Table 4.

Summary of ANOVA results for effects of elevated CO₂ and increased nitrogen fertilization on defensive response of maize.

Measurement	Treatment	df	F	P
POD	CO2	1	7.89	0.01
	N	2	13.41	<0.01
	Infestation	1	7.16	0.02
	CO2∗N	2	0.8	0.46
	CO2∗infestation	1	2.04	0.17
	N∗infestation	2	1.85	0.18
PPO	CO2	1	18.53	<0.01
	N	2	11.53	<0.01
	Infestation	1	13.6	<0.01
	CO2∗N	2	1.38	0.27
	CO2∗infestation	1	0.32	0.58
	N∗infestation	2	0.17	0.84
CAT	CO2	1	0.04	0.84
	N	2	5.82	0.03
	Infestation	1	1.92	0.18
	CO2∗N	2	0.99	0.39
	CO2∗infestation	1	5.82	0.03
	N∗infestation	2	6.54	<0.01
PAL	CO2	1	9.48	<0.01
	N	2	3.42	0.05
	Infestation	1	17.83	<0.01
	CO2∗N	2	0.87	0.43
	CO2∗infestation	1	1.55	0.22
	N∗infestation	2	0.64	0.54
PIs	CO2	1	1.03	0.32
	N	2	11.47	<0.01
	Infestation	1	7.82	0.01
	CO2∗N	2	0.35	0.71
	CO2∗infestation	1	0.8	0.38
	N∗infestation	2	10.84	<0.01

^∗PPO, polyphenol oxidase; POD, peroxidase; CAT, catalase; PAL, phenylalanine ammonia-lyase, PIs, proteinase inhibitors; N, low N fertilization level (100 mg N/kg soil mixture), middle N fertilization level (200 mg N/kg soil mixture), and high N fertilization level (300 mg N/kg soil mixture); CO₂, ambient CO₂ concentrations (∼380 ppm) and elevated CO₂ concentrations (∼750 ± 15 ppm); n = 3.