Table 6. Effects of Si and SAR on CAT, POD, SOD, and APX activities and H₂O₂ content in rice roots.

SAR (pH)	Si (mM)	H2O2 μmol·g-1(FW)	CAT U·g-1(FW)·min-1	POD U·g-1(FW)·min-1	SOD U·g-1(FW)	APX U·g-1(FW)·min-1
6.5	0	0.257±0.003 j	10.717±0.282 e	5.247±0.143 d	733.122±30.821 hi	26.556±1.020 ef
	1	0.216±0.002 m	2.525±0.070 i	4.674±0.147 ef	729.872±49.983 hi	25.509±1.069 f
	2	0.249±0.003 k	2.327±0.028 i	3.647±0.096 i	795.163±25.556 gh	27.744±2.239 def
	4	0.306±0.005 h	2.639±0.066 i	4.738±0.060 e	927.328±26.781 de	24.475±2.569 fg
4.0	0	0.238±0.003 l	16.151±0.271 b	3.757±0.095 i	673.442±26.393 ijk	28.339±2.342 def
	1	0.189±0.002 n	7.445±0.169 g	4.300±0.048 h	651.427±13.041 jk	43.282±2.345 b
	2	0.193±0.002 n	9.815±0.249 f	4.496±0.150 g	642.085±22.597 k	51.182±2.501 a
	4	0.284±0.002 i	7.533±0.224 g	1.583±0.064 l	708.695±29.520 ij	29.902±2.327 de
3.0	0	0.387±0.005 e	5.516±0.147 h	5.674±0.047 c	834.339±35.554 fg	19.797±2.501 h
	1	0.351±0.003 f	10.654±0.653 e	4.193±0.060 h	1318.142±35.187 b	31.305±2.216 d
	2	0.325±0.003 g	19.423±0.517 a	4.503±0.071 fg	1472.469±60.287 a	36.715±1.950 c
	4	0.385±0.005 e	13.478±0.239 c	2.223±0.111 i	988.815±42.872 d	28.147±1.497 def
2.0	0	0.512±0.004 a	1.986±0.061 i	2.001±0.066 k	874.758±26.359 ef	12.127±0.661 i
	1	0.431±0.006 c	10.257±0.223 ef	6.072±0.058 b	1066.686±41.675 c	18.778±1.432 h
	2	0.394±0.005 d	12.404±0.356 d	8.636±0.213 a	1122.326±54.544 c	20.576±1.647 gh
	4	0.465±0.004 b	9.914±0.168 f	4.176±0.056 h	953.960±52.680 d	14.243±1.693 i
F		178.961	4.336	4.176	20.131	38.219
p		0.000*	0.002*	0.002*	0.000*	0.000*

Abbreviations: SAR, simulated acid rain; Si, silicon; CAT, catalase; POD, peroxidase; SOD, superoxide dismutase; APX, ascorbate peroxidase; H₂O₂, hydrogen peroxide.

The values are the means ± standard deviation, n = 3.

Significant differences (p<0.05) are indicated by different letters in the same column.

^* Significant at the 0.05 level.