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    Applications of carbon nanomaterials in the plant system: A perspective view on the pros and cons
    (Elsevier, 2019) Verma, Sandeep Kumar; Das, Ashok Kumar; Gantait, Saikat; Kumar, Vinay; Gürel, Ekrem
    With the remarkable development in the field of nanotechnology, carbon-based nanomaterials (CNMs) have been widely used for numerous applications in different areas of the plant system. The current understanding about the CNMs' accumulation, translocation, plant growth responses, and stress modulations in the plant system is far from complete. There have been relentless efforts by the researchers worldwide in order to acquire newer insights into the plant-CNMs interactions and the consequences. The present review intends to update the reader with the status of the impacts of the different CNMs on plant growth. Research reports from the plant biotechnologists have documented mixed effects (which are dependent on CNMs' concentration) of the CNMs' exposure on plants ranging from enhanced crop yield to acute cytotoxicity. The growth and yield pattern vary from species to species and are dependent on the dosage of the CNMs applied. Studies found an increase in vegetative growth and yield of fruit/seed at lower concentration of CNMs, but a decrease in these observables were also noted when higher concentrations of CNMs were used. In general, at lower concentrations, CNMs were found to be effective in enhancing (water uptake, water transport, seed germination, nitrogenase, photosystemand antioxidant activities), activating (water channels proteins) and promoting (nutrition absorption); all these change when concentrations are raised. All these aspects have been reviewed thoroughly in this article, with a focus on the recent updates on the role of the CNMs in augmenting or retarding plant growth. Sections have been devoted to the various features of the CNMs and their roles in inducing plant growth, phytotoxic responses of the plants and overall crop improvement. Concluding remarks have been added to propose future directions of research on the CNMs-plant interactions and also to sound a warning on the use of CNMs in agriculture. (C) 2019 Elsevier B.V. All rights reserved.
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    Engineered nanomaterials for plant growth and development: a perspective analysis
    (Elsevier, 2018) Verma, Sandeep Kumar; Das, Ashok Kumar; Patel, Manoj Kumar; Shah, Ashish; Kumar, Vinay
    With the overwhelmingly rapid advancement in the field of nanotechnology, the engineered nanomaterials (ENMs) have been extensively used in various areas of the plant system including quality improvement, growth and nutritional value enhancement, gene preservation etc. There are several recent reports on the ENMs influence on growth enhancements, growth inhibition as well as certain toxic impacts on plant. However, translocation, growth responses and stress modulation mechanisms of ENMs in the plant systems call for better and indepth understanding. Herein, we are presenting a comprehensive and critical account of different types of ENMs, their applications and their positive, negative and null impacts on physiological and molecular aspects of plant growth, development and stress responses. Recent reports revealed mixed effects on plants, ranging from enhanced crop yield, epiigenetic alterations, and phytotoxicity, resulting from the ENMs' exposure, Creditable research in recent years has revealed that the effects of ENMs on plants are species specific and are variable among plant species. ENM exposures are reported to trigger free radical formation, responsive scavenging, and antioxidant armories in the exposed plants. The ENMs are also reported to induce aberrant expressions of microRNAs, the key post-transcriptional regulators of plant growth, development and stress-responses of plants. However, these modulations, if judiciously done, may lead to improved plant growth and yield. A better understanding of the interactions between ENMs and plant responses, including their uptake transport, internalization, and activity, could revolutionize crop production through increased disease resistance, nutrient utilization, and crop yield. Therefore, in this review, we are presenting actitical account of the different selected ENMs, their uptake by the plants, their positive/negative impacts on plant growth and development, along with the resultant ENM-responsive post-transcriptional modifications, especially, aberrant m1RNA expressions. In addition, underlying mechanisms of various ENM-plant cell interactions have been discussed. (C) 2018 Published by Elsevier B.V.
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    In vitro culture of Digitalis L. (Foxglove) and the production of cardenolides: An up-to-date review
    (Elsevier Science Bv, 2016) Verma, Sandeep Kumar; Das, Ashok Kumar; Cingöz, Günce Şahin; Gürel, Ekrem
    Digitalis L. (Foxglove, Plantaginaceae) genus is a representative of several medicinal ornamental plants that are widely used in the production of herbal medicines. Since the eighteenth century, human civilizations have been using the extracts from several Digitalis species for treating heart-related ailments. The active ingredient in the medicine is cardiac glycosides. Cardenolides, which are constituents of cardiac glycosides, have an important role in tumor therapy. Certain pharmacologically active compounds including cardenolides are isolated from plants, as the structural complexity of cardenolides impede an easy chemical synthesis. In modern plant biotechnology research, production of cardenolides in large-scale using in vitro techniques has become the need of the hour. The reasons are twofold: first, to reduce the excessive use of natural Digitalis population and second, to improve the plant quality vis-a-vis genetic preservation of the superior seeds for future use. The production of useful secondary metabolites depends on the overall wellness of the plant from which extraction is to be made. The subject matter of this review includes concurrent development and propagation of several Digitalis species based on direct and indirect regeneration methods. Herein, a compilation of up-to-date published research reports on in vitro culture of Digitalis L has been presented, including the authors' latest and yet-to-be-published work on Digitalis davisiana Heywood. The important steps to be followed for the implementation of any plant improvement/preservation program must include topic-wise requirements at various stages of micro propagation (viz., culture establishment, shoot multiplication, root induction and acclimatization) and also the requirements for plant regeneration (viz., somatic embryogenesis and organogenesis). These have been reviewed thoroughly and different methods for the in vitro production of cardenolides have been discussed. Critical comments on the prospects of highly scalable cultures and their importance to meet the ever-growing demand for Digitalis-derived products in pharmaceutical industries, have also been included. (C) 2016 Elsevier B.V. All rights reserved.
