Digital image correlation techniques for motion analysis and biomechanical characterization of plants

Abstract

Temporally and spatially complex 3D deformation processes appear in plants in a variety of ways and are difficult to quantify in detail by classical cinematographic methods. Furthermore, many biomechanical test methods, e.g. regarding compression or tension, result in quasi-2D deformations of the tested structure, which are very time-consuming to analyze manually regarding strain fields. In materials testing, the contact-free optical 2D- or 3D-digital image correlation method (2D/3D-DIC) is common practice for similar tasks, but is still rather seldom used in the fundamental biological sciences. The present review aims to highlight the possibilities of 2D/3D-DIC for the plant sciences. The equipment, software, and preparative prerequisites are introduced in detail and advantages and disadvantages are discussed. In addition to the analysis of wood and trees, where DIC has been used since the 1990s, this is demonstrated by numerous recent approaches in the contexts of parasite-host attachment, cactus joint biomechanics, fruit peel impact resistance, and slow as well as fast movement phenomena in cones and traps of carnivorous plants. Despite some technical and preparative efforts, DIC is a very powerful tool for full-field 2D/3D displacement and strain analyses of plant structures, which is suitable for numerous in-depth research questions in the fields of plant biomechanics and morphogenesis.

Stereo Camera Setup for 360° Digital Image Correlation to Reveal Smart Structures of Hakea Fruits

“…DIC evolved from classical photogrammetry with the advent of digital cameras in the early 1980s and has been continuously improved ever since [ 7 , 8 , 9 , 10 , 11 ]. Its first applications were in materials science, but over the years, DIC has been utilized more and more in other research fields, such as aerospace, including large-scale composite structures [ 6 ], civil engineering, such as bridge monitoring [ 12 , 13 ], human and animal biomechanics to analyse a wide variety of organs and tissues [ 14 , 15 ] and wood research, from entire trees to processed composites [ 16 ]. In recent years, DIC has also been used in plant analysis, namely to analyse plant tissue strains under tensile loading (e.g., mistletoe–host interface [ 17 ] or the branch–branch connections of cacti [ 18 ]) to analyse compression (e.g., citrus peels [ 19 ]), and to characterise plant movements, such as the snap-buckling closure [ 20 ] and reopening [ 21 ] of the Venus flytrap or the desiccation-driven motion of pine cone scales [ 22 , 23 ].…”