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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell, tissue and organ culture 15 (1988), S. 33-45 
    ISSN: 1573-5044
    Keywords: somatic embryogenesis ; tissue culture ; histology ; Trifolium ; zygotic embryogenesis ; regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The origin and development of zygotic and somatic embryos of Trifolium rubens L. was studied with the aid of paraffin sections and light microscopy. Zygotic embryos were collected, fixed and prepared daily from one to ten days after cross-pollination. Somatic embryos were obtained by plating petiole sections on modified L2 medium with 0.015 mgl-1 picloram and 0.1 mgl-1 6-BAP. Cultured petioles were collected and fixed daily from one to 25 days after plating. Two regions in the vascular bundle sheath of cultured petioles gave rise to callus. The first region was adjacent to the phloem fibers and produced friable callus. The second region gave rise to compact callus that was connected to the fascicular cambium. Somatic embryos originated from single cells in the cortex directly without intervening callus formation and from single cells in the friable callus. In addition, embryos arose from meristematic regions in compact callus. Many early stages of embryogenesis (one, two and four-celled stages) were observed in the cortex and friable callus. Zygotic embryogenesis in Trifolium differs from other legumes in that the suspensor is short and has a broad attachment. This arrangement was observed in zygotic embryos of T. rubens and in many somatic embryos. However, a continuum of somatic embryogenesis was observed where some young embryos had a Trifolium suspensor-like arrangement while others were attached to a long narrow suspensor-like structure more characteristic of Medicago.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5028
    Keywords: mas2′ promoter ; root-preferential expression ; sucrose-response element enhancer ; wound-inducible factors ; wound-responsive elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 318 bp mannopine synthase 2′ (mas2′) promoter element from the T-DNA of Agrobacterium tumefaciens can direct wound-inducible and root-preferential expression of a linked uidA gene in transgenic tobacco plants. Wound inducibility is further enhanced by sucrose in the medium. Promoter deletion analysis indicated that the sucrose enhancement is conferred by a region extending from −318 to −213. DNase I footprinting indicated that an A/T-rich DNA sequence in this region is protected by tobacco nuclear factors. Regions extending from −103 to +66 and from −213 to −138 directed wound-inducibile expression of a linked uidA gene when placed downstream of a CaMV 35S enhancer or upstream of a truncated (−209) CaMV 35S promoter, respectively. DNase I footprinting analyses indicated that proteins from wounded tobacco leaves specifically bound to three contiguous motifs downstream of the mas2′ TATA box. In addition to a common retarded band formed by the upstream wound-responsive element complexed with proteins from either wounded or unwounded tobacco leaves, two unique retarded bands were observed when this element was incubated with protein from wounded leaves. Methylation interference analysis additionally identified an unique motif composed of promoter elements and nuclear factors derived specifically from wounded tobacco leaves. We propose a model to describe the involvement of nuclear factors with mas2′ promoter elements in wound-inducible gene expression.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2015-04-28
    Description: Great attention has been paid to the potential of wastewater irrigation as a sustainable water source, particularly due to water scarcity and water pollution issues. However, few studies have focused on its adverse effects and on the health risks it may pose. In this study, the physicochemical properties of soils and plants irrigated with rural domestic wastewater and associated microbiological risks were investigated. The results showed that sewage irrigation could increase the production of vegetables and improve soil fertility. While the nitrate content of plants increased significantly, pathogens on plants and in soils increased after irrigation with raw wastewater. In particular, there was a wide range of pathogenic bacteria in the phyllosphere, which may indicate risks if contaminated vegetables are consumed directly. Treated wastewater irrigation was not significantly different from controls, which were irrigated by tap water; consequently, it can be used as an alternative water resource for agricultural irrigation. The presence of a wide spectrum pathogens in wastewater shows the necessity of long-term monitoring and further evaluation.
    Electronic ISSN: 2073-4441
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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