Optimal growth of tea plants at pH 4.5 revealed by morphological and physiological responses

Tea plants (Camellia sinensis) are naturally adapted to acidic soils, but excessive acidification poses serious threats to their growth and quality. This study aimed to identify the optimal pH for tea plant growth by examining morphological and antioxidant responses under different acid stress (pH 4.0–7.0) conditions. The results demonstrated that pH 4.5 most effectively promoted above- and below-ground part growth, root biomass, number of 2^nd and 3^rd lateral roots, root length, surface area, and average diameter, chlorophyll content, root activity, and antioxidant enzyme (superoxide dismutase and catalase) activities while minimizing oxidative damage (based on malondialdehyde levels). In contrast, stronger acidity (pH 4.0) or neutral conditions (pH 6.5 and 7.0) significantly inhibited tea growth and tested physiological functions. The findings highlight pH 4.5 as the optimal condition for tea cultivation and provide a scientific basis for managing soil acidity to enhance productivity and stress resilience in tea plants.