The Response of Antioxidant Enzymes and Photosynthesis Dynamics of Sunflower Exposed to Aniline Wastewater

Aims: In order to investigate the tolerance of sunflower to aniline, we measured the photosynthetic parameters, chlorophyll fluorescence parameters and antioxidant enzyme activities of sunflower in aniline wastewater.

Study Design: The experiment was conducted with oil sunflower No. 4 (Helianthus annuus Linn) as the experimental material. After five weeks of culture in half strength Hoagland’s nutrient solution, seedlings with uniform growth status were selected for aniline stress treatment. The concentrations of aniline stress treatment were 0, 60, 80, 100, 120, 140, 160 and 180 mg/L, respectively. Each treatment has five replicates. Leaf photosynthetic parameters were measured at fifth and tenth day after treatment under natural environmental conditions.

Place and Duration of Study: Place for the study was located at Shandong Agricultural University, Taian city, Shandong, China. The experiment lasted for 10 weeks.

Results: Five days after stress treatment, the net photosynthesis rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) of sunflower showed an upward trend at the lower concentration of aniline (≦100 mg/L) and turned to a downward trend at higher concentration of aniline (≥120 mg/L). However, ten days after stress treatment, Pn, Gs and Tr of sunflower of all concentrations decreased significantly (P=.05) as compared to the control. The photochemical quenching coefficient and effective quantum yield of PS II photochemistry decreased. At the end of the ten days experiment, with the increase of aniline concentration, the photosynthetic and chlorophyll fluorescence parameters of sunflower showed a downward trend except for intercellular CO2 concentration. The data indicated that nonstomatal limitation was responsible for the reduction of Pn. When the aniline concentration reached 180 mg/L, the activity of superoxide dismutase (SOD) and peroxidase (POD) reached the highest point, which was 3.49 times and 1.78 times higher than those of the control.

Conclusion: The low concentration of aniline (<120 mg/L) could promote the normal growth of sunflower in a short time. However, when the stress duration reaches a certain level, aniline will have a significant toxic effect on sunflower, thereby severely affecting the normal growth of sunflower.