Table 2.

Correlation coefficients among the seven phenolic compounds identified in the rhizosphere soil of wild oat (n = 11).

Phenolic compound	4-Hydroxy-benzoic acid	Vanillic acid	Syringic acid	Vanillin	p-Cumaric acid	Syringaldehyde	Ferulic acid
4-Hydroxybenzoic acid	1
Vanillic acid	0.824**	1
Syringic acid	0.273	0.651*	1
Vanillin	0.964**	0.926**	0.415	1
p-Cumaric acid	0.986**	0.814**	0.247	0.952**	1
Syringaldehyde	0.471	0.161	−0.499	0.384	0.439	1
Ferulic acid	0.713*	0.512	−0.194	0.670*	0.736**	0.835**	1

^{*, **}significant correlation at P ≤ 0.05 and ≤ 0.01, respectively.