Fig 1.
Phenylpropanoid biosynthesis through the shikimic acid and cinnamic acid pathways (referring to Maeda et al.
[7] and Rastogi et al. [10]). PEP: phosphoenol pyruvate; C4H: cinnamate-4-hydroxylase and 4CL: 4-coumarate:CoA ligase; CM: chorismate mutase; PAL: phenylalanine ammonia lyase; DAHPS: 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase; E4P: erythrose-4-phosphate.
Fig 2.
Morphological and physiological responses to light treatments in A. heterotropoides var. mandshuricum.
The leaf mass per area (LMA) (A) and average diurnal net photosynthetic rate (Pn) (B) at three phenological stages (18 May, 25 May, 2 June) of A. heterotropoides var. mandshuricum grown in four light radiations. Note: I, 100% full sunlight; II, 50% full sunlight; III, 24% full sunlight; IV, 12% full sunlight. Error bar represents standard deviation (n = 5); different letters on the bars mean significant difference (P <0.05).
Table 1.
The available light radiance of different light treatments in A. heterotropoides var. mandshuricum.
Fig 3.
Essential oil content in fibrous roots of A. heterotropoides var. mandshuricum plants grown in different light irradiations.
Note: I, 100% full sunlight; II, 50% full sunlight; III, 24% full sunlight; IV, 12% full sunlight. Error bar represents standard deviation (n = 5); different letters on the bars mean significant difference (P <0.05).
Fig 4.
Gas chromatogram of phenylpropanoid and aromatic compounds in essential oil from fibrous roots of A. heterotropoides var. mandshuricum plants grown in four light conditions.
A, 100% full sunlight; B, 50% full sunlight; C, 24% full sunlight; D, 12% full sunlight. cps = count per second.
Fig 5.
Heatmap displaying the variation of the relative content of phenylpropanoid and aromatic compounds detected in the extracted essential oil from fibrous roots of A. heterotropoides var. mandshuricum grown in four light conditions.
Plot colors reflect the proportion of the detected metabolites within the essential oil, ranging from low (black) to high (red). Black means not detected. Treatment I, 100% full sunlight; Treatment II, 50% full sunlight; Treatment III, 24% full sunlight; Treatment IV, 12% full sunlight.
Fig 6.
Activity key enzymes involved in the shikimic acid and cinnamic acid pathways.
Activity of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS) (A), phenylalanine ammonia lyase (PAL) (B), cinnamate-4-hydroxylase (C4H) (C), 4-coumarate:CoA ligase (4CL) (D) in different tissues of A. heterotropoides var. mandshuricum grown in four light irradiations. I, 100% full sunlight; II, 50% full sunlight; III, 24% full sunlight; IV, 12% full sunlight. Error bar represents standard deviation (n = 5); different letters on the bars mean significant difference (P <0.05).
Fig 7.
The ion chromatograms of four compounds.
(A) chromatogram of shikimic acid standard, (A1) chromatogram of shikimic acid in A. heterotropoides var. mandshuricum sample; (B) chromatogram of phenylalanine standard, (B1), chromatogram of phenylalanine in A. heterotropoides var. mandshuricum sample; (C), chromatogram of cinnamic acid standard, (C1), chromatogram of cinnamic acid in A. heterotropoides var. mandshuricum sample; (D), chromatogram of p-coumaric acid standard, (D1) chromatogram of p-coumaric acid in A. heterotropoides var. mandshuricum sample.
Fig 8.
Effect of light treatments of four precursor metabolites involved in the shikimic acid and cinnamic acid pathways.
Shikimic acid (A), phenylalanine (B), cinnamic acid (C) and p-coumaric acid (D) contents in root, leaf and whole A. heterotropoides var. mandshuricum grown in different light irradiations. Note: I, 100% full sunlight; II, 50% full sunlight; III, 24% full sunlight; IV, 12% full sunlight. Error bar represents standard deviation (n = 5); different letters on the bars mean significant difference (P <0.05).
Table 2.
The relationships between PAR, LMA, Pn, essential oil yield and precursor metabolites.