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Heavy metals are one of the important components of water pollution. Heavy metals such as copper, zinc and cobalt are essential for the growth of living organisms as micronutrients. However, copper above critical levels can pose serious problems for the environment and human health. The biospeckle observed in OCT have the potential to map dynamic activities inside the plants. We propose biospeckle optical coherence tomography (bOCT) and demonstrate that the technique can monitor biological activity in plants. In bOCT, the temporal speckle contrast variation of the OCT reflection signal is used as a parameter to characterize the internal activities of the aquatic plant (Myriophyllum). Plant stems were observed using the bOCT technique after 7 days of exposure to copper solutions of three different copper concentrations to 0, 30, 100 mg/l. In addition, statistical Interferometry Technique (SIT) system that is also a very sensitive optical measurement technique developed in our lab. SIT enables the direct observation of short-term displacement or extension / shrinkage of plant surface with precision of nanometer scale and on a time scale of seconds. Compared with the bOCT technique, it takes short time. It does not require 7 days of exposure time. In just 3 hours of experiment time, we observed that the plants were receiving heavy metal stress in the copper solution. Under the same heavy metal exposure conditions (7 days), enzyme activities in plants were also measured and analyzed to demonstrate the reliability of our two laser measurement techniques. It can be seen that the increase of copper solution has a significant effect on the activity of plants. It was not possible to observe the effects of 7 days of heavy metal exposure on plants by measuring their length or the color of their leaves. Compared with traditional bioassay methods, SIT technology is the fastest, followed by bOCT technology. Both technologies are advanced and can be used as a new method for the determination of plant bioactivity.
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