###### Abstract  
Plant fibers are sustainable sources of materials for many industries, and can be obtained from a variety of plants. Cellulose is the main constituent of plant-based fibers, and its properties give the characteristics of the fibers obtained. Detailed characterization of cellulosic fibers is often performed after lengthy extraction procedures, while fast screening might bring the benefit of quick qualitative assessment of unprooessed stems. The aim of this research was to define some marker spectral regions that could serve for fast, preliminary qualitative characterization of unprocessed stems from some textile plants through a practical and minimally invasive method without lengthy extraction procedures. This could serve as a screening method for sorting raw materials by providing an accurate overall fingerprint of chemical composition. For this purpose, we conducted comparative Fourier Transform Infrared Spectroscopy (FT-IR) prospecting for quality markers in stems of flax (_Linux usitatsimum_ L.), velvet leaf (_Abutilo theophrasti_ Medik. ), hemp (_Camabis sativa_ L.) and jute (_Corchorus olivoris_ L.). Analysis confirmed the presence of major components in the stems of the studied plants. Fingerprint regions for cellulose signals were attributed to bands at 1420-1428 cm\({}^{-1}\) assigned to the crystalline region and 896-898 cm\({}^{-1}\) assigned to the amorphous region of cellulose. The optimization of characterization methods for raw materials is important and can find immediate practical applications. cellulose; natural fibers; vibrational spectroscopy; textile plants; markers +
Footnote †: journal: Applied Sciences  
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applications [9]. Plant fibers have been used traditionally for fabrics, ropes, cordages, strings, canvas and mats [4]. However, lately, plant fibers are seen as versatile materials that can be used as fillers for reinforced composites, providing significantly increased durability and desired physical properties to matrices [6; 10; 11]. Such composites have wide applications today from automotive, aerospace to various other industrial and household applications [7; 8; 9; 12]. Besides their primary importance as a source of fibers, some of these plant species can present other secondary polarization opportunities, which increases their economic significance (Table 1). Plant fibers from stems and leaves are elongated sclerenchyma cells with lignified walls that confer mechanical strength to the plant [35]. The main component of the plant's lignocellulosic fibers is cellulose in the form of semi-crystalline microfibrils (Figure 1) that are embedded within a matrix of hemicellulose and lignin [36; 37; 38; 39]. Cellulose is a versatile biopolymer representing the most abundant polysaccharide on Earth and an inexhaustible renewable material [40; 41]. Its utilization is diverse from the textile and paper industries to pharmaceutical and food industries [42]. Cellulose comprises repeating unbranched subunits of glucose linked through glycosidic bonds that are arranged in parallel chains [42; 43]. Between the chains, strong hydrogen bonds are formed that hold them together. The cellulose microfibrils display high tensile strength that constitutes their fundamental property and ensures the structural role they have in plants, while also making them useful in industry [37; 43]. By comparison, lignin comprises three types of benzene-propane units that have a high molecular weight. It exhibits increased thermal stability while also decomposing slower. Hemicellulose has a structure that is random and amorphous [40]. The lignin and hemicellulose content in plants tends to increase with plant maturity [39]. The characterization of lignocellulosic fibers can be conveniently made based on analysis of the three components: cellulose, lignin and hemicellulose [40]. These constituents