Plant responses to ozone: Effects of different ozone exposure durations on plant growth and biochemical quality of Brassica campestris L. ssp. chinensis

Abstract Determining plant reactions to atmospheric pollutants is important in predicting and planning for new horticultural production management programs and challenges in the future. A high level of ozone in the troposphere is considered the most phototoxic air pollutant, and has strong oxidative potential. This study aimed to provide understanding on the role of ozone stress on early vegetative growth stage Pak-Choi (Brassica campestris L. ssp. chinensis). An experiment was conducted within airtight bio-chambers under 150 ppb ozone concentration with different exposure durations: control, 1 h/day and 4 h/day. The leaf area was not affected by ozone treatment, but the dry matter correlated negatively with increasing ozone exposure durations. In photopigments, the lutein, lycopene and chlorophylls were increased at 1 h/day exposure, however, total carotenoids and β-carotene were not affected. However, for the 4 h/day exposure condition, all photopigment contents were significantly decreased in comparison to the 1 h/day exposure. The total aliphatic and total glucosinolate (GLS) were significantly increased at 1 h/day exposure, and then significantly decreased at 4 h/day exposure. However, the total indole and aromatic GLS were significantly increased after 4 h/day exposure. Therefore, these results provide evidence about the impact of ozone stress on the specific secondary plant metabolites of Pak-Choi and this needs to be taken in account when selecting urban production sites for vegetables.