Influence of simulated acid rain on the physiological response of flowering Chinese cabbage and variation of soil nutrients

Flowering Chinese cabbages are widely planted in the south of China and often exposed to acid rain. However, the effect of acid rain on the growth of flowering Chinese cabbage is unclear. In this study, we investigated the influence of simulated acid rain (SAR) on plant height, soil-plant analysis development (SPAD) value (an index for chlorophyll content), proline, malondialdehyde (MDA), antioxidant enzyme activities, nitrogen (N), phosphorus (P), or potassium (K) uptake and variation of soil nutrients. Our results showed that SAR at pH 5.5 did not damage plant development because growth characteristics, photosynthesis, and superoxide dismutase and peroxidase activities did not change obviously at this pH compared to those at pH 7.0. However, 2- to 7-time of SAR exposure at pH 4.5 and pH 3.5 led to the increases of antioxidant enzyme activities, MDA and proline contents, and the decreases of leaf SPAD value and root activity. Nutrient analysis indicated that spraying 4 to 7 times of SAR at pH 3.5 reduced the uptake of N, P and K of flowering Chinese cabbage significantly. In addition, treatment with SAR at pH 3.5 decreased the pH value of the surface soil and the contents of alkaline-hydrolytic N and readily available K but increased that of readily available P in the surface soil by 8.5% to 14.9%. Taken together, our results indicated that SAR at pH 3.5 influenced the antioxidant enzyme system and the contents of soil nutrients, caused metabolic disorders and ultimately restricted the development and growth of flowering Chinese cabbages.