Physiological responses of Elaeocarpus glabripetalus seedlings exposed to simulated acid rain and cadmium

Abstract

Combined effects of cadmium (Cd) and acid rain on physiological and biochemical characteristics in Eleocarpus glabripetalus seedlings were investigated under controlled conditions. The single Cd treatment and the combined Cd and acid rain treatment increased growth at low Cd concentrations, while decreased growth and photosynthesis at high Cd concentrations. A low Cd concentration (50mg‧kg -1 ) combined with different acid rain treatments increased the seedling biomass, while there was no significant difference in chlorophyll fluorescence and antioxidative enzyme activities compared with the control plants. A high Cd concentration (100 mg‧kg -1 ) under different acid rain treatments significantly decreased the biomass, the Fe and Mg content, chlorophyll fluorescence, photosynthetic parameters (the maximum net photosynthetic rate, Amax, and the light saturation point, LSP). Relative electric conductivity and peroxidase (POD) activity were significantly higher while the reduced glutathione (GSH) content and catalase (CAT) activity were significantly lower at high Cd concentration under acid rain when compared to the control plants.The results indicated that the combination of a high concentration of Cd and acid rain aggravated the toxic effect of Cd or acid rain alone on the growth and physiological parameters of E. glabripetalus due to serious damage to the chloroplast structure.However, E. glabripetalus showed tolerance to a low concentration of Cd and low pH induced by acid rain.

Acid Rain Increases Impact of Rice Blast on Crop Health via Inhibition of Resistance Enzymes

“…We found that single acid rain treatments increased the PAL and CHT activities in leaves. Generally, acid rain stress can increase [ 11 ], or decrease POD activity depending on the stress intensity and duration [ 10 ]. The changes of POD activity in our study were in agreement with previous reports which suggested that increases in POD activity were observed in rice leaves under SAR of pH 5.0, 4.0, 3.0, and a decrease under SAR of pH 2.0 [ 22 ].…”

“…These results suggest that there would be a likely acidity threshold (pH ≥ 4.0) for rice defense system to acid rain stress, which would not affect the normal physiological activities of plants, but could improve the sensitivity of the plants’ resistance to stress. Below this threshold, the metabolic system would be destroyed and plant resistance would be reduced [ 11 ]. The changes in the contents of the flavonoids, total phenol and soluble sugar indicated that the single stress of inoculation with P. oryzae or acid rain increased the antioxidant metabolites, but the combined treatment stress of them under high acidity of simulated acid rain decreased and even inhibited the metabolites in rice seedlings.…”

“…With decreasing pH of acid rain, the total number of rice leaves first increased and then decreased ( Figure 3 ). The reason may be that acid rain enriched in N acts as a fertilizer, which then accelerates biomass accumulation in leaves [ 11 ]. The total leaf number is a key indicator for calculating the disease index, and it is significantly negatively correlated with the disease index ( Figure 6 A).…”

“…This discrepancy might be attributable to the crop variety, acid rain acidity, and pathogen type [ 5 ]. For example, different plants (rice, soybean and Elaeocarpus glabripetalus seedlings) have different tolerance to acid rain stress [ 10 , 11 , 45 ], so do the pathogens [ 5 ]. Hence, the interaction of different plant-pathogens to environmental stress would be varied.…”

“…In the field, plants are rarely exposed to a single hazardous stress. Most agroforestry areas are threatened by both acid rain and disease [ 11 ]. Additive, antagonistic or synergistic interactions between acid rain pollution and pathogens on plants have been reported [ 12 ].…”