Dual-camera sampling moiré measurement of root-induced stress distribution using a phosphorescent agar grid

Plant root growth generates deformation and stress in the surrounding medium; however, measuring stress distribution remains challenging. In this study, a dual-camera sampling moiré system was developed using a phosphorescent grid agar medium. The same grid pattern was observed from both sides, and the images were independently analyzed to obtain in-plane displacement distributions, resulting in calculations of strain and stress distributions, with a noise level of 15 µm determined from static measurements over 3.5 days. The rod insertion experiments showed that partial grid blocking affected the displacement distribution, whereas the opposite view reproduced the overall spatial trend observed in the simulation. Finally, the method was demonstrated during radish sprout root growth, in which the complementary view compensated for partial grid blocking, enabling the evaluation of displacement, strain, and stress distributions. Therefore, this dual-view system enables root-induced stress distribution measurements while assessing the influence of partial grid blocking.