## 1 Introduction  
Rice is a highly productive crop per unit area and one of the major agricultural products in the world, which has a potential impact on the world economy [1; 2]. Since rice is widely produced in many countries, descriptive understanding of the cellular regions, such as bulliform cells, aerenchyma cells, mid-vein and collenchyma cells are essential for increased yields. Bulliform cells are highly vacuolated cells, which are located on the adaxial epidermis between the vein ribs of the rice leaf blade [3,4]. Bulliform cells control leaf rolling (occuring due to certain mutations) and maintain the biological nature and structure of leaf [5]. The mid-vein of the leaf specimen consists of few aerenchyma, which are separated by parenchyma cell bands. Aerenchyma are composed of airy compartments that allow an exchange of gases between the leaves and other tissues [6,7]. Collenchyma cells consist of irregularly thick cell walls that provide support and structure to the leaf specimen. Figure 1 depicts a laboratory designed schematic diagram describing aforementioned rice leaf structural formation, emphasizing morphological differences. The yield of rice has been increased through the improvement of species, development of fertilizers, and development of farming tools [8]. However, genetically mutated disease pathogens and unexpected climate changes have reduced the annual yield [9]. Numerous studies confirmed that mutants change the number, size, and pattern of small veins, bulliform cells, parenchyma cells, and mesophyll cells, as well as vascular bundles, which leads to leaf rolling. Further, these mutations subsequently alter the leaf angle at later stages, such that a lower level of leaf area/unit land degrades the high photosynthesis rate [10, 11, 12]. To overcome the aforementioned drawbacks and disease related obstacles, numerous research groups have put enormous effort into gene modification and disease control [13, 14, 15]. Histological analysis and polymerase chain reaction (PCR) techniques have been frequently performed to identify the infected leaf specimens and observe morphological sections [16, 17, 18, 19]. Destructive histological analysis enables the observation of dyed cellular and tissue regions using an optical microscope or an electron microscope [18]. However, chemically immobilizing cells and tissues with formaldehyde or other chemicals can deteriorate cells and tissues very easily. PCR is a destructive molecular biological technique, which is widely used in agriculture to diagnose plant disease by detecting the DNA of the pathogen. Nevertheless, the amplification of contaminated RNA leads to the generation of plenty of errors during the experiment. As non-destructive inspection solutions for plant diseases, visual inspection, magnetic resonance imaging (MRI) [20, 21, 22], X-ray [23], positron emission tomography (PET) [22,24], confocal microscopy [25], and fluorescence spectroscopy have been utilized to overcome the limitations of histological and PCR methods. Three dimensional (3D) optical profiler is an alternative non-contact method, which can be used to obtain two-dimensional (2D) and 3D views of the leaf surface along with the optical profile graphs determining epidermal cellular height [26]. However, the analysis is limited to surface, while inadequate spatial resolution and lack of cross-sectional information hinder the extensive applicability in agriculture. Therefore, the aforementioned lack of resolution to identify microstructures and infected regions, high cost, and long acquisition time encouraged the researchers to seek a high-resolution, non-destructive, and real-time rapid inspection technique as an optimized solution. Figure 1: The schematic diagram of rice leaf structural formation. Note the use of the following acronyms in the figure: AC: aerenchyma, BUL: bulliform cells, C: collenchyma, L: lower epidermis cells, MV: mid-vein, PAR: parenchyma, SV: small vein, U: upper epidermis cells, V: vacuum regions, VB: vascular bundle.