Light intensity is a crucial factor that regulates growth, physiological traits, antioxidant defense, and metabolite acquisition in Dendrobium denneanum.

Abstract

Light intensity plays a pivotal role in modulating the development and secondary metabolite production of medicinal plants. This research thoroughly examines the impact of varying light levels (50 [A], 100 [B], 200 [C], 400 [D], and 600 [E] μmol m^-2 s^-1) on Dendrobium denneanum, focusing on its morphological traits, physiological and biochemical responses, and secondary metabolite content. Our findings indicate that an intermediate light intensity of 400 μmol m^-2 s^-1 markedly improves stem diameter, leaf dimensions (length and width), and the synthesis of photosynthetic pigments, including chlorophyll a, chlorophyll b, and carotenoids, with pronounced effects observed during later treatment phases. At 400 μmol m^-2 s^-1, antioxidant enzyme activities (CAT, POD, SOD) reached their highest levels, while malondialdehyde (MDA) levels were the lowest, indicating efficient reactive oxygen species (ROS) scavenging capacity. Soluble sugars and proteins accumulated significantly at 400 μmol m^-2 s^-1, supporting metabolic homeostasis and stress tolerance. Secondary metabolites (flavonoids and polyphenols) peaked at 400 μmol m^-2 s^-1. Principal component analysis (PCA) and resistance contribution diagrams revealed that 400 μmol m^-2 s^-1 achieved the highest composite scores across morphological, physiological, and metabolic indicators. This study not only pinpoints an optimal light condition for maximizing growth, ornamental characteristics, and the yield of valuable medicinal compounds in Dendrobium denneanum but also offers a scientific basis for precise, resource-efficient cultivation. These insights are valuable for enhancing the sustainable production and quality consistency of this and potentially other economically important medicinal and ornamental plants, supporting both the phytopharmaceutical and horticultural industries.