Effect of Chlormequat Chloride on the Growth and Development of Panax ginseng Seedlings

Ginseng is widely used in traditional herbal formulations in Korea, Japan, China, and Western countries. High-quality seedlings are the key to ginseng with high quality and high yield. Although tray seeding can yield large quantities of ginseng seedlings, issues such as dense planting and inadequate ventilation may result in excessive stem elongation. This elongation can lead to slender stems unable to support the weight of the leaves, resulting in seedling lodging. To inhibit the overgrowth of aboveground parts of ginseng seedlings, chlormequat chloride (CCC) was selected for foliar spraying at 0, 100, 200, and 300 mg·L−1 to study the effects of plant growth regulators on the growth and development of ginseng seedlings. When the leaves of ginseng seedlings are fully expanded, we sprayed once with 200 mg·L−1 of CCC. After 28 days, index measurements indicated that the height of ginseng seedlings decreased by 17.4%, stem thickness increased by 7.4%, leaf area decreased by 4.5%, root length increased by 6.2%, root-to-crown ratio increased by 29.8%, chlorophyll a content increased by 10.3%, chlorophyll b content increased by 12.6%, the actual chlorophyll fluorescence parameters of photosystem II under light quantum yield increased by 50.9%, electron transfer rate increased by 52.8%, photochemical quenching increased by 21.7%, nonphotochemical quenching decreased by 31.4%, antioxidant enzyme superoxide dismutase activity increased by 12.2%, catalase activity increased by 17.0%, peroxidase activity increased by 38.7%, and malondialdehyde content decreased by 18.1%. The number of intracellular starch grains increased significantly, the number of stromal lamellae in chloroplasts increased, the arrangement was more compact, and the cell wall thickness increased significantly. In conclusion, it is recommended to apply 200 mg·L−1 CCC as a foliar spray during production to inhibit seedling growth and enhance plant resistance to stem collapse and stress.