AGAR PHENOLIC IMPURITIES AFFECT THE BIOLOGICAL PERFORMANCE OF IN VITRO CULTURES

Abstract

Agars with different performance for Rannunclus asiaticus L. shoots, were analysed for their phenolic impurities content. Two main phenolic impurities appeared to be related to the agar brand. The first impurity (3-hydroxyphenylacetic acid-HPA) was recovered only from Roth and Merck agars; the second one, 2-dihydroxybenzene, or catechol-CAT, was only released from Oxoid agar. The widely used MS tissue culture medium contains about 4630 mg/L salts. According to the analyses carried out for the phenols agar powder, an uncontrolled pollution of the culture media could be reached till 0.1-0.2% of the total salt content. The diffusion of these phenolic impurities in gel differed between agars and a different amount could be immobilized in the media: up to 35%, 47% and 61% respectively for Roth, Merck and Oxoid agar. Good performance was found when Ranunculus shoots were grown on Oxoid gels, with the lowest total phenol content, the absence of HPA and the presence of CAT. The biological tests carried out to evidence the influence of HPA and CAT on Ranunculus shoot growth, pointed out that HPA behaves as an inhibitor of shoot multiplication and induces poor shoot quality. CAT appears to stimulate a weak increase of performance in shoots grown onto MK and RT gels supplemented with this phenol.