title: Highly sensitive optical interferometric technique reveals stress-dependent instantaneous nanometric growth fluctuations of Chinese chive leaf under heavy metal stress.
abstract: Plant growth apart from being a complex and highly dynamic is dependent on its immediate environment. Leaf expansion measurements using Statistical Interferometry Technique, a sensitive interferometric technique at nanometric accuracy and at sub-second levels revealed the presence of characteristic nanometric intrinsic fluctuations [Plant Biotechnology 31, 195 (2014)]. In this paper, we demonstrate that the nanometric intrinsic fluctuations are sensitive enough that they change under exposure of heavy metals, essential micronutrient zinc and non-essential element cadmium, at relatively low concentrations in the leaves of Chinese chive (Allium tuberosum). The nanometric intrinsic fluctuations of leaves were observed for 4h under three cadmium concentrations or two zinc concentrations. Results showed significant reduction of nanometric intrinsic fluctuations for all cadmium concentrations, and in contrast significant increase of nanometric intrinsic fluctuations for all zinc concentrations. There was significant reduction of nanometric intrinsic fluctuations for cadmium exposure of concentrations of 0.001mM for even an hour, and significant increment of nanometric intrinsic fluctuations under 0.75mM zinc from 1hr exposure. For comparison, antioxidative enzymes and metal uptake were also measured under 4hr exposure of cadmium or zinc. However, no significant changes could be seen in antioxidative enzymes within 4h under the smaller concentration of 0.001mM cadmium as seen for nanometric intrinsic fluctuations. The results imply that nanometric intrinsic fluctuations can be not only used as a measure for heavy metal stress but also it can be more sensitive to detect the toxic as well as positive effects of smaller amounts of heavy metal on plants at an early stage.
authors.affiliation: Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan; Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, University of Ruhuna, Hapugala, Galle 80000, Sri Lanka.
authors.forename: Kokge Thilini Kanchana
authors.initials: KT
authors.lastname: Muthumali DeSilva
authors.affiliation: Faculty of Food and Nutrition Science, Toyo University, 1-1-1 Izumino, Itakura-machi, Ora-gun, Gunma-ken 374-0113, Japan.
authors.forename: Uma Maheswari
authors.initials: UM
authors.lastname: Rajagopalan
authors.affiliation: Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan. Electronic address: kadono@mail.saitama-u.ac.jp.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Kadono
mesh_terms: D002104:Cadmium / Q000493:pharmacokinetics / Q000633:toxicity; D002374:Catalase / Q000378:metabolism; D027782:Chive / Q000187:drug effects* / Q000254:growth & development; D006861:Hydrogen Peroxide / Q000378:metabolism; D019216:Metals, Heavy / Q000493:pharmacokinetics / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects*; D009195:Peroxidase / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development*; D013482:Superoxide Dismutase / Q000378:metabolism; D015032:Zinc / Q000493:pharmacokinetics / Q000633:toxicity
chemical_list: D019216:Metals, Heavy; D002104:Cadmium; D006861:Hydrogen Peroxide; D002374:Catalase; D009195:Peroxidase; D013482:Superoxide Dismutase; D015032:Zinc
keywords: Cadmium; Growth fluctuations; Laser speckle; Optical interferometry; Plant growth; Zinc