Estimation of water flow velocity in small plants using cold neutron imaging with D2O tracer

Water flow imaging may help to better understand various problems related to water stress of plants. It may help to fully understand the water relations of plants. The objective of this research was to estimate the velocity of water flow in plant samples. Cut roses (Rosa hybrida, var. ‘Milva’) were used as samples. Cold neutron radiography (CNR) was conducted at CONRAD, Helmholtz Center Berlin for Materials and Energy, Berlin, Germany. D2O and H2O were interchangeably injected into the water feeding system of the sample. After the uptake of D2O, the neutron transmission increased due to the smaller attenuation coefficient of D2O compared to H2O. Replacement of D2O in the rose peduncle was clearly observed. Three different optical flow algorithms, Block Matching, Horn–Schunck and Lucas–Kanade, were used to calculate the vector of D2O tracer flow. The quality of sequential images providing sufficient spatial and temporal resolution allowed to estimate flow vector.