Medicinal Plant Research 2024, Vol.14, No.4, 234-244 http://hortherbpublisher.com/index.php/mpr 236 2.3 Nutrient absorption and water relations Nutrient uptake and utilization in D. officinale are facilitated by its symbiotic relationship with mycorrhizal fungi. These fungi enhance the plant's ability to absorb essential nutrients, particularly nitrogen. Studies have shown that the fungus Mycena sp. (MF23) can promote nitrogen uptake and NH4+ assimilation in D. officinale. MF23 upregulates the expression levels of nitrogen transport-related genes in D. officinale, such as DoNAR2 .1and DoAMT11, thereby enhancing nitrogen metabolism efficiency and ultimately promoting plant growth and yield (Shan et al., 2021). MF23 has also been found to increase the content of polysaccharides and secondary metabolites (such as dendrobine) in D. officinale. Research indicates that MF23 promotes polysaccharide accumulation by regulating gene expression of key enzymes in polysaccharide and metabolic pathways, and it may also increase carbon nutrient acquisition in the plant by enhancing photosynthetic capacity (Li et al., 2017). D. officinale exhibits efficient water use and robust drought response mechanisms, which are critical for its survival and growth under varying environmental conditions. The plant's association with mycorrhizal fungi enhances its water use efficiency and drought tolerance. For instance, plants treated with specific mycorrhizal fungi showed stronger drought tolerance and improved water use efficiency compared to untreated plants (Li et al., 2021a). These adaptations enable D. officinale to maintain its physiological functions and medicinal quality even under water-limited conditions. 3 Environmental Factors Influencing Cultivation 3.1 Light and photoperiod requirements Light plays a crucial role in the photosynthetic rate and overall growth of Dendrobium officinale. Studies have shown that varying light intensities can significantly impact the biomass and growth rate of this medicinal plant. For instance, shading treatments of 50% and 70% were found to significantly influence growth and biomass accumulation, with red light being particularly effective in enhancing growth and increasing the contents of polysaccharides and alkaloids (Van-Nguyen et al., 2023). Additionally, the use of red-blue LED light has been shown to increase anthocyanin content and improve the quality of D. officinale by optimizing transcriptomic and metabolomic alterations. The study by Jia et al. (2022) showed that, compared to the pseudobulbs under natural light (control group), those in the red-blue LED light treatment group and potassium treatment group turned purple, with anthocyanin content significantly increasing from 7.48 µg/g to 11.74 µg/g and 12.65 µg/g, respectively, displaying a statistically significant difference (p < 0.05) (Figure 2). Furthermore, short light/dark cycles (e.g., 4 h/4 h) can switch the photosynthetic pathway from CAM to C3, thereby enhancing daily net CO2 absorption and biomass accumulation (Cheng et al., 2019b). The photoperiod, or the duration of light exposure, is another critical factor influencing the flowering and development of D. officinale. Short light/dark cycles have been shown to improve the photosynthetic apparatus state and increase the accumulation of biomass and soluble polysaccharides (Cheng et al., 2019b). Moreover, manipulating the light/dark cycle can regulate the photosynthetic pathway, switching it between C3 and CAM, which in turn affects the plant's growth and development (Cheng et al., 2019a). The use of far-red light has also been found to promote the accumulation of flavonoids, alkaloids, carotenoids, and polysaccharides, thereby enhancing the plant's shade-avoidance response and overall production efficiency (Li et al., 2021b). 3.2 Temperature ranges for optimal growth Temperature is a vital environmental factor that influences the vegetative growth of D. officinale. Optimal temperature conditions are necessary to ensure healthy growth and high yield (Figure 3). The ideal temperature range for the vegetative growth of D. officinale has been found to be between 20 °C and 30 °C. This range supports the plant's physiological processes, including photosynthesis and nutrient uptake, thereby promoting robust vegetative growth (Ding et al., 2018). Additionally, maintaining a stable temperature within this range helps in achieving higher biomass and better quality of medicinal components (Yuan et al., 2020). Temperature fluctuations can have adverse effects on the health of D. officinale. Sudden changes in temperature can stress the plant, leading to reduced growth rates and lower quality of medicinal components. For instance,
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