Observing ion movement in living plants — Imaging technique opens door to new plant physiology research
October 17, 2012
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(A) Sequential images of [32P] phosphate in rice plant obtained using the real-time plant imaging system. The plant can easily uptake phosphate from the solution but seldom uptakes phosphate from soil. (B) The imaging system could be combined with a microscope to analyze both radioisotope distribution and visible image of a sample at the microscopic level. © Nakanishi Tomoko
Ionic nutrition is essential for plant development, and while many techniques have been developed to image and/or measure ionic movement in plants, most are destructive, preventing real-time or long-term analysis, or require special or dark conditions that limit the form of analysis that is possible.
Researchers at the University of Tokyo’s Graduate School of Agricultural and Life Sciences have developed radioisotope imaging techniques that overcome such restrictions and allow for real-time imaging of ionic movement in plants. A plant sample is provided with a radioisotope, and beta radiation emitted is converted into light by a scintillator and detected by a CCD camera. The scintillator and sample are separated by a thin aluminium film to isolate the CCD camera from the plant light source. The first system, called macroimaging, was developed to visualize and measure ion uptake and translocation between organs at a whole-plant scale. The group also modified microscopes to set up various solutions for ion uptake analysis at the microscopic level. By employing radioactive samples, both systems possess a wide dynamic range of detection and allow quantitative analysis of ion uptake. With this system, uptake of conventionally-available radioactive nuclides, such as 14C, 35S, 45Ca or 32P, can be visualized. The imaging system permits tracking ion movement from soil to root as well as from root to distal parts of the plant, for example for radioactive fallout Caesium.
These radioisotope imaging systems have a great advantage over other methods in sensitivity, resolution, wide dynamic range, numerical treatment of the image, and the ability to acquire the image under normal light conditions. These systems are expected to provide new insight into the physiology of living plants. In combination with other established techniques, these imaging systems should also stimulate the development of research into genomic expression and the movement of inorganic nutrients.
Satomi Kanno, Masato Yamawaki, Hiroki Ishibashi, Natsuko I. Kobayashi, Atsushi Hirose, Keitaro Tanoi, Laurent Nussaume and Tomoko M. Nakanishi, "Development of real-time radioisotope imaging systems for plant nutrient uptake studies", Philosophical Transactions of the Royal Society B 367 (2012): 1501, doi:10.1098/rstb.2011.0229.