Quantification of plant morphology and leaf thickness with optical coherence tomography

Abstract

Optical coherence tomography (OCT) can be a valuable imaging tool for in vivo and label-free digital plant phenotyping. However, for imaging leaves, air-filled cavities limit the penetration depth and reduce the image quality. Moreover, up to now quantification of leaf morphology with OCT has been done in one-dimensional or twodimensional images only, and has often been limited to relative measurements. In this paper, we demonstrate a significant increase in OCT imaging depth and image quality by infiltrating the leaf air spaces with water. In the obtained high-quality OCT images the top and bottom surface of the leaf are digitally segmented. Moreover, high-quality en face images of the leaf are obtained from numerically flattened leaves. Segmentation in threedimensional OCT images is used to quantify the spatially resolved leaf thickness. Based on a segmented leaf image, the refractive index of an infiltrated leaf is measured to be 1.345 ± 0.004, deviating only 1.2% from that of pure water. Using the refractive index and a correction for refraction effects at the air-leaf interface, we quantitatively mapped the leaf thickness. The results show that OCT is an efficient and promising technique for quantitative phenotyping on leaf and tissue level.

Computational 3D resolution enhancement for optical coherence tomography with a narrowband visible light source

“…The leaf disc was water infiltrated by putting it in a syringe with water and lowering the pressure. When the pressure is released, the gas-exchange cavities are filled with water, reducing the refractive index contrast [30]. The leaf disc was mounted in water between two coverslips, at a sufficient distance from the coverslip to avoid saturation artifacts from the coverslip reflection.…”

Label-free optical interferometric microscopy to characterize morphodynamics in living plants

“…IL: Illumination light and SL: Scattered light from the leaf ( Silva et al., 2016 ) (G) Elongation of a Chinese chive leaf ( Kadono and Kobayashi, 2009 ). (H) Cross-section image of an Arabidopsis leaf, acquired by OCT technique reprinted with permission from ( de Wit et al, 2020 © The Optical Society). e: Epidermal cell, m: Mesophyll cell, vb: Vascular bundle, mr: Midrib, ad: Adaxial side, ab: Abaxial side.…”

“…The method has a high potential for identification of seed viability during an early stage of germination and thereby facilitates seed selection ( Lim et al., 2019 ; De Silva et al., 2022 ). Biospeckle OCT has been used to screen for internal structural changes of pea seeds during germination process ( Li X. et al., 2022 ), the effect of Zn concentration on lentil seed germination and seedling growth ( De Silva et al., 2021 ), detection of microstructural changes in leaves during senescence ( Anna et al., 2019 ) and measurements of the RI and thickness of leaves ( de Wit et al., 2020 ). Figure 1H shows the central cross-section of an infiltrated Arabidopsis leaf wherein cell layers, epidermal cells, mesophyll cells, as well as vascular bundles can be seen.…”

Leaf Structure and Attenuation Coefficients of Citrofortunella Microcarpa Leaves Using a Portable TD-OCT System

“…It also extends to industrial, pharmaceutical, and poultry applications (27)(28)(29)(30)(31). In the field of agriculture, OCT has been used in the diagnosis of various infections or diseases in onions, melon seeds, kaki plant leaves, apple leaves, and orchids were analyzed to control and limit the spread of diseases (32)(33)(34)(35)(36)(37)(38)(39)(40). To our knowledge, this technique has never been applied in the Philippines.…”