Comparative Analysis of Pigment and Condensed Tannin Content between Red-stem and Green-stem Alfalfa

Purpose To explore the pigment composition and color mechanism of red-stem alfalfa.

Methods Red-stem and green-stem alfalfa were used as materials, the pigment components, and the contents of chlorophyll, carotenoid, anthocyanin and condensed tannin in stems and leaves were determined by chemical chromogenic method and spectrophotometer.

Results The stem of red-stem alfalfa mainly contained anthocyanin and flavonoids, and the stem of green-stem alfalfa had not anthocyanin. The contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoid were significantly higher in leaves of red-stem and green-stem alfalfa than those in stems (P<0.05). However, the differences between different colors of stems and leaves were not significant (P>0.05). The contents of anthocyanin glycosides and condensed tannins, and ratio of anthocyanin glycosides to total chlorophyll in the stem of red-stem alfalfa were significantly higher than those in the stem of green-stem alfalfa (P<0.05).

Conclusion The increase of anthocyanin and condensed tannin contents are the main reason for red coloration of alfalfa stems.