# Fluorescence Hyperspectral Imaging for Early Diagnosis of Heat-Stressed Ginseng Plants
## 1 Introduction  
Ginseng plants are long-lived and slow-growing species that take four to six years for optimal root growth [1]. Ginseng has been consumed for centuries in east Asia due to its health benefits [2]. Disregarding the roots, the aerial parts, including leaves and berries, are increasingly supplemented as food for high ginseng and phenolic compositions (\(p\)-coumaric acid, cinnamic acid, and syringaresinol) [1]. Along the life cycle, ginseng plants are constantly exposed to extreme stress conditions, with significant concerns related tothe projected global temperature increase of 2 \({}^{\circ}\)C by 2050 [3], since ginseng plants are susceptible to high temperatures [4], and their photosynthetic efficiency declines starting at 35 \({}^{\circ}\)C (48 h) [5]. Several studies have reported the adverse impact of temperature on ginseng plants. For example, subjecting ginseng to high temperatures has been shown to reduce plant and root growth, leaf size, and 29-59% of primary and secondary roots [6]. Additionally, based on reports of destructive methods [5; 7; 8; 9] high-temperature propositional impacts on medicinal compounds of the roots, for instance, cause its ginseng content to drop due to a decrease in photosynthesis and protein compositions in leaves [5; 9], which causing to damage plants growth and development [10]. Due to ginseng plants' sensitivity to environmental changes, ginseng grown under an artificial shade has illustrated a higher market value than that grown under direct lighting, as the former crop physically appears smooth, fat, and cream-colored and has few rings on its roots [11]. According to the reported studies, the environment directly affects ginseng's market value and functional food composition [12]. Therefore, the early diagnosis of biotic and abiotic stress has become extremely important for increasing agriculture productivity and crop quality. Moreover, perennial plants acquire various physiological and morphological characteristics in their life cycles. Therefore, the quality inspection of plants has become increasingly important. For example, in leaves with high levels of ginseng in one-year-old ginseng plants [13], exposure to heat stress was found to reduce the ginseng composition [7]. Ginsenoside has various medical applications, such as inhibiting reactions, antiaging, cancer treatment, and other health benefits [14]. Moreover, heat stress impacting the molecular composition of ginseng plants has been reported [9] under differential gene expression in two varieties, which presented significant decreases in chlorophyll (a and b) binding protein, fatty acids, cytochrome, and photosynthesis mechanisms. These studies have contributed significantly to ginseng plants' physiological, morphological, and biochemical inspection. However, these methods involve destructive approaches that require time and intense labor. Thus, these methods can only be used by specialists. Advances in imaging technologies offer opportunities for the non-destructive screening of plants' physiological, biochemical, and morphological characteristics [15]. Non-destructive visualization of plants' status in early stages will help to minimize non-optimal negative impacts and increase crop yield and quality, in addition to helping create better farm management practices and input efforts. Responding to non-optimal conditions is essential for increasing plants' nutrition status to avoid devastating consequences for high-quality crop production [16]. For example, the early detection of spotted wilt virus infection in tomato was realized using hyperspectral imaging (HSI) [17]. In other studies, a multispectral sensor was used to detect gray mold on tomato leaves [18] and in the early diagnosis of water deficiency in maize plants using HSI [19]. Moreover, near-infrared spectroscopy (NIRS) was used to monitor spinach plant texture and other quality assessments [20]. Furthermore, digital imaging, chlorophyll fluorescence, and visible NIRS were used to monitor bell pepper fruits' ripening stages [21].