Matsushima, Graf, Kardjilov, Shono, Herppich Bornimer Agrartechnische Berichte  Heft 69 ISSN 0947-7314 Leibniz-Institut für Agrartechnik Potsdam-Bornim e.V. (ATB) 106 Calculation of flow vector in plants by non-destructive imag- ing using neutron radiography Uzuki Matsushima 1 , Wolfgang Graf 2,4 , Nikolay Kardjilov 3 , Hiroshi Shono 1 , Werner B. Herppich 2 1 Faculty of Agriculture, Iwate University, Ueda 3-18-8, Morioka, Iwate 020-8550, Japan 2 Dept. Horticultural Engineering, Leibniz-Institut für Agrartechnik Potsdam-Bornim e. V. Max- Eyth-Allee 100, 14469 Potsdam, Germany 3 Institute of Applied Materials , Helmholtz Centre Berlin, Glienicker Str. 100, 14109 Berlin, Germany 4 Humboldt-Universität zu Berlin, Institut of Horticultural Science, Lentzeallee 75, 14195 Berlin, Germany Corresponding author:uzuki@iwate-u.ac.jp Abstract: Water transport in plants is one of the most important factors for life, because it guaranties plants photosynthesis, the basic process for live on earth. Cold neutron radiography (CNR) with D 2 O tracer provides visualization images of water flow in plants non-destructively. In order to calculate flow vector in plants, three optical flow algo- rithms, Block Matching, Horn-Schunck and Lucas-Kanade, were evaluated. The results showed that Block Matching was the optimum algorithm to calculate plant water flow from D 2 O tracers. This algorithm was successfully applied to in situ investigate the flow vectors in the peduncles of three rose cultivars (’Akito’, ’Milva’ and ’Red Giant’, respec- tively) having high, middle and low bent-neck susceptibility. The highest flow velocities obtained were approx. 45, 80, 19 mm hour -1 for 'Akito', 'Milva' and 'Red Giant', respec- tively. Also, for further grafting studies, calculations of flow vector in tomato seedlings were examined. Even if the seedling stem was thin, the high resolution of the CNR im- ages allowed the exact calculation of flow vectors. Thus, this D 2 O tracer vector method could most probably be applied in a great variety of plant water relations studies. 1 Introduction Water transport in plants is one of the most important factors for life, because it guaran- ties plants photosynthesis, the basic process for live on earth. Cold neutron radiography (CNR) with D 2 O tracer is a useful method to non-destructively visualize water flow in small plants from root via stem to leaf or flower (NAKANISHI et al. 2005, MATSUSHIMA et al. 2005, MATSUSHIMA et al. 2007). Velocity of water flow can be an indicator of water sink and source strength in plant tissues and/or organs. We developed a method to ob- serve steady water flow by cold neutron radiography using D 2 O as a tracer (MATSU- SHIMA et al. 2007, 2008). Compared to H 2 O the mass attenuation coefficient of D 2 O is smaller which allows for a better penetration of neutrons. As a result, the flow of D 2 O