Effect of Ozone Stresses on Growth and Secondary Plant Metabolism of Brassica Campestris L. Ssp. Chinensis

Determining plant responses to hazardous air pollutants is critical in predicting food security programs and challenges in the future. This study aimed to determine the effects of various ozone levels on plant growth responses (leaf area, dry matter, and number of leaves) and biochemical quality (photopigments and glucosinolates) on Brassica campestris L. ssp. chinensis (Pak-Choi). The experiment was conducted within test chambers under different ozone concentrations (60, 150, and 240 ppb for 2 h/day). Leaf area and dry matter were negatively correlated with increasing ozone concentrations, but the number of leaves was not affected by ozone treatment. Lycopene and chlorophylls also showed the same tendency. Even if the ambient ozone concentration was only elevated for a short time, various glucosnilates (GLS) have been diversely affected. The total aliphatic GLS content was reduced. In contrast, the total indole GLS increased at the highest ozone concentration, and the aromatic GLS significantly increased and then decreased as the ozone concentration level increased. These results provide evidence of the strong effect of ozone stress on the plant quality of Pak-Choi with respect to certain secondary plant metabolites. These findings provide an understanding of elevated ozone effects in urban horticulture sites on the growth and metabolite profiling of Brassica plants.