Effects of Different pH Values on the Growth and Physiological Characteristics of Anoectochilus roxburghii

Appropriate pH conditions are highly important for ensuring the healthy growth of plants and play a crucial role in the process of plant growth. Anoectochilus roxburghii is renowned for its high medicinal and edible values and is distributed in China and numerous Southeast Asian countries. The demand for this plant shows an increasing trend. To explore the optimal pH conditions for the growth of A. roxburghii, various pH values were used under hydroponic conditions to investigate their impacts on plant morphology, growth, and physiology. The results demonstrated that A. roxburghii had remarkable acid tolerance and thrived well within the pH range of 2.0-6.0. In particular, it had the highest survival rates of 83.33% and 77.78% under strongly acidic conditions of pH 2.0 and 3.0, respectively. As the pH increased, the survival rates decreased. The survival rate was merely 40.00% at pH 7.0, and all the plants perished at pH 11.0. As the pH gradually decreased, the enzymatic defence system of A. roxburghii was activated, and the peroxidase (POD) activity in the leaves tended to increase. Under short-term acidic conditions, the superoxide dismutase (SOD) activity in the leaves somewhat increased, but the changes were relatively small. Generally, the catalase (CAT) activity in the leaves initially decreased but then increased. In conclusion, A. roxburghii has strong resistance to acidity but has difficulty surviving under alkaline conditions. It can grow normally within the pH range of 2.0-6.0 and achieves the best growth in a strongly acidic environment with a pH of 2.0-3.0. This study provides ideas for improving the productivity of organic agriculture, facilitating the restoration of vegetation in acidic soils and the cultivation of stress-resistant plants, as well as optimizing the cultivation of medicinal plants and regulation of their components.