Computer Reconstruction of Plant Growth and Chlorophyll Fluorescence Emission in Three Spatial Dimensions

Abstract

Plant leaves grow and change their orientation as well their emission of chlorophyll fluorescence in time. All these dynamic plant properties can be semi-automatically monitored by a 3D imaging system that generates plant models by the method of coded light illumination, fluorescence imaging and computer 3D reconstruction. Here, we describe the essentials of the method, as well as the system hardware. We show that the technique can reconstruct, with a high fidelity, the leaf size, the leaf angle and the plant height. The method fails with wilted plants when leaves overlap obscuring their true area. This effect, naturally, also interferes when the method is applied to measure plant growth under water stress. The method is, however, very potent in capturing the plant dynamics under mild stress and without stress. The 3D reconstruction is also highly effective in correcting geometrical factors that distort measurements of chlorophyll fluorescence emission of naturally positioned plant leaves.

Multiangular Observation of Canopy Sun-Induced Chlorophyll Fluorescence by Combining Imaging Spectroscopy and Stereoscopy

“…Irregularities of leaf surfaces and shapes, overlapping between neighboring plants and mechanical movements produced by wind are among the factors that make accurate 3D reconstructions challenging. In the past years few methodologies, including structured light approaches [36], stereo imaging [37,38] and laser scanning techniques [39,40], have become available to estimate plant structural traits including leaf angle distribution. In particular, stereo imaging has been referred as a rapid and easy approach to characterize the outer canopy leaves, providing a good compromise between accuracy and versatility in the field [38,41].…”

High Throughput System for Plant Height and Hyperspectral Measurement

“…A lot of sensor technologies such as depth camera (Azzari et al, 2013), lidar (Zhang et al, 2012), structured light approaches (Bellasio et al, 2012), ultrasonic transducer (Gil et al, 2007), stereo camera system (Biskup et al, 2007) are used to obtain 3D structures of plants. Point-based sensors (lidar, ultrasonic transducer) employ a narrow FOV that usually results in the loss of the highest point of crops (Jiang et al, 2016).…”

“…Point-based sensors (lidar, ultrasonic transducer) employ a narrow FOV that usually results in the loss of the highest point of crops (Jiang et al, 2016). Depth cameras such as RGB-cameras offer a lowcost way to acquire 3D information (Bellasio et al, 2012), but due to the poor performance on sunny days, a shaded environment is required (Jiang et al, 2016). Close-up laser triangulation can provide 3D data of high precision, but a measuring arm or an auxiliary motion mechanism is needed.…”

High-throughput volumetric reconstruction for 3D wheat plant architecture studies

“…Clark et al 26 developed an axis of rotation (AOR) calibration technique to determine the orientation of the AOR in relation to the camera. Bellasio et al 24 used coded light illumination to obtain the 3D information. However, a complicated calibration technique would make the imaging system unaccessible.…”

“…As the measurement of leaf area could be easily made in surface model, surface model is suitable for plant canopy photosynthesis e±ciency and leaf morphology research. [23][24][25] While, volume-based modeling approach has been always developed to measure those traits of solid or thick organ with complex structure, such as root system (RootReader 3D software) 26 or tillers. That's because, in volumetric model, plants are represented as many voxels, which makes the measurements of height and volume easy.…”