Objective Acid rain affects the growth and development of crops. Exploration of effects of acid rain on physiological indexes of rice seedlings at the stages of germination and tillering can provide theoretical references for rice planting in those regions covered by acid rain.

Method An laboratory experiment was conducted to investigate physiological indexes of rice germination and growth under stimulated acid rain (SAR) stresses, with the treatments including pH 3.5, pH 4.0, pH 4.5, pH 5.0 and the control (CK) being pH 6.0.

Result After incubation for seven days, the germination rate of rice seeds decreased with the pH decrease of SAR, but the differences were not statistically significant among treatments. Under low stress of SAR with pH 4.5 and pH 5.0, there were no significant difference in either germination index or seedling length between treated and CK groups. The seedling length at pH 5.0 was 6.82 (±0.17) cm, a value being slightly higher than that under CK (6.78 cm± 0.13cm). Under high stress of SAR of pH 3.5 and pH 4.0, the germination index, vigor index and seedling length of rice were significantly lower than those in CK group. The plant height, root length and chlorophyll content of rice leaves increased first and then decreased during the range of pH 3.5-6.0 of SAR. Some physiological indexes were promoted under weak acid treatment relative to the CK group. Especially, under the SAR treatments of pH 4.5 and pH 5.0, the plant height was 23.54 (±0.97) cm and 24.44 (±0.57) cm, respectively, significantly higher than that in CK group (21.54 cm±1.8 cm). The chlorophyll content was 26.13 (±1.07) SPAD and 27.13 (±0.63) SPAD under the SAR treatments of pH 4.5 and pH 5.0, and that was significantly higher than that in CK group (23.91±2.00 SPAD). Moreover, the root length was 6.56 (±0.26) cm at the SAR treatment of pH 4.5, which was slightly higher than in CK group (6.50 cm±0.42 cm). In contrast, high stress of the SAR treatments significantly impressed the physiological and growth indexes of rice, which indicated that acid rain may exhibit low promoting and high inhibiting effect on rice growth.

Conclusion High acid rain stress inhibited the germination and growth of rice, while low concentration acid rain had a certain stimulating effect.