Response of three varieties of rice seeds to the acid rain stress in the germination process

This paper has provided its investigation and experimental findings over the effects of the acid rain stress on the following three varieties of rice (O.sativa) seed germination.The said three vari- eties of rice are known as Longanyou 8,Tianxie 1,Xieyou 57.The purpose of our research was to explore the corresponding response regularities of different rice varieties to acid rain.In doing our experi- ments,we have adopted six simulated acid rain (SAR) solutions,i. e.those of the pH 2.0,2.5,3.0,3.5,4.0,and 5.0,and neutral solution as the contrast group.As the first step,we placed the pre- treated seeds of the above mentioned rice varieties into culture dishes with filter sheets,letting them germinate in a cultivated container at a constant temperature of 25℃,in which each group to be treated in- volved three dishes with 50 seeds in each,respectively.In germina- tion process,the seeds were let to be exposed to the simulated acid rain that was replaced everyday.Then,the percentage germination, germination energy,germination index,the vigor index,as well as the percentage of abnormal germination were tested and measured un- der the acid rain stress.The results of our experiments show that the percentage germination,germination energy,germination index,vig- or index of the three seed-varieties initially increased and then de- creased with the decrease of pH value from 5.0 to 3.0.The rice seeds were found to germinate only abnormally at pH 2.5 and failed to shoot up at pH 2.0.Furthermore,significant negative correlation was found among the above said indexes,though a positive correlation was found to exist between the stress time (1-7d) and the percent- age of abnormal germination.This also shows that the germination threshold values of three seeds were all standing between pH 2.5 and 3.5.However,the stress time of Longanyou 8 and Xieyou under the condition,when the difference of the above said five indices between each treatment and the contrast group became significant 57 (4 d,2 d,2 d,2 d,4 d) proved longer than that of Tianxie 1 (3 d,2 d,2 d,2 d,3 d).Thus,the experimental data further prove that the three varieties of rice would reveal different degrees of sensitivity un- der acid rain stress,with Longanyou 8 and Xieyou 57 being stronger in their resistance than with Tianxiel.