Table 3.

Comparing the effect of air pollution stress on the catalase, ascorbate peroxidase and PAL activities of A. altissima, S. babylonica, and M. alba trees.

Trees	Sites	Catalase activity (∆OD min−1)		Ascorbate peroxidase activity (∆OD min−1)		PAL activity (μΜ cinnamic acid min−1)
		Summer	Autumn	Summer	Autumn	Summer	Autumn
A. altissima	1	0.45 fg ± 0.01	0.15j-l ± 0.01	0.20d-h ± 0.005	0.34bc ± 0.02	1.29p ± 0.38	2.96i ± 0.3
	2	0.44 fg ± 0.03	0.49e-g ± 0.04	0.34bc ± 0.03	0.23c-g ± 0.21	0.92q ± 0.48	1.92 m ± 0.28
	3	0.95ab ± 0.01	0.62c-e ± 0.01	0.2d-h ± 0.02	0.5a ± 0.01	1.76n ± 0.23	3.8e ± 0.16
	4	0.45 fg ± 0.08	0.14j-l ± 0.01	0.35bc ± 0.01	0.04i ± 0.005	1.97 m ± 0.45	4.52c ± 1.1
S. babylonica	1	0.12j-l ± 0.01	0.28 h-j ± 0.05	0.25c-f ± 0.01	0.3b-d ± 0.003	0.89q ± 0.21	3.22b ± 0.74
	2	0.45 fg ± 0.01	0.33 g-i ± 0.01	0.03i ± 0.02	0.11f-i ± 0.02	0.64p ± 0.1	2.5 k ± 0.63
	3	0.53d-f ± 0.03	0.65 cd ± 0.01	0.31b-d ± 0.01	0.27c-e ± 0.02	1.24p ± 0.57	3.61f ± 1.01
	4	0.12j-l ± 0.01	0.21i-k ± 0.03	0.05i ± 0.003	0.35bc ± 0.01	1.55° ± 0.16	4.15d ± 0.19
M. alba	1	0.71c ± 0.003	0.87ab ± 0.006	0.06hi ± 0.02	0.02i ± 0.02	2.57 k ± 0.55	4.12d ± 0.56
	2	0.34 g-i ± 0.003	0.43f-h ± 0.01	0.06hi ± 0.10	0.07hi ± 0.03	2.42i ± 0.66	2.82j ± 0.86
	3	1.05a ± 0. 03	1.02ab ± 0.01	0.16e-i ± 0.01	0.25c-f ± 0.04	2.96i ± 0.82	6.41b ± 1.7
	4	0.89ab ± 0. 02	0.96b ± 0.02	0.1 g-i ± 0.02	0.43ab ± 0.02	3.5 g ± 1.1	8.17a ± 1.3

Two seasons of Summer and Autumn at Sites 1 (Mirdamad Street), 2 (Mirza Babaei Street), 3 (Kargar Shomali Street), and 4 (Azadi Bus Station Street) Tehran. The means that have at least one common letter did not show a statistically significant difference (P < 0.05). Data are presented as mean ± SE.

PAL phenyalanine amonia lyase.