Arbuscular mycorrhiza improved drought tolerance of maize seedlings by altering photosystem II efficiency and the levels of key metabolites

Chemical and Biological Technologies in Agriculture

Table 3 Metabolic levels of free amino acids and polyamines in leaves of maize plants under drought and arbuscular mycorrhizal fungal inoculation (mean ± SD, n = 5)

Treatment	AAs (μmol·g⁻¹)	Arg (ng·mg⁻¹)	Orn (ng·mg⁻¹)	Put (ng·mg⁻¹)	GABA (ng·mg⁻¹)	ADC (U·g⁻¹)	ODC (U·g⁻¹)	DAO (U·g⁻¹)	GAD (U·g⁻¹)
W
NM	71.89 ± 8.50b	1.34 ± 0.08a	0.77 ± 0.14c	1.06 ± 0.16c	4.13 ± 0.49c	1.49 ± 0.32a	0.69 ± 0.09b	0.15 ± 0.02b	4.16 ± 0.76a
AM	56.20 ± 6.06c	1.25 ± 0.08a	1.01 ± 0.10b	3.00 ± 0.57b	2.99 ± 0.50d	1.45 ± 0.09a	1.01 ± 0.04a	0.18 ± 0.01a	3.23 ± 0.07a
D
NM	85.50 ± 8.13a	1.17 ± 0.39a	0.82 ± 0.03c	4.73 ± 0.63a	13.49 ± 0.36a	1.63 ± 0.22a	0.97 ± 0.08a	0.12 ± 0.02c	3.85 ± 1.45a
AM	79.65 ± 3.85ab	1.51 ± 0.35a	1.46 ± 0.18a	5.21 ± 0.63a	7.79 ± 0.38b	1.42 ± 0.31a	0.79 ± 0.12b	0.15 ± 0.02b	3.96 ± 1.02a
Two-way ANOVA
D	**	ns	**	**	**	ns	ns	*¹	ns¹
I	**	ns	**	**	**	ns	ns	*¹	ns¹
D × I	ns	ns	**	**	**	ns	**	–	–

Different lowercase letters in the same column indicate statistically significant differences between treatments at P < 0.05 by Duncan’s test
D drought stress, I inoculation treatment, W well-watered, AM arbuscular mycorrhizal fungal inoculation, NM non-mycorrhizal fungal inoculation, AAs free amino acids, ADC arginine decarboxylase, Arg arginine, DAO diamine oxidase, GABA γ-aminobutyric acid, GAD glutamic acid decarboxylase, ODC ornithine decarboxylase, Orn ornithine, Put putrescine, ns not significant
*P < 0.05, **P < 0.01
¹ANOVA outputs by nonparametric statistical test