Table 2 The assignment of Raman bands of plant roots

376–379

1. Syringyl unit, 2. OH torsion in CH₂OH

1. Lignin, 2. Cellulose

Cellulose

[22]

[23]

816

COH (stretching vibration)

Pectin

[24]

856

COC (skeletal mode, α-anomers)

Pectin

[25, 26]

897

β-anomers

Cellulose

[25]

983–987

CC & CO (stretching vibration)

Cellulose

[27, 28]

1002–1005

COOH (stretching vibration)

Pectin

[26]

1092–1098

1. CC & CO (stretching vibration)

2. COC (asymmetric stretching vibration)

Cellulose

1 [27, 28]

2 [22, 26]

1122–1128

C-O-C (symmetric vibration)

Cellulose

[26, 29]

1171–1173

1. CC (stretching vibration), CH (deformation bending) + CO (stretching vibration)

2. CH (in plane deformation vibration) & C-O-C or C-O (stretching vibration)

3. CH (bending vibration)

1. Ferulic/p-coumaric acid

2. Cutin & wax

3. Lignin

1 [27]

2 [22]

3 [22]

1266–1278

1. Aryl-O-CH₃ & Aryl-O of Aryl-OH, guaiacyl ring

with CO group)

2. CH (deformation bending)

1.Lignin: coniferyl aldehyde, ferulic/p-coumaric acid

2. Ferulic/p-coumaric acid

1 [22, 27, 28]

2 [27]

1367–1380

HCC, HCO & HOC (deformation, bending vibration)

Cellulose

[24, 26, 28]

1451–1463

1. O-CH₃ (deformation vibration), guajacyl-ring (by C = O group), CH₂ scissoring, C–H bending of OCH₃and CH₂

2. HCH & HOC (deformation vibration)

1. Lignin

2. Cellulose

1 [28, 30]

2 [28]

1599–1606

Phenyl ring (symmetric stretching vibration)

Aryl ring (symmetric stretching vibration)

Lignin

[27, 28]

1630

C = C ring (stretching vibration, conjugated)

Ferulic/p-coumaric acid

[27]

1688–1698

C = O (stretching vibration)

Lignin: coniferyl aldehyde,

COOH of ferulic/p-coumaric acid

[27]

2895–2898

CH (stretching vibration)

Cellulose

[22, 23]

2935

CH (stretching vibration)

Lignin

[23]