Medicinal Plant Research 2024, Vol.14, No.4, 234-244 http://hortherbpublisher.com/index.php/mpr 238 of medicinal components in D. officinale (Yuan et al., 2020). Maintaining an optimal humidity level helps in preventing water loss and ensures the efficient functioning of the plant's physiological processes (Ding et al., 2018). Air circulation is essential for preventing diseases and promoting healthy growth in D. officinale. Proper air circulation helps in reducing the humidity around the plant, thereby preventing the growth of pathogens that thrive in high humidity conditions. For instance, the presence of mycorrhizal fungi has been shown to improve the plant's tolerance to environmental stress and reduce the incidence of root rot caused by pathogens (Li et al., 2021a). Additionally, good air circulation ensures that the plant receives adequate CO2 for photosynthesis, thereby promoting healthy growth and higher biomass accumulation (Ding et al., 2018). 4 Nutritional Requirements and Fertilization Strategies 4.1 Essential macro and micronutrients Nitrogen (N), phosphorus (P), and potassium (K) are critical macronutrients that significantly influence the growth and medicinal quality of D. officinale. Nitrogen is essential for vegetative growth and is positively correlated with morphological indicators and polysaccharide content in D. officinale (Fan et al., 2023). Phosphorus plays a crucial role in energy transfer and root development, with optimal levels enhancing polysaccharide and flavonoid content. Potassium is vital for enzyme activation and osmoregulation, and its application has been shown to increase anthocyanin content and improve the overall quality of D. officinale (Jia et al., 2022). Micronutrients such as calcium (Ca), magnesium (Mg), and iron (Fe) are also essential for the optimal growth of D. officinale. Calcium is important for cell wall stability and signal transduction, while magnesium is a central component of chlorophyll and is crucial for photosynthesis. Iron is necessary for chlorophyll synthesis and various enzymatic functions. In samples of D. officinale cultivated in different regions in the north and south, variations in nutrient content were observed based on growth duration and geographic location. D. officinale cultivated in southern regions showed higher levels of nutrients such as polysaccharides and total phenols, while D. officinale grown in northern regions was richer in alkaloids. These findings highlight the potential impact of elements like calcium and magnesium on the growth and nutritional value of D. officinale in different environments (Guo et al., 2021). 4.2 Fertilizer types and application schedules Both organic and inorganic fertilizers can be used to meet the nutritional needs of D. officinale. Organic fertilizers, such as compost and manure, provide a slow-release source of nutrients and improve soil structure. In contrast, inorganic fertilizers offer precise nutrient formulations and immediate availability. Studies on varying concentrations of nitrogen, phosphorus, and potassium fertilizers found that nitrogen had the greatest impact on plant growth. Appropriate levels of nitrogen and phosphorus contributed to increasing polysaccharide and flavonoid content in plants. The optimal combination (nitrogen 1 500 mg/L, phosphorus 3 000 mg/L, potassium 500 mg/L) significantly enhanced plant growth and the accumulation of medicinal components (Fan et al., 2023). The fertilization schedule for D. officinale should be tailored to its growth stages. During the vegetative stage, higher nitrogen levels are recommended to promote leaf and stem growth. As the plant transitions to the reproductive stage, the focus should shift to phosphorus and potassium to support flower and pseudobulb development. An optimal schedule might include higher nitrogen application early on, followed by balanced NPK ratios as the plant matures (Fan et al., 2023; Wu et al., 2023). 4.3 Effects of nutrient deficiencies and toxicities Nutrient deficiencies can severely impact the health and quality of D. officinale. Research has found that under low nitrogen conditions, the growth and photosynthesis of D. officinale are inhibited, but its polysaccharide and flavonoid content increase (Wu et al., 2023). Phosphorus deficiency can lead to poor root development and delayed maturity, while potassium deficiency often manifests as leaf chlorosis and necrosis, affecting overall plant vigor and anthocyanin accumulation (Jia et al., 2022; Fan et al., 2023).
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