Insights into the β-carotene distribution in carrot roots

• The carotenoid distribution in carrot roots was analyzed by Raman spectroscopy.
• The β-carotene is concentrated in the secondary phloem tissue and periderm.
• The ν4 band intensity was used to analyze the pigment molecular configuration.
• It was found that the more planar configuration occurs in the cambium region.

This work reports the carotenoid spatial distribution in orange carrot roots measured by Transmission Resonance Raman Spectroscopy. Raman contour mappings of root cross-sections were measured over the spectral range from 500 to 2500 cm−1 as a function of the root radius. The overall β-carotene content reveals a heterogeneous distribution predominantly concentrated in the secondary phloem tissue and periderm. Furthermore, detailed measurements of the ν4 band intensities, the wagging mode associated to the CH out-of-plane motion, show how the higher relative values occur in the secondary phloem and the lower ones near the vascular cambium. This vibrational mode profile was correlated with changes in β-carotene molecular configuration depending on the different physiological properties of the investigated root tissues.

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