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Growth Regulating Substances in Mosses
Published in R. N. Chopra, Satish C. Bhatla, Bryophyte Development: Physiology and Biochemistry, 2019
Satish C. Bhatla, Sadhana Dhingra-Babbar
The accumulation of a substance within the cell is the combined effect of its influx and efflux. In the case of single-stranded filaments of the moss protonema we can assume that, because of their very narrow contact with the surrounding medium, exchange of substances between the cells and the medium is the most common mode of influx and efflux. However, a symplastic exchange of substances between adjacent cells also must take place because tip cells of the caulonema are required to maintain the filaments in a stable state of differentiation. Plasmodesmata exist between neighboring cells as symplastic connections.26
Neurotransmitters in Characean Electrical Signaling
Published in Akula Ramakrishna, Victoria V. Roshchina, Neurotransmitters in Plants, 2018
Vilma Kisnieriene, Indre Lapeikaite, Vilmantas Pupkis
Characean is very a useful system to study action potential propagation between plant cells. Two mechanisms of action potential transmission are well established in animals: one is the chemical transmission that takes place at synapses, and the other is known as electrotonic transmission, which occurs when currents can flow directly from cell-to-cell via gap junctions (Hille 2001). The communication between cells in plants is aided by the presence of highly dynamic structures called plasmodesmata (PD) under tight control of the plant. Gap junctions are the structures in animal cells equivalent to plasmodesmata in plants (Robards and Lucas 1990).
Quantifying the relative contribution of particulate versus dissolved silver to toxicity and uptake kinetics of silver nanowires in lettuce: impact of size and coating
Published in Nanotoxicology, 2020
Juan Wu, Qi Yu, Thijs Bosker, Martina G. Vijver, Willie J. G. M. Peijnenburg
All three AgNWs suspensions induced Ag uptake in plants roots. Contaminants can be taken up by plant roots via apoplastic transport through the intracellular spaces of adjacent cells along cell walls and via symplastic/transmembrane pathway through plasmodesmata/cell membranes between cells (Miller et al. 2016; Medina-Velo, Peralta-Videa, and Gardea-Torresdey 2017). In this study, Ag uptake via the plant roots was rapid and equilibrium was reached quickly. In addition, the data of AgNWs accumulation in plant roots fitted the one-compartment kinetic model well (R2 > 0.9). Taken together, these results indicate that in our study apoplastic transport was likely the major pathway for the uptake of Ag by plant roots after AgNWs adhere to the root epidermis. The limited translocation of Ag from roots to shoots in all AgNWs exposure treatments further confirmed this, as it is difficult for materials taken up by the apoplastic pathway to cross the casparian strip (a barrier limits the entrance of substances to xylem or phloem) and thus cannot be transported into the above-ground parts. Wang et al. (2012) also confirmed that CuO NPs pass through the epidermis into root tissues via the apoplastic route. All toxicokinetic parameters of dissolved Ag were much higher than those of AgNWs(particulate), demonstrating that the accumulation of Ag-ions in plants proceeds much faster than accumulation of particulate Ag. This implies that dissolved Ag is more bioavailable than particulate Ag.
Nonselective uptake of silver and gold nanoparticles by wheat
Published in Nanotoxicology, 2019
Wan-Ying Zhang, Qi Wang, Min Li, Fei Dang, Dong-Mei Zhou
Many studies have identified Ag- or Au-containing NPs in plant tissues. For example, Ag-containing NPs have been detected in plants by TEM-EDS and spICP-MS (Yin et al. 2011; Geisler-Lee et al. 2012; Pradas del Real et al. 2017), and they are located at root cell walls, apoplast, and plasmodesmata of plants using confocal laser-scanning microscopy and synchrotron based X-ray imaging techniques (Geisler-Lee et al. 2012; Stegemeier et al. 2015; Bao, Oh, and Chen 2016; Pradas del Real et al. 2017). Au-containing NPs have been identified in the cytoplasm or vasculature of the cell in plant root by TEM-EDS (Sabo-Attwood et al. 2012; Li et al. 2016). While one could conclude that these NPs within plants derive from direct uptake of NPs, an alternative explanation could be the uptake of released metal ions followed by their in vivo reduction to NPs. Indeed, there is consensus that plants can take up metal ions in the environment, and reduce them into metallic NPs within plants (Gardea-Torresdey et al. 2000; Li et al. 2017). In this study, by confirming the absence of Ag- or Au-containing NPs in plants exposed to equivalent amount of metal ions released from NP suspensions using spICP-MS analysis, the possibility of ionic uptake followed by in vivo reduction was ruled out (Figure 1(b,c)). Therefore, the presence of Ag- or Au-containing NPs in plants upon NP exposure, as revealed by spICP-MS analysis as well as TEM-EDS analysis, suggested the direct uptake of intact particles during 8-h exposure. Further, in both AgNP and AuNP suspensions, the released metal ions were far less than the initial NP concentrations, and had a minimal effect on Ag or Au accumulation in wheat relative to the control (Figures 1(b,c), S3, and S6). Significant accumulation of Ag or Au in exposed plant (Supplemental Figure S7), once again, suggested the direct uptake of intact particles.