plants in response to treatment with the phenylurea derivative, thidiazuron (N-phenyl-N'-1,2,3-thiadiazol-5'-ylurea; TDZ). Treatment with the cytokinin N(6)-benzylaminopurine (BAP) or the auxin α-naphthaleneacetic acid (NAA) did not result in stimulation of similar abnormal structures on the root tissue. Significantly more outgrowths developed on roots of plants treated with 10 µM and 20 µM TDZ than on control plants or those treated with 1 µM TDZ for the eight-week treatment period. Some outgrowths produced shoots and plantlets while still attached to roots, and regenerants were easily separated from the root tissue and transferred to soil in the greenhouse where they grew to maturity. Histological observations suggested these outgrowths originated from the vascular cambium region of the root.