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    In vitro plant regeneration of Ocimum basilicum L. is accelerated by zinc sulfate
    (Springer, 2016) Verma, Sandeep Kumar; Şahin, Günce; Das, Ashok Kumar; Gürel, Ekrem
    This article describes a fast, simple, and efficient plant regeneration protocol for Ocimum basilicum L. Two sets of experiments were performed. The first set was performed on Murashige and Skoog (MS) medium lacking zinc sulfate heptahydrate (ZnSO4 center dot 7H(2)O) and containing varying concentrations of indole-3-acetic acid (IAA). The second set used three different concentrations (8.6, 12.9, and 17.2 mg L-1) of ZnSO4 center dot 7H(2)O along with varying concentrations of IAA. In the first set, without zinc sulfate, an IAA concentration of 1.0 mg L-1 (MS4) was found to be most effective, producing a mean of 12.6 roots per hypocotyl explant, while shoots were not produced. In the second set, with zinc sulfate, a combination of 12.9 mg L-1 ZnSO4 center dot 7H(2)O + 1.0 mg L-1 IAA (MS11) produced significantly more shoots per explant (15 shoots) than a combination of 12.9 mg L-1 ZnSO4 center dot 7H(2)O + 0.5 mg L-1 IAA (MS10), which produced only six shoots. Later, the plantlets were successfully acclimatized (100%) and finally transferred to the greenhouse (ex vitro). In the O. basilicum plants grown using MS11 medium, total phenolic content and rosmarinic acid content were estimated from stem, shoot tip, and old leaf tissue of in vitro plantlets, ex vitro plantlets, and flowering plants. The highest amounts of total phenolic content (131.8 mg gallic acid equivalent g(-1) DW) and rosmarinic acid (13.0 mg g(-1) DW) were obtained in the old leaf tissue at flowering time. This rapid regeneration protocol for O. basilicum L. represents a major improvement over the conventional protocols for plant regeneration and propagation of this species.
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    Influence of auxin and its polar transport inhibitor on the development of somatic embryos in Digitalis trojana
    (Springer Heidelberg, 2018) Verma, Sandeep Kumar; Das, Ashok Kumar; Gantait, Saikat; Gürel, Songül; Gürel, Ekrem
    The present study reports the role of auxin and its transport inhibitor during the establishment of an efficient and optimized protocol for the somatic embryogenesis in Digitalis trojana Ivan. Hypocotyl segments (5 mm long) were placed vertically in the Murashige and Skoog medium supplemented with three sets [indole-3-acetic acid (IAA) alone or 2,3,5-triiodobenzoic acid (TIBA) alone or IAA-TIBA combination] of formulations of plant growth regulators, to assess their differential influence on induction and proliferation of somatic embryos (SEs). IAA alone was found to be the most effective, at a concentration of 0.5 mg/l, inducing similar to 10 SEs per explant with 52% induction frequency. On the other hand, the combination of 0.5 mg/l of IAA and 1 mg/l of TIBA produced significantly fewer (similar to 3.6 SEs) and abnormal (enlarged, oblong, jar and cup-shaped) SEs per explant with 24% induction frequency in comparison to that in the IAA alone. The explants treated with IAA-TIBA exhibited a delayed response along with the formation of abnormal SEs. Our study revealed that IAA induces high-frequency SE formation when used singly, but the frequency gradually declines when IAA was coupled with increasing levels of TIBA. Eventually, our findings bring new insights into the roles of auxin and its polar transport in somatic embryogenesis of D. trojana.
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    Influence of nutrient media on callus induction, somatic embryogenesis and plant regeneration in selected Turkish crocus species
    (Elsevier B.V., 2016) Verma, Sandeep Kumar; Das, Ashok Kumar; Cingöz, Günce Şahin; Uslu, Emel; Gürel, Ekrem
    Callus induction, somatic embryogenesis and plant regeneration were initiated in selected five species of Turkish crocus using three diffrent explants (leaf, stem and corm) cultured on four different media (MS, GB5, LS and CHE). The highest frequencies of callus induction (100%) and shoot regeneration (70%, with 7.2 shoots/callus) were found in the crocus species Crocus oliveri ssp. Oliveri, using the MS medium containing 5% (w/v) sucrose supplemented with (4 mg/L NAA + 4 mg/L TDZ) and (2 mg/L IAA + 2 mg/L TDZ + 2 mg/L BAP). When the embryogenic calli were transferred into the four nutrient media containing (2 mg/L IAA + 2 mg/L TDZ) and 100 mg/L ABA, these further developed into cotyledonary embryos. Maximum number of somatic embryos (2.9 embryos per leaf explant, with a frequency 46.6%) was obtained in C. oliveri ssp. Oliveri. During subculture using the half strength media, cotyledonary embryos gradually developed into plantlets. © 2016 Published by Elsevier B.V.